My 82 crossfire at a cold start runs well, takes fuel and produces nice cones at both TBI's. I throttle the tbi's and it doesn't miss a beat. About two minutes later it idles down like someone hit a switch and idle becomes rougher and when you try to give it gas it backfires at each Tbi's . It appears that some sensor sent a message to the ECM to lean the fuel to the TBI. Any ideas what sensor may cause this?

 

sounds like a closed loop problem. I would check for any stored DTC's and pay attention to the O2 sensor and temp sensor.

 

Thanks, the temp sensor is located on the drivers side of the block, correct?

 

NO...not that sensor...the sensor in the cylinder head on the drivers side is to tell you what the coolant temp is for the gauge.

The coolant temp sensor is in the front of the intake manifold...pointing towards the radiator....and has a yellow and black wire going to it. This sensor is critical...and usually will set a code that you can pull to verify.

I would check the MAP sensor. It should have 1.4 volts between ports A and B when the engine is running and at idle. Companies sell a jumper that allows you to check these terminals so it is still connected when the test is being performed. Higher than that can be that you have a vacuum leak. So if it is idling...and you know for a fact that your fuel pressure is CORRECT...and your voltmeter shows 2.2 volts....you have a vacuum leak(s) somewhere.

I would check the TPS setting also. It should be .525 volts...and you can get a special jumper for it also.

I would be curious if your fuel pressure is correct. It should be 9 to 13 psi. It also takes a special tool to do this also.

Many other issues also can cause this but we have to start somewhere.

DUB

 

thanks I'll get started.