engine rpm surging while on cruise control

[lsu-kev]

coming home yesterday my 2005 hr admiral with the gmc 8.1 liter was set on cruise doing about 65. engine was turning 2200 rpm but kept surging up to around 2600-what could be the problem here guys?

[RottenRalph]

Just a couple of questions.
On Sept 19th your ABS light was on. Is your ABS light still on?
Does the tranny act like it's shifting or slipping?
Could it be the torque converter going in and out?

[George Z]

Fuel Filter.

[lsu-kev]

rottenralph-abs light actually was not on on the way home. have not had the recall done yet-on a wait list for that. transmission seemed fine-very low miles on this engine only driven around the new orleans area-very flat. is the fuel filter as easy to change as the oil and filter and if so how do i get to it?

[DriVer]

Quote:

Originally Posted by lsu-kev ... is the fuel filter as easy to change as the oil and filter and if so how do i get to it?

The fuel filter is inside the chassis rail directly behind and above the rear axle on the left side of the vehicle. You are not going to be able to buy the filter over the counter unless you go to a Workhorse dealer.

You may have to seek alternate resources for the fuel filter.

[lsu-kev]

hey driver-can you buy that filter from napa or only a workhorse center(i don't have one of those anywhere close to me)

[Clay L]

The 2003 filter was the old style - one inlet and one outlet type - and I got mine at NAPA. Driver may be thinlking of the newer three inlet/outlet type .

[UFO Pilot]

OP said he has a 2005 Coach. Check out Oemy's Web Site - Fuel Filter Adpater for stock filter or adapter to use "old" style filter.

[DriVer]

Quote:

Originally Posted by Clay L Driver may be thinlking of the newer three inlet/outlet type .

Bingo!

[sknight]

That's about the correct RPM range for the torque converter clutch to be unlocking/locking. If the load changes that's the first thing the engine does before a downshift. Could the angle of the road have been changing in synch with the RPM change?

[Clay L]

Quote:

Originally Posted by wthomas1 OP said he has a 2005 Coach. Check out Oemy's Web Site - Fuel Filter Adpater for stock filter or adapter to use "old" style filter.

You are right. I somehow misread it as 2003

[lsu-kev]

sknight-road angle was not changing. completely flat highway from baton rouge to new orleans-thats why it has me concerned. up and down hills i would expect that.

[sknight]

Quote:

Originally Posted by lsu-kev sknight-road angle was not changing. completely flat highway from baton rouge to new orleans-thats why it has me concerned. up and down hills i would expect that.

Could be the clutch doing it, the trick is now to figure out why. We can say it isn't the road, so that leaves the coach itself. Easy, wasn't it?

OK, we have two possibilities. I'm going to assume by the year model you have an Allison trans. That's controlled by a TCM separate of the ECM.

Since you didn't say it was chattering we're going to assume the clutch itself and it's oil feed circuit is fine. That leaves electrical. I've seen the solenoids themselves overheat and randomly open and close themselves. Close, get hot, open, cool off. Wash, rinse, repeat.

The other possibility is the TCM is commanding it on and off for some reason. That runs the gamut. It could be a faulty but still in range TPS, ECM issues, a programming fault that decided to appear now, etc.

First things first, someone needs to watch it with a scan tool to see if it's being commanded off and on. If so, then the issue is in the control side. If not then the trouble is in the mechanical side, wiring from the TCM to the solenoid.

All these things can happen without setting a code if conditions are just right.

EDIT-Something that's very simple and easy to diagnose yourself. It very well could be an out of adjustment stop lamp switch. The TCC opens when the brakes are applied, if you have a switch that's just "Right there" being on or off then every crack in the road could make it send a signal the brakes were mashed. Have someone follow you and see if the brake lights randomly come on or come on with just the lightest touch.

[Dagwood]

I believe there was a previose thread on here and someone suggested an abs problem would do the same thing. The abs sensors could be marginal and givin g an erronniose ( i give up on that word) signal.