Weird issue, when I 1st start my 91 gta 350 it takes a few to start and the idle is about 800. it lopes like it has a big cam in it as well. I have no loss of power at all either but the rough idle is pissing me off. no codes, new injectors, new fuel pump new fuel filter. I want to suspect the egr valve but if that was bad wouldn't it stall or have no power? Also theres a new IAC valve as well. The exhaust smells like a 69 camaro's exhaust as well. Very strong. I also suspect that maybe I do have a beefier cam in it and I'm just chasing a demon that doesn't exist. I'll check all vacuum lines tonight and tomorrow and keep everyone posted.

 

The EGR won't necessarily cause a loss of power or stalling. In fact, it's normal for the EGR to be open at higher throttle openings/engine loads to prevent high cylinder temps. Generally, if the EGR isn't working right you should get an EGR code. But never assume that because there is no code, the EGR isn't the problem. Otherwise, you may have an air leak somewhere on the intake manifold.

 

so this weekend I chased the demon and thought I found him. I replaced a cracked line going to the egr selonoid that exits the swith and goes to the EGR. I replaced the cap, rotor and also bought a new coil. I fired it up, and she ran much better then ever. I let her run for about 20 minutes to get to operating temp and it was strange. The idle started to rise quickly to about 1100 then drop then back up and then drop, then went smooth at 1000 RPM's. It was like it was going to die. Lo and behold, SES light comes on. So I run the codes, code 22 and 32. The idle was always low at startup, around 8-900 and 650 in gear. Getting tired of all the small thing's that keep going wrong.

 

Code 32 is your EGR. Recheck your connections and if you can access the valve, try lifting the diaphram with your fingers to see if the engine drops off or stalls as it should. Code 22 is TPS low. Check out the TPS and wiring. Use a DVOM or scan tool to test TPS signal voltage. Should be about .5 volts closed throttle and 4.5 wide open throttle.

 

Once the engine reached operating temp is when the car tried to stall, caught itself and raised the idle, then tried to stall again and it did this back and forth until the ses light came on.

 

That is an interesting symptom. It almost sounds like a heat related failure of the TPS or a wire that melted through against a hot part of the engine. Using a scan tool on datastream, you could run the engine and watch for this symptom to return while you monitor TPS voltage. If no scan tool, you can back probe the signal circuit of the TPS with your DVOM and watch the voltage while you recreate the failure.

 

I grabbed the codes after it happened, went and checked them out. Took the tps off and slowly ran it through its motions, then screwed it back on making sure it was tight, making sure the connector was also in tight then started the car again. The idle fell back to 800 in park then 700 in drive and the codes did not come back again. My neighbor is gonna let me borrow a dvmeter hopefully and I'm going to test the voltage. I have a weird feeling that it is shot due to the fact when I replaced the cap and rotor and coil, it looked it was original from 1991 0.o

 

I see most TPSs last for the life of a car and others go bad in a few years. Be sure to verify power ground and solid signal circuit to the ECM before condemning the sensor.