I've been working on chasing down a gremlin in my car, and was wondering if you guys could help me out. I've done a TON of searching and reading, and I find a lot of people asking for help with problems, but nobody seems to post their fixes when they do figure everything out.

My car: 1989 IROC 'vert with LB9, 700R4, 57000 miles

My problem: Intermittent code 33 accompanied by surging/loss of power/shuts off at stop lights occasionally. Doesn't seem to happen when the car is cold/cool, only when warmed up, and usually immediately after hitting a bump or rough surface, then it will fix itself after less than a minute.

What I've done so far: Replaced cap, rotor, and coil, had the ignition control module checked about 30 times, it's good. Checked the reluctor pickup with a Ohmmeter, it was good, Replaced injectors with Bosch III's, replaced CTS, replaced IAC valve, set TPS at .54 then .64 Volts to see if that would help with the code 33, no go. (TPS tracks well) EGR solenoid unhooked, vacuum ports capped

What I'm thinking: I need to change plugs/wires, I think this could cause the idle issues, but could this cause a code 33? I don't think it's vacuum related, or it would be consistant. Could heat/vibration cause MAF sensor issues? (Doesn't seem likely to me)

I'd love to hear any ideas or direction. I'd really like to hear from anybody that's had similar issues that figured out their solution. Thanks guys!

 

Forgot to mention, switched out the MAF power and burnoff relays too...

 

Well a code 33 is a MAP sensor issue, but you said MAF if your post. It shouldn't be the MAF sensor itself, if it's a cold/hot issue. That's usually in a pretty decent place to get mostly cooler temps. I would trace all your wires. I believe the map sensor wires are routed through the looms that go between the intake manifold and the valve cover on the pass side. Check for a rogue wire that might have been pinched, or made it all the way down to the exhaust manifold and is grounding out.

Did the issue start happening after you switched out the power and relays? Or did you do that in an attempt to fix the issue.

You might want to try and find a junkyard MAF and see what happens when replaced. They're a bit too expensive to buy new just to test something. Also, check all your grounds. I had a bad ground that would make the computer go nuts after the engine bay warmed up (Car wouldn't run well/suck down gas, tachometer needle would be all over the place)

 

Thanks for your reply!

On '89's, code 33 is for the MAF sensor, it uses the same code as the MAP cars. I can't find a single Third Gen at the junk yards around here, so that might be a problem. I need to meet somebody with a Third Gen. I replaced the relays after the problems started, so I know they are not the problem. I'll check the grounds, that's easy enough, and the wiring all looks pretty good as far as I can tell.

I have heard of many problems throwing a code 33 on these cars... anybody ever gotten one from plugs/wires?

Bad ECM seem likely to anybody?

I wish the problem was consistant, it would make troubleshooting alot easier!

 

Check the wires on the relay plugs. Over time gravity pulls the insulation down exposing the bare wire, they could ground out and cause problems.

 

Ok, sounds good, I'll check those too. How about the knock sensor? It's usually going over bumps that the car acts up.

 

Okay, so I start up my car this morning to let it warm up. I come back 5 minutes later to head to work, I get in the car, shut my door, and the car shuts off. No funny sputter, nothing, just shut off. Any ideas guys?

 

Anybody? I replaced my plugs and wires last night, still acting up. I was able to reenact my door slamming car shutdown once more, but it won't do it anymore. It's something vibration related that is causing a code 33 and the car to run crappy intermittently.

 

seems like a bad wire connection somewhere, check all the wire to the maf back to the computer

 

I'd go around and lightly tap with a rubber mallet in different areas of the car and see if you can narrow down where the issue might be located. Sounds like a wire issue - either being shorted or opened causing the issue. It would be easier if it was blowing a fuse or something but since it seems fairly reliable with the vibration maybe the mallet might work.

don't hit stuff too hard else you might not be able to locate it or you might cause other damage

 

So I think I may have found my problem. The C1 connector harness to the ECM. If I wiggle the wires around or knock on the dash, the car starts acting funny, and if I wiggle the wires enough, the car will shut off. Guess what's plugged into the C1 harness? Among other things... the MAF sensor! So question is... do I replace or rebuild the harness? Does this make sense to anybody but me?

 

if your wire savvy you can re pin it, otherwise best and easiest would be to change it out.

 

Any idea where I might get a new one?

 

Just ordered a new pigtail from Mike at EFI connection. If you guys ever need wiring harnesses, this is the place to go, two thumbs way up.

 

Just to update, I wired in my new harness pigtail and the car runs like it's brand new! So, add this to the long list of things that can cause a Code 33!