My 85 TA for years has run horribly when first started. Seems to run real rich and do a lot of idle hunting. No codes.

Using my scanner I can watch the injector pulse width increase so much that the engine would frequently die. When it didn't die the pulse width would decrease and the engine would purr like a kitten. Then the pulse width goes up again and it starts stumbling again. The only way to keep the engine running would be to constantly tickle the throttle until the car goes into closed-loop mode (or warmed up). Every once and I while I'd get a code 44 (low O2 voltage) when I sat at a light for a long period of time.

While looking for a rattle under the hood I used a car stethoscope to determine it was coming from either the A.I.R. pump bearings or the alternator. Since my A.I.R. pump has it's own belt I took it off. That didn't cure the rattle as it turned out to be a bolt holding the alternator was loose.

Here's where it gets interesting. I didn't put the belt back on the pump and when I went to start the car this morning it started and idled great. However I got a code 34 (low MAF voltage) now. Like the other code, it only seemed to pop up when the engine maintains a constant RPM.

I cleared the codes and performed a MAF check per the FSM and it says that the MAF sensor needs to be replaced but check to insure that the burn-off module is functioning properly.

So my questions are, could the diverter valve for the A.I.R. system be defective and is there an easy way to check the MAF burn-off operation. I havn't dug too far into it yet because this was just this morning before work.

 

Change the O² sensor. While that may not theoretically seem to have an effect n the open loop operation, if the ECM is working correctly, it has been writing data to the integrator/BLM and skewing the fuel tables toward the rich end while your sensor has been degrading. A new sensor, cleared ECM, and a few trips should start to write good data to the BLM.

You also need to test fuel pressure and injector leakage, make sure the cold start valve and control are working correctly, and check the FPR for internal leakage. Also verify the PCV is connected and working correctly, and that the PCV fresh air is coming from the connection at the throttle body.

As is always the case with an idle/surging problem, you should make sure the IAC is clean and working, and that the TB minimum air setting is correct. Once those are good, verify the TPS voltage setting. A high TPS can contribute to the MAF error coding as well as enriching the mixture a bit in closed loop.