1987 Camaro Iroc Z28
TPI 305 5.0
Series F

Started out with a bad stumble, car would run fine, but once it got warm, car would start to idle really low then jump. Took it in to firestone, got them to look at it, they can't figure it out at all. We brought the car home and got the engine codes ourselves by grounding A and B and the service engine light flashed the code 12 three times, then flashed three quick then three more quick which is code 33 (low vacuum, MAF sensor).

Right now, the car will not stay running unless keep giving it gas. The whole car shakes and it is spitting out a ton of black smoke out the exhaust.

We have tried unplugging the MAF sensor which made no difference, and want to make sure it is the MAF sensor before we go spending $170 on a new one.
We have also tried replacing the alternator with no luck.

We have an appointment for Wednesday at a GM dealership, but I would really like to do it myself rather than spend big $ for the dealership to look at it.

Any help would be appriciated.

 

Start tracing the wires to the maf connector, but first, replace the maf power, and burnoff relay. they only cost 12 bucks or so each, and is a likely cause. Common for these cars. They are located on the firewall, drivers side. I'm sure you know what relays look like. There is a wiring diagram probably in the tech section that will tell you what ones are which on the fire wall. There are 3 total, maf power, maf burnoff. and the fuel pump relay.

 

We have it narrowed down to the relays, the MAF sensor or the ECM. Picked up the relays today at napa and will install them tonight, hoping that fixes it because I would rather pay $12 then $170 for the MAF or $220 for the ECM.

 

Neither the power relay, nor the burnoff relay solved the problem. Guess its down to either the MAF sensor itself, the ECM, or it could be a short in the harness.

Any more ideas are greatly appriciated.

 

Check the TPS voltage at closed throttle.

 

We have already replaced TPS, I don't have a way right now to check the voltage, but I should be able to pick up a reader tomorrow.

 

The car will always run rough and crappy when the 33 error code is present, the ECM goes into the "limp home mode". Been there many times.

Clear the code by disconnecting the negative ground at the battery and re-connect after 2 to 3 minutes. Now drive the car, How does it run?

If it runs fine until the 33 error code comes back, there is nothing wrong with any of your components, most likely. The 33 error code is set when all 3 of these conditions are met at the same time:
1) engine under 2,000 RPM, 2) MAF registering more than 45 gms/sec, 3) less than 25% throttle.

I got so good at setting this code, that I could set it at will. The only sure fire way to get rid of the 33 error code is to have a Eprom chip burned for your car with the special mission to get rid of the code.

 

I was getting a code 33, then a code 45; car doesn't run crappy till it gets hot.

 

Yes, make sure you check that.

 

I've had some that have "survived" after the MAF error threshold was bumped to 60, and the TPS was run near the very high end of the range, like about 0.63V. This is one of those places where a cam profile change can make a significant difference in a MAF installation without tuning.

 

So when I pulled off the wire going to the TPS I saw that the whole plastic casing on the terminal was cracked and gone; see attached pictures. Firestone replaced the TPS, but mentioned nothing about this.

Any idea as to where to get a new terminal?

 

i had the same problem years ago and the dealer told me it was a map sensor for 180.00 bucks, found out from honest mechanic it was the map sensor relay on back firewall for about 20.00 bucks instead try that first to save yourself some big wasted dough. let me know.

 

See above

 

So I taped up the connection as best I could, car still ran the same. Of course that really isnt saying much considering the condition that connection is it. But we tried moving it around while the car was running and you would think that there might be some response but there wasn't. Guess we are heading to GM dealer on wed.

 

check the pickup coil and its connector inside the distributor. pop the cap off and check to see if the connection is all corroded and nasty. On my car, the plastic body of the connector was like mushy, and the connections had lots of oxidation. had to scrub that up for awhile and put it back together without the plastic, and it cured a no-start, rough idling holding the pedal down slightly issue. If its an original distributor, it's a problem that is apparently common.

 

I will take a look tonight

 

this may sound way out there, but my buddies 86`iroc had a simillar problem, but now, like i said this out there, but my buddies ran ok (not good but ok cold) and horrible when it was warmed up and we took a look at the timing chain and it was shot, replaced it and was good till it sold 2 years later?!

 

I would`nt be suprised to know that your MAF is bad however, I noticed those to be as finicky as our x-girl friends, regardless of make and model!

 

Alright, got it pretty much figured out for anyone else having this problem. MAF is bad and therefore the mixture was running much too rich, because of the rich mixture, the plugs got coated and wouldn't create the spark. Got the plugs cleaned off and ordered a new MAF. Then we got to get the rear end rebuilt.

Thanks to everyone who tried to help me out with this.