Bucking at light throttle 60mph

[leadrofthepak]

I have a 1999 Dodge Ram Sport with a 5.2 and an automatic tranny. The truck starts good, runs good, drives good except for around 60 mph with little to no throttle it bucks like it wants to throw me out of the truck. It feels like the transmission is popping in and out of gear or something. I have done the plenum repair, new plugs, wires, cap, rotor, coil. Trans service and band adjustment. U joints are fairly recent. Most of the research I can find on this issue leads to the plenum vacuum leak. It seems like it would be a fuel issue to me since it only occurs under very light throttle. Lift the throttle it goes away, put my foot into it a little more and it goes away. Any advice would be greatly appreciated. Thanks y'all.

 

[dodge dude94]

Tried turning OD off when it happens, yet?

 

[leadrofthepak]

Tried turning OD off when it happens, yet?

Yup, still does it with the OD turned off.

 

[dodge dude94]

Well, that rules out a low rpm misfire from the equation. Fuel wouldn't be an issue, it would be an issue at WOT since the engine is pulling more fuel. I'd be putting a vacuum gauge on it to try and see what how much it's pulling at a given RPM and at idle.

 

[leadrofthepak]

Don't have one unfortunately. It is pretty darn cold out right now so hunting for a vacuum leak might have to wait for a warmer day lol. I am gonna change out the TPS and see if that changes anything.

 

[dodge dude94]

lol Alright, but that's where I'd start looking since it seems to act up when vacuum is supposed to be real high.

 

[leadrofthepak]

Changed out the TPS and (knock on wood) I haven't been able to make it surge like it was. Funny thing this internet... searching for surging/bucking/skipping/hesitation under light throttle at cruising/highway speeds does not yield many results that direct one to the TPS... however, if you search for TPS issues, wouldn't ya know it, one of the most common symptoms of a bad one is (pause for effect)... surging at highway speeds with an automatic tranny

 

[dodge dude94]

Good to hear you got it fixed!

You did have the battery disconnected though, right? That allows the PCM to clear out its set parameters and learn the new part.

 

[leadrofthepak]

Yeah, my neg battery cable never really tightens down super tight so it is easy to wiggle off. Thanks for your assistance in the matter, I am sure I will need to chase down a vacuum leak someday as it seems to be a common issue with the 2nd gen rams.

 

[dodge dude94]

Quite possible on the vacuum leak.

For your negative cable, if you don't want to replace the clamp (like I did. lol) wrap the post with aluminum foil to snug it up.

 

[leadrofthepak]

I actually wrapped the terminal with a small piece of thin copper flashing just to get it snug enough to maintain a connection. I know I should replace the connector but this works for now, mixed metals and all! My science experiment for the month.

 

[dodge dude94]

lol I know a guy that shoved a finishing nail into his. I went ahead and replaced mine last summer since I was tired of the headlights flickering at idle. lol

 

[leadrofthepak]

When I got the truck it has a wood screw holding wedged in between the strap and terminal...

 

[dodge dude94]

New clamps are only like 7 bucks for the pair you know.....

 

[leadrofthepak]

Yeah but it's REALLY cold outside, lol.

 

[dodge dude94]

I can't blame ya for that. lol Like I said, I did mine in the summer.