I have a 1990 Jeep Cherokee, 4.0L Inline 6. I recently purchased the car used with 140K miles on it. When I test drove the car, it ran great. But after buying it, I got on the highway and it started hesitating really badly under power/acceleration. It felt like the engine was misfiring.

The car is lurching under acceleration after 1) being driven for 30 minutes or more and 2) idling for 5-10 minutes or stop-and-go traffic. I have replaced wires, coil, and distributor to no avail.

Could this be a grounding issue? After reading around some it seems that this is what most people suggest. How many ground points are there that I should check?

 

havent read but the first sentence... but ill bet its the o2's

 

If only O2 sensors were the answer for everything...

It sounds like it may be your TPS. That would cause the lurching. As far as the idle, you can clean the IAC valve and see if that helps. There are some great write ups with pics on how to do a throttle body/IAC cleaning. Also testing with a multimeter is a great way to trouble shoot. The ground wires to start with are the one located on the passengers side of the block near the oil dipstick tube, and the second is on the end of the head, there's a grounding strap that connects to the firewall. Good luck!

 

I was thinkin a wonky map sensor myself....unplug the connector from it and see what happens. Also if you want to check your sensors http://www.lunghd.com/Tech_Articles/...iagnostics.htm here ya are.

 

Only if it's wonky though....

 

Wait a second..... this sounds also like it could definitely be an egr or egr solenoid issue.

 

There are not two seperate problems. The lurching happens only after the car is idling for an extended period OR is in stop and go traffic (essentially idling the whole time). I may try the IAC clean though and will check the TPS. I've actually been meaning to check the TPS since recently it has started to not drop RPMs after putting the clutch in when it is cold, but problem goes away when it warms up so haven't worried about it too much.

 

is there a way to test this? I have Haynes manual so it might be there, but at work so can't check right now.

 

Gotcha...I would have to defer to slick761 on this one with the EGR valve anyone. He knows his stuff...

 

Thanks, Slick. This page is awesome.

I used to have a 92 Stealth and the community around that car was amazing. I expected as much from the Jeep community and you guys did not disappoint. I appreciate you helping me out.

 

Whit the egr let it idle till it acts up and unplug the vacuum to the solenoid on the fender... the one farthest from the plug should not have any vacuum. If it does its activating the value improperly. Also slip your finger in the housing on the egr where the rod is and kinda try to move it in and out. If the diaphragm is weak or sticky it could be getting stuck open a little. I'm really betting.g this is where your problem lies.

 

Thanx catty :-)

 

Normally I'd say if the truck lurches forward at a stop light, or while you're idle at a stop sign or something. A bad EGR valve will make your truck do this.

BUT...where you say it happens after the vehicle warms up and starts to loose power, it may be your catalytic convertor.

After you drive it look under the truck to see if it's glowing red or anything. A bad cat would make you loose power.

 

Tony - I've heard this too, but have yet to check it. I will do that as well.

Thanks everyone for your input. I'll figure this out eventually, maybe before spending $1000 in parts.... :P

 

Hey all, if you're still listening...

I looked at the Cat and it looks fine, wasn't glowing after about an hour of driving and displaying the symptoms.

Recently it's been having much more trouble starting. Occasionally it will not start at all, and I'll have to try several (10+) times and eventually it will start. I've decided it's the CKP, since it seems to go out frequently.

Does anyone have a brand recommendation or does it matter?