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90 xj 4.0 low idle and stall or hesitate on accel

E

edlepp

NAXJA Forum User
Location
northern b.c. canada
well i have finally got the cps bolt out of the bell housing but have a new prob. it seems like it is idling 2 low and hesitates or stalls when coming off the throttle the back on, ie: cornering, or backing out of the drive way then going forward. as this is a new jeep to me only had it 2 weeks i do not know if it did this before, but it did not seem to do it before i changed the cps. I have changed a lot of parts in this time including
cap rotor
plugs wires coil
cps
ground to dipstick and body
positive to starter
fuel and air filter
fuel pressure good 34 psi
fixed 2 vac leaks
set tps
have also traded a air idle switch thing with another xj. when i unplug it it makes no diff???
gone through my whole useless haynes manual and followed what ever procedures that fit a Renix. now I am totally stumped. I did have to pull starter and split the tranny back about half inch to get my cps bolt to drop. any help would be great.
 
i only have one of those push on compression testers and can't get the same reading on one cylinder twice. so i haven't bothered to test them all till i can find another one. I have just stripped the tb and cleaned it and the iac the re adjusted the tps now i iam going to take it for a drive and get it all warmed up as see what happens. i also just cleared the pcm so hopefully it will pick up all new setting and parts and be good.
 
well went for a drive ran great till it warmed up now its the same thing. sitting here in the driveway if i let it idle then lightly push the gas it will run like a bag of $#*t. if i press the gas quickly it will run fine ????

please help
 
grabbed a set of pliers and forced the egr closed, clapped the vacume line and went for a drive. seems like the bogging on lite throttle is gone but now if i quickly press the throttle and release it dies. go figure. i am ready to give this damn thing a vacume leak just to get the idle up and say screw it and sell it.
 
sure, why not give it a vacuum leak--pull a line off the manifold and see if the idle kicks up.

Are you running rich? Rich mixture = lower idle.

Here is a link to testing Renix sensors: http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm

Things to test for: bad CTS (coolant temperature sensor); bad o2 sensor; exhaust leaks upstream of the o2 sensor; MAT and MAP sensors.
 
well playing under the hood again and have found that when I unplug the aic nothing happens. Should this affect it? I would think you should notice a idle diff. any way i can test to see if it is moving?
 
Well you arent the only one with this problem, mine is very similar. If you take a look I have changed damn near every sensor there is. If you figure this out, please be sure to say what it was, I will do the same. Im going to run a comp test on my wifes xj this afternoon, so Ill update shortly.
 
well now i am just unplugging every sensor 1 at a time to see if i can figure it out. just talked to the old owner and he said it stalled a few times so he put a alligator clip in where the idle adjustment screw is and drove it :idea: he's pretty smart hey!!!!:wstupid:
 
can any body help me set the base timing ? there has to be a way but i cannot figure it out with this one. seems like mabey it's out. and is there any way I can keep it a closed loop system, (i think thats what i want. to keep it from reading any sensors) It seems to drive great when it is cold and running on the preset settings. I was also reading on here that there is a scanner that will read these renix computers, can anybody tell me if it is true and which one if it is?
 
seems to work again but does stumble and just about dies if i do a quick rev and let go but i can deal with that for now. will order new part tomorrow if it stays working but after 3 days and a lot of headaches i quit for today. thanks everybody for your help and input.
 
I would recommend you clean your throttle body with some cleaner. You would be surprised how much that would raise your idle. There is also an air screw on the side of the throttle body that you can adjust your idle speed with.
 
IH392 said:
I would recommend you clean your throttle body with some cleaner. You would be surprised how much that would raise your idle. There is also an air screw on the side of the throttle body that you can adjust your idle speed with.
Click to expand...

any chance you could send me a pic of that screw? I have only found the one that stopps your butterfly from slamming shut.
 
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