90 4.3 rough idle, runs rough.

[BruiserCruiser]

bought the truck non running. Traced it down to a coil, replaced that and she fired up... but it idles very rough (sometimes dies), dies when you put it in gear, and drives like butt.

It has new plug wires, plugs, dist cap, rotor.

Ran the codes, the only one its throwing is TPS low signal.

I can't imagine that would cause it to idle/run so rough. It seems to be running really rich (like it will murder you if you leave it running in the garage even with garage door open.

Anybody every have a TPS cause such idle/driveability issues? It's cold and snowy outside, but I guess I better go out there and do some testing with a multi meter.

 

[WhiskeyTango93]

Ive never had a tps affect idle on a TBI, unless its stuck open a bit ( speculation) I'd suspect a stuck injector or bad FPR.
Double check the firing order?

Oh yea, check the IAC

 

[BruiserCruiser]

So just to make sure I did this right... Blue wire from the tps should be around .5 at an idle? Well when I test it, I'm getting 12v ground. I unplugged the sensor and tested the blue wire again, and it was still 12v ground.

About to unplug the computer and and test the wire again. If its not grounding out with the computer unplug, then replace the computer????? If it's still grounding out with the computer/sensor unplugged, then a short in the wire?

 

[BruiserCruiser]

With the computer unplugged it's no longer grounded... Computer time I guess?

 

[Schurkey]

Stop testing with a multimeter, start testing with a scan tool.

Most of what you'd want to look at is right there on the data stream.

Beyond the scan tool, verify fuel pressure, verify cranking compression, and make sure the usual "tune-up" pieces are in good condition--cap, rotor, plug wires, plugs, air filter, fuel filter, vacuum hoses, PCV valve, engine grounds, etc.

Just because stuff is "New" does not mean it's "good".

 

[thinger2]

A bad TPS will definetly cause performance issues on a TBI.
The ecm uses TPS input to adjust the air/fuel mix and timing.
Set everything else first.
Base timing egr vacuum leaks fuel pressure etc..
All that
Then check the tps.
Some are adjustable. some are not but you can make them adjustable.
And, as mentioned above, new parts are not necessarily good parts.
Once you diagnose a part as being bad,
You need to do the same procedure again to make sure your new part isnt bad.
They quite often are.
They dont make any of our parts in the US anymore and the GM, Delco, Delphi label doesnt mean a damn thing.
That box your part came in that is labelled "made in america"
That means the box was made in america, not the part
"assembeled in america"
That means the box wasnt even made here.
They ship the parts and the box here just stick a flag on it.
An "American Owned Company"
Thats a shell corporation trading on Nasdaq but owned overseas.
But, the one thing you really dont see anymore that used to be real common?
The Union Lable
When is the last time you saw a flag waving red white and blue product with a union endorsement
That is my rant for today