Ran after 120k, then quit. Mindblown. Help.

[maik3r]

[*]To get you up to speed, I came across this 90 Z32 NA w/ AT and having wanting a 300, I jumped all over it. I'm the 3rd owner and when I caught up with it, it had not run in 7 years. I've done everything to this car from injectors (the hard way) to paint and body. The only things not replaced or repaired on this car to date have been the block and trans.

My dilemma started when I stopped working on it myself and took it to a shop. Due to a hectic schedule and a lack of time I did my homework and found a shop whose nissan man has 10+ years working on Z31s and 32s. I had him do a 120K tune up.

The problem: I've put 10 miles on it since the new timing belt and tune up and it's shut off on me three times, the last forcing me to tow it in. After speaking to the mechanic he said it must be a fuel or spark issue, not knowing that I replaced the plugs with NGK, replaced all new injectors, coil packs, all connecting clips, belts, angled cam sensor, MAF sensor, coolant hoses, vac lines, fuel pressure reg, fuel filter AND pump. ALL parts throughout the entire project have been replaced with OEM parts from Z1, with exception to the MAF-reman from NAPA. Everything was replaced prior to the 120K tune up, nothing afterwards. After the 120K; Cranks fine, idles seemingly normal, but when I try to give it gas it hesitates but between 2500-3000 rpm it runs fine. Slowing to a stop it idles rough as hell. On three occasions it idled to a stall, each time harder to restart with the last having to be towed. Now, when turning ignition to on, fuel pump primes like it should and it turns over like it should but it doesn't crank.

Thought's?

1st Question: Has anyone experienced this problem post 120K? Or do I have reason to believe the timing belt job wasn't done properly?

2nd Question: Before this last time it took a dump; I was able to pull over and pop the hood to watch and hear it stutter. Frustratingly I looked at it like but the way it was idling it led me to believe it was a faulty MAF. I wiggled the plug and it hesitated and stuttered more, unplugged it and it shut off. I plug it back in and it started right up but within 10 seconds shut off for the last time...I had to tow it in. Is this a faulty MAF or am i looking at a deeper issue?

3rd Question: Any chance it could be the IAC?

Kick some ideas around with me. Thx

[maik3r]

I got to tinkering on the car with my best assistant (my 5yo) and in going through the basic motions of troubleshooting we got spark and compression. We are also getting power to the fuel pump and therein fuel, but to make sure I cracked the lines and sure enough there's fuel present and pushing through on crank.

After cracking the line, the car started. Kind of at a loss. Any thoughts?

[DCaff300ZX]

These are the toughest problems to solve on the Z32, many idle and vacuum issues can be related to other issues and sometimes the issue may not be where you were working.
I am going to guess that since you have replaced so much in the engine compartment that you should not have issues with those parts and repairs, but that it's elsewhere in the system...the PTU harness connections. It can become unstable when heated and cause issues, then when cool the problem disappears for a bit or is not as bad because of a partial connection. They will surely be corroded like all the others you replaced, and can and will affect idle and other areas when corroded badly. Clean both well and see where that gets you, moving to the mentioned IACV next to clean or replace those connectors. I recommend the upgraded IACV harness which is weatherproof unlike OEM, and my own Z guy recommends a whole new one as the old IACV's go bad enough quickly (don't get a used one for replacement purposes as I did...), and cannot be fully rebuilt to spec.
I'll stop there and see where that gets you...but also toss in that the OSM has a lot of testing procedures that can be helpful in digging out your problem or problem area.
Let me know how it goes!

[maik3r]

I'll look into it. My frustration stems from the fact that I wasn't having these issues prior to the timing belt change. From my initial test it seems the timing is right. I'll try the cleaning up PTU harness connections. Thank you!

[DCaff300ZX]

Your welcome, and just be aware that the Z32 can be this way a lot...I was also doing much of what you are doing with my Z when it did much the same- working on injector connectors and such, when done it fires right up and driving around is great, but then starts degrading and stuttering and idling poorly, and dies. I get it home and it fires up, frustrated I wiggle the wiring everywhere until when nothing else was an issue and I moved to wiggling the PTU harness, it starts doing the same thing and I have my answer.
Two years later doing some front end repairs, the next day it won't run after 5 minutes on the road and after I get it back home and I cool off enough to reason, I get to checking that harness and viola- it's corroded again and same problem. Both times this happened within hours or days of other work, and was hard for me to determine because of the fact I'd done the other work.
Good Luck!

[NolimitZ32]

Have you confirmed the timing is set correctly?

[maik3r]

The more I dig into it the more I am begging to think it is a timing issue. The timing belt was the only thing so far that I've not done myself. I had a shop do it.
After having it towed my daughter and I cracked the fuel lines before and after the fuel filter. There's fuel, it cranked.
I started it this morning to see what it would do and it started right up but after less than 5 minutes it s*** off. Won't crank.
If it were a timing issue would it run, sometimes? I figured if the timing was off it wouldn't even start or run like crap, back fire, maybe? It doesn't. It runs smooth as a crap but then s*** out. Any thoughts?
I've cleaned up the PTU contacts as they were
corroded. I'm going through and checking power continuity and making sure it's firing off like it should. The ACS is new but would having new timing alter or cause it to falter, causing it to not fire? Drawing a blank outside of that.

[NolimitZ32]

Only other thing I can think of is like DCaff said the IACV, it doesn't make sense that it would just full on shut off when going to closed loo especially if the only thing that was done was the timing belt.

[maik3r]

Today I cleaned connectors and checked power points at various harness connections. I check power and resistance to injectors and checked power to coils. I could not get the car to start therefore wasn't able to duplicate the problem (the shut down). I'd over looked it bc it was replaced early on but I have loosely pin-pointed the issue to the MAFS. It'll crank when it's unplugged and not when it's plugged. It'll run when I replug it but won't run well past 2500-3000 Rpms, but if I leave it plugged and shut it down, it won't restart. This was a reman so I've ordered a new one. Keep yall posted.

[DCaff300ZX]

Sounds like you've made some good progress, hope that fixes you!

[maik3r]

Thanks to your and everyone's input and suggestions. I appreciate it

[tsflstb]

I had a similar ghost after the car sat for a few days in high humidity while doing other work. Ended up it was the Coolant Temp Sensor connection...code "13" on the ECU. I cleaned and greased the connection and problem solved...couldn't believe it was that simple.

[maik3r]

Will definitely check that connection now too.

I wanted to throw this back into the mix and hopefully one of you guys can steer me in the right direction. It is my understanding that the MAF should betting 5V and I know how to check that but how do I check to see that everything else is sending correctly back to the ECU? I know for a fact that the issue is in or around the MAF. I got a new one from Z1 and the problem persist. When it's unplugged it cranks right up and idles, runs rough at 2500 RPMs like it should do without the MAF. As soon as I plug either MAF in (old and brand new) the car chokes and shuts off and won't crank.

[NolimitZ32]

That doesn't mean its the MAF, when you unplug the MAF you force the car into open loop operation, plugging it back in switches the car back to closed loop and it starts reading all the sensors, here is where your IACV, vacuum leaks, bad O2s, etc. etc. etc. could be the issue.

[maik3r]

Good stuff. Thank you.

I have no substantial vac leaks, but still haven't checked the IACV & honestly hadn't even thought of the O2. I'll work on those and hopefully won't have to find all the etcs.