Help with '91 Lumina 3.1

[Lando Griffin]

About 3 weeks ago, it started skipping out once the engine got hot (driving 85mph for 45 minutes.) Then once I slowed down it died sometimes, in a seemingly random way.

 

Driving home from work the other day my car just died while driving normally, for fear of making the problem worse. I couldn't get it started again, so I had it towed to my storage unit, where all my tools are. Thinking it was a coil pack, I hooked a spark plug up to an old wire I had laying around (since the wires in my car are such a bitch) and tested both points on each coil pack. Getting good spark from all of them. Next, I pulled a spark plug and it was black as hell, so I went down to Oreilly and bought 6 new plugs and wires. It still idled rough, so we checked fuel pressure, which showed as a constant 38psi.

 

On the way from there to my friend's house, which is down the road, my car was jerking really bad under any sort of load (i.e. acceleration), and having a tough time idling too. He went and bought some fuel injector cleaner, and we dumped that in at his house (thinking the injectors were sticking, thereby killing the engine and blackening the plugs). I started it up and let her idle outside his house while we ate dinner. It idled for a good 30 minutes straight, so I thought the problem was fixed.

 

Then, on the drive home, it would get REALLY rough under any load (acceleration from a light, out of a turn, etc.)

 

I don't even know what to try. Something tells me it's a sensor somewhere mis-reading something, thereby causing the engine to miscalculate the mixture. It idles fine now, but won't drive.

 

I also am NOT getting an SES light, although one of the times it died, the light came on for 5 or 6 seconds first. Not since then, though.

 

I NEED my car to get to work tonight.

 

Advice?

[Lando Griffin]

Oh and also... HI! I'm new to the board (obviously) but I've been working on that Lumina for a long time. This is just the first thing she's ever done that completely stumped me.

[Robby1870]

First of all, nice screen name......Family Guy rocks. Now, it sounds like the crank position sensor to me. That tells the ECM when #1 is at TDC and how to base the spark off that. If its not getting a signal, it wont send spakr, making for your sporadic problem. The wire for that sensor may have rubbed bare and grounding out to the block (that happened to me, had the EXACT same symptoms as you).

[Brian P]

after that, check for a possible ignition module partial failure.

 

 

Oh and don't do toad.

[mihela816]

Because when you lick a toad, you are licking every toad that toad has ever been with.

[Lando Griffin]

I'll search for it as soon as I post this, but someone wanna give hints as to where the CPS lead wire is?

 

Robby... where did yours ground? I'm pretty sure my engine layout is almost the same as a grand prix.

[Brian P]

The sensor harness runs from the sensor in the back of the block (basically way below the alternator) runs across the top of the block with other wiring inside loom, then to the front of the block to the ignition module. Easy to recognize- it's 2 wires twisted together its entire length to prevent electrical noise/distortion.

[Dirty Rockstar]

Trycheckin the IAC.. Mine just failed. I put a new one in, and now you can feel the plugs need to be changed

[Robby1870]

I'll search for it as soon as I post this, but someone wanna give hints as to where the CPS lead wire is?

 

Robby... where did yours ground? I'm pretty sure my engine layout is almost the same as a grand prix.

 

It was grounding on the back of the block. Somehow over the years, it had rubbed bare and started grounding out. Good luck!

[Lando Griffin]

I give up. I've got too much other stuff going on right now. I took it to the mechanic my aunt's been using for the past 10 years. He's a really honest, fair guy. So... hopefully I'll know what it is by tomorrow, and I'll let you guys know when I find out.

 

Thanks for all the advice! This place is definitely getting a bookmark.

[Lando Griffin]

You guys were right. It was the CPS and the IAC. Oh well. Mechanic's charging me $288 total for the parts, labor, and check-out & testing fees. Seems pretty fair to me. I'm driving an engine I'm completely unfamiliar with. Now, when I get my 300ZX with a small block chevy running, that will be a different story. No mechanic will be touching that thing but me.

 

 

Anyways... thanks for the help. I know where to come next time.

[god910]

It would be fair to me if the CPS broke off. :shock: Other than that, I'd keep my money. Welcome aboard. 8)