TBroosteRR

97' GC engine hesitation problem
Hello, great fall weather isn't it. 1997 Grand Cherokee, 2 WD, 4.0 straight six cylinder (190HP), automatic transmission. 260K on speedo. change oil and filters every 3K. usually starts right up, choke seems to work correctly. air filter replaced as per manual. this engine/transmission has been maintained as per manual.

Problelm: when the engine gets moisture from weather (rain or humitity) carwash etc. it hesitates, dies, misfires, runs sluggish. speddo goes haywire. intermettant then runs then without warning does it again. warning lights come on, sometimes goes off and then on again, etc.

History:
this has been a constant problem. its been in the shop for it, Ive done search and recovery many times to correct problem, to no avial. I go to Autozone and get code read/diagnostics, usually replace sensors again, then it is corrected for a small time, then acts up again.

What I've done.
1. had codes read, replaced (Crankshaft positioning sensor) replaced air oxygen sensor on carb.
2. replaced coil, plugs, plug wires, fuel filter, air filter, pcv valve, rotor, distributor cap,
3. cleaned throttle body and intake manifold with seafoam and berrimans, added marvel mustery oil, removed all carbon from throttle valve and body. This usually helps for about a week or so then she'll have another temper tantrum.
4. about 100K ago, the A/C drain line started leaking on the passanger floor board, leaked for months, Jeep dealer drilled a hole in frame and added drain opening and hose for condensation drain and solved the wet floor board.
5. at about 60K fuel pump replaced with new.....still in.
6.

C. What I expect to do is through some $ at it.
1. double check (dc) all the ground connection on battery, engine and frame at fire wall. maybe there is some corrosion causing the electronics to perform poorly? maybe replace the negative wire.
2. dc all the fuel injectors to see if there are any bad ones. (replace at $60 ea)
3. dc the temperature sensor ($24) at the thermostat.
4. dc the throttle positioning sensor ($47) TPS.
5. dc the O2 sesor (upstream) ($67) at the exhaust manifold.
6. dc the MAP ($70) manifold air pressure
7. dc the PCM ($197) powertrain control valve.

It could use a head rebuild. ($350)


Any help is greatly appreciated.
TBroosteRR

rickybarth

you have a 4.7 six cylinder? is it a stroker or is it a 4.0 six or a newer 4.7 v8 in a zj

TBroosteRR

Excuse me rickybarth, I changed the engine size back......but it runs like it has a 4.7 stroker!!! LOL

rickybarth

yea that woulb be really cool did u run into any major problems over your 260k mile jeep

TBroosteRR

With regular maintainance as per the manual, I've been fortunate enough to not have any major problems with the engine or transmission. Just the continuous problem of when its wet or the moisture in the air is heavy the problem with hesitation kicks up........She still runs great and doesnt drip or burn oil. This hesitation cituation is a minor but major problem. I need the vehicle to be dependable on the rainy days, and I like to keep her clean and taking her to the car wash is always a gamble. I've recently had the notion that on colder days when I use the heater that she responds better in the rain. It might be that a temperature sensor or switch is something I'll look into. I put some fuel injector cleaner in her last night and I unplugged each fuel injector one at a time and she barely acted up at each, the warning light turned on. I got the readings of code 27, 25 & 55. Does anybody know what code 25 & 27 mean?
Thanks a bundle, have a great day!
GOD bless.
TBroosteRR