I posted this in the General Tech section and somebody told me to post it in here to see if anybody could help me. So here goes...

Car: '87 Z28 w/ V8 and TPI (don't know if it's a 305 or 350)

Problem: Car idols fine when first started, but as soon as it warms up the rpm's start bouncing up and down. It basically goes from idol to near dieing, back to idol etc. When you press the gas pedal, the car bogs down like it basically shuts off, but as soon as you take your foot off the gas, it goes right back to idol like if it's fine. If you mash the gas real hard it will rev up (crappy) but then it will bounce up and down again (rpm's) until you take your foot off the gas. Car throws a code 45 (oxygen sensor rich).

Fixed so far: New Spark plugs, New Wires, New Fuel filter, New Rotor, New distributor cap, Cleaned the IAC, checked the fuel pressure (good), Checked the TPS voltage (good).

Just looking for some suggestions or advice in case somebody has heard of anything like this.

 

Well I had a TBI 305 do that and it was the coolant sensor gone bad . It created a rich condtion . Check that out ( cheap) . Or ( this is reaching a bit) you may have a problem with the cold start injector ?

 

First off i would check the resistance on your injectors, take a multimeter and touch both contacts on the injectors should be around 16ohms or so, under 10 is junk. Another posssibility is the ecm, check to see that your timing is advancing with a timing light. I would start there should only take ya 10 minutes or so to check those out let us know what you find.

 

Okay...I will replace the coolant sensor this weekend.

Of course first I will test the injectors, but I'm not really sure how to use a multimeter. I have one, but I don't think I have instructions on how to use it. Is there a wright up or anything on how to do this? I also don't have a timing light, but I will rent one this weekend and check that as well.

Thanks guys! Anybody else have any ideas while I'm at it?

 

on the mutlimeter, not to hard to use. also should check fuel pressure

 

when you said it warms up, how hot is it exactly getting?

How old is the O2 sensor? Might be another thing to try and replace thats easy. If its going into closed loop and running off the O2, and the O2 is reading funky, it could cause it to run bad. Just a idea.

 

Dan...Fuel pressure is good, already checked.

Matt...When I say warm up, I mean maybe like 5 minutes or so. The temp gauge doesn't work, but the water seems to flow and the oil is fresh and filled, so I can't imagine it's overheating.

Don't know how old the O2 sensor is....just bought the car, but would imagine it's pretty old. Will look into replacing that this weekend also.

 

If its only running maybe 5 minutes i doubt thats the problem. The car shouldnt be using the O2 that early, should still be running of what the computer tells it to.

 

check out the South Central regional board. There's a big Houston crowd that gets together once a month. There's some guys there that could give you excellent advice on a TPI setup.