Engine/Transmission (1994 - 1998) Idle increases during braking

[Vaughn MacKenzie]

My '96 started doing a funny thing last week. Occasionally when I drop it in neutral and am slowing down for a stop, the engine idle ramps up to about 950 RPM, then drops back down to the normal 850 after 3-4 seconds. It really got my attention the first time it did it. It usually happens after I've been braking for a few seconds and am close to a complete stop. It's not an instant spike like a jab on the pedal, but a smooth increase taking 1/2 - 3/4 second.



The throttle linkage feels fine, nothing appears to be binding up, but I'm puzzled why it acts like someone's gently depressing the accelerator when my foot is on the brake. Just a tad bit spooky



Any thoughts? Maybe it's just possessed :-laf



Vaughn

 

[DSiemens]

Sounds like something is sticking or dry from lack of lubrication inside the inj pump. Are you using a fuel additive?



Dan

 

[Turbo Thom]

Check the ball joints on the rod. Usually, something about the position of that one seems to get a little more water than the front one. It only takes one spot of rust or dirt to make it stiff.



. . Preston. .

 

[Vaughn MacKenzie]

I'll check over the linkage Thom. Hope it's not something with the pump Dan, I always use Amalgamated.

 

[K5IP]

Since both the brake system and cruise control interface with the vacuum system, there is a possible common link here. How, I can't imagine but you might disconnect the cruise control cable and see if it makes any difference.

Rog

 

[Vaughn MacKenzie]

K5IP I am going to try that. It is getting worse and it's pretty annoying. The engine was really jumping erratically at idle yesterday like someone keeps tapping the throttle and my foot is on the brake.



The brakes work great, so I don't think it's a vacuum problem.



Vaughn

 

[Evan A. Beck]

Sounds like the rack is hanging up a bit, or the governor is out of whack... Full pump rebuild time...



P-pumps are dropping like flies around the shop. Done 6 rebuilds in the past few weeks. Plus we got three 5. 9's in need of rebuild as well. It's shaping up to be a good winter!

 

[Vaughn MacKenzie]

Evan I wonder if there's some real garbage fuel going around these days? I've been using almost double the amount of fuel conditioner on every fillup the last few months but I wonder if it's a coincidence you're having to do quite a few or if the fuel quality is taking a dive?



Vaughn

 

[Evan A. Beck]

Well, its rarely a fuel related problem with these past few trucks. One had a pretty scored up P&B, but thats all. Seems most of the problems lie in the governor linkage, etc. Fuel has to get pretty bad to ruin a P-pump, but I would not rule it out. Sometimes it only takes a small amount.



On another note, we had an 04 with 6 stuck open injectors. Removed and checked out the CP3 too, and it did have some signs of damage. Turns out the guy got a load of contaminated fuel, and had 6 fleet trucks all with severe damage. Lawsuit is in the works as of now. 6 trucks times about $2,500 in damge to each one... It adds up fast.



BTW, are you running dual throttle return springs?

 

[Forrest]

On another note, we had an 04 with 6 stuck open injectors.

Wow ... i'll bet the Dodge database is full of that problem. Brutal.

 

[cahammer]

i have the same problem as vaughn but mine will stick at a little over 1300 untill i let out my clutch while its in gear i have redone my bushings in the linkage and checked and replaced the ball joints and still cant figure it out would my 4kgsk be missing this up thanks in advance