97 Maxima: Im stumped.........can you figure this out?

[ROCKART]

alright let me start by saying i have been a member of Maxima.org for several months. ive been posting about this issue for quite some time, but no one seems to be able to figure it out.

i am just going to copy paste the posts from maxima.org.

POST#1

and this is a 1997 GLE with 48k and an auto transmission.

THE EFFECT:

--> if i leave my car parked overnight, or the 9 hours i spend at work, and i come out to start it, it starts fine. by fine i mean the car ignites quickly, catches quickly, and the RPMs shoot up to the normal starting parameters (~1200-1500). i refer to this as a "strong" start.

--> if i drive my car around for 30 minutes or so, and then turn it off and leave it for 15 minutes, and then come back to start it, it starts VERY VERY weakly. by this i mean that the car ignites quickly, and it catches, but the RPMs sputter around 200-300 for about a full second before going up to the ~1200 mark.this causes the car to shake a bit. twice, in the three weeks this has been going on, the RPMs sputtered around the 200-300 mark before just giving out and stalling the car (it almost seems like this is a power issue [starter/alternator/grounding], but i dont understand why it would only happen when the engine is warm).

--> if i drive my car around for 30 minutes or so, and then turn it off and turn it back on immediately, it will start perfectly fine, as if the engine was cold.

THE CAUSE:

**some of this stuff may be inconsequential, because we found whatever problem it was and fixed it, but i figured i would include it in case it could have caused another problem that im not thinking of.

three weekends ago i spent the day at a Nissan dealership (with an org member who works there) installing the following:

a) NWP Thermal Intake Spacer Kit (one throttle body spacer, two lower intake spacers and one plenum gasket spacer)b) Budget Y Pipec) Replaced Valve Cover Gaskets

and then some other random things:

d) Replaced Rotorse) Replaced Charcoal Cannister and Valve (to get rid of my CEL)f) Flushed Brake Fluidg) transmission Drain/Fill

initially, after the 7 hours of labor was complete, when we tried to start the car up, the idle was very erratic and jumpy. we discovered that in the process of redrilling those brackets, and putting the IM back on, the EGR gasket slipped a little and allowed a leak. we removed the IM again, redrilled the brackets and corrected the problem. the idle was normal once again.

the next few days, i began to notice that when i was sitting at a red light, my RPMs would be at 600-650 and then drop down to 550 and 500 and make the whole car shake and rumble. i would have to give it gas to get it to sit back normally (this was from a plenum gasket leak, but i didnt know it at this point).

also in that same week after the big install, i was driving on the highway going about 70-75 and i decided it was time to test out the new bolt-ons. i gunned it past a slow moving car on my right, jumping from about 75mph to 85mph in a matter of seconds and my CEL light suddenly appeared. i drove to Autozone the next day and had it read: code 0707 or P0136, which is the rear bank 02 sensor (the one behind the main cat).

i drove back to the dealership the next weekend and i told him that i was having idle issues when in D, plus my CEL popped on for an 02 sensor. he tested the NWP plenum gasket for leaks, and found one right in the front. it was fixed, and so was the idle at red lights, however my 02 sensor code which i attributed to the leak, DID come back after clearing the codes.he plugged my car into the Nissan Consult and it read EVERYTHING as perfectly normal, including the so-called "faulty" 02 sensor that was tripping the CEL. we had it run a variety of diagnostic programs on the engine, both while i was driving and while it was at idle - everything came back as nomal.

he actually had an extra 02 sensor laying around, so he figured we could just swap the two and see if the new one would end up with the same problem. he put my car up on the lift again and went to unscrew the rear 02 only to learn that it had been rusted into the bung, and that removing it ran the risk of stripping the threads and having to replace the whole section. he suggested trying to find that main cat + rear 02 bung used off an org member/junk yard. obviously, we had to hold off on that experiment.

AS IT STANDS NOW:

i know ive read and heard from a variety of org members that sometimes adding an aftermarket y pipe can cause the 02 sensor to malfunction because so much extra air is now hitting it. then again, some of you drive around with your Y pipe with no CEL problems at all. regardless, i just learned what an 02 simulator does and will plan on getting one if i cant figure out how to make this rear 02 stop reading as faulty.

anyway, i have no more idle issues, the car seems to drive fine, except i still have this starting issue, and i still am looking at this 0707 CEL all the time.

would a faulty rear 02 sensor cause this weird starting problem? why would it only happen when its warm? exhaust gases?

what i dont want is to spend money on a new rear bung/new rear 02 sensor and have this problem re-occur, in case there is actually something CAUSING the rear 02 sensor to read as faulty or in case this isnt even the problem to begin with.

im pretty ****ing pissed that ive spent this much already......

THE SUGGESTIONS:

im still not sure if this is from the Y pipe or spacer kit, or a combination of the two.

these are the suggestions ive gotten, both from org members and local people:

1) ECTS (engine coolant temperature sensor). this would most likely be throwing a code if it was broken, plus it would be pretty strange for this to coincidentally break on the same day i was putting all this aftermarket stuff on. the nissan mechanic who did this stuff with me said hes never seen one fail in over a decade.

2) Exhaust gases getting caught in the pipes (this is from the Autozone employee). basically, now that i have a high-flow y pipe, but the rest of my exhaust stock, the exhaust is getting caught up around the main cat and choking my car. this would make sense, because only when the car is warm would gases still be in there (when its cold, the gases have had time to dissipate) but, ive heard from a number of maxima owners who say they used an aftermarket Y with stock exhaust and had no problems.

3) Fouled Spark Plugs (from a guy i work with). he said when the car is warm, the oil is still consolidating down at the bottom of the crankcase, so its possible they saturate one or two of the plugs. when the engine is cold, all the oil has settled, and leaves all the plugs free to fire. this doesnt really make that much sense, because a fouled plug is a fouled plug, and i would get starting issues all the time. he said either that, or some kind of sensor issue.

4) two org members have said Bad Coil Packs, but this would cause misfiring right? and why would the start issue just happen when the engine is warm if one of the coils was bad all the time?

5) Grounding Issue. the org member that helped me with all these installs thinks that putting the spacers in has somehow eliminated a ground for the engine. he thinks that the upper IM and lower IM, that were touching before the spacer kit, ground off each other, and now that there is a plastic 1/4 spacer between them, they can no longer do that. we ran a jerry-rigged grounding kit from the ECM grounds to the neg battery terminal (actually to try to fix the weird 02 code), but that hasnt done much. he said he would try grounding the bottom of the oil reservoir to the transmission case as well. but why would this only happen when the engine is warm? and then there are about 20 other org members with these spacers and no grounding problems.

6) Starter is dying from exhaust gases. Essential1 (a local org member who works at an autoshop) met me this weekend to check out the problem first hand. he seemed pretty sure it was the starter on its way out, but that doesnt explain why my car only has these weak starts when its warm. he mentioned something about exhaust gases corrupting the starting solenoid, and that i would need to replace the starter alltogether, we well as put some sort of gas shield over the new starter solenoid. but if this is actually the problem, and my y pipe is spewing exhaust onto my starter, i dont want to just go replace the starter again - because in 6-12 months ill just have the same problem....

CONCLUSION:

im sorry this is so long, but i am ****ing stumped here. no one seems to be able to figure this out. and quite frankly, knowing what i know now, and how much money ive dumped into these "bolt-on" mods, i would NEVER have done it.

the added power is no where near worth all these problems. i would have thought for 800 plus dollars of experimentation, i would be making my car stronger and faster, but it has made it weak and tempermental, for not that much more hp. im pissed. i should have just left it stock.

POST #2

im going to drive up to him next weekend and spend a few hours trying things (finding leaks, grounding the starter, grounding the oil pan to transmission case, etc. etc.)

if all those things fail, im going to remove the spacers and hope that fixes the problem and then try to resell them (i guess.....) for half of what i paid.

and by the way last night was the worst start ive ever experienced. ill give you guys a detailed account, in case any of this has to do with anything else.

- drove 30 miles on the highway to my house.- was in my house for 15 minutes and decided to drive to the video store. started up my car and it had a semi-weak start, not bad tho - spent 5 minutes in the video store. started my car again, same weak start, but not bad- drove from there the 5 minute drive to the supermarket. spent 30 minutes in the supermarket.- i pack my groceries in my car, go to start it and it ignites, catches, but then just gives out around the 200-300 rpm range. i try again, goes up to about 400 and gives out. let it sit for 15 seconds, try again and it BARELY starts. the weakest of them all.....

so i guess the "peak weakness window" is like 30 mins sitting after getting the engine hot.

POST #3

alright this is what i have listed to eliminate as possibilities:

- Clean all grounds- Ground Oil Pan to transmission Case- Ground Starter (8 AWG wire from starter bolt to battery, or transmission)- Check Spark Plugs- Run Coolant Bypass- Check ECTS- Starter Solenoid (getting hit with exhaust?)- Vapor Lock possibility? Gas line near something hot? - EVAP canister wtf? - Improper crankcase ventilation? PCV hose damaged/not secure? - IACV damage/miscalculation? (having trouble “keeping up” with warm motor) - Vacuum leak test?

POST#4

alright..............

the following was done this weekend:

1) installed my homemade grounds (8 AWG wire) which grounded the following:- timing chain cover- front of the crankcase- throttle body- upper intake manifold- neg battery terminal to the existing ground on drivers side- grounded bellhousing to starter to upper oil pan

2) i also resanded the two other factory grounds.

3) installed the 02 simulator and cleared the code (not sure if this is 100% working or not, because it usually takes a week for the ECU to throw the 02 code after its been cleared, so we will see)

4) ran the NWP coolant bypass (the step we skipped before)

5) adjusted the idle, only to have the ECU adjust it back. it seems the screw on the IACV is totally worthless, because whenever the idle is changed, the computer just changes it back.

6) plugged the ECU into the Nissan consult. CPS, TPS and ECTS all seem to be fine.

got to finally drive my car today and i have the same exact problem.

CONCLUSION HERE (today) - cliffs

car is running perfectly fine

installed aftermarket Y pipe and thermal spacers.

CEL comes on for rear bank o2 sensor.

car drives fine, cold starts fine, but warm starts are BAD.

wtf?

[NutriaforBreakfast]

Sounds like your getting spark and air

what about the fuel pump pressure, filter etc?

[ROCKART]

plugs were replaced in December with NGK platinums, all come pre-gapped but i checked them anyway.

in January i replaced the fuel filter with a 300zxTT fuel filter (same thing, but bigger).

i have had 0 problems with this car previous to the spacer/ypipe install in april.

[Graberhieny]

Do you think that you ma have an exhaust leak anywhere...which I am pretty sure that can cause problems in idle but i am not sure about the starting problems though. I am not expert though.

Hope this helps....keep us posted

[ROCKART]

there is no problem with my idle. it idles fine and always has.

my problem is with warm starts only.

[ROCKART]

to the top

[jltibbs]

Try this: Drive around for a while and get everything warmed up. Stop the car, turn it off, and see if the hard start happens again. If so, take your ECU out, throw it in the freezer for a few minutes. Take it out, re-install it, see how it starts then. If it starts fine, then you need to replace the ECU. If not, I have no other ideas. That's my take.

[coolhand]

Try testing or replacing you coolant temp sensor for the hell of it. Maybe at warm up the temp sensor is flaking out causing you strange running problems. You should be able to find a test procedure on line or in a service manual.

[ROCKART]

yea quite a few people said it could be the ECTS

i guess thats my next stop

[NutriaforBreakfast]

Sometimes the ECU just needs to be unplugged to relievethe static electricity and give the system a re-set

I still think you might check the output on your fuel pump

[lightsout]

i get a small sputter on my Max sometimes...and sometimes it doesn't like warm starts too(rarely tho)

what filter do you have in the intake????? oiled, dryflow, paper???

is your MAF(mass air flow sensor) dirty/oily?

fuel pump-bigger doesn't always mean better

exhaust leak--run an exhaust pressure test(if there is such a thing)

i don't understand how the "exhaust gases" would mess with the starter....maybe "exhaust heat".

did you say you have 2 throttle body spacers?? not good it can confuse the ECU b/c the airspace in the IM has a specific volume capacity...but with 2 throttle body spacers, and one IM Plenum spacer, you have substantially increased the IM volume while the ECU computes that it should have a certain air volume and pressure.

the ECU is confused.

Maxima's are sensitive...they have to be babied sometimes.

if your 02 sensor is SUUUUPER rusty, it may have a sporadic or below spec's ground.

that's all i have for now...but i'm always my brain...so i'll be back!!

[ROCKART]

the spacer kit is two LOWER IM gaskets, one plenum gasket and one throttle body gasket.

yea it does make the IM bigger overall, which makes sense it would mess up the predetermined volume for the rest of the working parts, but i know several 4th gens with this exact spacer kid and no problems.

and since the day of these problems, ive had the Nissan consult plugged into my ECU several times. each time it reads everything as normal - not throwing any codes except rear bank o2 (which has been corrected with the simulator).