hesitation issue
 

new to forums and hoping to get some help. searched through the forums and didnt really find anything that fit my issue so im hoping someone can lend some help. just bought an 87 jeep cherokee and changed fuel filter, plugs, wires, valve cover gasket and cap and rotor. starts up fine and seems to idle pretty good but in hitting the gas it hesitates before reving up. i see there can be many things that can cause this but has anyone had this happen and know how to fix it??? i checked coil and and it seems to have tested good. so im not sure where to start next being that i have never owned a jeep before. thanks in advance :-)

was it doing this before you did this work or after?

not sure exactly what it was doing before...it was my cousins jeep and he said he had stalled on him before. it was sitting at his house for awhile and all he did was start it up on occasion. i got it from him and drove it home it ran pretty rough and blew out a lot of carbon build up when i gunned it onto the freeway. so i gave it a tune up as mentioned and it ran a whole lot better its just the hesitation when hitting the gas to rev it. the idle seems pretty good and doesnt seem to have a miss to it

Two thing s come to mind right off.
Check the fuel pressure.

2nd) unplug the O2 sensor, that will cause the ecm to default to .5 volt(also known as center) if the hesitation is gone then replace the O2 sensor if it remains check the fuel pressure regulator for proper vacuum and repair or replace it if needed

P.S. Welcome to CF
Attachment 17952

ok i will check that out thanks!! also is it normal to hear what sounds like gas going from engine back to gas tank when standing in front of jeep after you shut it off???

no, are you sure it is gas

truthfully i have no idea what it is...just sounds like water going back into something so i figured it was gas going back to tank or something

Oh, OK

should i also be getting vacuum from both hoses coming from the valve cover ?????

The water going back into something you hear is likely coolant draining back into the radiator. It's somewhat normal but you may be a bit low on coolant. All 3 of of the XJ's I've had have done that even when pretty much full, but check the coolant levels.

The 89 I've got and am working out the kinks on now is doing the same hesitation thing. The 87 I had did the same thing but not as bad. It's likely one or more of a few things, IAC, TPS, CPS, dirty throttle body, possibly 02 sensor related. I've got a new IAC, new exhaust (but you didn't mention exhaust noise) and new EGR solenoid and mines running way better than when I got it but still has the hesitation issue. I'm going after TPS and throttle body cleaning next.

Post your results and I'll post mine, seems this is common with the Renix models and I'm going down the list of fixes I've found searching here as I have time and money but haven't seen many say which of these actually fixed their issue :) Mostly people like us trying to figure ours out.

Cheers and welcome!

are you leaking oil? because i hear a slurping sound. or "water" moving back an forth. but my rear main is leaking. so it could be your oil.

Mine does that to i have the theory that is is hot oil or coolant mine i think is hot oil it comes from in the pan.< on mine I Am pretty sure it is oil seeing as how i hear it in oil pan and i just changed oil so its nice and fresh.

Dont know on Renix style on my 91 they are both breethers detached from air box and the intake No reall vacum on intake it is just a cycle breather. The rear one when detached should be sucking from the valve/opening on the intake. <hard on mine nice suction and when covered with finger The engine actually changes tempo.



Oh P.s. i forgot i had hesitation in my 91 Changed the FUEL FILTER and solved a ton o the problem. took it out and couldn't even blow through it.

already changed out the fuel filter and i do think its low on coolant from removing hoses out of my way changing plugs and valve cover gasket...thanks again for all the suggestions everyone...ill start looking into it more this weekend

ok just got the jeep registered so now ill be driving it...but to let everyone know...i talked to a buddy of mine and he said hes pretty sure its hesitating due to carbon build up. i floored it on freeway and a huge carbon cloud shot out the exhaust. so i bought some good fuel cleaner to clean it all up and hopefully it will cure the hesitation. thanks for everyones help and ill keep you posted!!