1991 300zx Z32 NA starts but then dies runs very rich

[hendersonw2012]

Hi all, I'm getting pretty desperate with my car. It's been hesitating for a few months and running rich with a few backfires. Recently it would stall at red lights and bog down on take off, until it got to the point where it couldn't be driven because it bogged down so much. Ran the codes on my ecu and it was telling me coolant temp sensor. I replaced the coolant temp sensor and it ran great for about 1 minute then died again and couldn't get it going, and to make matters worse, the diagnostic screw on the ecu is just spinning. Please help! Don't think it is the aav because when i got it running it idled pretty high and i had to adjust it to make it lower. it was idling beautifully at 1000 rpms and then like someone flipped a switch it went back to running really rich.

[solaire]

You check the o2 sensor connectors yet? They can corrode or the sensor could be bias lean coming and going causing the ecu to run rich

[ThisIsSparTTa]

grab a consult to USB connector for $30 off Ebay, and use (free) ECUTalk. It lets you run codes and gives you sensor readings. This has been invaluable for me recently as it helped point out 1) My TPS reading was maxed out (broken wire) 2) My o2 sensor was giving a 0 reading (bad harness BS). Pro-tip, if you do look at the O2 readings, they should be varying back and forth. If they stay at 0 or 1V there's a problem.

[solaire]

grab a consult to USB connector for $30 off Ebay, and use (free) ECUTalk. It lets you run codes and gives you sensor readings.

No idea they even had this. I'm so getting one to see if I can figure out this 91 I've been working on for almost 2 months now.

[hendersonw2012]

Yeah really I picked one up I bet it'll help so much

[hendersonw2012]

Update: I ran the codes again and I'm still getting code 13 Coolant temp sensor. Another code though was code 21 ignition signal circuit. I did a little research and I was thinking maybe it could be a coil pack because in the summer i had to replace a coil pack which snapped in half when i was changing my spark plugs. I grabbed one from a j30 but it was still running fine. I've checked the 4 easy coil packs where you don't have to remove the balance tube but I'm waiting to do more research to look at more. I also looked at the connections to the ptu and although they were a bit green they looked alright but I sprayed some connection cleaner just in case. Still having the same problems as before when I start the car up it's just dying. Another thing I've heard is the tps may be bad because it responds better when I press the gas pedal less. Please let me know what you think it could be, I want to drive my baby again

[hendersonw2012]

Another question would be that since the coolant temp sensor wiring and the wiring to the ptu are on the same wiring harness could there be a bad connection or something, maybe a blown fuse/fusible link? I'll check the circuit diagrams and get back if i find anything

[solaire]

I know most nissans use a 3 wire coil for power, ground and reference. The newer V6 (year after the z32, early VQ35s and late VG33s) were notorious for the injector circuit code and you'd have to replace all 6 coils since it didn't say which one was bad but however I never saw this cause a stall condition. I'm not 100% sure if the reference doesn't go through the PTU before returning to the ECM either.

[hendersonw2012]

yea I did some research and it said there was a recall on the early z32 ptu's and it looked like mine had already been replaced with the newer model ptu. i found another ptu on ebay for like $15 so i figured I might as well give it a try. glad I finally discovered ebay for buying parts but it just makes me want to improve my car. hopefully when I get this new part it makes a difference otherwise im going to start checking the coil packs and change the spark plugs again. in case they got fouled because of all the rich running.

[hendersonw2012]

Latest update: Changed PTU and the car started running and sounding a lot better. It sounded peppier and like all cylinders where firing, more responsive to throttle and all but it wouldn't idle until i ran it for about 5 minutes, will this go away? I think I'm going to go to autozone and get sparkplugs since running rich for so long may have fouled them up.

[ThisIsSparTTa]

If you do grab spark plugs grab the NGK PFR6G-11 : http://z32.wikispaces.com/Spark+Plug

[hendersonw2012]

Ok Haven't changed the plugs yet but update, it is now throwing no codes but still won't stay running rpms fluctuate like crazy and there are lots of backfires, could I be getting bad spark? I plan on running the consult on Sunday but I might need to go buy parts before then.

[ThisIsSparTTa]

Could still be lots of things. Did you grab that consult cable and ECUTalk? will help you see if the sensor readings are off. In the mean time you can check the TPS, might be an easy place to start. Also, have you checked for air leaks in your system? Leaving a hose connector open can cause wild idle fluctuations.

[ZL8NING]

You mentioned autozone for your spark plugs! Your spark plugs need to be the OEM NGK's. This might not be the ultimate root cause of your problems, but you definitely need to go ahead and spend the $80 at Nissan on the right plugs,once and for all.