Help!! idle problem
Guest
Posts: n/a
Help!! idle problem
ok here's what happens: i fire it up and it idles at 800, and it stays there at stoplights too, etc. all good. Ok well after driving it i put it in park and the idle jumps up to 1600. if i put it into reverse it goes to 1000. if i put it into neutral it idles at 1600. What's going on here? it's a 89 XLT with a 351 3 sp auto. I was thinking tps or idle screws but it's affected by what gear so i'm lost for ideas.
Guest
Posts: n/a
Help!! idle problem
>ok here's what happens: i fire it
>up and it idles at 800,
>and it stays there at stoplights
>too, etc. all good. Ok
>well after driving it i put
>it in park and the idle
>jumps up to 1600. if
>i put it into reverse it
>goes to 1000. if i
>put it into neutral it idles
>at 1600. What's going on
>here? it's a 89 XLT with
>a 351 3 sp auto.
>I was thinking tps or idle
>screws but it's affected by what
>gear so i'm lost for ideas.
>
The first thing I would do if I were you would be to clean out the throttle body. Buy some carb cleaner and a new throttle body gasket before starting this- remove the coolant lines (some coolant will leak out), unplug the vacuum lines, and unplug the electrical connectors from the throttle body and remove the four nuts holding it on. Once you have the throttle body removed, remove the Idle Air Control (IAC) unit from the throttle body and spray the inside bores of the throttle body and scrub it down with an old toothbrush. Then remove the electrical IAC solenoid from the IAC unit and clean the unit out also. Be careful not to get any electrical components wet with the carb cleaner and try not to get anything into the intake manifold. Once everything is cleaned up, reassemble everything and don't forget to use a new throttle body gasket and remember to put the vacuum lines and coolant lines back in the same places. This should solve your idle problem unless it is something else in your system. Total cost should be under $10 and takes less than two hours for a first-timer.
>up and it idles at 800,
>and it stays there at stoplights
>too, etc. all good. Ok
>well after driving it i put
>it in park and the idle
>jumps up to 1600. if
>i put it into reverse it
>goes to 1000. if i
>put it into neutral it idles
>at 1600. What's going on
>here? it's a 89 XLT with
>a 351 3 sp auto.
>I was thinking tps or idle
>screws but it's affected by what
>gear so i'm lost for ideas.
>
The first thing I would do if I were you would be to clean out the throttle body. Buy some carb cleaner and a new throttle body gasket before starting this- remove the coolant lines (some coolant will leak out), unplug the vacuum lines, and unplug the electrical connectors from the throttle body and remove the four nuts holding it on. Once you have the throttle body removed, remove the Idle Air Control (IAC) unit from the throttle body and spray the inside bores of the throttle body and scrub it down with an old toothbrush. Then remove the electrical IAC solenoid from the IAC unit and clean the unit out also. Be careful not to get any electrical components wet with the carb cleaner and try not to get anything into the intake manifold. Once everything is cleaned up, reassemble everything and don't forget to use a new throttle body gasket and remember to put the vacuum lines and coolant lines back in the same places. This should solve your idle problem unless it is something else in your system. Total cost should be under $10 and takes less than two hours for a first-timer.
New User
Joined: Oct 2000
Posts: 1
Likes: 0
Help!! idle problem
If you could, please let me know when and what you find that is giving you this irregular idle problem. I own a 1993 F250 with a 351 automatic and am having the same problem. Lately, I've noticed that when I shift from drive to park and back to drive, that it's doing this. I've also noticed that when the truck is idling in park, the idle still changes slightly although not as severly. I've replaced the throttle position sensor twice so if nothing else, I can pretty much exclude that as a suspect from your truck. Good luck!
Senior User
Joined: Aug 2000
Posts: 473
Likes: 1
From: Richmond, CA
Help!! idle problem
[font size="1" color="#FF0000"]LAST EDITED ON 20-Oct-00 AT 02:47 PM (EST)[/font][p]I have an 89 Bronco full size XLT. Had an idle problem ranging from 1500 to 2000 rpms in park and in nuetral. Put it in drive or reverse it dropped to 1000 rpms. Last weekend I took the upper Intake plinnum off cleaned a little, still some buildup. It turns out that the upper intake gasket was shot. So I replaced all the gaskets for the upper intake, Valve cover, Throttle body, and the Idle Air Control (IAC)unit gaskets. Put every thing back together and now crankes up at 800 rpms. Adjusting the idle screw I had it down to 600 but now stays at a consistant 800 rpms. Too much air loss and build up inside the throttle body and intake plinnum causes havoc with the computer. I havn't been able to drive it yet, because my rear-end is in the shop getting completely rebuilt and upgraded. I should be able to get rear-end back next weekend. In the mean time it gives me a chance to fix some of the minor problems like the idle.
Hope this helps
Hope this helps
