Engine revs between shifts

[jfcasey]

I've got some kind of IAC or vacuum issue I can't seem to pin point, and I'm looking to see if anyone has had the same issue and found a solution.

The trucks a 98 3.0 with a manual transmission.

When you depress the clutch to shift while rolling, the revs jump up ~500rpm. If you pop it out of gear into neutral, it does the same thing. I have shifted into neutral with and without the clutch and rolled for 3/4 of a mile and the engine stayed steady at 2500rpm.
Now it sounds like a idle problem right? Well, once I come to a stop, the engine idles fine, right around 900rpm and it drops to that idle the split second the truck stops moving.

I have replaced the tps, iac, intake manifold gasket, and cleaned the MAF. I have also driven with a cone filter and the factory air box and that didn't change a thing.

Any ideas?

 

[Earl43P]

Normal operation, but on the high side. If you take out a fuse that kills the speedo (I forget which one) that drop in rpm will happen as soon as you lift the throttle. That's still high tho'.

Look at the PCV elbow for cracks. Pretty common issue if you've never looked at yours. You can slather it with RTV until you get a new one.

http://www.therangerstation.com/forums/showthread.php?t=46472&highlight=pcv+elbow

Post #14

 

[Johnny_SJSU]

I got 99 and same thing started to happen to mine after I replaced the heads, mechanic to me it was normal, ive driven it like that for 3 years now wit no problem..

 

[jfcasey]

Anybody got a wiring diagram off alldata or mitchell handy for the circuit with the speedo? It would be interesting to find a way to kill this trait without loosing the stock speedo.

Its not the worst thing in the world but it gets pretty old when you are trying to save a few bucks on gas and coast places. I could understand the engine reving a little for 5 seconds or so but just flat out sticking like it does is pretty lame.

 

[Earl43P]

I have 2000, which should be close if not the same.

It's supposed to prop up the idle between shifts and uses the VSS signal to the PCM to know you are rolling. Yours seems high to me. I recall 1800-2000ish on my old 2000 3.0.

I think you have a vacuum leak.

PM me an e-mail address.

You could easily interrupt that wire to the PCM with a switch, but I think you should fix it properly first, then decide it's not that bad. Or whatever you decide to do.

I drove mine for a while with the ABS fuse pulled. It's different to actually have engine braking.

 

[--weezl--]

abs fuse pulled allows you to get more engine braking?

this does NOT sound like a vac leak to me, as a vac leak would not cause a high idle only while moving

not sure what it is though

 

[Earl43P]

Yeah, notice the idle drops just as the speedo hits about nothing.

Take away the VSS signal and that happens at road speeds, providing engine braking.

I was doing different size tires ABS / no ABS brake tests and pulling that fuse killed the speedo (VSS signal) conveniently without cutting a wire. 98-2000 4wABS uses the ABS controller to modulate the VSS signal to the PCM/speedo. That's why that fuse does it.

I don't know if 2wABS is quite the same though. I sent him schematics.

 

[jfcasey]

I got your email and sent ya one back. I do have the RABS. Its all coming together sorta though, I get a abs/brake light on the dash every in a while, after learning what yall had to say I'm going to inspect my vss and possibly replace it. I figure it may be going out and causing the ABS light and the higher than normal revs between shifts.

 

[2011GT]

I have this same exact problem. I will try pulling those fuses in the morning.

 

[2011GT]

I have this same exact problem. I will try pulling those fuses in the morning.

Bummer. Pulling the fuses did nothing to fix my problem.

 

[2011GT]

I unplugged the connector going into the rear differential. The truck now idles great and while shifting the RPMs don't hang anymore. What's the deal with this?

 

[jfcasey]

Well I believe thats the wheel speed sensor for the ABS, which that other fellow said is tied into the PCM to control the engine revs.. Thats interesting. Does your speedo still work?

 

[2011GT]

Well I believe thats the wheel speed sensor for the ABS, which that other fellow said is tied into the PCM to control the engine revs.. Thats interesting. Does your speedo still work?

Unplugging it caused my speedometer to always read zero, airbag light is on along with an ABS light.

 

[Onefunranger]

I am having the same problem it's driving me crazy has only body had the recall done and it fix the problem oh yeah I have a 2003 edge

 

[2011GT]

I am having the same problem it's driving me crazy has only body had the recall done and it fix the problem oh yeah I have a 2003 edge

What recall?