Engine Dies after Pushing in Clutch

[rmlamp]

Hey everyone, I have a 91 NA completely stock other than a pop charger. I recently had a bad coolant temperature sensor which caused the car to not start when warm, replaced it and it was good to go. Now I have another problem...well two actually.

The first is more of curiosity than anything. I know the hydraulic lifters can start sticking causing a ticking sound. At around 1000 rpm, I get a pretty loud clattering sound from the valve train on one cylinder on the passenger side. Its coming from the top end so I'm pretty sure that it's not a rod knock. Should I dig deeper or is this just the lifters sticking?

Problem 2: After driving for awhile, if I push the clutch in (coming up to red light) the engine will drop RPM down to around 250 bounce a couple times and then die. Turn the key and it starts right up, though it has a bit of a rough idle that bounces around from 500-1000. Other than that, it runs and drives great. I was planning on running codes, cleaning out the IAC system and changing balance tube O-Rings. Has anybody dealt with this before or have any ideas on how to fix this? Thanks!

[MrFeesLaw]

That is a really tough one without codes. Does it seem to only do it warm? Or only cold? Only after interstate/high speed travel? Or only during in-town driving? Any other specifics you can give? Does the oil pressure drop just before it dies?

[rmlamp]

That is a really tough one without codes. Does it seem to only do it warm? Or only cold? Only after interstate/high speed travel? Or only during in-town driving? Any other specifics you can give? Does the oil pressure drop just before it dies?

I'll check codes, CEL isn't on but it wasn't on with the coolant temp sensor either. There's no condition I can tack down that it happens under. It really only does it after going higher speeds (45+). It in general just has an erratic idle at times. I'll take a look at the codes and see what it's throwing, if any.

[MrFeesLaw]

I would double check that there isnt any air in your coolant, and that you have no coolant leaks. If you just replaced the temp sensor then maybe something didn't seal correctly. If there is air near the sensor it will make the sensor think the car is overheating, which will cause all sorts of problems. Probably not the case, but would rather check all the "easy" options first.

[nissanfreak12]

Search up on "flower pot mod 300zx" Some, not all 300zx's when you have a pop charger will cause the MAf to read air incorrectly or have turbulence when air is passing through. This could cause the car to stumble, hesitate, and possibly stall. This is a cheap mod and may help you.

I still will check the ECU as stated from mrfeeslaw, but once you read up on the flower pot mod, it has the issue you are describing to a T.

[rmlamp]

No codes on the ecu. I cleaned the throttle bodies, though they were already pretty clean. Seems to have helped quite a bit. I'll look into the flower pot mod, thanks.

[evildky]

iacv

[DAZ VIII]

I am having the exact same problem of the car cutting off after pushing the clutch in after being at a higher speed. It doesn't do it when casual driving around the neighborhood for example. Mine doesn't idle oddly and I have the stock airbox though.

My mechanic is saying it is likely the MAF is starting to fail. Is that a part that can slowly stop working or do they just give out entirely?

[evildky]

It's the iacv. very common issue. It gets dirty and sticky and when you let off the gas pedal the throttle slams shut and it cant open up quickly enough so the car stalls. take it off clean it up issuing carb cleaner put it back and most likely your problem will go away.

[DAZ VIII]

Thank you sir. I am all for free trouble shooting especially when the alternative is like $400. I have done a little research and am comfortable being able to take off the entire AAC assembly. From there do I just remove the IACV and clean it off real well with carb cleaner? Also, I know to replace the gasket when I reinstall the entire unit but is there anything else I should replace while I'm in there?

Sorry if these are dumb questions, I'm just a novice with this. Thank you.

[evildky]

Don't over think it. Just pop it off, hose it liberally with the carb cleaner get every inch of it you can then slap it back on, and unless you tear the gasket you can reuse it.

[DAZ VIII]

Thank you for all the help evildky. So I took off the IACV and cleaned it thoroughly with carb cleaner and put it back on. The gasket wasn't damaged so I reused it. On the test drive it did the exact same as before. At about any speed above 35, the car stalls when pushing in the clutch for too long.

I swapped out the MAF with one I found at a salvage yard and no difference after that either. The mechanic I took it to said they found good signals to and from the ECU to the IACV but found that the MAF was failing at times and should be replaced. Any chance I just got a used MAF with the exact same problem?

[evildky]

Have you calibrated the tps?

[DAZ VIII]

I just checked the hard idle switch and have continuity when the throttle is closed and no continuity when the throttle is opened. Measured the voltage of the TPS and it was .41 with the throttle closed and 3.9-4.0 when open. Adjusted it to 4.4-4.5, unplugged the connector and back in. Still doing the same thing as before.