Got this car 2 weeks ago, and this forum has been very informative so far. I've done a ton of reading, but I'm going to throw out a few questions to make sure I'm on the right track.

For the record, I'm not a DIY newb. Many decades (lol..well, over 2) of car building and repair, but lately I've been speaking german to work on my cars and my japanese train of thought is rusty..not to mention those german cars are and average of 10-20 years older than this one.

Okay, so here we go. 2003 6mt coupe, 113k miles. Mods are K&N Typhoon CAI, some type of stainless long tube headers, no cats, stainless midpipe and some ebay stainless exhaust. Light weight flywheel, and supposedly an ACT st3 clutch. Not that it matters to this but also running on D2 coilovers (true style).

Last week I replaced the spark plugs with OEM spec NGK Plat.. they were never replaced before by the look of it. Spark plug seals leaking in #4, #5, #6 mildly. While the plugs were out I decided since the car was new to me with no known history or docs that I would do a cylinder compression test. To do this, I removed the INJ fuse in the underhood fuse box and the kick panel fuse box. I floored the gas pedal to WOT and crank 10x on each cylinder for consistency. Results were good as far as I know, consistent at 205-211psi across all 6 on a dead cold engine. I haven't looked up nominal values.

I replaced all 4 o2 sensors since I was throwing a SES for o2 sensor heater low input on one of the downstream sensors. i figured that I may as well make them all new. I used the Bosch universals, like I have many times before.

After the compression test, i disconnected the battery and left it off (neg) while I put the car back together. i figured this would be sufficient to reset the ECU.. maybe not. All the fuses and plugs were reinstalled before the battery was reconnected.

Since the tuneup.. I have a low idle condition, even sputtering at idle and I have stalled a few times when coming to a stop.

The other day I removed the MAF and cleaned it. No change.

Looking like I will be cleaning the TB next since I'm sure that it has never been done. I have found several threads on here about how to do it..resets..etc. Once and for all, what is the correct way this car tolerates? I don't want to screw anything up, this town sucks for parts availability. Is the TB gasket metal and re-usable?

Should I do the riverdance on the pedals ECU reset and see if it changes anything next?

And to top it off, I still have an SES light for Bank 1 Sensor 2 (passenger side downstream) heater circuit low input. Wondering if that is because of the lack of a cat, or if it is a wiring issue.

I'm getting ready to be off work for the rest of the week and thru the weekend so I'm looking forward to nailing these issues down and getting on to enjoy the car.

Thanks for reading the novel..lol

 

http://www.nicoclub.com/archives/g35...-learning.html

Also, I'd look into changing the Cam Position Sensors while you're there. For the SES, my guess would be due to the lack of cats on there. I have a set of stock cats if that's what you're looking for. I'm pretty sure the TB gasket is metal as well.
Recheck the gap on the plugs and then replace the sensors above. After that, I'd start looking into a possible fuel line/pump issue.

 

The gasket is metal and you can re-use it without problems. I've cleaned the TB once and won't do it again unless I have to. It took me like 50 times to get the idle back correctly after doing it.

I'm not sure if the Bosch ones work quite well with our car. Are you sure you don't have any vacuum leaks? I usually disconnect both cables from the battery and hold them together to reset the ECU.

 

are you saying 50x of doing that idle reset procedure in the link above?


what is the plug gap on these cars? come to think of it, I never even checked the gap on the plugs out of the box, being that they were platinum..brain fart I guess. in any case the gap was MUCH smaller than the eroded plugs I pulled out.


I'm headed to the store to pick up the MAF cleaner and something to clean the TB out with. I used seafoam right as soon as I got the car, suctioning 1/4 of the can into the intake right after the TB so I'm interested in seeing what it looks like. That was the week before I changed the plugs and disconnected the battery, did the compression test..etc.


I really think that I flipped something out by holding the gas pedal WOT and cranking 60x for the compression test (10x crank x 6 cylinders)


And in regard to my SES light for the o2 sensor. I viewed the engine data on my obd2 scanner and the bank 1 #2 sensor is reading very slow. maybe it is just a bad sensor out of the box. my luck.

 

Yep, I finally got the idle to take on like my 50th time, lol. It wasn't worth the hassle of cleaning the TB. Big thing I remember that wasn't written down is: make sure all your electronic devices are off, steering wheel completely straight, headlights in off (not auto), and once it gets to the correct idle...you need to turn it off and back right away.

Spark plug gap is .043 inches I think, I never checked mine when I took them out of the box, but wouldn't hurt I guess.

How does the car work prior to getting into closed loop mode?

 

the car runs fine, doesn't seem to miss when driving at all. the miss is intermittent at idle only. the only thing when driving is that occasionally it will stall when coming to a stop.


I bought all these parts and cleaners last night, and all I did today was reinstall the front lip spoiler that got ripped off in a puddle last week. :/

 

Okay so for an update.
I can feel a surge or miss when driving low speed in the higher gears. I also hear/feel the exhaust or headers banging against the bottom of the car, mainly in turns. I have new mounts for the motor and trans to try and solve this.

Replaced: Valve cover gaskets, RTVd the tube seals, cam sensors on both sides, PCV valve


Cleaned out the MAF, intake manifold/plenums and TB


Installed the SxExCx grounding kit.


Slight increase in mileage, I'm in the mid 18s now, but I don't drive it easy either.


I have been doing a lot of reading on this forum lately. I think that I have an exhaust leak on the passenger side header flange. I found what I think might be the answer when reading the ART pipes thread, almost to the end.. they mention that the scavenging effect of a leak there would lean it out, causing an over rich condition to compensate. This jives with my experience because if I'm driving the car and just de clutch and pop it out of gear, the car will shut off. I can push the clutch back in and still rolling it will start it again. However if I de clutch and heel toe the gas and brake as I come to a stop, the car will come to a stop and idle fine.. at least for the most part, a little sputter here and there that seems to come from that side.


I'm going in tomorrow to tighten the header flange bolts and nuts, I may even be missing at least one. Damn POs (Previous Owners)


I have the TopSpeed headers and cats I bought off of here, along with a new y pipe on the way since mine is badly welded up and leaking.. I'm going to hold off on the headers and see if the y pipe and header bolts make any changes.


stay tuned!

 

I tightened the header nuts a few days ago, Just 2 on the bank 1 header flange had backed off. No real change in the idle. Still have not gotten the midpipe I ordered that was supposed to have arrived on Saturday, so there is still that leak to factor in.
Interesting side effect of the grounding kit is that my fuel gauge now reads accurately. It actually went all the way to the top when I filled up.
Ordered some injectors and had them shipped to a rebuilder to have them made good as new. Still feeling like I have leaking injectors that may have been the reason I don't currently have cat converters in the car
The extra fuel dribbling out would kill the mileage and would have melted and plugged the cats.

Stay tuned.

 

OP, please join this thread. I think you have the the same unsolved problem. I want it solved.https://g35driver.com/forums/g35-sed...hift-mode.html

 

I read over that thread and it doesn't sound like what I'm dealing with. I don't have a stutter in acceleration that I can tell. I'll reserve judgement until I get the new mid pipe on the car, and I'm going to pull apart my bank 1 sensor 2 wiring on the new Bosch sensor and see if it has separated maybe.

Also noticed on the way home from work this morning that the idle is better, and didn't seem to drop when coming to a stop. I had the AC on, so maybe it was idling it up. May very well be a vac leak somewhere. I have checked and double checked hoses, changed clamps etc.. going to install a catch can off the pcv too. I don't use the AC often, a habit I developed from daily driving a 30yr old Porsche before this. .lol.

 

And today was the day. I installed a set of freshly rebuilt injectors, along with a custom catch can setup. It was obvious that the stock injectors were leaking when I pulled them out, the tips were still wet with gas and the smell of fuel was strong when I pulled off the plenum.

I could already see the oil paths from the PCV system even though I fully cleaned it all out just over 1000 miles ago. Catch can was going to be a definite.

I installed the new injectors, built the catch can setup with braided 5/8" poly hose and popped it all back together. The catch can routes the PCV and the driver side VC port into the front of the can, and another fitting on the back of the can (filtered thru stainless steel wool) goes to the intake just before the throttle body. The PCV port on the lower plenum is capped.

To finish it all off, I reset the ECU and took off for a drive. The in gear surging is totally gone. Idle is near dead smooth at 700-750. If I de clutch from 5th or 6th while cruising, she no longer stalls..drops to 750 and stays there. The power is SO much more crisp now too. I guess I can go ahead with some more mods now to finish it out. Time for a plenum spacer and a tune.

to quote a show from my younger days.. "I love it when a plan comes together"

 

I'm a few hundred miles in since this fix and I have to say it is definitely fixed. The leaking injectors were the problem, spot on. Has not stalled once, A/C on or off, no in gear surging, no stumbling idle.
Gas mileage is much improved, not spectacular but I actually passed 150 miles before 1/2 tank this time, and the first 1/4 was before the new injectors so the next full tank will be even better.

Just an idea of something else to check if you are having similar problems.

 

This is very interesting actually. I know a lot of people use the cheapest gas possible (including both 87 octane as well as cheaper mom n pop stations). I have been using (exclusively) chevron 91 octane for the last year (always used 91 [CA] but would jump station to station).

Since I've been exclusive to chevron I have noticed that my guage always fills to full (not the 3/4 that most people have a problem with) and I've gotten much much much better MPG. I think it supports your injector theory, being as that it took me time to see better results (better gas cleaning injector nozzles over time). I am at this point (after a tune mind you) getting around 25-26mpg (85%H, 15%C) and i think it has to do with many factors, but the biggest being an ultra clean fuel system. If your previous owner used **** gas it could have really fouled things up.

 

With I'm guessing a compression ratio north of 9.5:1 it is a crap shoot using that low octane junk gas. Basically, with the few dollars difference in a tank full of 87-91/93.. you're dumb if you don't use the gas that is recommended for the car. Really dumb..

Honestly, all gasolines have the same detergents whether they are 87-89-91-93 that doesn't matter. The octane rating in the gas is the safety window to prevent detonation. That being said, using the full tank, running it low picking up sediments from the bottom of the tank, never using a fuel system cleaner..will all eventually clog a fuel system.

Since buying this car I have used nothing but 93 Exxon from a small local station that is non-ethanol. I used SeaFoam on it right after buying it for the first tank, then ran a tank of Chevron Techron fuel cleaner thru it for the next. No major change. Changed the super bad looking spark plugs. Minor change.. 1-2 mpg.

In fact I think the fuel cleaners may have broken loose sediments in the 113k mile lines and tank and pump, and made the injectors worse. The stalling got worse, the surging got worse.

I knew that it had to be a physical problem, and the regulator and damper didnt appear to be bad. There was a strong gas smell in the plenums though, so it had to be leaking injectors. It was confirmed thankfully when I pulled them out and they were still dripping wet.

I think I'm going to send these injectors out to the same place that just rebuilt the ones I bought from Digital Deviant and had rebuilt. I am dying to see a flow chart on them as delivered. They will be up for sale too once I get them back freshly rebuilt for someone else to solve their problems and so I can break even.

Question though, for those that know. Are the 2003 injectors usually purple like these? the 2005 injectors I bought were flowed at 312cc and they are black and yellow. Just wondering if these are normal?