92 is stumbling at takeoff

[BSLAVIK]

I have a 1992 w/auto trans Lt1 and have been chasing around a hesitation and backfireing problem for a month or more now? I have noticed that it runs really good cold at start up, and then as it warms it missfires and stumbles at take off, it seems to run ok at 55-65 mph though? I have installed new o2 sensors and spark plugs and have not cured the problem? I did find out that if I leave the o2 sensor leads unplugged that it is at least driveable? however the check engine light comes on after warm up. I have also added injector cleaner the last two fills and that hasn't changed anything either, I have also checked for vaccum leaks and haven't found any yet. my next area to check will be the egr system, any ideas on how best to diagnose the egr system would be helpful.

 

[Hrtbeat1]

Coolant Temp Sensor.

I think the LT-1's still have them. On earlier cars it is just below the TB on the front of the intake manifold. It may be in the same location. Should be a small "D" shaped connector with three wires.

 

[BSLAVIK]

The temp sensor is reading the coolant temp because I can see the temp increase on the dash gauge cluster as it warms up. or is that reading comming from somewhere else another sensor perhaps on the radiator?

 

[regalniz]

clean your maf sensor with some of that aerosol electrical spray cleaner stuff. gunk makes the one i use. spray it on the wires and let it dry. do not touch the wires with your fingers or anything else.

 

[BSLAVIK]

I dont think my 1992 has a maf sensor, I thaught it was first introduced in the 1994 LT1?

 

[C4Tom]

I think you may be on the right track, perhaps in the egr system. Bad egr valve? egr valve gasket leaking?