Hey guys,

First off, thanks for taking the time to read this. I'm in a hurry (30 days starting today) to get this car inspected so I can get the title transferred.

The car has a hard time maintaining idle. It is acting like there isn't enough air for it to run. I did a search on the boards and I was pointed to cleaning out or resetting the IAC, TPS, and to get a WinALDL cable to talk to the 'bird. I will execute those suggestions.

However in the time that it takes to make the cable, I'm hoping you guys may have already run into this issue. I am fairly confident that this is a computer/sensor issue, because when I reset the timing to manufacturer specs, I disconnect the ECM. When I do that, the engine runs like a champ!!! Once it's reconnected though, it goes back to running like crap.

One thing I neglected to do was to disconnect the battery to clear out the tables in the computer. I'll attempt that tomorrow.

Any ideas?

Thanks!

~Toast

 

Here's some more information now that I got ALDL to *finally* work.

Looking through WinALDL, it shows raw MAP sensor as zero. I am not sure what to think here.

First off, to my knowledge my car does not have a MAP, rather a MAF. My hypothesis is that it meant MAF but WinALDL is configured to show it as MAP.

Going on that assumption, then my MAF sensor is shot. The WinALDL shows the trouble code for that as well. It also shows the trouble code for ECT, but that may be because I reset the timing day before yesterday. I'm going to go and disconnect the battery and reconnect to see if it will throw that ect code again. Hopefully (not for my wallet) it will just throw the maf sensor again.

I'll keep updating... btw, attached is the log file from WinALDL, maybe you guys can make more sense out of it for me. It's already in Excel format for your convenience.

 

Not sure how the data is supposed to read, but, a couple things I noticed...

MAT is all over the place, getting over 300* in places. I would guess that is wrong.....

Battery voltage only shows 5 volts??

Does not appear to be going into closed loop.

Block learn to high. (Adding gas?)

Does it run any better if you disconnect the maf?

 

I just disconnected the battery and reconnected, and after starting the car (and dying), the only code present by shorting the terminals was Code 34. According to the Haynes, it's Mass Air Flow sensor.

To ploegi:

To be honest, that was the first time I ever used WinALDL, so i'm not sure what to tell you about the MAT. Is there a way to test that to make sure?

I have no clue about the battery voltage. It definitely can't be 5 volts.

I don't think it would go into closed loop because I had to jumper the A and B port with a 10 ohm resistor, which I believe puts the car in ALDL mode. Hence forth, ignition is no longer controlled by the computer, only the static timing (it ran great when I jumpered the port).

I was adding just a tad of gas once or twice to keep the 'bird alive.

I seem to remember disconnecting the MAF, and noticed no difference. I'm beginning to wonder if the MAF is really bad, or if there's a short or cut wire somewhere.

Thanks!

 

Even more information now:

I probed the wires going into the MAF sensor, and here's what I got:

black wire - 0v
black/white wire - 2.3v - 2.5v (varying)
Red(ish) wire - 13v

Do these numbers make sense (varying voltage)?

I found this information resource which goes into trouble code diagnosis on FI vehicles. It says a code 34 can also be thrown due to idle issues with IAC and TPS... i'll give those a try.
http://books.google.com/books?id=9wd7BxUDL5MC

Click on "Preview" and you'll see what i'm talking about. "How to Tune and Modify Chevrolet Fuel Injection By Ben Watson"

I also read on another thread there is a MAF relay, and MAF fuse. I'm going to check those out next. It makes sense that the computer would detect 0v from the MAF if the fuse was blown...

 

I checked via continuity test the two 20 amp fuses located on the passenger side next to the charcoal canister. Both registered good. I'm still curious if 2.5v from the MAF is normal... I'm going to check the TPS next. Apparently that can cause a code 34 as well...

 

So as I was napping today, I came to a conclusion, that I just verified:

According to the Haynes, the MAF puts out a voltage of 0.5v to 5v depending on the amount of flow across the sensing unit.

My MAF read 2.5v. I first thought this was normal until I realized "while I was sleeping" that the MAF was 2.5v at idle.

So I woke up, went downstairs and measured the voltage of the middle pin on the MAF when the key was in the "on" position (not started).

It measures 2.5v, but went down to less than a volt every not so often (5-6 seconds between negative spikes).

So if the MAF is giving 2.5v without the car even started (but key in the "on" position), it makes sense to me that the MAF is shot.

What do you guys think? I'm assuming that at idle (or off), the MAF should either give a voltage of 5v or 0.5v, and 2.5v is way off.

 

You may want to re-post this in the V6 section. There are guys there who go MAF crazy over there...

It seems to me that you have a MAF issue. I wish my car was here with me; I'd love to measure it and see what it's doing. What repair manual do you have? I am using a Chilton's Total Car Care manual. I'll see what it says...

 

Thanks for the suggestion KrisW. I am reposting (and continuing) this thread on the V6 forum.

https://www.thirdgen.org/forums/v6/4...-firebird.html

Thanks!

~Toast