Franko

93 5.8, 110k miles. Driving on a short trip 16 miles one way, not much of the problem shows up. Return trip, at about 7-9 miles, when feathering throttle, get a jerk as if motor died and caught right back. Mainly felt in drive train. Closer to home as speed limit drops, throttle doesn't seem to decrease as I let off pedal. The other day, when I turned on my street and into driveway and put in Park, RPM was 3000 and just had to shut it off.. Day or two later, when I had to leave, cranked up just fine. My first thought is TPS but I don't know if being this old even has one. Next thought is vacuum. Don't know how too run codes but can learn. OBDI. It always has to be something crazy with me, but any help in getting me to the problem would be appreciated.

PerryB

Step one would be to clean the throttle body. I suspect it has a build-up of oil varnish/dirt that's making the throttle blades stick.

raski

Also, idle air control. When you clean throttle body, remove the solenoid and clean the pintle and its bore of carbon buildup. Chunked carbon can be causing it to bypass more air into intake and raising RPM.

Steve83

Before anything else, pull the floor mat back from the gas pedal. It's a known problem that has spooked many owners of these trucks.

Never clean the TB - cleaners will strip off the coating that makes it tolerate the buildup of sludge. Read the cautions in this caption:


(phone app link)

On the Right side, look at the 2nd label down, then look closely on your truck's TB:


(phone app link)

The IAC must be disassembled before cleaning. If the IAC can't be disassembled, it shouldn't be cleaned.


(phone app link)

techrep

iTrader: (1)

Franko

Thanks for the answers. Gas pedal is clear. Will see if TB is problem.

raski

Correct, I have cleaned mine several times with this product with no stripping of the coating. That was an issue back in the day before the proper cleaning products were engineered.

Steve83

You can't see the coating - certainly not when it's under the sludge, or when it's dissolved off - so you can't know if it's still there, or gone. In any case: the sludge isn't hurting anything.

Franko

A little slow, but cleaned the TB yesterday. It's sucking so much air sounds like 2 J-79's in an F-4. TPS gave me a little trouble, but got that straightened out too. It was so dirty. Where does all that oily mess come from. I noticed the intake is same way. Not in the mood to pull that and clean properly. Thanks to all for your input. Truck is running about 500 hundreths too high but I can live with that.

Steve83

The sludge behind the TB comes from the PCV & EGR. It's normal, and not something that needs to be removed. If it's forward of the TB, it's coming from reverse-flow through the PCV breather, which indicates either a blocked (neglected) PCV valve, or excessive blowby from the rings.


(phone app link)