1993 Bonnie SE cranks but won't run...

[crash93ssei]

It doesn't necessarily sound like the same issue I had with my old '93 SSEi, but mine died and would roll over but not start as well. I went through a TON of troubleshooting before finding the issue, so this thread may be of some help with the ignition side to make sure all is well. http://www.pontiacbonnevilleclub.com/fo ... c2371.html

Another thing I would do is pull the plugs or at least the front ones and see how they look after cranking but not running, see if they are soaked with fuel.

[Plemmons]

That actually sounds really close to the problem I'm having! The PCM fuse on the passenger side fuse panel was blown, I just replaced it a couple days ago. My fuel pump also doesn't cut off anymore at all, let alone after the 2 second prime. I noticed it running as long as the key is on. I'm going to pull the alternator tomorrow and remove that cluster of wiring that runs behind it and see what it looks like. I've replaced the upper and lower intake manifolds last year and it's possible I may have sheared a wire during that job. I did notice the wiring there to be really degraded, I suppose it's to be expected after 310,000 miles of wear! Thank you for referring me to that post and hopefully I have time to get to it tomorrow after work.

[J Wikoff]

Why did you replace the upper and lower intake manifolds?

[Plemmons]

I did it because they were leaking coolant. I did it about a year ago, and didn't replace the lower intake, just the gaskets. I bought a new upper intake made by dorman along with the gasket set and installed that, too. These bonnevilles are notorious for blowing intake gaskets!

[RJolly87]

I did it because they were leaking coolant. I did it about a year ago, and didn't replace the lower intake, just the gaskets. I bought a new upper intake made by dorman along with the gasket set and installed that, too. These bonnevilles are notorious for blowing intake gaskets!

Not really. Series 1 is being notoriously less powered and GM couldn't make up their mind with the computer and used a plastic heater pipe that always breaks.

Series 2 is the manifold gasket shredder (95+), and warrants the reputation you describe.

[Plemmons]

Alright... I spent a couple hours working on the car today and found quite a bit of torched wiring, much like what crash93 posted. None of them are broken thus far, but i still have a lot to look at. I'm gonna go ahead and pull the power steering pump, alternator and engine mount so I can get to the rest of it, but that may very well be the problem! After turning the engine a few times, I immediately pulled a spark plug and it was soaked with fuel, too. I must not be getting spark after all: I did have spark after replacing the crank position sensor, but that was when it ran for about 15 minutes and then died, having not started since. I'm certainly leaning away from fuel delivery issues now and looking more heavily at the mess of melted wiring. The PCM fuse and circuit are still good, though, so it hasn't fried that again. I'll post again when I'm certain that I've cleaned up all the wiring and verify continuity there.

[Plemmons]

Ok, so I found a ton of wiring that was burned and frayed. I cleaned all of it up, installed new conduit to protect it, and when I got everything put back together, it fired up and ran for about 3 seconds or so, then died again. It will run for a couple seconds now, but won't stay running. This time, I also noticed a slight buzz or hum from the PCM when I turn the ignition switch on. However, this time I couldn't hear the fuel pump running when I turned the switch on. I've not yet tested all the circuits to verify voltage and continuity, but I'll do that another day since I'm out of daylight. If the circuits do end up checking out ok, other than the iac valve or fuel pump I'm totally lost!

[Plemmons]

And im mistaken about the fuel pump, it is actually running when I turn the key. I guess i couldn't hear it before because of the traffic nearby.

[crash93ssei]

When it starts up, if you hold the throttle open slightly will it stay running or die anyway?

[Plemmons]

I can keep it running for longer by playing with the accelerator pedal, but I can't hold it at a constant level and keep it running, nor can I let off of it and keep it running. It almost acts like a carbureted engine with the venturi port open.

[Plemmons]

I did try holding the throttle slightly open and fluttering it a bit to try to keep it running; it ran for maybe 2 more seconds than usual and then backfired really heavily at the end, haha. I haven't tried doing that since.

[Plemmons]

Ok, I can't seem to find my multimeter so I'm going to get another one on my way home tonight. However, I've noticed that my car won't really even try to start unless I hold or flutter the gas pedal when I try to start it. If I do that, I can let off after it starts (never runs right, though) and it will run poorly for a few seconds and then die, usually shooting a gush of air out the intake. I'm going to trace all my vacuum lines once more just to be sure and then also check the fuel pressure once a friend of mine gets back into town from vacation.

[Plemmons]

I'm happy to report that my bonneville is running again... But only for a short while. After cleaning up all the wiring I could find, it will fire up and run great for about 1 minute, provided I have the air cleaner off. If I leave the air cleaner on, it runs a little rougher upon startup, but will still run. After about 60 seconds, I hear this huge rush of air like it's just randomly pulling more air into the intake all of a sudden and then it sputters to a point where it nearly dies, but it will barely stay running. I tried unplugging the MAF sensor and got no change. I'm not sure if it's a sensor crapping out or if it still has something to do with the wiring... I think I'm going to go to a local salvage yard and clip all the wires from the firewall to the sensors and spend a day transplanting them. My engine bay wiring has never caught fire, but it's just so melted and crappy that i couldn't imagine it working properly. Let me know if you guys have any input or suggestions here. Thanks!

[J Wikoff]

Have you tried cleaning the MAF?

[Plemmons]

I haven't tried cleaning the MAF yet. I'll try that when I get back from out of town... I did clean it about 3 years ago and it did run better afterwards, I suppose it is about time to do it again. It's possible that all that backfiring through the intake soiled or ruined that sensor too, I didn't even think about that until now. Good call @J Wikoff

[Plemmons]

Ok, so I cleaned the MAF today and didn't really see any change. Car runs fine for about 1 minute, then sucks a bunch of air through the throttle body and it dies. It's an immediate reaction, too... Like a sensor just randomly sent a bad reading. This car has 310k on it and the MAF is original, but those things aren't cheap and I don't want to replace it unless it's defective. I can turn the ignition switch off, immediately fire it back up and it runs fine again for 60 more seconds. If any of you guys have an idea about what to troubleshoot, I'm all ears... Thanks again, everyone here has been a HUGE help over the last few months!

[Plemmons]

Alright, I went as far as to swap the MAF for a known good one and didn't change a thing. Runs fine for about a minute and then starts sucking a ton of air and sputters out. I wouldn't think it to be a vacuum leak considering I can tell that the extra air is going through the intake. The TPS seems to be functioning, but I don't know if it's functioning properly. If I unplug it, the RPMs steadily climb, but it will still sputter after a minute or so. I don't know a whole lot about MAP sensors, but I'm wondering if that could be a problem. Other than the TPS and IAC valve, as far as I know it's the only sensor I haven't replaced, including the O2 sensor. Let me know what you guys think!

[J Wikoff]

Any new codes?

You don't even have a MAP sensor, so don't worry about that one.

It's gotta be losing spark or fuel. You know it's getting air. I don't know why fuel would drop off after a minute, so I'm thinking it's spark. It doesn't seem like a crank sensor to me. I'd be most suspicious of the ICM or the PCM.

[Plemmons]

Thanks for clarifying the MAP thing, I wasn't sure if I was missing it or it didn't exist, lol. As far as the ICM goes, I just tested it with a DIS tester and it was green across the board... Tested great! As for the PCM, I did swap it out with a new one (and swapped the PROM) and nothing changed, but that was before I found the shorted wiring in the engine bay. The PCM fuse (passenger side fuse block) was blown when I was troubleshooting that wiring, I replaced it about a month ago but I'll check to see if it's blown again. Also, the crank position sensor is brand new, too. I always thought that the crank position sensor and ICM handed off timing control to the PCM right after startup, that's why I haven't been troubleshooting the PCM. If the PCM takes control after about a minute, then that makes sense. I can turn the switch off, fire it right back up and it runs just fine again for the exact same amount of time, then dies. Sorry to ramble, just want to be as specific as I can!

[J Wikoff]

ICM's can test fine and still be bad.