Jeep TJ - RPM's Slow to Reduce when Shifting

[crusty]

Hi Folks.
I have a 04 TJ Sport - 6 cyl. The RPM's are slow to reduce especially when the engine is cold when I push the clutch pedal while shifting between 1st and 2nd and again between 2nd and third. I've cleaned the throttle body and AIC motor. My next step is to check for vacuum leaks but I thought I'd check with others to see if there is something more likely causing the problem.
Any suggestions are appreciated.
Thank you.
Crusty

[binare]

Sounds fine to me. Is it sticking at a certain rpm?

[crusty]

Not sticking, but takes about 4 seconds to drop from 2000 RPM to where I can get a smooth shift at 1200 RPM or less. If I shift immediately, I can feel a sticking point on the shifter.

Cheers.
Crusty

[binare]

Is this your first Jeep? These things arent cars... take your time shifting... just like a truck. That being said... you shouldnt have to wait to shift no matter what rpm.

[crusty]

This is my first standard TJ. When I first bought it last summer it shifted smoothly and I didn't notice if the RPM's quickly dropped when shifting 1 to 2 and 2 to three. Now I noticed the RPM's not dropping quickly and the hard shifting if I don't wait for them to drop. By hard shifting I mean that you can feel a distinct engagement on the shifter like it's not quite meshing.

Cheers.
Rick

[birdo]

Ok...here's a few suggestions you might want to consider.
1. Any chance the throttle cable is sticking somewhere along the way?
2. Could your gas pedal be sticking especially if it's cold?


Regarding shifting.....
Do you still have a rubber shifter boot? That boot gets really stiff when the temperature drops. I got so tired of mine that I got rid of it and had a friend make me a nice new soft leather boot. Best thing I ever did. Huge difference.
Change your transmission gear oil out and replace it with synthetic. Makes a world of difference and much smoother shifts.

[crusty]

Thanks Birdo. I've checked the gas pedal and cable and they are not sticking. I changed the tranny oil to royal purple synchromax last week and no change. Maybe I'll remove the shifter boot and see if there is any differance. It's funny the RPM's drop quickly shifting from 3 to 4 and from 4 to 5 but are slow dropping from 1 to 2 and from 2 to 3. I was thinking it's maybe the TPS but why would there be a differance in RPM drop between different gear shifts.

Thanks for the advice.
Crusty

[birdo]

Weird......now I'm thinking vacuum leak as well....but it doesn't explain the difference from one gear shift to another. Any chance the throttle return spring is damaged, worn out, or broken? One other thing and this could be a longshot......I wonder if there's a problem with the ECM (engine computer) but it's not throwing a code. You could try disconnecting the negative terminal on the battery and waiting 10-15 minutes. Then reconnect and go for a spin and see what happens. This gives the ECM a bit of a re-boot. You said this happens usually when it's cold? Next thing I'm thinking is a faulty O2 sensor. Any idea as to how long yours have been in? When mine failed the engine would run like crap until it warmed up but when I let my foot off to shift, mine would cough and buck....still...if your originals are still on and you have a whack of miles, it maybe something to consider.

[crusty]

Hi again Birdo.
I think the throttle return spring is good but I'll check it again. I hope it's not the ECM. OBDII does not indicate any codes. I've tried disconnecting the battery overnight and found no change. The jeep has 120000K on it and I'm pretty sure the 02 sensor has not been replaced. Do you know if it's possible to test it or clean it? I'm thinking of checking for vacuum leaks using a plumbers propane torch but I won't be able to get around to that for a few weeks.
Thanks for all your suggestions.
Cheers.
Crusty

[birdo]

Well.....your O2 sensors have probably reached the end of their life. There are 2 on a TJ...one is before the cat and the other is after. There's no real test for an O2 and in my case, they never threw any codes. If you want to change them they will need an overnight soak in Liquid Wrench and you're gonna need a 22mm or a 24mm (memory fails me)  open ended wrench and some muscle and/or a breaker bar to loosen them off. Don't forget to disconnect the electrical connectors) I have a 3 inch suspension lift so getting to the sensors for me was easy. This may be the sort of thing you might want to take to Jay at Chanda to have done. Get OEM sensors from Jeep. They last a lot longer than after-market ones. I had an after-market one crap out after 100 kms. Sensors run about $80.00 each.

This may not be the cure for your issue but it is one of those things you're gonna have to address pretty soon.
Also, Jay can run a probe over the ECM to see if there is anything sinister going on in there.

Good luck.