Running out of ideas

[buckeyz1]

First off, hello, I'm new to this site though I've looked at several posts when they've come up under my searches. I'm not particularly new to the Z. I own a 1986 300ZX that I've had for almost 5 years and have done almost all the work on it myself, and I bought a 1992 300ZX n/a 5 speed a little over a month ago. It's straight piped- I don't know what brand mufflers the p/o has on there.

From the time I got the Z32 running up until just a few days ago it would always idle high, around 1200-1500rpm, but it ran great. I followed the instructions I found here http://www.nicoclub.com/archives/adjust ... level.html to adjust my idle. Everything seemed to go well. I walked around to the back of my car after adjusting the idle and found it was splattering soot and water onto the ground as it idled (which I had never noticed it doing this before). While driving it, the exhaust had a different sound to it and the get up and go was practically gone. I brought the idle back up, but the car was still running sluggish. I bought a stethoscope and listened for the injectors, which were all firing. I tried testing the fuel pump, but I don't think the autozone tester I had was working properly since it was giving me 0psi while either priming the system or actually running the car. I had noticed the fuel pump was making some loud noises, then stopped making noises all together. I ordered and installed a Walbro 255 today- the car starts right up, but it's still sluggish. I've run codes on the ECU and got a 55. I don't know if it could be clogged mufflers, timing is off, or if there's some other gremlin lurking in that car. Any insight would be helpful. I don't have a timing light at the moment, so I can't check timing that way until I can get out to a parts store. Are there any other systems I should be looking at that could cause poor acceleration?
Thanks in advance.

[mrmoose]

fouled plugs or bad coil maybe... and for the water, its normal for a straight piped car, mine does the same thing... product of gasoline combustion water and a bunch of other crap

[buckeyz1]

Thanks. I'll check the coils first thing tomorrow, unplugging to see if it changes anything. After that I'll check spark plugs, though I had changed them 2-3 weeks ago. I'll report back with my findings. I had actually started testing the coils before I went fuel pump, but got taken away from testing by my lady friend before I could pull the plug off my first coil pack.

[buckeyz1]

Coils 1-4 are good. When I unplugged 6 I got no change in idle. I'll go ahead and test the resistance of that coil pack and see where it leads me. If it's good, I'll test the connector. May have broken something loose while trying to adjust my idle.

*update* I tested the connector for #6 and it appears it's not getting any power. Any tips on chasing down the broken connection?

[buckeyz1]

The red/blue wire isn't giving me any current. I tried splicing into it just to make sure it wasn't the connector itself and still didn't get anything out of it. Are there any diagrams that show where it leads to? Or maybe one of you already knows. Would it be connected to the PTU? I'd hate to have to trace it all the way up there, but I'm prepared to

[buckeyz1]

decided to check the PTU connections and found


Looks like I'll work on cleaning the contacts before anything else.

[t.mcginley.jr]

Yeah try cleaning the PTU connectors first and see what happens. Corrosion on the connects is a common problem on these cars as you've probably read. Do you have the newer style PTU?

[buckeyz1]

Cleaning the connectors from the PTU to the coils didn't give me any results. I have a series 2 PTU. If the PTU were malfunctioning, wouldn't I get a code 21? And it seems it's just that one wire that's dead. Should I try using a known good PTU and seeing if it changes anything or should I just re-run that one wire? Or could there be something else causing this problem? A new one is only $139 from AutoZone, but I would rather not waste the money if that isn't the cause.

[t.mcginley.jr]

It would be cheaper and easier to try re-running the wire first. Here's the wiring diagram for the PTU and coil packs:

http://imageshack.us/f/243/ptuwiringdiagraman7.jpg/

You could try checking for voltage at that specific pin where the dead wire connects.

[buckeyz1]

Alright, tried testing continuity on the PTU, and it seems to fail at least one test. Heading out to AutoZone now to get a new PTU, testing that one compared to my old one to make sure they don't get the same results (and that I've done the test wrong). Hopefully this solves my problem. I'm having Z32 withdrawals while driving my Z31

[buckeyz1]

Bought a new multimeter at Harbor Freight to test the old and new PTU's. The old one had weaker readings than the new one when I did the tests, but nothing that was super definitive (I think my old multimeter was on the fritz). Knowing if I plugged the new PTU into my car I couldn't return it, I decided I could at least get some of my money back by selling it to someone else that definitely needed it. I plugged it in, checked known good connections vs the old bad connection, and the bad connection is back in business. I guess the PTU can fail just enough that it won't kick an ignition code on the ECU diagnostic.

Thanks mrmoose and t.mcginley.jr for your guidance.

[t.mcginley.jr]

Bought a new multimeter at Harbor Freight to test the old and new PTU's. The old one had weaker readings than the new one when I did the tests, but nothing that was super definitive (I think my old multimeter was on the fritz). Knowing if I plugged the new PTU into my car I couldn't return it, I decided I could at least get some of my money back by selling it to someone else that definitely needed it. I plugged it in, checked known good connections vs the old bad connection, and the bad connection is back in business. I guess the PTU can fail just enough that it won't kick an ignition code on the ECU diagnostic.

Thanks mrmoose and t.mcginley.jr for your guidance.

Great to hear its working again! 20+ year old electronics just go bad sometimes, its normal