Jumpy Engine Speeds

OUMike · July 29, 2007

Hey fellas, so recently I stumbled across a problem that came back as Throttle Position Sensor. When the truck was in park and idling the rpms would jump around. After changing the TPS everything seemed to go back to normal.

Now however while cruising along at a nice and steady speed I notice my engine speed will randomly jump around. This usually occurs between 40 and 50 mph, and I don't think I've seen it happen at lower speeds.

I was thinking Idle Air Control as Mike stated in my last post, but I'm not very familiar with this part. Does this effect air at all engine speeds or just at idle?

Thanks a lot everyone.

98 Z71 SLT · July 29, 2007

I would make sure that your TPS is adjusted correctly. Do a search on this, and you can adjust TPS by using a DVOM or a regular scan tool.

IF TPS is within specs, I'd investigate a torque converter lock-up problem. Torque converter clutch apply is at the speed you specified in your post.

OUMike · July 29, 2007

I would make sure that your TPS is adjusted correctly. Do a search on this, and you can adjust TPS by using a DVOM or a regular scan tool.

IF TPS is within specs, I'd investigate a torque converter lock-up problem. Torque converter clutch apply is at the speed you specified in your post.

Is this something I can have done at AutoZone with their scan tool?

Thanks a lot!

OUMike · August 2, 2007

Okay..so. I got another code that came up as Idle Air Control. After replacing both Idle Air Control and Throttle Position Switch, things manage to level out fairly nicely. However yesterday afternoon I starting having same problem again.

When I swapped out the IAC I did notice that the connectors plugging into IAC and TPS are really worn and have become brittle. The "pigtail" connector is pretty cheap (only $13.XX) but I think the hard part is going to be actually getting the old one out.

I'm not sure where the other end connects to. Fuse box? Or does it end at the junction box on the firewall? Is there anything I should know about this job that might pose a problem?

Thanks guys.