Decided to park the Trans Am for winter, so I have a 1991 Chevy Corsica with 2.2 tbi. I runs fine except sometimes after it's been running a while it idles low and rough, sometimes stalls but starts up again fine. It's fine once you hit the accelerator. That's the only thing wrong with the car, I couldn't pass it up for $100. I've had someone say to check IAC so I'm going to clean that all up and tune it up. I just wanted any other suggestion just in case that doesn't work. Thanks a lot.

 

It would be worth checking the Throttle Position Sensor on a car that age. It is a variable resistor, much like a volume control on a radio. You know how they get scratchy and noisy when they're old? It can send goofy voltages into the computer even at idle and make trouble.

 

I'll check that. I don't want to drive it too much when it's acting like this and when I turn up the heat I smell antifreeze too. I'll just have to check heater core as well. Thanks

 

The Dawg has a good idea. Check the TPS, clean the throttle body, and clean/lube the IAC. If none of that cures the problem, you might want to take a close look at the ignition wires and plugs. Those things are very sensitive to plug problems, since two plugs fire at once, and a problem with one can ground out the opposite one or at least cause weak spark.

Wow, you got the LAST year for the 133" TBI engine. Subsequent years all got PFI. I've got a "mighty" 133 in my S-truck.

 

86,

Did you get a new belt installed yet?

As for the fuel problem, it certainly does sound like the engine is flooding. That would explain the strong fuel odor, stalling, hard starting, and ineffectiveness of the starting fluid (it already has too much fuel). The extended wait period between starts would allow the fuel to evaporate, making the flooded condition less severe, and would allow the engine to start.

Have you checked to stored error codes?

The fact that is takes a short while after starting to eventually flood and stall leads me to believe that the problem is not catastrophic, but a minor rich mixture condition (little four-cylinders can be SO sensitive).

Things that will contribute to a rich/flooding condition are an incorrect CTS reading, ignition pulses that are intermittent, high fuel pressure, leaking injector(s), incorrect MAP signal, incorrect or completely blocked PCV valve, leaking fuel pressure regulator (not necessarily on a TBI) and probably others that I'm forgetting.

Just to eliminate the random possibilities, grab you meter, keys, and paper clip. Scan the error codes. Disconnect and meter the CTS resistance. At an know or presumed coolant temperature, you should get a resistance reading similar to this:



Find your MAP sensor, and make sure it has a good supply of manifold vacuum. If it is like my 133" 4-banger, it is directly connected to the intake. However, you TBI is probably different and still uses a hose and remote sensor. Make sure the hose is intact. Break into the MAP sensor harness and measure the output voltage at idle. Back-probe the WeatherPack connector at the MAP on the 'A' and 'B' terminals. The output voltage of the sensor will vary from 0-5 VDC depending on the absolute pressure (vacuum) that is applied.



The voltages at vacuum should be close to this:




Inspect the PCV hose, valve and filter. That little bit of PCV air can make all the difference in mixture at very low intake flows (like idle speed), and especially on a small engine.

It might be a good idea to get some carburetor spray cleaner and thoroughly wash out the IAC air passages on the TBI, if you haven't already done so.