I'm having the same issues, all of the hoses check OK, but I am currently having P0401 (EGR Valve) issues as well. Maybe the EGR is feeding unmetered air in somewhere? Anyone have any definitive solutions?
High idle in P & N after driving (1600-2000 RPM's). Anybody have similar issue?
- Thread starter S.CarolinaFZJ80
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I get the same thing under almost the same conditions mentioned here - always warm to hot out. I have always been able to pop the hood, and twist the throttle lever on top of the engine to slow it back down. The next time I hit the gas - it comes right back.
I do not believe it is un-metered air causing it but something physically binding that is the issue.
I do not believe it is un-metered air causing it but something physically binding that is the issue.
how about the idle position sensor? the screw arm on the throttle body (which i adjusted on mine) that i mentioned in an earlier post, which makes contact with a plunger (which is black). I believe the plunger is an idle position sensor. so either adjust the screw so it compresses the plunger more so the cpu will think the throttle body has returned to idle, or replace the sensor.
this is purely theoretical as i have no fsm, but adjusting the screw worked on mine.
this is purely theoretical as i have no fsm, but adjusting the screw worked on mine.
The issue I have with that is that it doesn't explain why it idles normally 90% of the time. It does not generally happen around town but it does if it is hot out and I take a longer drive - like up to camp.
as to it only happening whith high temp. maybe the high temps cause what ever metal in the sensor to expand in a way that doesn't allow them contact as well. like what happens in a temp switch/ breaker/theromastat, but i'm not an engineer. peyton
SUMMIT CRUISERS
SILVER Star
My 92 is experiencing the same issue. RPM's are up about 300 to 400 more than they usually are. Just a thought, In order for the engine to operate "properly" it requires more air when hot outside. Possibly the MAF sensor is actually opening a little further with the passing of more needed air, hence raising the fuel mixture and idle. I'm not a chemist or know much about air density with relation to higher temperatures, maybe someone can chime in on my theory.
an IAT temp of a 160* seems a little high to me. What is the ambient temps at that time?
I have had almost this exact same issue on my 1996 when it is hot outside. I have also found that going under the hood I can move the throttle by hand and bring the idle RPM back down to normal. To me, there are two possible culprits:
1. If there is an actuator that adjusts the throttle position at idle based on information from sensors, then this actuator may be holding the throttle open (for whatever reason) and allowing more air into the engine, therefore increasing engine RPM. The problem I see with this theory is that if the throttle can be moved by hand to decrease engine RPM, why wouldn't the sensors tell the actuator to move the throttle back to its original position as soon as you take your hand off? Maybe by decreasing the airflow into the engine the sensors are now giving the computer updated data and the computer does not see the need to increase the idle back to 1800-2000 RPM. But then why would it see the need to have the RPM that high in the first place? Those questions make me lean toward a mechanical issue.
2. When things heat up, they expand. Different materials expand at different rates so when whey you have parts made of plastic, aluminum, steel, cast iron, etc. all interacting you could get some binding, especially if there is some kind of lubricant that may have existed years ago but is no longer doing its job. Since we are talking about the throttle plate and the things attached to it that could restrict movement back to the proper idle position, I would say some possible culprits are: friction between the throttle shaft and the bore in which it rotates, friction between the throttle cable and its tube (same with cruise control actuator but this should be slack at idle), inadequate force from the return spring, or some other mechanical interference I can't think of.
I have not spent much time trying to fix mine but those are my thoughts based on my observations so far.
Jonathan
1. If there is an actuator that adjusts the throttle position at idle based on information from sensors, then this actuator may be holding the throttle open (for whatever reason) and allowing more air into the engine, therefore increasing engine RPM. The problem I see with this theory is that if the throttle can be moved by hand to decrease engine RPM, why wouldn't the sensors tell the actuator to move the throttle back to its original position as soon as you take your hand off? Maybe by decreasing the airflow into the engine the sensors are now giving the computer updated data and the computer does not see the need to increase the idle back to 1800-2000 RPM. But then why would it see the need to have the RPM that high in the first place? Those questions make me lean toward a mechanical issue.
2. When things heat up, they expand. Different materials expand at different rates so when whey you have parts made of plastic, aluminum, steel, cast iron, etc. all interacting you could get some binding, especially if there is some kind of lubricant that may have existed years ago but is no longer doing its job. Since we are talking about the throttle plate and the things attached to it that could restrict movement back to the proper idle position, I would say some possible culprits are: friction between the throttle shaft and the bore in which it rotates, friction between the throttle cable and its tube (same with cruise control actuator but this should be slack at idle), inadequate force from the return spring, or some other mechanical interference I can't think of.
I have not spent much time trying to fix mine but those are my thoughts based on my observations so far.
Jonathan
Any resolution on the high idle?
I took my 80 wheeling for the first time over the weekend and here in NC the temp was in the lower 90's. My idle climbed to over 2500 RPM in P and N. I am sure the engine was pretty hot as we were of course going slow and all the airflow through the radiator would have been due to the fan. I am not convinced of what the real culprit is; computer/sensors telling the throttle to open (maybe to flow more air and keep engine cool?) or mechanical binding.
I took my 80 wheeling for the first time over the weekend and here in NC the temp was in the lower 90's. My idle climbed to over 2500 RPM in P and N. I am sure the engine was pretty hot as we were of course going slow and all the airflow through the radiator would have been due to the fan. I am not convinced of what the real culprit is; computer/sensors telling the throttle to open (maybe to flow more air and keep engine cool?) or mechanical binding.
I found where the problem is, now I just need to figure out how to fix it. Where the two cables come into the throttle body that run the throttle (one for the gas pedal and the second for the cruise control) there seems to be a third pulley the is designed to pull the opposite way. Here, it seems like something is amiss. When the throttle runs high as described, I can manually retard the throttle back to normal by moving the butterfly back. There seems to be some play in the butterfly assembly. Either the "return" cable is not doing it's job, or some nylon washers or stoppers have become loose within the assembly. I'll get into this and rip it apart and poke around but it won't be anytime soon. I'm enjoying driving the thing around way too much to take it out of commission.
If anyone has a TB assembly already ripped apart, or a spare laying around, it would be great to know what the reality is in there.
If anyone has a TB assembly already ripped apart, or a spare laying around, it would be great to know what the reality is in there.
BTW, it's not just in P and N where this happens. When in drive this just transfers into engine load. I was up in the hills last night in low range trying to descend when this high throttle thing kicked in, it was all sorts of fun trying to overpower the low range on a descent with brakes. For a second there, it felt as if I lost the brakes altogether because the gearing trying to run at 2000 RPM.
Check the throttle levers themselves on the TB. I drove from MN to CA and in AZ it started idling way high when I got off the throttle. If I lefted the pedal with my toe it went back to normal.. The cable itself was fine. I am not sure exacly where or with what but the arms.. sectors? The pully shaped things LOL were sticking. A bit of carb cleaner followed by some PB blaster made it go away..
Another time I had it happen be cause the kid was playing around in the truck and had pulled on the carpet where the old brick phone wire came thru and the carpet rubed on the accelerator..
Another time I had it happen be cause the kid was playing around in the truck and had pulled on the carpet where the old brick phone wire came thru and the carpet rubed on the accelerator..
I had that same experience this weekend NerdNoise. Trying to come down easy off the backside of rocks I had just driven over while pointed downhill it was all I could do to stop my 80. I actually put it in neutral when gravity was enough to keep me going just to make the braking easier.
I have a similar high idle problem. '96 LX-450 periodically idles about 1800 rpms in N or P. Other times idles fine. Does not seem tied to hot weather. I have not tried to fix it yet, but will try some of the things mentioned above. If any of you have solved your problems, what were the fixes?
OK, I have a theory.
I have an idea as to what might be causing it. I need a schematic/drawing of the cable and pulley system on top of the throttle body to study this further. I do not have a FSM and I'm hoping someone can scan one in and post it.
I'm mostly interested in the pulley assembly and the little vacuum driven something underneath.
--Mike
I have an idea as to what might be causing it. I need a schematic/drawing of the cable and pulley system on top of the throttle body to study this further. I do not have a FSM and I'm hoping someone can scan one in and post it.
I'm mostly interested in the pulley assembly and the little vacuum driven something underneath.
--Mike
Hello?
Is anyone still paying attention to this post? I am continuing to have these issues and I am looking to proceed further. If no one is interested I won't bother writing about it if no one is going to read it so in conclusion, I'm just curious if anyone is still following this thread. I have some good ideas and tried test results.
Is anyone still paying attention to this post? I am continuing to have these issues and I am looking to proceed further. If no one is interested I won't bother writing about it if no one is going to read it so in conclusion, I'm just curious if anyone is still following this thread. I have some good ideas and tried test results.
I'm following for sure - but slightly distracted by non LC issues at the moment. I'll try to get a scan for you tonight.
