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Engine power problems please help!

S

Seanlee08

NAXJA Forum User
Location
Owens Cross Roads,Alabama
i have a big problem with my 1989 Laredo i bought and need seiouse help! im getting very fustrated with my cherokee.It drives grate but for some reason after it warms up a little while (maybe 5 min or so) it has a very bad surge and will only rev between about...well 2000 and 2500,never over 3000 RPM while driving. While in park will reve up to 4000 or 5000 no problem. this surging is very awkward when driving and the transmision has no kick down it wont work the RPMs still dont go above 3000. early tonite i unpluged the battery and reset the comp and it was a little better i burned out at the end of my sterr and watched the tac go up to 4000 rpms taking off no problem but after it warmed up the surging came back slply lick it was turned on and the kick down still didnt work and it went back to the regular 2000-2500. I have read around and this is a problem for other people im glad im not the only one. i have figured it to be a number of problems and(correct me if im wrong)

1. Crankshaft position sensor
2. O2 sensor
3 Throttle position sensor ( since the rpms seem to have problems)

PLease help with my problem! im willing to try almost anyhting to get my beloved jeep to run right :flipoff:
 
Have you replaced the ISA (idle speed adjustment i think) motor. I have had this same problem on my old 88 cherokee ltd, and after cleaning a ton of junk out of the ISA motor housing (used carb cleaner an q-tip - not recommended, but had no choice) waiting for cleaner to evaporate and replacing ISA motor, it worked great.
 
Also check your fuel delivery ie; fuel pump, filter and pressure regulator.
 
95% probabilty it is the TPS that is bad, or both the TPS and O2 sensor based on your tests so far.

The O2 sensor and TPS can be tested with $10-20 analog volt / ohm meter.

Search for the "RenX files" thread here in Oem foum, use the advanced search with Ecomike as thread author, it has all the info you need on O2 sensor testing and some links on TPS testing and special test data on TPS testing for 87-90 Renix jeeps.

Also see:

http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm
 
thanks 2 everyone! i have figured out what my problem was
thanks to ecomike,he was rite when he said it was he TPS sensor sure enough i went out for a drive and ( not recomended by me,im sure its probobly not good) i had only gone a few mile from my house and pulled over opened the hood and unpluged the TPS sensor and sure enough on the way back home it had NO surge,and the RPMs went way higher than 2000 or 2500 the jeep also lacked power before and this was solved too. It is a very very quick jeep i love the power and the way it handels it picked up to 80-85 mph no problem thanks to all that replied :gee: :)
 
Seanlee08 said:
thanks 2 everyone! i have figured out what my problem was
thanks to ecomike,he was rite when he said it was he TPS sensor sure enough i went out for a drive and ( not recomended by me,im sure its probobly not good) i had only gone a few mile from my house and pulled over opened the hood and unpluged the TPS sensor and sure enough on the way back home it had NO surge,and the RPMs went way higher than 2000 or 2500 the jeep also lacked power before and this was solved too. It is a very very quick jeep i love the power and the way it handels it picked up to 80-85 mph no problem thanks to all that replied :gee: :)
Click to expand...


I tried to tell you that in your thread over on jeepforum.com(I'm 89warwagon over there)......:lecture:
not being a dick....glad you got it fixed.
 
I also looked through som old JP magazines,and this solved many problems ( JP aug 2006 ) has a whole story on sensors that go bad in Jeep 4.0L and some 4.0L H.Os sry to outlander im new to ths website n everythign wasn tryin to be a ass n not listen too you
 
my '90 4.0 is also acting up. It takes a while to start and idle is sometimes as low as 250. Also in gear I can't floor it because it seems as if it is going to stall, but if I do it while in park I can rev it no problem. could it also be my tps???
 
Seanlee08 said:
well im starting to gwt pissed lol it came back the other day while i was driving i let it sit for a while and it was fine no problems but it just randomly came back any ideas?
Click to expand...

Did you replace the TPS/ Did you calibrate it?

What else have you done?

Have you tested the O2 sensor?

IF it is heat saturation related it might be an exhust leak heating up an injector, or something odd like that. Oh, what about the EGR valve, it might be sticking!!!
 
slowjeep said:
my '90 4.0 is also acting up. It takes a while to start and idle is sometimes as low as 250. Also in gear I can't floor it because it seems as if it is going to stall, but if I do it while in park I can rev it no problem. could it also be my tps???
Click to expand...

Yes if it has the Automatic transmission the TPS could be the problem, but part of it could also be clogged, busted internally cat converter, a loose vac line to the MAP sensor, mixed with a sticking IAC, dirty IAC port in the throttle body.
 
Seanlee08 said:
near as i can tell i just have to adjust the TPS does anyone know how? please tell me :)
Click to expand...

See the link in post #6 in this thread, or search in advnaced search for "RenX files" and Ecomike as the poster.
 
am having similar problems only after i had the head gaset redone i can run it then after some time it starts to acted up like it is not firing in ordor. I changed plugs,wires,cap and rotor. i thought it could be the vacuum line but there alright. thinking that he did not put the injetors back right. it a 4.ol cherokee 4x4 4dr. I dont know wat else to do? does anyone know were i can own load the injector set up at??????:repair: :gonnablow
 
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