low idle and oil pressure idiot light.....

[rnobles]

OK, so after a little seafoam in the gastank and a new MAP sensor plug, things seemed to be goin well.

after a little test drive down the road, the motor would idle REALLY low when coming to a stop, making turns, etc. so low that it actually shut off a couple of times. The oil pressure idiot light would also flicker on at the same time.

after i made it back home i could start the truck fine, it would sit and idle..a little low, but as soon as you put it in gear it would shut off and the oil pressure light would come on. the only way this would not happen is if you gave it gas.

 

More of an engine gunk problem or oil pump problem?

 

i did see another thread with a similar problem, but didnt see the final solution.

[mythreesons]

From your description, the oil sender is telling you that oil pressure is low (turning on the oil light) which is caused by the low idle you are talking about. The bigger problem is why has your idle gone kaput?

 

Before we all start to tell you our experiences with idle problems with MJs.......How about you tell us what you have. It will help a lot in trying to help you get the monster running right. The easiest way would be to add the year, model, engine, tranny info to your signature from your user control panel after login. If you are one of those kind of people that hordes MJs, then you will need to specify which one your working on with which problem. You can see how that could be confusing. :D :D

 

Scott

[Geonovast]

Get ahold of a mechanical oil pressure gauge, hook it up where the sender is, and get a reading with the motor revving. I'm betting that your oil pressure is probably fine.

 

The light will come on when it dies because with the motor not spinning, there will be no oil pressure.

 

Check your IAC. If that's dirty and sticking, it will cause a low idle. My first two XJs were 4.0s with a 5 speed(88 and 89), and both of them had a habit of dying when I threw in the clutch because the IAC wouldn't let it idle.

[Oizarod115]

check the TPS for the correct signal (Should be .8ish volts at idle) also clean the idle motor like they said.

 

also like said, i wouldn't worry about the oil light yet because the truck is idling low enough to shut off, so i would expect super low oil pressure. you need rpm to build pressure. (sounds like you could use full gauges though!)

 

makes sense if it was idling to low it will die when you load it up by putting it in drive. idle should drop 1-200 rpm in drive i would think.

[rnobles]

Before we all start to tell you our experiences with idle problems with MJs.......How about you tell us what you have. It will help a lot in trying to help you get the monster running right. The easiest way would be to add the year, model, engine, tranny info to your signature from your user control panel after login. If you are one of those kind of people that hordes MJs, then you will need to specify which one your working on with which problem. You can see how that could be confusing. :D :D

86 2.5L automatic 2wd.

 

Going to try to get my hands on some gauges so i can actually see whats going on this weekend.

 

Friend of mine mentioned that it could be the intake manifold gasket since it starts after the engine gets hot. does this sound possible?

either way, i should be ok to drive it on little short trips shouldnt I?

 

Changed plugs tonight, and pulled up the rubber mat on the interior (caught the rust before it got out of hand, i think :brows:)

[mythreesons]

Ok going from very vague memory here.............

 

Did this problem just start after running the seafoam through it? If not, is the low idle why the seafoam or were you working on something else? If so, then I might say that it has loosened some gunk and at low idol there might not be enough fuel flow. Did you change the fuel filter? If I remember correctly, the 2.5L engine on a 86 has one injector so any fuel system blockage will be a big factor.

 

Fuel pump pressure I think is fairly straight-line, so I might look a little farther down the delivery system line.

 

Others are going to have to chime in with any other suggestions. There are a couple of members here (whom I can't remember right now) that just love those 2.5L engines.......Maybe one of them will catch this and straighten us out. :D

[rnobles]

ok, I havent really had time to address this situation yet. AND i don't have access to the proper gauges or a multimeter at this time. (guess i may just have to bite the bullet and buy one)

 

I did however, get to take it out for about 50 miles round trip, and it seemed to do ok (except for when i would have to stop, then the oil pressure light would come on). The truck wouldnt shut off if i threw it up in neutral OR when i just GRADUALLY came to a super slow stop. it would kinda stumble a little and idle rough.

Can i adjust my 2.5 TPS in the same manner as the 4.0s (i know there is a thread for this, but from what i can tell its for the I6)?

My throttle is actually resting on my ISA, from what i have read, this is NOT correct. and it seems that if the throttle was moved just enough to get it off of the ISA that it would solve the low idle problem (right?) but the "adjustment screw" is dang near impossible to get at to adjust (esp. when motor is hot.) My dad said that it seemed like it could be a timing issue, but the timing is not adjustable, right? he suggested rotating the distributor assembly ever so slightly and see how it acts.

 

 

There is also a noise around the mid to upper RPM range (sounds like something with a bad bearing, i have no idea what an actual bad bearing sounds like in a motor, but you get the idea) You can hear it when in park and rev the motor or when you are cruising along without any real load on the motor. just seems to be in a certain rpm range. any ideas?

 

I have been told to just drive the d@#m thing, but for some reason i feel like i have to baby it. And that SUCKS!!!!!! lol I'm learning as i go and i just don't want to do any damage.