My Jeep yjs idle drops to 500 rpms when I coast in neutral even though I have it set to 750rpms. Is this a problem with my fuel mixture or a vacuum leak?
Idle drops when I coast in neutral
- Thread starter louie
- Start date
Id say its your speed control sensor doing its job. What year is your YJ? You say you set it to 750 is your carbed? BTW, Vac leaks create higher rpm's
Mine (4.0) has always done this as well. I've had lots of dash rattling low idle vibrations over the years and haven't figured out if I have a problem or not. Mine seems to idle where everybody else's does for the most part but sometimes drops low. I think I've only ever noticed it because of the stiffer motor mounts I had for the last 10 years. I've gotten rid of those now but haven't driven. Mine would definitely dip the idle low while coasting in neutral as well.
For what it's worth, I've changed every sensor, and the PCM and inspected wiring for issues, never found a problem. I only wish I had more YJs to compare with so I can know what is normal or not.
For what it's worth, I've changed every sensor, and the PCM and inspected wiring for issues, never found a problem. I only wish I had more YJs to compare with so I can know what is normal or not.
Flyer58
YJ Enthusiast
I had a cycling vibration at idle on my 2.4 with a steady rpm and changing the front harmonic dampener solved it.
As for the low rpms I found a spray can of Gumout solves a lot of problems.
As for the low rpms I found a spray can of Gumout solves a lot of problems.
Hello Louie
what is under this hood.? what year Yj, 4cylinder or the inline 6. (3 engines used) a/t or m;/t gear box?
500rpm if spark is good and fuel good. (is it a daily driver or found in barn all crusty?)<<< bad fuel>/?
500 means IAC is dead on injected engine, is it? or is this a 1987 carb monster.
500 RPM on the most old engines had that nasty EGR that sticks open
please fill out profile and tell drive train. so helpers do not guess and lead you astray.
and jeeps have this habit (open hood , and huge shock,OMG what is there?, wow that is not stock.!?
the fire well VIN decodes online to say what was there new. google FREE vin decoder.
or the service manual free has it too, under VIN page.
good luck?
the automatic in DRIVE uses more energy than Neutral.
the PCM controls the IAC at all times, if not injected there is no IAC (idle air controller)
There are no PCM idle adjustments (by law) but on carbs YES. The PCM has tables for hot/coldde and neutral and DRIVE if A/T is there)
on carb the settings are all very different. (do tell if is carb)
so how did you set 750rpm , what method,?
the chock comes off high idle ( some go 1500 rpm cold)
then the choke and high idle cam is released
and now hot idle adjust screw is next on carb.throttle shaft.
need the FSM , is free.
no year told. no engine told. a/t or m/t gear box not told
only 1 clue told (besides 500)
I have it set to 750rpms << crystal ball tells me it is CARB engine, this but , seen people endlessly set the never ever touch screw on TBI body, MPI fuel injected engines vast (whats on the road now is this, not carbs)
vacuum leaks below carb goes lean. and means too slow RPM. (unless choke is stuck on that is)
no year told, no photo top of engine presented.
sometimes the VIN lies about drive train, on old cars and swaps endless.
then the choke and high idle cam is released
and now hot idle adjust screw is next on carb.throttle shaft.
need the FSM , is free.
no year told. no engine told. a/t or m/t gear box not told
only 1 clue told (besides 500)
I have it set to 750rpms << crystal ball tells me it is CARB engine, this but , seen people endlessly set the never ever touch screw on TBI body, MPI fuel injected engines vast (whats on the road now is this, not carbs)
vacuum leaks below carb goes lean. and means too slow RPM. (unless choke is stuck on that is)
no year told, no photo top of engine presented.
sometimes the VIN lies about drive train, on old cars and swaps endless.