TPS and drivability loss

[dtownmikebrown]

I'm wondering what the symptoms of a bad TPS are. Ever since the car has been running I've had an issue that feels like a misfire or a fuel cut and I'm having a difficult time trying to diagnose it. Sometimes it will rev up and make boost and then sputter out, sometimes it won't make boost at all and cuts out around 3k rpm no matter what I do.

 

I've already serviced the distributor and replaced the vacuum advance unit, replaced the coil, replaced the injector clips and had the injectors flow tested, replaced the fuel pump, cleaned up the grounds and fusible links, etc etc...It all needed to be done, but I'm surprised that none of it has helped at all.

 

I did the TPS/ISC reset procedure not too long ago before I fixed all the ignition stuff. I had a voltmeter attached to it and it read .5v at idle all the way up to ~4.8 at WOT when I was finished. That didn't seem to make much of a difference. Now that I've got the LED check light hooked up its giving me 5 blinks for the TPS. When I unplug the TPS entirely it doesn't seem to make too much of a difference. I dunno what else could be causing it at this point.

[Starfighterpilot]

Have you removed the round rubber orange cover inside of both ends of the TPS electrical barrel connector and checked for internal corrosion or broken wires?

 

Is the plastic female TPS shaft connector to it's TB shaft male "tang" broken? Gotta remove the TPS to verify this. Make sure that you index the TPS housing to it's TB mount before you remove it so it goes back in it's correct location during reassembly.

 

Let us know what you find.

 

For What It's Worth.

 

KEN

[dtownmikebrown]

OK, I took all the plastic connectors off of all the parts on the throttle body and inspected and cleaned where necessary. The engine is still idling right around 900rpm when warmed up and I'm getting the proper .9v reading from the ISC. I'm getting the same voltage reading from both halves of the TPS connection, but now it's doing some weird stuff.

 

-If I take it off the throttle body and turn it by hand I get readings from 0 to 4.95V, but a few times I caught it sticking at 4.3 and not going any further. Maybe I just found part of the problem right there.

-When its attached to the TB I can't get it to go past around 0.2V when it's turned all the way clockwise. I know I've got it positioned correctly because if I open the throttle by hand or put tension on the cable I can get the voltage to go the rest of the way to 4.95V.

 

So it looks like the TPS is malfunctioning intermittently, but why the low voltage at idle?

Edited May 7, 2014 by dtownmikebrown

[Starfighterpilot]

OK, I took all the plastic connectors off of all the parts on the throttle body and inspected and cleaned where necessary. The engine is still idling right around 900rpm when warmed up and I'm getting the proper .9v reading from the ISC. I'm getting the same voltage reading from both halves of the TPS connection, but now it's doing some weird stuff.

 

-If I take it off the throttle body and turn it by hand I get readings from 0 to 4.95V, but a few times I caught it sticking at 4.3 and not going any further. Maybe I just found part of the problem right there.

-When its attached to the TB I can't get it to go past around 0.2V when it's turned all the way clockwise. I know I've got it positioned correctly because if I open the throttle by hand or put tension on the cable I can get the voltage to go the rest of the way to 4.95V.

 

So it looks like the TPS is malfunctioning intermittently, but why the low voltage at idle?

 

Low voltage at idle may be caused by the bad internal TPS rheostat. That portion of it at idle RPM"S may be pitted. You need to get a good used TPS and see what happens then.

 

For What It's Worth.

 

KEN