For a while, the stock 85 MAF worked on my car, which now has a 165 ECM. After a while, it started throwing a 34 once I started driving. It does this more often than not.

So I throw it on the GTA. On that car it works flawlessly.

I take my Wells SU145, which also works well on my GTA. I stick it on the IROC, and the goddamned car just starts and stalls immediately.

Now here's the kicker... once the IROC is warmed up, the Wells works beautifully. But it won't start with it.

With the other MAF, it starts fine, then won't drive.

So I borrow a Bosch MAF. Same deal as the stock 85 unit. The car will start and idle fine, but as soon as I pull out of my driveway, code 34.

This is really pissing me off.

 

Is the MAF seeing the full 5V ref voltage? Also, did you try any data logging while it is running? This may show something. Check all of the connections for the MAF, both sensor end and ECM. I'd imagine you tried a new power relay?

 

I really haven't checked much of anything yet. If they all behaved the same way I'd be a little more motivated to find the problem. All of the relays only have a few hundred miles on them, but it's easy enough to throw a spare in to see what happens.

 

Since each MAF is responding a little differently I would suspect a power or ground problem in the circut, one MAF may be a little more tolerant of under/over voltages.

 

Jim,
Did you try swapping the 165 computer out of your GTA into the Iroc?
I had the same type problem, and by swapping out computers, I found out that it was no good rather than the MAF sensor.
Good Luck!

 

I haven't swapped the computer yet, although I think that's going to be my next step. Maybe if we don't get a monsoon tonight I'll have a chance to try it.

 

roflmao, but how about a nice SD swap?

 

Ed, I'm determined to make this POS work properly instead of just swapping it. The whole reason I swapped to this was to get away from my non-functioning 85 setup. Somewhere I need to draw the line and figure out why my car sucks so fricking bad all the time.

So anyway... I put the GTA computer in. Now the car starts with the Wells, but pops a code 34 after a minute or two.

5 volt signal at the MAF is good, and both grounds test ok. I change the MAF relay for sh*ts. Start the car and don't get a service engine code, but it takes forever to get into closed loop. As it sits there idling, it goes in and out of closed loop.

 

Try canging the coolant temp sensor, and if that doesn't do it, try another O2 sensor. The cycling in and out of closed loop sounds like one of those 2 is sending flakey signals.

Didn't you have another thread on this subject? If not, my bad. I thought I mentioned to check the ECM and you (or who ever) said "gonna try it", never heard back on that thread about it though.

 

I had a thread floating around in the PROM section too. I haven't had a ton of time to work on it. Last night I did, so I swapped computers like I mentioned above.

Anyway, according to my scan tool, my CTS is working properly. Coolant temps are shown accurately on my scan tool. Oxygen sensor cross counts go up quickly even before the car makes it into closed loop. The oxygen sensor status goes to "Ready" but the car still stays in open loop for a while, then goes in and out... but the crosscounts keep going up and the sensor stays "ready". Plus, I just changed the sensor a few thousand miles ago. I need to hook up the heating element of the sensor to see if that's helping. Maybe it's not getting fully heated with the car just idling... although if that were the case I'd expect my crosscounts to accumulate more slowly.

 

The coolant temp and O2 status are supposed to be the 2 factors that determine weather the ECM is in closed or open loop. Is the coolant temp doing anything funny at the times when it is cycling in and out of closed loop? Also, the wire from the O2 sensor to the ECM may be partially broken, able to ohms check good but unable to carry the full load.