hello i just bought a 92 laredo 4.0 5 spd.. 183k miles..

it runs and starts great when cold, once its up to 210 it stumbles real bad arouns 1000-2000 rpm and is real hard to drive like that lol i has stalled a bunch of times and to start it you have to hold the gas Wide open till it starts.

it also idles around 1000-1100 to.. the previous owner said it had a check engine light and the code read fora crank sensor, not the light isnt on now..

im sure im forgetting something, but help is appreciated!

 

alright if its idling high check for vacume leaks. Heres how to do this do a visual inspection for broken vacume lines if none are visible- buy a can of brake-clean and spray it on the intake gasket while its running if it changes the RPM when you hit the leak now you know wear the high idle is coming from. as far as CK sensor code it's a common thing your lucking it's still running. that controls the injector and spark timing. I would replace it if it was throughing that code.

 

i vote tps. Poss. map--

 

has a new map sensor, he said it helped but not cured, ill check the intake tom. havent heard to much intake gasket problems, is it kinda rare?

i was also thinking tps, can i clean in w something?

 

no you can't clean the tps sensor when it malfuntions thats it it's a non servicable part

 

how in the world do you get to the crank sensor? top? bottom?

 

go through the bottom with about 2.5 feet of extensions and a universal joint.

 

UPDATE! today same thing, hard starting, stumbles off idle idles high..

check the codes today came up as coolant temp sensor- not running hot enough.

so i unpluged the temp sensor, it started right up and ran B E A utiful...

only gave me a problem once where it was stubling, then fine but i noticeed the electric fan didnt comeon (god knows if it works) and idk if it would overheat at all b.c its unplugged??.

should i also change the o2 sensor?

and it still idles around 1000, occasionally comes down to 8-900.. has NO vaccum leaks!

 

I think service intervals are 60k for your O2. I don't know about your year, but on my Renix, the fan won't come on without a jumper, if you disconnect the temp sensor. You can always add a switch however or replace your sensor. In traffic, offroading or during the summer it will likely overheat if the aux fan isn't running.

 

Unplugging the temp sensor only masks the real problem.

As your Jeep warmed-up, the PCM started monitoring the O2 sensors in "closed loop" and adjusting the pw of the injectors.

With the sensor unplugged, the PCM never sees it warming-up and stays in open loop.

Open loop will give decreased performance and decreased fuel economy. Yes, you say it runs better... but it will still not run as well as it could with the system working properly.

 

so what should i do? im going to get a junkyard sensor and see what happens from there.

 

The temp sensor is not likely the problem. I would check the O2 first. The temp sensor sounds like it's doing it's job.

 

Have you checked the Idle Air Control Sensor? My Jeep idled high(13-1400 RPM's) when it was warmed up and I just couldn't take it anymore and took the IAC off and cleaned it really good with some brake parts cleaner and it cured the high idle problem. It was full of carbon gunk.