1990 Renix low idle and random high idle on startup
Thread Starter
Junior Member
Joined: Feb 2012
Posts: 38
Likes: 0
From: Washington
Year: 1990
Model: Cherokee
Engine: 4.0
Sooo, 90 renix, 285k, dd.
Runs smooth but idles around 350rpm in park.
Randomly shoots up to 2,000-3,000 rpm on start up, have to shut down and restart and hope it goes back to normal. The most it's happened was 3 startups in a row.
There's a new and clean iac valve, new fancy intake gasket, new tb gasket, clean tb, iat/mat sensor is probably original but cleaned.
Map is newish, new o2, cts is probably original, tps I believe is original and was adjusted to no avail.
New and clean grounds...
Having troubles back probing some connectors with my hand me down dmm, I know, need to upgrade.
What have I missed? And when revved at idle it throttles down fine to a "normal" rpm, then drops to 350-400rpm.
Runs smooth but idles around 350rpm in park.
Randomly shoots up to 2,000-3,000 rpm on start up, have to shut down and restart and hope it goes back to normal. The most it's happened was 3 startups in a row.
There's a new and clean iac valve, new fancy intake gasket, new tb gasket, clean tb, iat/mat sensor is probably original but cleaned.
Map is newish, new o2, cts is probably original, tps I believe is original and was adjusted to no avail.
New and clean grounds...
Having troubles back probing some connectors with my hand me down dmm, I know, need to upgrade.
What have I missed? And when revved at idle it throttles down fine to a "normal" rpm, then drops to 350-400rpm.
Thread Starter
Junior Member
Joined: Feb 2012
Posts: 38
Likes: 0
From: Washington
Year: 1990
Model: Cherokee
Engine: 4.0
I've done all those, and upgraded the ground strap.
Besides the connector/receptacle cleaning, they have all looked good so far. Relay block could use some cleaning. But on the iat connector, one of the male pins is off center and kinda have to give them a wiggle to connect them.
Besides the connector/receptacle cleaning, they have all looked good so far. Relay block could use some cleaning. But on the iat connector, one of the male pins is off center and kinda have to give them a wiggle to connect them.
Thread Starter
Junior Member
Joined: Feb 2012
Posts: 38
Likes: 0
From: Washington
Year: 1990
Model: Cherokee
Engine: 4.0
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,578
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Thread Starter
Junior Member
Joined: Feb 2012
Posts: 38
Likes: 0
From: Washington
Year: 1990
Model: Cherokee
Engine: 4.0
Or into the plug probe style?
My dmm only has probes, recommendation for a good inexpensive MM?
Research shows everyone says get analog
Trending Topics
Thread Starter
Junior Member
Joined: Feb 2012
Posts: 38
Likes: 0
From: Washington
Year: 1990
Model: Cherokee
Engine: 4.0
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,578
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
[QUOTE=Chad'sCheep;3189337]OK, so digital is fine for checking tps sweep? Mine is an older equus model with probes only and the points aren't very streamlined[/QU
Sweep won't be an issue. Digital is fine.
Got a grinding wheel?
Sweep won't be an issue. Digital is fine.
Got a grinding wheel?
Thread Starter
Junior Member
Joined: Feb 2012
Posts: 38
Likes: 0
From: Washington
Year: 1990
Model: Cherokee
Engine: 4.0
[QUOTE=cruiser54;3189417]Yah, 4inch, dremel, samdpaper. Won't hurt anything reshaping those tips?
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,578
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Thread Starter
Junior Member
Joined: Feb 2012
Posts: 38
Likes: 0
From: Washington
Year: 1990
Model: Cherokee
Engine: 4.0
[QUOTE=cruiser54;3190420]Ok, I'll do it again. If I remember correctly, the reading fluctuated a digit or two after adjusting and rechecking the numbers. I'm somewhat inept with the dmm. What is the arrow in the low part of the ohm section?
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,578
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
[QUOTE=Chad'sCheep;3191567]Stay with the flat 3 wire connector.
Thread Starter
Junior Member
Joined: Feb 2012
Posts: 38
Likes: 0
From: Washington
Year: 1990
Model: Cherokee
Engine: 4.0
[QUOTE=cruiser54;3191644]I always refer to your write up when I do it to be sure.
What's the deal with the IAT sensor, only Crown sells them? For kicks I asked the O'Reilly guy, and he even pulled out the book, but closest one had a male plug
and mine is female
What's the deal with the IAT sensor, only Crown sells them? For kicks I asked the O'Reilly guy, and he even pulled out the book, but closest one had a male plug
and mine is female
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,578
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
[QUOTE=Chad'sCheep;3191667]Remove it and clean the rip with a sofr toothbrush and carb cleaner. It CAN be tested, ya know.


