Help- Rough Idle, power lost/shift delay

I'm Kate, I live in Northern Colorado and I am in a little deep with my Jeep.

Please help.


I have a 2000, 4.0 and it's given me nothing but problems lately. Just got a engine replacement done and the guy that did it for me did one of the worst swaps ever. Took it back 3 times(just one of the stupid decisions I made) for stuff I found wrong with it and they still didn't put the torque converter in right. After a shaky ride back from Utah, I am now a transmission deep as well.


The newer engine has 95,000 miles on it, the transmission has about 112,000. So I just got it back from the shop(different from the engine shop) and I notice I have a rough idle. Then she decides to slowly lose power, RPMs not reflecting the gas, just not moving past an idle crawl after I try to accelerate from a stop. I ran it 90 miles before this point in the trip so she was warmed up.I get it to the side turn it on and off had to hit the gas a little to get her going.


Next day I read up on common problems and see the IAC/ throttle carbon build up being a problem. So I cleaned up the throttle body and ran Seafoam. I'm driving it around it seems to be doing ok, shifting nice not slowing, except for tonight.


I went to go to work and it wouldn't start until i pushed the gas a little, then ran it to work seemed to lose power/little shift delay periodically. After work started it up and it gave me shift delay into drive.


Any thoughts?


I love my Jeep and I'm not willing to give up even though that may have screwed me over, I can't think of any vehicle I want more(in my price range of course). Not to mention, I've put too much money into it to give up now. Since I'm hopefully done with the huge (hard to do by myself) stuff, I want to do this on my own. I'm sick of giving other people money to make a bigger mess of my xj. I also can't keep harassing my boyfriend for help or he's going to end up burning it when I'm not looking.


I have a realllllyyy basic knowledge of this stuff so go easy on my wording in this, I'm in the learning process still. I'll be really appreciative of any advice.

wow, that's a lot of issues! It's going to be hard to pinpoint any one thing, but I can get the ball rolling a bit. What year jeep did your new motor come out of? There can be differences with the computers that could be causing some of this stuff. The loss of power and not shifting at the right time is leading me towards your catalytic converter being clogged. Mudderoy was having some of those issues caused by that. Being hard to start, hmm... when was your fuel filter/pump assembly last changed? It's no fun because you have to drop the gas tank :( Timing could also be off, the motor could also have issues... was it compression tested at the shop?

Not having all the vacuum lines hooked up or just having a vacuum leak in general could add to your issues too. Is your check engine light on?

check ya tps ....

It is a lot of issues, it's making me a vehicular-hypochondriac.

I'll double check the vacuum lines and give the TPS a shot tomorrow.

Check engine light isn't on, both the motor and transmission were out of the same year as chassis. Supposedly the compression was tested and checked out fine, but I won't count on it.

I can check the catalytic converter, I was missing hanger by the cross member causing it to rattle, fixed the rattling but could still be damaged.

I have no clue when the fuel pump/filter was changed. I've had it for about two years, so not in that range at least. I can give that a look after I check out the others.

Thank you guys, ill post up how those go.

As wayne said. Alot of those problems are symptoms of a bad TPS.

I think the throttle position sensor is not operating properly too. But I have questions. You said the cat was rattling. Does that mean it was rattling inside too? If so, it is toast and needs to be replaced. How long has it been since the O2 sensor was replaced? Also, what year is the computer that runs it and what year is the engine?

I would not replace the Cat just yet just empty it out first. 2nd on checking Vac. hoses.

Sorry, I never responded on this but the TPS fixed this particular time it happened. The O2 wires had some damage too got them all straightened out and it was on to the next problem. A very later thanks everyone for the advice!