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OK I don't think I am hasta, though it may sound like it at first. If you have any Renix experience please read this, as I think it lends a new perspective to an old, preplexing, frequent problem with high idles.
My old high idle Nemisis has returned uninvited. :bawl:
I have discovered that when I start the Jeep (87 Renix, 4.0), and if it idles to fast (recently started idling at 1000 to 2000 rpm again) and if it refuses to drop back down to normal, then if I disconnect the TPS sensor, the idle IAC control will finally operate ( there is about a 3 to 4 second delay) and lower the idle speed to a normal idle.
Then if I plug the TPS back in (re-connect the harness) the idle stays normal, unless I press the throttle again, (which I do not do because it eventually screws up the idle speed again if I do, not always right away, sometimes right away, sometimes it is a slow creep over minutes).
Then once I have gotten the IAC idle speed adjusted to the normal idle as I just described, I then unplug the IAC and drive the jeep. One of the interesting things is that once I have done this procedure the jeep runs great, including a roughly 30 to 50% increase in apparent horspower :cheers: when in gear that it has been lacking since I bought it 2.5 years ago.
I have tested the above problem, resolution procedure at least 8 times over the last week, and it is quite (100%) repeatable! Also if I disconnect the TPS and then press the throttle the engine dies right away.
Now it occures to me that the TPS must be working properly based on its flawless performance when the IAC is disconnected, and that it is still actually doing something control wise (data input to the ECU). It also must still be doing something, feeding good data to the ECU since it runs great when connected and dies when I press the accelerator if it is disconected!!!!! Right?????
Also, since the IAC works correctly when the TPS is disconnected, I must conclude that the IAC is also working when given the correct ECU instructions.
So what the hell could be causing this?????
To the best of my knowledge there are no battery, alternator, ground wire, or ignition problems (all of the ignition parts are new), and all the sensors have checked out recently and are fairly new.
I am looking for the non-obvious solutions.
I am thinking that either the ECU is getting faulty RPM data at some point, which makes no sense at all based on the way the engine runs, or it is giving faulty information to the IAC, but only when the TPS is connected and the throttle is pressed, or when the engine is first started. But why would it do this?
Why would it correct the idle speed, operating the IAC only after temporarily disconnecting the TPS????? Wiggling the connections at the IAC and the TPS has no effect on the system.
I eventually have to temporarily plug the IAC back in for real cold morning start ups, otherwise it tries to run and idle at about 250 rpm taking 20 minutes to warm up as a result on real cold morning first starts.
My old high idle Nemisis has returned uninvited. :bawl:
I have discovered that when I start the Jeep (87 Renix, 4.0), and if it idles to fast (recently started idling at 1000 to 2000 rpm again) and if it refuses to drop back down to normal, then if I disconnect the TPS sensor, the idle IAC control will finally operate ( there is about a 3 to 4 second delay) and lower the idle speed to a normal idle.
Then if I plug the TPS back in (re-connect the harness) the idle stays normal, unless I press the throttle again, (which I do not do because it eventually screws up the idle speed again if I do, not always right away, sometimes right away, sometimes it is a slow creep over minutes).
Then once I have gotten the IAC idle speed adjusted to the normal idle as I just described, I then unplug the IAC and drive the jeep. One of the interesting things is that once I have done this procedure the jeep runs great, including a roughly 30 to 50% increase in apparent horspower :cheers: when in gear that it has been lacking since I bought it 2.5 years ago.
I have tested the above problem, resolution procedure at least 8 times over the last week, and it is quite (100%) repeatable! Also if I disconnect the TPS and then press the throttle the engine dies right away.
Now it occures to me that the TPS must be working properly based on its flawless performance when the IAC is disconnected, and that it is still actually doing something control wise (data input to the ECU). It also must still be doing something, feeding good data to the ECU since it runs great when connected and dies when I press the accelerator if it is disconected!!!!! Right?????
Also, since the IAC works correctly when the TPS is disconnected, I must conclude that the IAC is also working when given the correct ECU instructions.
So what the hell could be causing this?????
To the best of my knowledge there are no battery, alternator, ground wire, or ignition problems (all of the ignition parts are new), and all the sensors have checked out recently and are fairly new.
I am looking for the non-obvious solutions.
I am thinking that either the ECU is getting faulty RPM data at some point, which makes no sense at all based on the way the engine runs, or it is giving faulty information to the IAC, but only when the TPS is connected and the throttle is pressed, or when the engine is first started. But why would it do this?
Why would it correct the idle speed, operating the IAC only after temporarily disconnecting the TPS????? Wiggling the connections at the IAC and the TPS has no effect on the system.
I eventually have to temporarily plug the IAC back in for real cold morning start ups, otherwise it tries to run and idle at about 250 rpm taking 20 minutes to warm up as a result on real cold morning first starts.
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