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2003 Infiniti G35 No Power in Low Rpms

28K views 109 replies 4 participants last post by  40914 
#1 · (Edited)
Bought car for 9k in 2013 @60k mi
Car had minor defect to paint, and interior was like new
Car had small hole in exhaust near muffler that made the car more responsive, deeper growl, and more fuel efficient....until the hole widened, then the performance went away, and my story of modification started...

Mods:
Stillen Cold Air Intake, Z-Tube, K&N Cone Filter
370z Injectors
ACT Stage 1 Racing Clutch
ACT Lightweight Billet Aluminum Flywheel
Stillen Headers
Stillen High Flow Cats
Stillen True Dual Exhaust Gen 1
Walbro 255LPH Fuel Pump

Hi everyone, I have been chasing the original responsiveness the G had when I first bought it to no avail.

I have added many modifications(the ones you see above), and replaced almost every sensor/electronic/component under the hood:
Knock Sensor
Knock Sensor Harness
Cam sensors
Crank Position sensor
Maf Sensor
Rear 02 Sensors
Front 02 Sensors (1 twice on drivers side)
Spark Plugs -OEM
Coil Packs -OEM
Coil Pack Sub Harness(connects to coils 1 and 3)
Injectors -2008 370Z
Battery(cleaned Ground)
Clutch Slave Cylinder
Differential Oil
Transmission Oil
Front/Rear Wheel Speed Sensors
Throttle Position Sensor
VTC Solenoid Valves
Evap Canister Purge Solenoid Valve
Fuel Pressure Regulator Passenger Side
Fuel Pump/Filter
Oil Pressure Sensor

Sadly, after replacing all of these parts, the only thing I have left I can replace would be the Accelerator Pedal Position Sensor, and the ECU that I know of...

I should mention that the car has been flashed with Osiris and dynoed at 280rwhp, however, the car does not feel like it has anywhere near that amount of HP at the wheels. The car is very sluggish on takeoff(feels like it is going to stall), and has no power up until 4800 RPM

I am very confused, but optimistic, and willing to learn about what could be causing this problem.

If anyone has any idea as to what could be causing this vehicle to have 0 balls in the low rpm range, please give me some insight...
 
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#3 ·
I don't recall seeing the orig post last week so I'm not sure why that is. ( ?? )

I usually take note on most of these even though I'm not usually the better person to respond. I'm not a mods / builder-gifted person so my experience and know-how is pretty limited but I can sometimes pick up something or learn from others.

I'm confused a small hole in the exhaust would make a noticeable change in actual improvement (measured/proven) performance. I def know the better sounding exhaust makes about 15 % more butt-dyno hp by all that have experienced that magic though! lol

A bigger or growing hole could/should very likely affect the exhaust flow and back-pressure. Messing with that on a car or motorcycle is a bit of a science and for that reason, lots of R&D goes into it since improving on the OEM design is not always an easy task for an unrelated engineer.

As for how to insure or test there is a performance loss and find the culprit, others may have some good ideas or related experiences. You have a giant list of things that were changed out, yet it sounds like the car lost it's juice around the time of the muffler issue and it was never investigated or figured out before you went on your shopping spree and mod changes.

This time of year, the forums are a bit slower but someone will chime in for sure if they have some ideas .....
 
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#5 ·
Yeah ... I was beating around the bush.
The variables are beyond my math looking at the changes but the simplest approach may be a systems health check.....

- If the motor has good compression and the injectors are metering the correct fuel and the afr is correct, then I suppose the devil is in the other details.

-Have the Osiris mapping checked and verified.

-Make sure the total exhaust system is air tight.

I see no mention of Check Engine Lights or SES so maybe that is a good sign for the various sensors and such.
I'd be leaning toward something that was wrong earlier and did not get the chance to be fixed or improved with all your add on's. If the motor compression wasn't effected by anything you did, it could be the culprit and would STILL be the culprit. Think about things in those terms first and work your way through it. IOW, assume the common denominator hasn't changed even though your list is of changes you did. Separate the two.

Gilley's point really is the worst case scenario ..... the problem wasn't tracked down earlier and now, there is a distinct possibility any number of the new adds or changes could be introducing troubles and you'd not even know it. When troubleshooting or even doing add-on mods, many times, the owner takes it once step at a time until each item has proven itself before going on to the next one and accordingly, you'll see lots of posts where someone is looking for help to pin down a problem after they added 3 or 4 new mods.

I can imagine a situation where a person gets their car in a shop for some exhaust or muffler work on Wednesday and a new clutch on Friday. Then lets say on Sunday they are driving it for a few hours on errands and hear some strange ratting or metallic noises. Maybe it's a pipe rubbing under the car from exhaust work or a heat shield or maybe it's something with the clutch ... ? ?
 
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#9 ·
Yeah ... I was beating around the bush.
The variables are beyond my math looking at the changes but the simplest approach may be a systems health check.....

- If the motor has good compression and the injectors are metering the correct fuel and the afr is correct, then I suppose the devil is in the other details.

Had motor compression checked, 286 across all cylinders except 5(5 has always been odd with plugs, and oil on plug due to valve cover, 280 here-no worries) not sure how to check if the injectors are metering or atomizing properly(I suspect this could be an issue though, running bg44k today with italian tune up, I'll let you know how that goes). According to the tuner at ECS performance in CT, wicked intelligent guy, the AFR is at stoich throughout his dyno pulls, drops to 12.5 without hesitation at wot, and has a flat line on top of each gear shift-meaning no Knock sensing that would retard timing.

-Have the Osiris mapping checked and verified.

How do I do this? can I do this myself with my standard version of osiris?

-Make sure the total exhaust system is air tight.

Had my Stillen full cat back exhaust welded at the mid pipe connection sleeve(shitty design allos air to escape both sides, and replaced cheap clamps that Stillen provides towards the Axle back portion of the muffler with heavy duty full wrap clamps from NAPA.

I see no mention of Check Engine Lights or SES so maybe that is a good sign for the various sensors and such.

I agree here, but I hate my life right now also because there have been no lights, until the c1109 c1108 u1000 intermittent stored abs codes reared their ugly faces.

I'd be leaning toward something that was wrong earlier and did not get the chance to be fixed or improved with all your add on's. If the motor compression wasn't effected by anything you did, it could be the culprit and would STILL be the culprit. Think about things in those terms first and work your way through it. IOW, assume the common denominator hasn't changed even though your list is of changes you did. Separate the two.

Trying, and thanks for the helpful advice...I'm going to figure this out, and have the first ever G35 with every sensor completely replaced with 100k from 2003 at some point it seems.

Gilley's point really is the worst case scenario ..... the problem wasn't tracked down earlier and now, there is a distinct possibility any number of the new adds or changes could be introducing troubles and you'd not even know it. When troubleshooting or even doing add-on mods, many times, the owner takes it once step at a time until each item has proven itself before going on to the next one and accordingly, you'll see lots of posts where someone is looking for help to pin down a problem after they added 3 or 4 new mods.

I've completely fucked up here. Now, that my mind has matured, and my wallet has flattened considerably, I will for sure take this approach going forward. Thanks for introducing that perspective.

I can imagine a situation where a person gets their car in a shop for some exhaust or muffler work on Wednesday and a new clutch on Friday. Then lets say on Sunday they are driving it for a few hours on errands and hear some strange ratting or metallic noises. Maybe it's a pipe rubbing under the car from exhaust work or a heat shield or maybe it's something with the clutch ... ? ?
Also, I wanted to note that after I had the exhaust mid piece welded, and replaced those cheap clamps near the axle, I went down for another dyno run, and saw 300whp in 5th gear!! ECS record for this car. **Also, I would like to note that the car seems to run without issue on the Dyno, but once it's on the road it starts to limit the engine output considerably...so much so that I wouldn't race an old woman with a rusted minivan full of groceries and children.
 
#7 ·
I'm going to invent a butt dyno. It'll be a simple iron-on patch to the back of pants with a respective patch on the seat of the car. These sensors will compute based on the acceleromter/g-force rating.
Inputs will vary with the size and weight of the driver.

Extra points will be awarded for 'pucker-factor' although I'm not going to detail how and where that sensor hooks up.

 
#8 · (Edited)
Bachman and Gilley, my apologies for not responding to your replies, but I never got a prompt in my email for some odd reason saying you both had given some valuable info. But onto the good-ish news, see below.

***FINALLY FIIXED*** The front wheel speed sensors were the source of my problem.

Since I have owned this vehicle, I have been chasing this AFR problem, where the engine has been running extremely rich, and not throwing any codes. I hope that anyone experiencing this issue gets the chance to read this.

I have replaced every sensor (some O2's twice) that I could find on the vehicle:
MAF, O2's front and rear, Coolant Temp, Cam Sensors, Crankshaft Sensor, etc

I have replaced my spark plugs 8 times in the last 2 years at least, replaced injectors, replaced coil packs, replaced air filter, replaced oil pan, replaced differential oil, replaced transmission oil,

Replaced Clutch, Replaced Flywheel, Replaced Wheel Hubs front and rear (bearing included) Cleaned every engine ground, Cleaned all grounds under dash

Basically, I have tried everything to correct this rich running condition with no CEL stored or active.

After 2 years of trying and failing, finally I received 3 stored codes:
C1108-Front LH Drivers Side ABS wheel speed sensor
C1109-Front RH Passengers side ABS wheel speed sensor
U1000-ABS grounding issue?

Coming full circle, I finally found out about the wheel speed sensors, which have a tremendous effect on my manual transmission(can only imagine how much they affect the AT models). Sure enough, I pop off the front tires, and the sensors are eyelet contact sensors, where the conductive portion of the contact was severely eroded and oxidized from road wear/moisture. FOUND THE PROBLEM and REPLACED with 2 new sensors,

car drives and sounds powerful again!!!!BUT ONLY INTERMITTENTLY and when I stomp the gas pedal at high rpm(no power 4k and under), but I have my eye on the 2 rear wheel speed sensors located under the differential in the rear now, and the Vehicle speed sensor in that same area sticking out of the transmission. This problem seems to be electrical, but with optimal combo of fuel, air, and spark needed on these newer cars, who knows. Any suggestions are welcome, as this car has me feeling like I should stick to computers and leave engines alone sadly....

I will update everyone with how this goes, in hopes that if someone has this same issue, they can have some light shed on what is a deal breaker for most in the same given circumstance.

Just to sum up, this journey has been hell, but I'm happy I have hope of a fix now that I'm finally at 100K miles after getting the car at 60k 4 years ago
 
#10 ·
Gilley, I get where you're coming from with the butt-dyno, but my real dyno numbers aren't translating to the pavement. When I first got the car without any mods done and the small exhaust leak near the axle muffler, we had 260whp(impressive for no mods on a car with 280-298bhp, something must've caused the torque to be that high up I'd imagine.... just my 2 cents) Now that we saw 300whp in 5th gear and the car feels slower/less responsive than it did(under 4k) when I first bought it?!

I'm certainly not trying to be a proponent for the mass butt dyno wave of thought out there, but when this car was stock with a hole, it would do burnouts on the highway in 3rd gear, grab, and send you into the back seat....If I tried to that now, the person in the passenger seat would look over at me while sipping their hot coffee and ask me how much longer till we get to the store without even budging.

Either way, I appreciate the feedback man, I'm just trying to understand this problem to have a better understanding of cars to come(GTR)
 
#11 ·
Glad to hear you have made some progress. Unfortunately, with computers and technology, come variables that are 100-fold when trying to diagnose. I say this because even an older GTR surpasses these by a mile with other techno-opportunities ... (thinking; GET WARRANTY) .... lol

Your findings thus far will likely help someone else so thanks for getting back on this.
 
#13 ·
Thanks again guys, Ill keep chasing the issue.

Have an appointment booked with lia infiniti up here in albany,ny for thursday.

Im going to have them drive the car with the consult II connected to look for can communication abnormality; due to the fact that the engine performs perfect at a stand still or on dyno.

Hoping its something related to front wheel sensors, g sensor, tcm, abs/vdc unt, or grounds.
 
#14 ·
Good luck, that'll be interesting to get resolved. A dyno should be designed to create a 'load' on the drive-train/motor, yet it won't duplicate road surfaces such as undulations, bumps or curves etc.... Those in fact do cause variations and potential for sensor alignment and other factors that might be involved.
 
#15 ·
Right, and the guy that tuned the car for me on the dyno went for a drive with me afterwards, but it was raining, so he wasn't able to see the difference from dyno-to-road that I see with his computer monitoring engine input/output parameters.

Hopefully the super proprietary consult II will find what cipher can't...

I'll keep ya posted, and thanks again for all the input on this bud
 
#16 ·
Yep, good luck. Try to focus on creating / re-creating those situations on the road so you can either demonstrate first hand or train the tech on driving it to engage those gremlins.

When my VDC was acting up, it was always on a right hand sweeping curve at 35 to 40 mph min speed. I could demonstrate it like clockwork.
 
#17 ·
new possibility

So, I just spoke with the dyno tuner that has been a huge help getting me so much power out of the car(on the dyno), and he suggested that the OCV(Oil Control Valve) or "VTC Solenoids" on this car may be the issue.

Due to the fact that the car runs optimally on the dyno, and then runs horribly on the pavement, he may have a good point here.

I will let you know how the appointment with Infiniti and the consult II go tomorrow morning.
 
#18 ·
It will be interesting to find out if the dealer diagnostics can seek out and identify aftermarket mods or equipment as the issue. Good luck and keep us posted.

Your tuner shop may really benefit from these findings as well.
 
#19 ·
So after "extensive" testing at the Infiniti dealership in Albany NY, the techs came to the consensus that my vehicle is "running a little rich", and the pulley belts are a "little bit worn".

Just so I'm not going crazy here, "running a bit rich" cuts the engine power in half?

Looking up the number to the second closest Infiniti dealer now...in Connecticut.

If the dealer in Connecticut confirms the dealers opinion in Albany, then I will release all the hair from my head with my finger tips, sell the car, and buy a 95 ford tempo so I stop spending time and money on a car that is not responding to anything I do, that "checks out fine" according to multiple certified dealerships.

p.s. I couldn't make this up. The tech and I were doing a test drive together(tech was driving). We stopped at a red light with a Honda minivan next to us. The tech mashed the gas pedal at the green light to about 5k rpm, switched gear, rinse-repeat, until 4th gear. We look over to see the same minivan ahead of us on the left. I said "so, that minivan must have an engine swap or something huh?" he replied, the minivan "got a head start". It was at this moment, I almost pinched myself to remember I'm not in the twilight zone.
 
#22 ·
I was thinking that might happen; dealer blames the mods and other work or tuner shop and whether correct or not, I can understand how other work and mods can complicate things making it tougher to solve sometimes.

From a business perspective, the dealers and most shops are faced with work on cars from customers that is pretty straightforward. Given a choice to work on those that = all but guaranteed fast and easy money with most services they are experts at, hands down they are likely to turn their nose at other work.

My excuse for passing on mods and big builds (besides limited budget for expensive toys and 'extras') is the long list of variables to resolve or be haunted with if or when something goes haywire. Seeing threads by owners going years with problems of one sort or another helps solve that decision before I'd even have the money to throw at it.

** On the the other hand, I do realize these haunted money pits are not happening all the time and many owners do proven mods and builds with few complications and probably come in close to the 'budget' forecast.
 
#23 ·
Thats exactly what it felt like when we got back to the office after the test drive. The tech walked in, told his boss "everything seemed fine, but I will do a 1 hour troubleshoot for him anyway". this is the point where I looked at the head tech, his boss, the facility, and thought about what is really important to these guys....my money, and making sure it reaches their pocket, for minimal work.

As you said Bachman, these guys are experts in this craft, when it comes to stock vehicles that need user manual advised maintenance, but once you say anything about aftermarket(regardless of how much more quality) they instantly short circuit, spin while overheating, and let out a blurb like "thats not in the field ser-vice mann-uaa..." (And the robot shuts off).

I still have hope that z1 motorsports will come through clutch again for me with these vtc solenoids they happen to keep a mass quantity stock of in a used oem quality, just like that extremely shoddy knock sensor sub harness they remanufactured that Nissan/Infiniti should hang there heads in shame for making.

Ill keep you posted on whether or not the vtc solenoids are causing all of this unresolved power loss.

Shipped yesterday, should take me 10-15 mins to throw them in and give you the thumbs up, or freak out and start looking for a reliable car , like a 95 ford tempo with the rusted hood.
 
#24 ·
Sounds like a good plan and if not resolved fairly easily with a few ideas, it may not hurt to follow up with the tuner shop to see if they know good aftermarket troubleshooters.
My guess is the independent shops have those that think outside the box of O.E.M. and have that experience going for them.

In my near 40 years of car ownership, some DIY work/service and lots farmed out to others, there have a few memorable times when the 2nd or third shop was the one that caught on to a strange issue and it was sometimes just the luck of the draw. It sounds like this;

" Oh yeah, I know exactly what's going on because I seen this on a car for the the first time ever a few weeks ago and we figured it out ."

Do keep us informed on what you find out.
 
#25 ·
Man just to hear those words would make my year hahah thanks for the vision of hope.. Ive had that happen at jiffy lube once with an older dodge neon. The guy noticed the timing belt cover wasnt all the way fastened due to a bolt that was out of reach that never gets tightened by most mechanics he said. Hoping to get a similar outcome with this issue.
 
#26 ·
So, after installing the used vtc solenoids and their new gaskets from z1 motorsports, nothing changed.

I have no other possible leads, no check engine light, no local infiniti dealership that can help, and no understanding as to how this car is performing so well on the dyno, but horribly on the street.

I'm going to replace all 4 gaskets from the plenum down (except head gasket) because they are overdue.

I'm going to check the brake booster and all vacuum lines for blockage/defectiveness.

let you know how it goes...
 
#27 ·
Weird,,, Under actual load on the street = problems, yet the simulated load on dyno is fine.

If this happened ever in our universe, some other dyno shop should know of it and hopefully have some tips.
The car (something on it) has to know the difference to behave differently but I'm not sure that is a helpful clue other than a supposed lead toward electronics or ECU.
 
#28 ·
Yeah this is definitely not a problem for the person that gives up easily.

We are considering that once the vehicle is in motion, fluids like oil, coolant, etc are going to pulled towards the back of the car while moving forward.

The wheel sensors showed a big change in power/drive-ability when I changed those out, and they were the front 2 sensors that don't move on the dyno when load is simulated. However, that did not last long before the ecu started to protect itself by retarding the timing.

Bachman, you just made me think of something though that has been very interesting, maybe you would be able to lend some thoughts...

Whenever I slowly feather the gas pedal from a a 1st gear roll, I can feel the gas pedal start to stiffen, and the engine becomes more responsive(this might be due to the timing of the cams lining up..not sure here), but I do notice a huge difference in power when I feather, wait for it to "kick in" and then hammer it, but the power doesn't last throughout the whole rpm range.
Also, if I feather the gas when the RPMs are in the 4k+ range, the same "kick in" of power/timing will happen,but again, not through the whole rpm range.

Also, I recently saw a P0303 at wot towards 6500 RPM on the highway in third gear. CEL blinked 5 times and went out. I have since changed out the cylinder 3 spark plug, coil pack, fuel injector, and also replaced the 4 gaskets except the head gasket from the beneath the lower plenum to the upper plenum. CEL has not returned(checked stored codes with cipher ABS/ECU- none) I have also performed the idle air relearn procedure, cleared the learned fuel settings, and unplugged the battery several times thereafter to no avail.
 
#30 ·
Yeah this is definitely not a problem for the person that gives up easily.

Whenever I slowly feather the gas pedal from a a 1st gear roll, I can feel the gas pedal start to stiffen, and the engine becomes more responsive(this might be due to the timing of the cams lining up..not sure here), but I do notice a huge difference in power when I feather, wait for it to "kick in" and then hammer it, but the power doesn't last throughout the whole rpm range.
Also, if I feather the gas when the RPMs are in the 4k+ range, the same "kick in" of power/timing will happen,but again, not through the whole rpm range.

Also, I recently saw a P0303 at wot towards 6500 RPM on the highway in third gear. CEL blinked 5 times and went out. I have since changed out the cylinder 3 spark plug, coil pack, fuel injector, and also replaced the 4 gaskets except the head gasket from the beneath the lower plenum to the upper plenum. CEL has not returned(checked stored codes with cipher ABS/ECU- none) I have also performed the idle air relearn procedure, cleared the learned fuel settings, and unplugged the battery several times thereafter to no avail.
I'm not too good at diagnosing so I throw around a few ideas... sorry I can't be of more help. (Just back from some vacationing so I missed this 7-19 post).
What you describe there could be ECU interfering or I wonder if you are getting a linear feed as demanded for fuel metering or supply? Dirty injectors ... ? Still, that wouldn't seem to behave different on the road versus on a dyno unless as you mention on other fluids, the g force or pull has some effect.

Don't you have an old aunt or uncle that is a retired NASA engineer or something ?? This would be the perfect person to enjoy such brain damning challenges !! :wink2: lol
 
#29 ·
Installing new PCV Valve w/new O-ring(cheap), new pcv to manifold vacuum hose, new intake to manifold vacuum hose, and new bank 1 to bank 2 vacuum hose because of a subtle idle change I noticed when spraying brake cleaner around the PCV vacuum hose the other day.

Also, replacing the Oil Pressure Sending unit located near the oil filter, and all spark plugs.

I'll update with any changes to power/responsiveness thereafter
 
#31 ·
Glad to hear you got a nice vacation in bud, I've been taking some long weekends myself, drinking in excess.

It's funny you say that, because my grandpa was a mechanic on the blue angels for the navy for 20+years, but he's more turbine/carburetor familiar.

I'm hoping by changing out all of these vacuum lines, that will make a change in power. I just can't get over how many sensors are on these cars/how much of an impact they have on the engine timing.
The only big difference we've noticed thus far was when we changed out the front wheel speed sensors(which would make perfect sense as to why on the dyno all the power is there, versus on the pavement,all the power disappears). I do have aftermarket wheel bearings on the front, which have the tone ring on the back, that the wheel speed sensor is picking up the wheels rotational signal from. I'm wondering if I swap those out for Nissan OEM bearings if any difference will be noticed, seeing as how it is strongly advised not to use aftermarket O2's, cam sensors, gaskets, etc on Nissans.

Do you happen to know of a way that I could disable the wheel speed sensors by disabling the abs module or something for troubleshooting purposes?
Just seems like the same engine power cut that occurs when our slip/vdc lights pop up on the dash is occurring prior to me even moving the tires.

The saga continues...
 
#32 ·
Not sure if a fuse or relay would disable the feature temporarily or not,,, does bypassing the VDC do it or not ? It's default is ON so you have to manually switch it off.

As for the turbine/carb skills, think of it as troubleshooting rather than necessarily picking out a person who is an expert on any one thing. He may well bring some good objective ideas to the table on troubleshooting a blender, washer dryer or your car. He may have a natural or learned knack for the understanding of how things work and that is key to troubleshooting .... think 'systems'.

:smile2:
 
#33 ·
Yeah i saw both an abs fuse and a vdc fuse next to the battery ... Wondering what will happen if i pull both of those and take it for a quick drive or something to see if any difference in power is made.. Dont want to just pull them without knowing all affected components :)scream::fire:
 
#34 ·
I've driven my car a few times with VCD canceled so that would be the first thing I'd do. You know of that switch and feature ?
It will negate the sensors for pitch and yaw.
As for the fuse, I don't see how it would do anything other than a temporary change but if it set off a code, you'd know why or what it is anyways.

No doubt the ABS VDC ECU and BCM are all very elaborate and expensive systems but I think the fuse just acts like and on/off or bypass mode in the case of what you are checking and seems the fast and easy way to get some variables ironed out.
 
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