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> 1991 240 Rough Idle, Starts brilliantly but idle become rough once warm
froynglaven
post Dec 16 2013, 07:34 PM
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I have a 1991 240 wagon, and about a year ago the check engine light came on. I was living in OR at around 2300ft msl. I recently moved to chicago, 700ft msl, and my car idles very rough once warm. The car starts immediately, and idles strong until it warms up, then the idle goes too low to maintain even idle, and wants to die unless i ride the gas. I briefly tried adjust the adjustment on the throttle cable, but that didn't help much. If I increase the rpm's with a little throttle, idle is smooth and doesn't sound too high, but currently without gas and the 15-25F temps the car will die without gas when in Drive or Neutral at stops.

Occasionally when warm the idle is strong when coasting up to a stop (I'm often in Neutral now anticipating giving it gas), but then something shifts as I come to a stop and the idle drops way down. This happens 1/10 stops. When it idles it is often pulsing too low, such as almost dying then idling then almost dying, and the headlights flicker as the rpm's drop as the alternator isn't producing, etc...

The confusing part for me is that when it's cold it runs and idles brilliantly, but once warm it wants to die. Might it be just too low a throttle? Might the higher oxygen in the air be doing something?

I read some other questions but they are the opposite, starts rough, but runs well once warm. Didn't help me.

Anyone have thoughts or suggestions? thanks in advance

This post has been edited by froynglaven: Dec 16 2013, 07:37 PM
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danielm85948
post Dec 17 2013, 06:15 AM
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QUOTE (froynglaven @ Dec 16 2013, 07:34 PM)
I have a 1991 240 wagon, and about a year ago the check engine light came on. I was living in OR at around 2300ft msl. I recently moved to chicago, 700ft msl, and my car idles very rough once warm. The car starts immediately, and idles strong until it warms up, then the idle goes too low to maintain even idle, and wants to die unless i ride the gas. I briefly tried adjust the adjustment on the throttle cable, but that didn't help much. If I increase the rpm's with a little throttle, idle is smooth and doesn't sound too high, but currently without gas and the 15-25F temps the car will die without gas when in Drive or Neutral at stops.

Occasionally when warm the idle is strong when coasting up to a stop (I'm often in Neutral now anticipating giving it gas), but then something shifts as I come to a stop and the idle drops way down. This happens 1/10 stops. When it idles it is often pulsing too low, such as almost dying then idling then almost dying, and the headlights flicker as the rpm's drop as the alternator isn't producing, etc...

The confusing part for me is that when it's cold it runs and idles brilliantly, but once warm it wants to die. Might it be just too low a throttle? Might the higher oxygen in the air be doing something?

I read some other questions but they are the opposite, starts rough, but runs well once warm. Didn't help me.

Anyone have thoughts or suggestions? thanks in advance

two things clean your idle control valve with throttle or carb cleaner..the other is clean your butterfly valve in your throttle body.again with carb or throttle cleaner.
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NorcalBrick
post Dec 21 2013, 10:13 PM
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Have you checked for which code is causing the check engine light? The car has a built-in OBD-1 reader in the engine compartment, there should be some threads that explain how to use it. If not, let me know and I'll do my best to walk you through it.
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vlvwagon
post Dec 30 2013, 05:00 PM
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QUOTE (NorcalBrick @ Dec 21 2013, 07:13 PM)
Have you checked for which code is causing the check engine light? The car has a built-in OBD-1 reader in the engine compartment, there should be some threads that explain how to use it. If not, let me know and I'll do my best to walk you through it.



My '91 245 does the same thing. I've just been dealing with it (driving with both feet basically). This weekend I checked the codes and got 1-1-1 in the fuel system checks (#2 position) which means no faults and 1-4-3 in the ignition system checks (#6 position) which is 'Knock sensor signal faulty or missing, ignition timing retarded 10 degrees.' I've swapped the knock sensor with another one I had (I think its good) and so far so good after one day. I'll run it this week and check codes again.

Mine did idle fine (well, ok) about half the time so I suspect the knock sensor is not the only problem and won't be sure its cured until I run it for a week or so - It does seem to idle better and smoother but that might be my imagination/optimism.

I'm focusing on the EGR system next as I believe it could be clogged, stuck, or sticking. Since I need to remove the throttle body to really get to it, I'll be cleaning that too. I'll post updates to this thread and let me know what you find too!

This post has been edited by vlvwagon: Dec 30 2013, 05:02 PM
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danielm85948
post Dec 30 2013, 07:44 PM
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QUOTE (vlvwagon @ Dec 30 2013, 06:00 PM)
My '91 245 does the same thing. I've just been dealing with it (driving with both feet basically). This weekend I checked the codes and got 1-1-1 in the fuel system checks (#2 position) which means no faults and 1-4-3 in the ignition system checks (#6 position) which is 'Knock sensor signal faulty or missing, ignition timing retarded 10 degrees.' I've swapped the knock sensor with another one I had (I think its good) and so far so good after one day. I'll run it this week and check codes again.

Mine did idle fine (well, ok) about half the time so I suspect the knock sensor is not the only problem and won't be sure its cured until I run it for a week or so - It does seem to idle better and smoother but that might be my imagination/optimism.

I'm focusing on the EGR system next as I believe it could be clogged, stuck, or sticking. Since I need to remove the throttle body to really get to it, I'll be cleaning that too. I'll post updates to this thread and let me know what you find too!

adjust the dwell angle on the distributor timing out.
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vlvwagon
post Dec 31 2013, 03:38 PM
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QUOTE (danielm85948 @ Dec 30 2013, 04:44 PM)
adjust the dwell angle on the distributor timing out.


I am reluctant to mess with things like the timing, idle speed, air/fuel mixture, etc but will give it a look. The ECU should be adjusting things as needed (based on the sensors input) and I don't want to throw everything off by tweaking things to compensate for other problems. I suppose there is a baseline setting so I'll make sure that is correct. Thanks.
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danielm85948
post Dec 31 2013, 10:52 PM
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QUOTE (vlvwagon @ Dec 31 2013, 04:38 PM)
I am reluctant to mess with things like the timing, idle speed, air/fuel mixture, etc but will give it a look. The ECU should be adjusting things as needed (based on the sensors input) and I don't want to throw everything off by tweaking things to compensate for other problems. I suppose there is a baseline setting so I'll make sure that is correct. Thanks.

your baseline is at top dead center,remove the distributor cap. the metal tip of the rotor arm should line up ,with the cut out on the edge of the distributor body.if not you adjust it to do so.but a common trouble is the weights.when the distributor turns .throw out to compensate as it spins faster they can stick due to rust.
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vlvwagon
post Feb 13 2014, 06:24 PM
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I got around to a few more tests/repairs on mine:

-Replaced the ECT. The old one was a bit corroded and out of spec based on Bentley at different temps.
-Removed and cleaned the throttle body which was pretty dirty but nothing totally clogged or sticking.
-Removed and cleaned the IACV. It was a bit dirty but seemed to move freely.
-Tested the EGR system. I manually opened the valve with a vacuum pump at idle and it did stumble as it should. I also tested the vacuum actuator by running the test program and it does kick on and off so no controller or wiring problems. There are no vacuum leaks and I've got 20psi of vacuum at idle.

PROBLEM: At normal engine temp and part throttle, the vacuum actuator for the EGR valve doesn't open. I'm guessing some other dependency is not being met. My only other thought is the ECT not getting enough coolant flow (air pocket) and not telling the controller its hot enough to open the EGR. Thinking this because only a couple of drops of coolant leaked out when changing the sensor-Long shot I know but I'm going to try and purge the cooling system as best as I can.

After doing the EGR tests and after a few hundred miles, I checked for error codes again (#6). I got 1-5-4 which is 'EGR system flow too high' or too hot basically. Could be the EGR temp sensor which mine has since its a '91. Weird though because I have no 'Check Engine Light' on which this code should trigger and since I didn't have the code before, it could be from the tests I ran.

Anybody have a similar problem or thoughts? I think I have the timing solved with the knock sensor and it is holding idle now (so far) with the other work I did. I'm cleaning the AFM next and testing the hot air intake flap in the air box.

This post has been edited by vlvwagon: Mar 1 2014, 05:18 PM
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vlvwagon
post Mar 1 2014, 05:39 PM
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I cleaned the AFM and replaced the air filter which was fairly dirty, but not clogged. The hot air flap is fully closed and even when I put it on ice it still stays closed - Not a big deal here is CA though. I also checked the coolant for air as best as I could and replaced the EGR valve temp sensor. It runs and drives really smooth and holds idle well (maybe a little on the low side at hot start but it doesn't stall.)

PROBLEM: EGR valve still won't open. Does anyone have any thoughts on what else that circuit is dependent upon to open? The ECT is new and the EGR temp sensor is new. It could be the TPS, but I think it would be running horribly if that was bad. I can hear the TPS click also when I manually check it. Could it be my O2 sensor? Is that linked to the EGR valve operation?

I failed NOx and need to make sure that EGR valve is opening before I go back and try again.

Any help would be awesome.

This post has been edited by vlvwagon: Mar 1 2014, 05:40 PM
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danielm85948
post Mar 1 2014, 07:51 PM
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QUOTE (vlvwagon @ Mar 1 2014, 06:39 PM)
I cleaned the AFM and replaced the air filter which was fairly dirty, but not clogged. The hot air flap is fully closed and even when I put it on ice it still stays closed - Not a big deal here is CA though. I also checked the coolant for air as best as I could and replaced the EGR valve temp sensor. It runs and drives really smooth and holds idle well (maybe a little on the low side at hot start but it doesn't stall.)

PROBLEM: EGR valve still won't open. Does anyone have any thoughts on what else that circuit is dependent upon to open? The ECT is new and the EGR temp sensor is new. It could be the TPS, but I think it would be running horribly if that was bad. I can hear the TPS click also when I manually check it. Could it be my O2 sensor? Is that linked to the EGR valve operation?

I failed NOx and need to make sure that EGR valve is opening before I go back and try again.

Any help would be awesome.
clean all of your crankcase breather system and clean the AGR valve it will have a build up with carbon try clean it with carb cleaner.

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vlvwagon
post Mar 3 2014, 01:36 PM
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QUOTE (danielm85948 @ Mar 1 2014, 04:51 PM)
clean all of your crankcase breather system and clean the AGR valve it will have a build up with carbon try clean it with carb cleaner.


Thanks but the EGR valve itself is not the problem (see earlier in this post) and I've replaced the flame trap and any split hoses (along with a lot of other stuff.) I'm starting a new thread on this topic here: Egr Valve Actuator Conditions
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vlvwagon
post Mar 9 2014, 01:21 PM
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Closing the loop on my '91 245 issues. After re-checking the Throttle Position Sensor (TPS), it does 'click' when you just start to open the throttle so I thought it was fine. After checking it again with a multimeter, it was actually NOT working. On the TPS, there should be continuity between the #2 terminal (closest to the motor) and the center terminal (ground) at closed throttle and there was not. I tried adjusting it and it worked, but when I tightened it down it stopped working again. When I tried opening the throttle and letting it snap back closed it would work sometimes. Classic Gremlin! I replaced it with a new one and now the car idles beautifully. I'm shocked it idled pretty well without the TPS working and kicking the IACV on--A testament to how much the system can adapt to keep the car running. I also adjusted the throttle linkages to spec which needed just a minor tweak due to age and wear.

As for the EGR actuator... I tested that again too and found it to be kicking on under part throttle with the engine warm. The problem is the flow of vacuum is leaking out of the actuator internally and not making it out of the actuator through the EGR valve vacuum hose port. [This also makes this a vacuum leak at part throttle with the engine warm.] Again, its a bit of a Gremlin and the tests in the Bentley do not confirm the internals of the EGR actuator are working. I shelled out $232 for a new actuator (ouch!!!) but look forward to installing it and having a great smog test result! (knock on wood!!)

Going through all of this, I really did learn a lot about all these systems and how they interrelate and a lot of the mystery is now gone--Its not as complicated as I thought. Also, the lesson learned is that's its usually not only one thing. I recommend just digging in one-by-one if you have similar problems and you'll be really satisfied after. Hopefully this helps someone else.

This post has been edited by vlvwagon: Mar 9 2014, 06:35 PM
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