c1eddy

4.0L. Bought it a year ago. Ran pretty good...but gave lots of nuisance warnings (rear light out, service 4WD switch). The alarm system sometimes would go off randomly. Also...it started a countdown and is now showing "0 miles to service". Like a dork...I ignored em' all. Began having starting problems (well before it got to "0"). Then began dying when idling...occassionally shuddering. Then one day it died and appeared it could not be restarted. It finally started an hour later...but only ran for about a minute. 1/2 hour later it started and ran for 1/2 minute. 1/2 hour later it ran for 15 seconds...enough to get it home. Since then...it has started just 3-4 times out of 15 or so tries...and ran from 10 seconds to a minute. When it ran for a minute...it was rough and blew grey smoke. I've replaced the battery (had 1 dead cell), the spark plugs, and the fuel filter. Now cranks fast...but no start. I can hear the fuel filter run/start when I turn the key.
After much internet forum reading, wife thinks crank position sensor is bad...but I wanted to ask you folks before I try to apply my very limited mechanical skills. Would it have started at all with a bad CPS? If not, any idea what most likely issue is?

ET JEEP

How many miles does it have? First, check for a spark at the plug. Remove plug, reconnect to plug wire and lay plug on metal surface that provides a good ground. Have someone crank engine and look for spark at plug. If you have a spark, it may not be ignition, could be fuel. Check for spark first.

The information display starts at 7500 miles and counts down as a reminder to do routine service. Once you do service, you reset it back to 7500.

c1eddy

Got about 136,000 on it. Thanks for instructions on checking for spark. Will do it and post back...hopefully tomorrow.

c1eddy

Has spark. Crazy...but it started and ran/idled well for 2-3 minutes tonite. Then it began running kinda rough. Died a minute later. I tried it again about 1/2 hour later. Ran good for about a minute this time...then rough for another 1/2 minute before dying. During the periods it was idling well, it was responsive to the gas peddle. Any ideas on what to check next are greatly appreciated.

wanagojeep

spark plugs jumping, shortin, grounding out. my neighbor has a problem like that on his tuck and cant figure out what it is. he drove around for 10 mins and at an intersection it idles fine then it just died. no spit sputter just died, at an idle.

zjrog

Check your fuel pressure with a gauge on the schrader valve. It is on the fuel rail. WHile it could be something else, you are describing a bad fuel pump.

kwdaye

What is the fuel pressure supposed to be?

kwdaye

I'm having similar problems, just rough sometime while driving down the road.

fourx4junkie2

Ok guys I am new to this forum stuff but I am at the end of my nerves. I have a 93 Grand Cherokee w/ 4.0 Iit has set for 4 years. I lifted it and am running 35's the fuel pump was bad so I found where a guy used a summit in line electric pump and followed his step by step how to and did the same. The jeep ran great then out of the blue it dies then would fire but idle really rough and was sucking major air through the throttle body. I winched it up a hill to the flat and poof it started and I drove it the rest of the evening. Then took it to Wa****a and drove it for like 3 hours, shut it off why my buddy was fixing his Jeep went to start it and the same thing rough idle and sucking major air, and if you touch the throttle it dies. messed with it for an hour ckecked every vacuum line, found nothing. Decided to winch it out. As soon as we got it turned down the trail it fired up and I drove it for another hour or so then took it home.Now a few weeks ago I was out in a trail it was running good then started cutting out and died this time would not start. Checked and there was no spark so changed the coil and got spark the Jeep then fired but now got the same rough idle and air suction. it ha new plugs, cap, rotor, fuel pump, crank sensor, sensors on the throttle body, no luck please help