playin4funami

Hey guys need help! I have a 1990 cherokee with the 4.0 and automatic,it starts and idles just fine and will rev in neutral and park just fine everything seems tip top, then when I put it in gear it runs great as long as I am standing on the gas hard, but once I let up it will run fine and stumble now and then,but if I try to give it more throttle it will cough lose power and pop and backfire real bad, it is undrivable it is so bad.

I have replaced the cap and rotor
spark plugs
plug wires
took off and cleaned the TB
oil and filter change
cleaned the air filter(K and N)


help what do I check next! really need the beast running good again,

Deanxj97

Is a check engine light or anything on?

playin4funami

actually no, just my low washer light,lol.

Deanxj97

Ha i didnt even know my jeep had one of those till the other day lol. Well I had the same problem and it turned out to be the fuel pump, but mine didn't backfire like yours.

playin4funami

thanks, it does run hard when i am on the gas it just won't run at a regular speed without cutting out.

freegdr

check the cps bolts make sure there tight

playin4funami

cps??? sorry long day oh, cps= crank position sensor?

playin4funami

from what I could see in the dark with the snow falling heavily the cps looks okay

what else could it be, I'm making a list to check tommorrow. distributer itself? the cap and rotor helped it alot but not enough? timing? coil? I am lost and don't just want to sling parts at it.

freegdr

yes i read a post some one was having the same prob he found one of the bolkts ahd fell out another thing to check is fuel pressure you will not have a check engine light you have a renix xj does not even have one

playin4funami

thanks bro! now I just got to fiqure this thing out,this one is new to me and it has issues, the motor is a oem rebuilt one with only about 50,000 on it. I am about to yank it and drop it in my other jeep if I can't fiqure this nightmare out.

freegdr

did it start doing this after all this work was done or you did all this work to try and fix it

playin4funami

I did all this post messing up attempting to fix it! and just general maint. only owned it for a month, but it ran hard and ran good then this happened and I need to get it going, it also has a lift and 31 dick cepek tires. it has a nasty hesitation now when accelerating unless I really am getting on the gas, at normal speed it pops and cackles and won't run, if I try to accelerate normal it just starts popping and rumbling and no go for awhile then all the sudden will take off, the po has a cold air intake on it and I don't know if that will effect anything.

freegdr

it ran fine when you first bought it correct i dought the intake would have any thing to do with it if it was on there when you bought it

freegdr

i would check the wiring harness around the cps plug and the wires to it for cracks and bear spot touching the engine causing it to ground out

The Rooster

taking the motor out of this Jeep and putting it in another one won't solve your problem... you will have the same problem in another Jeep... I would check your timing.... and change your fuel filter check your fuel pressure... and double check your firing order... when did this problem happen exactly..??