Hey everyone,
I'm hunting down what I /think/ is an MAF problem. I wanted to get your guy's thoughts before I start replacing too much.

Recently, my '89 2.8L firebird started intermittently dying almost immediately after a cold startup. It would be fine for the first second or so, but then it would rev down and die. Things were much better if I got going, though if I let off the accelerator quickly it would sometimes die. It doesn't happen as often for warm starts, but it will still occasionally freak out and die.

SES light would come on after dying, and it would give just code 34 everytime . Started it up again after SES light, ran decently well, and it didn't die anymore (I assume it went to the internal fuel tables). I started with physically playing with the connectors, but didn't see any change so I assume those are alright. I checked for leaks in between the MAF and throttle body, and that looks alright as well (the rubber seal around the TB is starting to deteriorate, but visually it still looks good and is clamped down well).

I replaced the MAF and MAF burnoff relays with no change. Just to confirm, I replaced the relay on the passenger side radiator support (the MAF relay) and the middle relay of the set of 3 on the drivers side firewall, by the brake booster (I believe that's the burnoff).

Other threads (https://www.thirdgen.org/forums/tech...r-can-you.html) have suggested the immediately dying problem could indeed be a bad MAF, so I'm replacing that next. Before I do that though, do you guys have any ideas or suggestions on other things to test?

 

1. There is no burnoff relay on a V6. Those relays by the brake booster are fuel pump, coolant (radiator) fan, and the A/C compressor clutch relays, not necessarily in that order, but that's what they're for. There is no burnoff circuit on the V6, as the V6 uses a digital hot film sensor and not an analog hot-wire type which requires a burning-off of the goop and stuff that can and does accumulate on the wire (which eventually requires cleaning regardless due to the goop adhering to the wire).
2. There are only 2 ways to test the MAF, and neither is cheap. One is to get a DMM that measures frequency and plug it between the blue output wire and the black ground wire. The other way requires a scanner of some sort. Other than that, if you can get the engine to warm up to operating temperature (requires holding the gas at about 2K for about five minutes) and get it to idle, you can tap on the sensor with the end of a screwdriver. If the engine falters, the sensor is bad.
3. Code 34 does not actually mean a MAF malfunction. Code 34 means that the ECM is being sent a lower than expected air flow signal. This can be caused by a vacuum leak.

 

Haha, figures. Oh well, at least they were cheap. Does "goop" still gather over time on this type of sensor?


Unfortunately I don't have a DMM with frequency counter or oscilloscope, so those are out the door. I should be able to get it going long enough after heating up one of these times, I'll make sure to try the whacking test. I assume you mean whack the plastic sensor body, not the actual sensor film?

I've got a vacuum gauge; a leak would mean low vacuum correct? What kind of vacuum levels should I be looking for?

 

1. The "goop" is the crud that manages to make it through the air filter. The hot-wire tends to be more sensitive because of the burnoff function that kind of melts the stuff and makes it even harder to remove from the wire, which is why there are MAF cleaning solutions available.
2. Hit the black box attached to the sensor body where the electronics are housed. It's kind of hard to whack the film when the engine is running, with the screen on the end of the sensor and the duct on the other. Don't hit it too hard, just a firm tap is all you need. Also, remove the sensor from the air system and look at the film against a light (reflect some light off of the film). If the film appears as the surface of a lake or otherwise not flat, you will want to look for a new AC/Delco unit. An AC/Delco unit is recommended because I have had 2 "new" ones that were aftermarket, one wasn't built anywhere near right and neither one lasted more than a year and a half. Since you have a Bird, there is also the problem of the plastic elbow between the air filter can and the sensor on the aftermarket ones. On both of them I had, when the air filter can was put into the elbow properly, like it's supposed to be from the factory, the plastic elbow cracked and broke. Which kills the sensor eventually.
3. The engine should be pulling around 16" of vacuum or more. Also, just take a feel of some of the vacuum hoses. If any leave black on your fingers, they all probably need to be replaced.