My car has been running fine for about 150 miles since I put a stock motor back in it, but today I went to lunch and when i got done came out to start it and the O2s are showing 1200, when they should normally be 450ish. and the injector pulsewidths are 5.5 cranking and 10ish when it barely starts, normally they are 1.9-2.0 when idle. 94 camaro, open loop program, tried new PCM, cant find any broken wires, have spark from the coil. Any help?

Thanks
P

 

Test the coolant temperature sensor in the water pump.

 

can you elaborate as to why?

Thanks
P

 

I believe his idea is that the computer thinks the engine is cold and therefore it stays in open loop and richens the mixture.

If you remove it and measure the resistance, at room temperature the resistance would be about 3400 ohms and at the boiling point it would be about 177 ohms.

Assuming you don't have codes for the sensor wiring.

 

Open loop program. Any other suggestions?


Thanks
P

 

not only is it the open loop, but a faulty coolant temp sensor can just cause massively rich conditions. its worth a shot to check, and its a simple 8$ fix.

 

Checked it and its fine, the only thing that I can think of is the PCM or the opti, I dont get the correct 1-4 VAC, I only get .75-.8 but I'm getting spark from the coil. I guess I could swap in another opti since its pretty easy to do.

ANy other suggestions?

Thanks
P

 

I really dont understand this, I checked the signal from the opti and get 1.5 VAC, which is with in the 1-4 VAC that is needed. But whn i crank it over I'm getting pulse widths starting in the 24s then dropping down to 0 after a few cranks.

Anyone have any other suggestions?

Thanks
P

 

What are you talking about?? The AC signal that will range from 1-4 VAC doesn't even go near the opti? Its the ignition control signal from the PCM to the ICM. It's on the white wire.

If you're talking about the feedback signals ( hi and low res). They don't fall into the 1-4 VAC range since they are a square wave. They can be checked by looking at them on the DC range of a multimeter and slowly rotating the engine over by hand. I look at them with a Vantage scope. Some have used the AC setting of a DVM but it's not the level they are looking for, it's frequency. The absolute best way to look at them without a scope is to rotate the engine by hand and view them with a voltmeter.

If however you have lost either one of the feedback signals, you would throw a code for that. Specifically, the low res signal which is most critical will throw a DTC 16 but will NOT set the SES. A 36 would indicate you have low res and no high res. and that WILL set the SES.

Start by putting a plug and wire in the coil. Check for spark there. If that's ok, check a few plugs for spark.