Hi Everybody this question is obviously about my 1987 Firebird with a 2.8. The question is will a bad MAF sensor keep a car from starting?

A little background - My check engine light has been coming on every now and then and when I checked the codes I got code 33 and sometimes code 34. One is MAF voltage too low and the other is voltage too high. Those are the only codes it's ever shown (besides 12 of course).

So the other day I'm just driving down the road and slowing down to stop at a light when the car starts running so rough I thought I'd hit a bunch of pot holes then it died and wouldn't start back up. It turns over but won't fire. Yeah, oh joy! Of course it was rush hour and me and my 15 year old daughter had to push it out of the middle of an intersection - more joy. But that's beside the point.

I had the car towed home and have almost decided it's an ignition problem... Why? Well no spark or only intermittent spark. So now I'm getting my mindset to go out and start the no spark diagnoses routine but since I'm really sort of lazy and I really don't want to (since I don't know anything about HEI ignition cars - this is the newest car I've ever owned give me a pre 1970 car and I'm good!) and since the MAF sensor is the only code it's ever shown I thought maybe someone could save me from all that and tell me if a bad MAF sensor would cause all this.

 

Check all wiring between the distributor and the ignition coil for breaks, and then check the wire for the pickup coil inside the distributor (2 wires, the only connector INSIDE the dizzy) if you don't find any. All else fails, the ignition module (the black thing inside the distributor that's bolted to the base, if you don't know) is probably kicking the bucket. You can remove this (3 connectors and 2 bolts, DON'T get the white heat sink grease all over you or it WILL be hard to get off) and take it to AutoZone to be tested. Advance sells a GP/Sorenson unit with a LIFETIME replacement warranty. You might want to take it because that bugger goes bad a LOT. I know a guy that keeps spares in his glove box in his S10 for when they fail...
As for the MAF, check that wiring as well. You've probably got some wiring in the harness rubbing together somewhere where it shouldn't be, which is why it alternates between high and low readings. Failing that, go to Advance Auto or partsamerica.com and pick up a NEW one for $80 or whatever it is now, and never have to worry about the bugger again (LIFETIME warranty). Also, you might want to grab a Haynes manual for the car and locate your fuel pump relay so you can switch it with the relay (the black box) mounted to the frame next to the MAF to see if that is bad.
Bad MAF sensors will NOT prevent the car from starting. They will just make it run like crap until such a point that the ECM either rejects the signal, you replace it, or it warms up enough to put out a workable signal. I know I have a bad MAF when I have to hold the gas pedal until my temp gauge actually registers so I can let go and let the engine idle normally.

:edit: OH, I forgot to mention 1 thing. Code 12 doesn't just mean that the engine isn't running. It also means that the ECM is not picking up reference pulses from the pickup coil in the dizzy. This signal MUST run through the module to be interpreted by the ECM. However, the module receives power from the coil through the TAN/WHITE wire in the 2-wire connector, which is BLACK on the coil end. The GRAY connector is ignition switch power INTO the system, and the WHITE wire coming out of this is for both the Tach and ECM reference... Check all of the wires in all of these connectors. I have had the TAN wire break on the coil end and mess everything up...

 

Well thanks Maverick. It was the coil which I've replaced and the car is now running again.
Oh about the relay for the MAF I actually already did that - thing is the parts stores here were calling it an air conditioning compressor relay, hmmm... I don't know if it makes a bit of difference but one code sets when when the car is going down the road usually after I've been driving for a while and the other only happens sometimes when I start the car - it will run funky for a few seconds maybe a minute then the check engine light comes on and the car smooths out and runs fine.
Now I just hope this MAF sensor thing won't keep it from passing smog - life in California - what can I say.

 

If you've got an active (on) CEL, you can pretty much bet you're going to FAIL the smog tests, since that is one of the things they check (if their tests out there are anything like they are here in NY). I guess the A/C uses the same relay as fuel pump and MAF do... who'dve guessed? Either way, there is also a fuse next to the air cleaner, in one of the weatherpack connectors bolted to the frame rail. That is constant power for the MAF relay. Start there and work your way to the sensor for broken/cut/rubbing/otherwise damaged wiring. There HAS to be a wire rubbing something it's not supposed to. My guess would be that there is a broken wire at the relay connector. Don't know how that would be if the car has been untouched (except for a mouse problem), but that is what it seems like to me, not being able to see it for myself. Yes, you are going to have to remove the crappy wire wrap (hopefully without breaking it too bad) and try to stuff the wiring back in it.
If you PM me your email address, I can send you some GM troubleshooting flowcharts (easy to read and follow and have wire diagrams with them) for both codes 33 and 34... I hope you have both a test light and a multimeter, you're going to need both if you want to fix this problem.

 

Maverick I forgot to mention that I do have a test light and a multimeter as well as the wiring diagrams that are in my Chilton.

I just don't know how to use said multimeter.

Anybody know a good link to 'Multimetering for Dummies'?

 

I'll get you those charts when my laptop decides to cooperate and let me change the file format on the PDF I have them in (unless you wouldn't mind having the charts for the coolant temp sensor, the vehicle speed sensor, the intake air temp sensor, and the torque converter clutch circuit).

A DMM is easy to use. The primary setting you need, if you have a manual range meter, is 20 VDC, and the auto ranging meter will adjust itself. The readings will be either a ranging reading around 2.3V at the sensor output, 5 VDC for input, or 12.6 VDC (or whatever your battery voltage is, measure this FIRST) for the power side. Also, while checking the wiring, look for green corrosion (similar to what you will find with a battery), broken wires, greasy wires, and contamination by the factory's dielectric grease, which is a heavy, goopy, black grease which you ABSOLUTELY do NOT want to get on you because it's a real pain to get off, even more so than wheel bearing grease.