Isuzu Rodeo high idle problems

logancloganc Member Posts: 1
edited June 2021 in Isuzu
Hello everyone I have a 1991 Rodeo 3.1 with an
idle issue. it is at 185,000 miles and has
slowley developed an idle issue.
@ 115,000 miles it recieved a jasper engine.
@ 135 the idle problem started.

it likes 2500 rpm and two things will change its
mind (for a minute anyways untill the light
changes) 1: flashing the ignition switch works
half the time and 2: coasting in gear untill the
point where speed matches gear and the tranny is
neither pushing or pulling and then the engine
will chug and i can press the clutch in and idle
is fine....

i have replaced a slew of parts
including plugs cap and wires, many vaccume
hoses, MAP sensor, IAC (idle air), TPS, and
carburator gasket (its really a TBI unit)...its
time for either an EGR ($65) or fuel injectors
($105 each) does anyone have any ideas? How can
i test the injectors? Test EGR? I would really
appreciate some help this is killing gas mileage
and clutch!


  • hdion75hdion75 Member Posts: 1
    I recently acquired a 3.8 cougar 1990,and can not figure what is causing a high idle.The vacuum lines appear okay and disconnecting the ais motor changes nothing.Any help would be appreciated. :(
  • subfixer1subfixer1 Member Posts: 2
    Has anyone figured this out yet?

    I have a 91 Isuzu Trooper, 2.8 TBI.
    Two problems:
    It takes about 10 tries to get the truck to start. I have to keep my foot to the floor or it won't start. It runs real rich until I get the revs up to 3-4K rpm. Then it clears up.

    It does this every time I try to start it, warm or cold.

    Once it starts, then it idles at around 2K rpm.

    If I block the air feed to the IAS, I can get the idle down to around 850 rpm. I replaced the IAS, but there was no change. TPS is correctly set also.

    The high idle sounds like a vacuum leak, but I have yet to find it. Don't know if the hard starting is related, but I assume it is.

  • mzannonimzannoni Member Posts: 2
    Hi. Have you figured this out. I have the exact problem with my '92 Cougar. It seemed somewhat high since I've had it (about 3 months), but now it idles at 2500 in Park, about 1200 in drive with brake on. Cannot find any vac leak, but voltage is really high to the injectors. Put in an identical junkyard brain box, no change. (Of course it could also be bad . . .). Please let me know if you've made progress or had success in fixing. Thx.
  • mbentsmbents Member Posts: 4
    My 92 ran so bad and after a while would barely start. I discovered that it was tied to the throttle body fuel injection. Drove me nuts, but found that if I pulled the ecm fuse, then started the engine, shut it down, put the fuse back, then did a reset sequence (depress accelerator slightly, start engine, run for three seconds, shut off for ten seconds, then restart) it went back to normal and has run fine for months.
  • kf4clnkf4cln Member Posts: 1
    It works............ I have a 93 rodeo and the ecm fuse trick works.
    My Rodeo would rev to 2500 rpm when the clutch was pressed, sounded like John Force staging at the Gator nationals !
  • isuzu94isuzu94 Member Posts: 1
    Thanks very much for this answer. I just tried it on my '94 Rodeo, and it worked like a charm. After weeks of tracking vacuum hoses and checking connections without finding any solution, it's finally now not zooming up to 3,000 RPM every time it idles.

    The only slight difference is that when I tried to start it without the ECM fuse in place, it wouldn't. So, I just cranked it a few seconds and stopped. Then put the fuse back in place and followed the rest of the directions. Bingo! Test drive proved no more problem.

    Thanks, Thanks.

  • ozziwiozziwi Member Posts: 1
    :confuse: hi there im new here - so bare with me :-) i have a 1991 4 cylinder 2.6 rodeo and i have been in here reading up on the high idling issues ... mine is idlying at around 1200-1500rpm and cant seem to find where to knock the idling speed down, there is one by the throttle cable/arm adjusted that --made no difference -- any ideas would be greatly appreciated

    Cheers Kev - ozziwi
    Brisbane Australia
  • mrkenguemrkengue Member Posts: 1
    edited November 2010
    Rodeo 98 2.2L 5 speed

    Got mine used about 2 months ago with 222,000 miles from a car auction but it was very well maintain for what I can see, but after a week start idling to around 1500 to 2000 rpm. Went to Auto Zone and got a product called " Sea Foam " and added to my full tank of gas and after a week is idling at 750 rpm that should be normal idling speed . And by the way there is no idling adjustments on the ones w/throttle body. Good Luck. Hope this help in some way.
  • isuzumksmecrzyisuzumksmecrzy Member Posts: 1
    I have a 92 rodeo with an idle problem it idles high at times then normal. constistantly goes back and forth, I want to try thr ecm fuse but am not sure where it is. Can someone please tell me where this fuse is?
  • wilindawilinda Member Posts: 3
    I have an isuzu rodeo and the brake pedal got hard randomly so I was told to replace my brake booster. After doing this now the truck wants to shut off like it's being suffocated. If you keep giving it gas it's fine and if you pump the brakes the truck idels up.! What could have happened here please help
  • chavo21chavo21 Member Posts: 5
    Mine does the same.. it dies like some one is taking the life away. i too am looking for answers with this problem.

    or maybe its not the lack of air it may be Too much air i dont know.
  • Ravid824Ravid824 Member Posts: 1
    Thank you mbents member, Your advice was really helpful and saved me a lot of time. It solve me the problem on my 1998 Honda passport. I tried several time the sequence mentioned above and it didn't work, I was not sure what the reset sequence is. I found a video in this regard that explain how to make the reset sequence and once I did it properly it worked. So below you will find the updated process that worked for me on my Honda Passport.

    After disconnecting battery or removing intake parts (Throttle Body or replacing IAC for example) you may run into symptoms that when starting the car the engine run on high 2500 RPM or very low RPM or rattling. In these cases you may need to run idle learning procedure. This process is learning the EMC to properly read and control the IAC (Idle Air Control valve).
    Pull the ECM (Engine Control Module) fuse.
    • Started the engine few seconds (5 sec) and stop (the engine will not start because the ECM is not active).
    • Turn the ignition Key to OFF position
    • Put the ECM fuse back
    • Turn the ignition Key to ON position, then push slowly the accelerator pedal until the end and release all the way back slowly. Push and release 5 or more times
    • Start engine, run for 3 seconds (engine might still run high RPM)
    • Shut off for ten seconds, then restart

    Enjoy, I hope it helps
Sign In or Register to comment.