Well, after a few weeks of lurking around using the search engine I decided to join up so I could take part.

So here's the deal. I have an '88 Camaro,2.8L MPFI.

I bought the car a few weeks ago from some ******* crackhead. If you saw the car, and what he had done to it, you would understand why I say that.
When I started working on the car last week I pulled several codes. I've eliminated all but two of them. I'm still getting a code 15 and a code 21. Coolant Temp Sensor and Throttle Position Sensor. Today I replaced the CTS, Unplugged the battery for 10 minutes to reset the codes.

Hooked everything back up and started it up. It didn't run 5 seconds and the SES came on.
Shut it off, and pulled the codes again. Same codes.

So I guess at this point, my questions are these:
As far as the Code 15, What am I missing? The Sensor has been replaced, what else could it be?

As for the Code 21.
I hooked a voltmeter up to check it out. The highest I can get the reading on my Fluke meter is .057 volts. Haynes is calling for .54. My reading at WOT was .064 so I'm going to assume that the TPS is shot. Bummer.

If anybody has any ideas or thoughts, I'd love to hear them.

 

Replace the TPS and see what happens.

 

i've seen the connectors for the cts fail before (wires broken inside insulation)

 

AND make sure that the geniuses at the auto parts store gave you the coolant temp sensor for the ecm and not the sending unit for the gauge!

 

Where was the coolant temp sensor located that your replaced? in the back of the head on the pass side or in the intake under the throttle body?

 

It was in the intake under the throttle body.

 

That sounds like the right one, but it shouldn't set a code that quickly. The ECM does allow for engine warm up. I'd suspect a damaged wire, probably shorted somewhere to ground or completely open, is the cause. Double and triple check the pins in the connector as they are cheap and need to be tightened up when the sensor gets replaced sometimes.

Definitely replace the TPS.

 

Well, I replaced the TPS. Hooked up my trusty Fluke meter, and nothings changed. Still can't read anything over .056 volts on the initial setting. When I go WOT I get a whopping .030 volts.

I double and triple checked the connections on the CTS, I'm almost certain they are making a connection.

While crawling around under the car I did find something interesting though. Coming out of the wire harness running under the engine on the crossmember directly below the PS there are 4 wires sticking out of the harness not connected to anything.Green/white,Light Blue/black,Green,and Black.

The only thing I can find not plugged in is the A/C compressor.

Any ideas?

 

Better check the wires going to the ECM and the TPS. Also, you better check all of the connections on the way back to the ECM in the harness.

Sounds like you got hacked by a former owner...

 

Well, I've spent the better part of the day today following/checking wiring and plugs. (you know, some of those plugs are a bear to get to)

I cannot for the life of me find anything out of the ordinary. With the exception of the 4 wires I mentioned in the earlier post, I cannot find anything.

When it starts up it is running SUPER rich,backfires through the intake if you even think about touching the gas. Once it has warmed up for about 10 minutes, the backfiring goes away but it still runs rich.


I am still getting the same codes from the ECM. 15 & 21

I'm really starting to get frustrated.

 

http://www.autozone.com/az/cds/en_us...rInfoPages.htm


Looks like the green/white and light blue are the ac, the diagrams might help you out. Good luck

 

Next thing to check is the MAF. It can make you get horrible mileage and the rest as well.

 

Backfiring like you're describing indicates a tps prob. Have you checked out the fuses? both the tps and coolant sensor ground to the same area, maybe you've got a short...

 

Checked the fuses. They checked out fine.

Do you think that a poor ground might cause a low voltage reading? Kinda like when your headlight ground is bad the bulb is very dim.

I ask because of the very low voltage I was reading on the tps. It didn't change with the new tps so I'm inclined to think that it isn't the sensor so much as something else. Like the wiring.
Should a person be able to take a voltage reading off the CTS? If so, how much voltage should there be?

 

A bad ground is a possibility. You can get a reading off the cts, but it varies with coolant temp. I have no idea what voltage correlates to what temp.