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Unholyskorn86 10-30-2010 06:08 PM

RPM Surge!
Ok, this is getting to me. So I am going to beg for help now.

Recently my 99 WJ started acting odd. When I drive it gently, (and only gently) my RPM will surge about 200-400 RPM always around the same spot/gear.

I will always be able to replicate this by driving in a straight line, putting slight pressure on the gas and holding it almost steady or steady.

It will shift normal, then again. THEN it will surge right after for about 200-400 RPM tops. It is SOOOOO annoying. It feels like a slight jolt of power, then back to normal RPM.

I know I am being vauge, but don't know how else to explain it. If I beat the Jeep or drive it a little heavier then I want to, it will NEVER surge. Only when I feather the pedal like less then a quarter. Enough to go through all the gears at a nice pace.

Surge goes from a dead stop, shift.....shift surge...then back to normal driving RPM. It does not feel violent or clunky, more like a shot of gas or something to make it hum/ slightly surge for a second no more.

Please ask any other questions you can think of to help me solve this.

List of things I have done recently....

Transmission fluid and filter change.
Transfer Case and tranny seals redone and case cleaned.
Installed Ported Throttle body and ALL NEW sensors.
Tuned with Flashpaq Jeep 3875.

The problem seemed to present itself right after the throttle body was installed. But was assured it could not cause these types of problems, only maybe amplify the problem to where it could be noticed?

Flashpaq and throttle body sensors came after problem arose. Throttle body itself then problem arose. Tcase and tranny where done before. About a month before to be exact.

Thanks for your help in advance!

cheapjeep 10-30-2010 06:28 PM

Re: RPM Surge!
Hey Skorn try the flashpaq in diagnostic mode and see if it gives you any codes as this could be a number of things from tps to converter lockup also does it do this in 1st gear pulling out as this is the only gear that the tc doesn't lock up in?

Unholyskorn86 10-30-2010 06:35 PM

Re: RPM Surge!
It never does it in 1st. Same spot every time.

Shift......shift surge. Same area all the time.

If I do it around a corner...lets say at a four way stop....the minute i straighten it out and hit that spot it'll do it too..... Around 30mph and 1500-2000RPM around.

Goes hum up 200-400RPM and then back to normal.

The thing drives like a champ. How do I run the flashpaq in diagnostic mode?

cheapjeep 10-30-2010 06:44 PM

Re: RPM Surge!

Originally Posted by Unholyskorn86 (Post 293287)
How do I run the flashpaq in diagnostic mode?

I think its in the first screen.Tune, diagnostics and something else I cant remember

Unholyskorn86 10-30-2010 07:28 PM

Re: RPM Surge!
No DTC at all.

cheapjeep 10-30-2010 09:07 PM

Re: RPM Surge!
Well that probably rules out any tranny suspicions. Still got your old tb? Maybe try that again to rule that out.

Unholyskorn86 10-30-2010 09:40 PM

Re: RPM Surge!
That is gonna be my last bet. Too lazy to keep switching stuff out. Any other ideas? Tranny would give trouble codes for worn packs or ageing TC?

cheapjeep 10-30-2010 11:02 PM

Re: RPM Surge!
Yeah there's a bunch of tranny codes for lock up,speed sensors,input vs output speed(slipping),solenoids,etc.
If it was me I'd try the tb next to make sure you're not
chasing ghosts.That and I'd drink ALOT. Good luck bud
Let me know how it turns out.

Unholyskorn86 11-01-2010 02:51 AM

Re: RPM Surge!
Still haven't got around to doing anything yet. I have heard there might be a way to flush the torque converter because that is separate? Maybe when I had my fluid and filter done on the tranny...the converter needs to be done too?

Because I know when I drove it after having that done it drove SOOOO much smoother. Maybe it's just something I'm picking up now from it being so smooth from that and I need to do the torque converter also?

Dunno just read it online somewhere I have no idea. Can you flush it easily if that is the case?

I also note that when I had this done the person said it looked clean in the pan really....

Thanks again!

Unholyskorn86 11-01-2010 05:34 PM

Re: RPM Surge!
No one has a 1999 Grand Cherokee with a torque converter? :(

cheapjeep 11-01-2010 06:45 PM

Re: RPM Surge!
You could take it somewhere and have it hooked up to a tranny flush machine for about a $100 but you're loosing the new fluid you already have changed and probably a filter again.I truly believe if it was a tranny issue it would have thrown a code by now.When my wife's went a few years ago I had a couple different codes.I hate to keep harping about the throttle body but in your first post you said that is when your troubles began Me,that's the first place I'd look. Thats the first rule of troubleshooting.Who knows maybe its just not compatible.Throwing more money at it isn't always gonna fix
things. Good luck bud

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