Engine/Transmission (1998.5 - 2002) Surging while on cruise control

[ILIANBG]

Hi everyone. Today I felt something that I never felt before. I turned the cruise on, and felt surging-kind of on /off power. Almost like I was stepping on the gas pedal and letting it go. I almost never use the cruise, but the time that I used it before, it worked perfectly. I first felt it on a very bouncy stretch of the freeway- some stretches are concrete and it's the expansion slots that make the rear end bounce at some speeds when empty. I thought it's a loose ground somewhere, but only happens when the cruise is on. So I do not think it's a bad ground.

Has anyone seen that? What could it be?

Thanks for all of yours help.

Ilian

 

[Chief USA]

Have you checked for any codes?

 

[ILIANBG]

Haven't checked yet, will do tomorrow.

 

[Mikey-KE7LBB]

I experienced something similar with my 92 and it was a leaking vacuum line that controlled the actuator and frayed cable catching. I just use my foot and a "fuzz buster" now :-laf

On my 01 the only thing that makes it surge with cruise is when the Quad is turned up past 4 and a friend had the same issue with his Smarty turned up.

 

[ILIANBG]

Checking with the ignition key there were no codes stored. So I have no idea what to look for. I will check vacuum connections I guess. I thought the cruise on these trucks is not vacuum operated. It's a manual transmission, 2WD truck.

 

[Chief USA]

Have you tried the cruise control on straight and level highway? To some degree, it is normal for the cruise control to create a strong surge of power to maintain speed. This is much more pronouced on steeper rolling roads. On staight and level roads it should not surge and maintain a nice smooth pace.

 

[PC12Driver]

I thought the cruise on these trucks is not vacuum operated. It's a manual transmission, 2WD truck.

You are correct. The cruise on your truck is directly controlled by the ECM. Software doesn't wear out, so it has to be one of the sensors (one of the speed rings or the MAP would be my first guess) or the injector pump itself. It's odd that you don't feel it with the pedal though. Any fueling mods besides the RV injectors?

 

[ILIANBG]

Fuel mods:
Draw Straw
Vulcan's 1/2" lines from the tank to the VP-44
Airdog 100
Stock fuel filter and canister still in place and functioning

That's it. Will go and test again on smooth portion of freeway to see if that'll happen again. Thank you all, as always.
Ilian

 

[mhenon]

... . and felt surging-kind of on /off power. Almost like I was stepping on the gas pedal and letting it go... ...

Could be the APPS too.

Mike

 

[mhenon]

Opps. . sorry. You said you where in cruise control. Scratch the APPS.

 

[ILIANBG]

I did a search. What others reported, it could be a speed sensor, mounted I guess at the rear end. I have to check that. I would make sense- from all that bouncing.

 

[muchsnow]

Cruise control bouncing....bucking...

I did a search. What others reported, it could be a speed sensor, mounted I guess at the rear end. I have to check that. I would make sense- from all that bouncing.

Did you ever fix this somehow? Mine is doing the same as described. . bucks on cruise comming over a crest right where it would normally reduce throttle input... . works fine when using your foot.....

 

[ILIANBG]

I have not changed anything yet. But to be honest, I've only used the cruise few times since then- haven't had a chance to go on long trip. Most of my driving is street, stop and go.
The few times I've used it it did not do it. Maybe the truck "forgot" it was a problem before. I think I bought a speed sensor and I have it somewhere
Let us know what you find out, I will be interested to find out.
Ilian

 

[muchsnow]

I just haven't used it at 75+ for a long time. That's when it showed... . I ordered a speed sensor... . Probably won't happen anymore now...

So far it's been repeatable... .....