Here are my symptoms:

When I start up, all works fine. I drive about 5 minutes and then the idle seems to die out at lights. I can keep my foot on the gas pedal and idle it myself at 1,000 and all is great.

If I take my foot off the gas it will either die, or drop to below 500, then up to 8-900, then back down, maybe die, sometimes reverting back to working(smooth idle at 900-1000).

Also on occasion if I hit a big enough bump, the engine will cut out. If I am driving on the highway(or street), and it cuts out, it will only cut out for a fraction and then continue like nothing happened.

**** Over the past month I have noticed a drop in HP and MPG.

I'm thinking sensor, but what should I check first? This is my DD and like most of us I don't have much time or money to be chasing down issues and replacing every sensor(although I probably should).

 

ive got a similar issue. there is a hesitation and it backfires, and wants ro cut out. it will choke and sputter at a stop, but wont actually cut out. so far ive replaced the TPS, IAC valve, plugs/wires, cap/rotor, blown out gas lines, checked the fuel pump/filter assembly... and nothing has stopped it yet. i think there is still an issue with the IAC valve (idle air controll) when you put your foot down far enough on the gas there is a point when it switches from low, to high idle. i NEVER have this issue in high idle. that is about the only clue i have towards this problem. the other things i could still do is replace the coil, the upstream o2 sensor, or, drop the cash on replacing the pump/filter assembly. i was thinking that maybe its something in the ignition, but im really at a loss for what to do next.... good luck! hope its not a gremlin in the wiring somewhere...

 

it does sound like your fuel pump is on it's way out and not supplying the required fuel pressure. Easy way to check is to hook up a guage to it and find out if it's with in spec. 95-98 should be around 49 anything old is 39 i think.

 

I know the older models are different but try your relays. My mothers actually fell most of the way out and cause it to just die. just a thought...

 

I had a similar problem where my mpg were going down and loss of power. It would idle fine sometimes and then others want to shut off or it just sounded like it was missing real bad well it turned out that my CAM sensor was going bad so it would batch fire the injectors at times instead of it being sequential so if you have access to a scanner that you can watch the data I would start there and watch the fuel sync

 

Update-

I have figured out that it corresponds to my engine temp. When it is cold, it runs great.

When I run it for a bit, it tends to even out (i.e. still idle horribly, not not get worse).

When I sit in traffic and the temp rises, the issue gets worse to the point where it begins to stall at lights/stops.



BTW - Thank you all for your ideas.

 

Unfortunately, I can not hook up a diagnostic tool, mines a 1990, no odbII

 

I would try the crank and the cam sensor. When my crank sensor was on the way out it would do the same thing, expecially when it became heat soaked, it would idle at lights just high enough to stay running. Will also cause less mpg n horse power if the cps is reading wrong and throwing timing out.

 

Same issues buy mine gets better with heat???

 

Very good possibility your oxygen sensor is failed or lazy. When the engine comes up to temp, the O2 sensor is supposed to come into play. If it's failed, the eCU relies on a fixed mixture to feed the engine. Can cause low idle/poor idle.

Have you ever checked your TPS with a meter to see if it's good and in adjustment?

Have you ever refreshed your engine bay grounds? If not, the ECU gets poor signals from 4 or 5 sensors and things don't work right.

 

crank sensor. i just went through the exact same thing

 

Same issues but lack of power should I just replace o2 then go from there

 

I have a 1999 cherokee with the same problem I replaced the front oxygen sensor and it fixed the problem.

 

How much did u pay for that o2

 

i had a similar problem with mine.. it turned out to be the water temp sensor... mines a 99 so it would read cold to the computer even when engine was at operating temp...

also double check that all your ground connections are clean and tight...chassis grounds are important....