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No Acceleration

B

brandonmcnulty

NAXJA Forum User
Location
Arkansas City, Kansas
I have an 89 Jeep comanche and a couple weeks ago it started not accelerating at all. first gear would be fine then it would shift into second and it would bog down and have no power whatsoever. 3 of my injectors were leaking so i replaced all six so i wouldnt have to worry about it for along time. But i still have the bog down problem and also it takes forever for it to start.
 
Alright just checked the fuel pressure (found some gages) i hooked them up and fired the truck up and had 32 lbs at idle. I didnt rev it up or anything but i thought that 32 was acceptable at idle. I figured that if it was workin at idle the pump would work all the time. I think im gonna pull some plugs and see how they are doin
 
brandonmcnulty said:
Alright just checked the fuel pressure (found some gages) i hooked them up and fired the truck up and had 32 lbs at idle. I didnt rev it up or anything but i thought that 32 was acceptable at idle. I figured that if it was workin at idle the pump would work all the time. I think im gonna pull some plugs and see how they are doin
Click to expand...
It can be ok at idle but drop off under load,if the filter is plugged. Weak spark would also cause that problem.
 
Alright it has gotten alot worse. it will hardly idle now. Idles right at the line on my tac about 250 rpm or somthin and when i put it in gear it just dies or if it doesnt die i step on the gas and i get about nothing. I pulled a plug and its just fine, doesnt smell gassy at all though. I just replaced the fuel injectors two days ago. I had the map sensor tested and its good. How would i test the spark? im going to go get a new fuel filter tommorrow. But it seems that if it ran at idle yesterday and i could drive it, but now i can hardly get it to idle, it doesnt seem like it could be the fuel filter. But i am really new at working on cars and this is my Daily Driver so i need some help
Thanks
Brandon
 
brandonmcnulty said:
Alright it has gotten alot worse. it will hardly idle now. Idles right at the line on my tac about 250 rpm or somthin and when i put it in gear it just dies or if it doesnt die i step on the gas and i get about nothing. I pulled a plug and its just fine, doesnt smell gassy at all though. I just replaced the fuel injectors two days ago. I had the map sensor tested and its good. How would i test the spark? im going to go get a new fuel filter tommorrow. But it seems that if it ran at idle yesterday and i could drive it, but now i can hardly get it to idle, it doesnt seem like it could be the fuel filter. But i am really new at working on cars and this is my Daily Driver so i need some help
Thanks
Brandon
Click to expand...
Test the spark by seeing how far it will jump.Your looking for about 2" of blue spark at the plugs. Use a piece of plastic to hold the wire.
Wear rubber gloves though
spark-4.jpg
 
Last edited:
Check your O2 sensor. I had the same problem yesterday and have been following this thread. I changed my O2 sensor last night and that made a world of difference. By the way mines an 89 w/157,000 miles. So it was time anyway.
 
I been watching too.
I have a 91 thats doing it too.
Just aint had a lot of time to spend with the jeep yet.
Have done the tun-up and fuel filter and cleaned the TB.
 
Cat could be clogging up. Do you (or did you) have a rattling noise from the pipe at idle? Chunks may have gone back into the muffler, creating a cork effect. No exhaust output means no air can get in! If the cat is clogged, temporarily removing the O2 sensor for a "short" drive will have your power back.
 
Alright, checked the spark, good, replaced fuel filter, replaced plugs and wires and checked the cap. All good. I looked down at the o2 sensor and i can tell its never been out and i have about 166k on her. It will start then idle fine for awhile then just die or if i try to keep her runnin she backfires through the intake and sometimes through the exhaust. I dont have a cat that could be clogged. I call oriellys and they have a Universal o2 sensor for 22 bucks the UNIVERSAL part kinda scared me. and auto zone has an OE one for 52 bucks. Any help is appreciated
Brandon
 
Universal means you have to cut the wire off your old one and put it on the new one. They come with the crimps and heat shrink to do it.
 
Alright i unplugged the o2 sensor, ran the same plugged it back in and unplugged my TPS and it ran about the same, a little different. plugged it back in and it still runs the same. so i have no clue whats wrong. I cant just be replacing parts right and left. im still in high school so i have no money. I just think i might have the dealership take a look at it. Any suggestions? i dont want to pay a whole lot of money for them to replace my O2 sensor or somthin
BRandon
 
If your idle is not high rpm, then your TPS is not likely the problem. My 1990 (same Renix ignition as you have) shows a high idle when the TPS gets out of spec. A really old O2 sensor is suspicious- mine runs rough, gives poor mileage and idles a little low (not way low) when the O2 sensor is failing. When the EGR fails, it will run OK at mid to high rpm, but bogs down and stalls at idle. When the IAC went, it would not idle properly either. Have you taken off the air supply rubber tube and looked down the throttle body? You may need to clean the IAC (Idle Air Control) and air passages it uses. This is pretty easy, remove the IAC (two screws), spray it off with intake cleaner, spray out the passages and the butterfly area, reinstall. Do NOT move the TPS, unless you want to recalibrate it. Not sure about that fuel pressure number- does it run OK at higher RPM (where the fuel demand is higher)?
 
At first it would idle just fine and run just fine while in park. It would just bog down when it shifted into second gear. Then it got to where it would hardly go at all. Couldnt hardly get it into the driveway from the street. Now it wont hardly idle at alll. It will start up fine then idle at about 2 grand for a sec then idle down like it always has then a couple seconds later it will really bog down and try to die. I can give it gas and sometimes it will pick back up and run but i can tell its not runnin right cause i can floor it and it will take awhile to rev up.
 
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