My fiance's '87 IROC threw a code last week for the mass air flow burnoff. I've never heard of this before, and the car is frustrating us so badly we are very close to selling it. We have had it at 2 different shops over the last 2 or 3 weeks. In fact we just got it back today after having it at a shop for a week and a half and the guy said he couldn't get it to act up, only for it to die on us after we picked it up today.

What it has been doing is it will idle really rought out of nowhere, just randomly drop RPM's at idle. And at stoplights or anytime she comes to a stop it will just shut off completely and she has to restart it. Sometimes it won't even start back up. Tonight the SES light kept flashing off and on every few minutes. I'm getting ready to send this car to the salvage yard if we can't figure out what is wrong it is frustrating us that badly.

So what is this mass air flow burnoff anyways?

Things I have replace: Mass air flow sensor, fuel filter, relay for the fuel pump, plugs and wires, distributor cap and rotor, distributor has been semi-rebuilt.

 

There is a maf burn off relay by the brake booster. I would check it out and its wiring.

 

you should have three relays by the brake booster on the firewall. MAF burn off relay, MAF relay and I forget the other one

Just go buy a new relay and replace it--see if it throws the code--you'll know you did the right one if it doesn't.

 

I've been fighting that one myself. The parts store said the didn't have the right relay in their system, but the fuel pump one should be the same. Even after I changed the relay my car was running really bad. I changed back to the original relay a few weeks later when the car wouldn't quit stalling out. It ran ok, but pig rich. So I swapped in a used maf (found out the tps wasn't set also) and reset the ecm. So far it runs alright, but the o2 sensor is likely poop from the running rich. none of the codes have come back either. I never really figured it out. My new relay made the problem worse, and the old one kinda works now.

 

I found a part number for one of the MAF relays but they didn't have a number for the other one. Will the same relay work for the burnoff and the power?

 

Ok so I put the IAC sensor on, a new MAF sensor, and a new MAF burnoff relay and i took it out for a test drive and it seemed great. TOok it home, walked away for 10 minutes and came back, it started right up again with no problems.

Then 2 hours later I go to drive it and it starts but the check engine light comes on immediately, and it was idling really rough, like it was misfiring or something. I drove it up the street and it died while I was sitting at a stop sign. It wouldn't start back up for me for about 3 minutes, finally I got it to fire back up and the check engine light never came back on when I turned the car back on. As I'm driving home I go to take a corner and the light comes back on again and the car surges really badly, like it was going to die right as soon as the light turned on. It only lasted for a second and I managed to get it to a shop where it sits right now.

I'm really running out of ideas here...

 

Bump, any more ideas?

 

This may sound crazy but what maf did you get?I got the one with the chip micro tech i think and it does the same thing.Put a bosch maf back in it and problem goes away.If you have a way to try another maf try that.You may also want to replace the icm.I have had them do stuff like this also.

 

So what are the error codes that you are getting? 33, 32, 34, xx, yy. Some of the part stores will pull the error codes for you at no charge. Also, you can get them yourself using the "manual" method, using a simple paper clip.

 

I put a Bosch back in it. What is the ICM?
I'm going to try driving it around town again tomorrow and see if I can get the light to turn on, and if so I'll take it up to AutoZone. They will check it for me.

 

Depending on the year of the iroc, there is a MAF burnoff module piggybacked onto the ECM. If it's an 85, or has an 85 ECM and wiring in it, it will have this module. GM incorporated the module into the circuitry of the ECM starting in 1986, so those don't have the module.

I see in your original post, you asked what is a MAF burnoff? When you turn off the car, the ECM sends voltage to the little heated wires in the MAF to burn off any contaminates like dust, grease, etc. that make it past the filer, thus why it's called the "MAF burnoff".

Another possible thing to check is to make sure you have the right MAF for your car. Through the years, GM made little calibration changes, the biggest being in 1987 when the 350 came out. A 350 MAF has a different calibration than a 305 MAF. Your symptoms after replacing the MAF are similar to symptoms my old Camaro had at one point. My car was exhibiting similar symptoms, and I too replaced the IAC, TPS, etc, only to find that the MAF took a poop and never set a code. A mechanic that had worked on the car previously gave me a Corvette MAF, which was obviously the wrong one for my car cuz I have a 305 and vettes got the 350. When I tried it in my car, it would stumble, hesitate, misfire, not run...a real mess. But the only difference between your issue and mine is, I didn't get a SES light for anything. This proved the MAF that was in the car was bad and though the vette MAF was working fine, its calibration threw the ECM off, so it was sending the appropriate 350 rate of fuel to the injectors for the airflow it saw, which was too much for the 305.

Also, don't trust those shitty auto zone mafs. I bought one, then a week after the shitty 20-day warranty ran out, it crapped on me. At the time, it was the only warranty on the MAF.

If you can get a code out of the ECM, post it up, and I will do my best to post a troubleshooting flow chart from a GM service manual, for a MAF car with that code. However, do it before tomorrow night, as I will not be around internet till Monday morning.

Too bad you live in ST. Louis, and gas is a million bucks a gallon, otherwise, I could help you. I have been through a lot with MAF cars...best advice, dump it and go speed density

EDIT: Also, I just re-read your original post and have yet another gem of wisdom for you. You mentioned the SES light was flashing rapidly. Usually, that means there is an ECM or PROM issue. It could be a possibility that the ECM or PROM went bad. Without consulting my tuned port bible, I *think* a code 51 will set for that. It may be a problem in the MAF burnoff circuit in the chip or ECM, but the ECM sees it as a problem with the burnoff system itself, so it throws a code for that.

Bottom line...get me a SES code somehow. 99.99999999% of the time, that is a good spot to start at when diagnosing a FI system.

 

ICM is ignition control module.irocz28keven where did you get your info about the 350maf and 305 maf this is the first time I have ever heard anything like this.Bluezee28 what do the relays look like on your firewall?If you have the one square and the two round ones Azone dosent list the relay but it is the same relay as the electric fan.

 

I got my info from a mechanic at home who makes a living working on GM TPI cars. His specialty is Corvettes. He rarely if ever works with much else.

Also, look up p/n on autozone for a MAF for the same year car, but a 305 and then a 350. The numbers will be different.

 

I'm also getting a code, 33, 34, and 36 I've checked all the terminals and connections and grounds are clean. And since I'm going to school to become a automotive technician, I used the diagnoses process from ALL DATA for code 33, and I'm doing code 34 tomorrow after work, and after the test for code 33, it says it may be a faulty MAF, but until I took the car apart, it was fine, and the MAF sat in my basement for 5 years, until last weekend, so I don't think its the maf. I'm also going to finish the diagnoses work for code 36So if I may ask, What do you think it might be?

The Maf burn off relay's working, because after I shut the car off, the burn off relay, burns up the MAF wire, so its working. I don't think having 1.6 roller rockers or advanced cam should be affecting it though.

 

Well heres the deal, this is funny, it was actually nothing wrong, lol.

I first did the normal method of clearing codes on any OBD I GM vehicle. Pull the ECM fuse out for 10 seconds, put it back in, and your good to go. So I did that like 4 or 5 times, put the fuse back in, and checked the codes, and still codes 33, 34 and 35.

Then I pulled the fuse out as All Data said for 5 minutes, tried that a few times; still same thing, 33, 34, 35 codes.

Then I went ahead and did the older, slightly more pain in the *** method, but no big deal, pulled the negative battery cable for about 12 seconds, put it back on, checked the codes, GONE! Then ran the motor, a few times checked codes again, and GONE!

I mean before I was setting up my New CAI I need since the new radiator is bigger than the stock, plastic core junkers, that break. My 87 irocs and my formula both broke the same way, so after the have 125K on them, the plastic turns to shi* and cracks. So I bought a summit universal fit one, and its larger than the factory one, which is good anyway, because this motors making more power now, and I'm fabbing up my upper radiator hold down, and the two attaching points for the fans to bolt to. So anyway, I'm just finishing that up, and have the first half of my CAI done, I just have to cut one more piece of 3" tubing, I'll cut in my machine class, because the band saw does a much nicer cut than a hack saw and straighter than a saw zahl. So I'll post pics of that in a few days.