Another 22RE weird idle thread
04-11-2012, 04:07 PM
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Another 22RE weird idle thread
Before anyone accuses me of not knowing how to use the search bar, i have spent many long hours researching this problem. I have had the problem with a fluctuating idle for about 6 months now. After warming up, when the brakes are applied, the idle will drop very low and almost stall, and then rev back up to normal repeatedly (the hole process takes about 1 second.). I have removed the throttle body and cleaned it and the IACV or AAV, whichever one that year has. That didn't fix the problem. I replaced plugs, wires, distributor cap, and rotor button recently. I have checked all hoses for vacuum leaks and decided to check the AFM. Before anyone asks i didn't remove the 2 screws on the wire harness. With the engine running, when i remove the air hose from the throttle body to the AFM the engine dies. (I have a pretty good automotive knowledge and do most mechanic work myself but this is confusing to me) I stuck a screwdriver in the AFM output and manually opened the metal flap, and the engine started and ran very rough. When i removed the screwdriver it immediately died. I'm not sure how the AFM controls the engine but it seemed weird to me that it didn't run with the hose connected, even though it was still getting air flow. I have no idea what might be causing this problem, but it has been going on so long i'm about ready to start replacing random parts. I've been told that i could have an air leak at the plenum, but haven't had a chance to check it. If anyone has any idea what it may be it would be VERY helpful. If y'all think posting a video might help diagnose it, i would gladly do that. Thanks in advance and sorry for the long post.
P.S.- I replaced the TPS and ECU with new parts and the AFM from a low miles truck about 6 months ago also.
P.S.- I replaced the TPS and ECU with new parts and the AFM from a low miles truck about 6 months ago also.
04-11-2012, 08:45 PM
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Before anyone accuses me of not knowing how to use the search bar, i have spent many long hours researching this problem. I have had the problem with a fluctuating idle for about 6 months now. After warming up, when the brakes are applied, the idle will drop very low and almost stall, and then rev back up to normal repeatedly (the hole process takes about 1 second.). I have removed the throttle body and cleaned it and the IACV or AAV, whichever one that year has. That didn't fix the problem. I replaced plugs, wires, distributor cap, and rotor button recently. I have checked all hoses for vacuum leaks and decided to check the AFM. Before anyone asks i didn't remove the 2 screws on the wire harness. With the engine running, when i remove the air hose from the throttle body to the AFM the engine dies. (I have a pretty good automotive knowledge and do most mechanic work myself but this is confusing to me) I stuck a screwdriver in the AFM output and manually opened the metal flap, and the engine started and ran very rough. When i removed the screwdriver it immediately died. I'm not sure how the AFM controls the engine but it seemed weird to me that it didn't run with the hose connected, even though it was still getting air flow. I have no idea what might be causing this problem, but it has been going on so long i'm about ready to start replacing random parts. I've been told that i could have an air leak at the plenum, but haven't had a chance to check it. If anyone has any idea what it may be it would be VERY helpful. If y'all think posting a video might help diagnose it, i would gladly do that. Thanks in advance and sorry for the long post.
P.S.- I replaced the TPS and ECU with new parts and the AFM from a low miles truck about 6 months ago also.
P.S.- I replaced the TPS and ECU with new parts and the AFM from a low miles truck about 6 months ago also.
The AFM measures the amount of air going to the engine. If you remove the hose from AFM to throttle body, then the AFM is getting the wrong information, so engine dies. Screwdriver fake the AFM into thinking air is flowing into the engine.
04-11-2012, 09:22 PM
#3
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After warming up, when the brakes are applied, the idle will drop very low and almost stall, and then rev back up to normal repeatedly (the hole process takes about 1 second.).
Firstly, this should tell you the engine is having trouble maintaining under such a large vacuum load as brake booster. There's a number of reasons that could cause the problem, but the brake booster is a first thing to rule out....as benmlee stated. Now, if it's not a problem in the booster (how do the brakes feel?), you may have insufficient amount of vacuum being produced by the engine. Compression loss is one culprit. Not saying that's what it is....you'd have to check it. But, low compression....for whatever reason...can also cause a funky idle related to temperature. Particularly on a 4 cylinder engine.
Case in point, I have a buddy with a VW Westy with a 1.9L 4cyl. Whenever the motor gets hot, the thing won't start unless he hooks up his deep cycle auxiliary battery that has more starting power than the little main battery. I've witnessed several times. Wouldn't you know, two cylinders are low on compression due to ring wear. And, it has a funky idle no matter the temp
With the engine running, when i remove the air hose from the throttle body to the AFM the engine dies. I stuck a screwdriver in the AFM output and manually opened the metal flap, and the engine started and ran very rough. When i removed the screwdriver it immediately died. I'm not sure how the AFM controls the engine but it seemed weird to me that it didn't run with the hose connected, even though it was still getting air flow.
That's really no way to test an airflow meter. It doesn't tell you anything other than you've created a big vacuum (as far as the ECU's concerned) by removing the hose and confusing the ECU by way of signaling to the ECU that more air is entering than there really is. The AFM simply transmits a varying voltage pattern according to the travel of the little arm inside the unit. Voltage is sent to the AFM, that voltage is modified in amount by the varying resistance in the signaling board, and sent back to the ECU telling it how far open the flapper is. That may not make sense as it is a crude way of putting it, but really the only way to test the AFM is by metering it so you can see how the signal is behaving and if it's behaving correctly according to the flapper movement. Run a search on testing the AFM or see the FSM.
I can tell you this; whenever I've had a bad AFM, it's never had any bearing on brake actuation. Only the idle, sluggish performance, and poor mileage.
I've been told that i could have an air leak at the plenum, but haven't had a chance to check it. If anyone has any idea what it may be it would be VERY helpful. If y'all think posting a video might help diagnose it, i would gladly do that. Thanks in advance and sorry for the long post.
It's possible...an air leak at the plenum, but that's such a consequential place to have leak you ought to be able to track it down with ether if there's one in that area. Spray all around the plenum mating area with ether before the engine gets hot. The engine will race a bit if a leak is found.
Firstly, this should tell you the engine is having trouble maintaining under such a large vacuum load as brake booster. There's a number of reasons that could cause the problem, but the brake booster is a first thing to rule out....as benmlee stated. Now, if it's not a problem in the booster (how do the brakes feel?), you may have insufficient amount of vacuum being produced by the engine. Compression loss is one culprit. Not saying that's what it is....you'd have to check it. But, low compression....for whatever reason...can also cause a funky idle related to temperature. Particularly on a 4 cylinder engine.
Case in point, I have a buddy with a VW Westy with a 1.9L 4cyl. Whenever the motor gets hot, the thing won't start unless he hooks up his deep cycle auxiliary battery that has more starting power than the little main battery. I've witnessed several times. Wouldn't you know, two cylinders are low on compression due to ring wear. And, it has a funky idle no matter the temp
With the engine running, when i remove the air hose from the throttle body to the AFM the engine dies. I stuck a screwdriver in the AFM output and manually opened the metal flap, and the engine started and ran very rough. When i removed the screwdriver it immediately died. I'm not sure how the AFM controls the engine but it seemed weird to me that it didn't run with the hose connected, even though it was still getting air flow.
That's really no way to test an airflow meter. It doesn't tell you anything other than you've created a big vacuum (as far as the ECU's concerned) by removing the hose and confusing the ECU by way of signaling to the ECU that more air is entering than there really is. The AFM simply transmits a varying voltage pattern according to the travel of the little arm inside the unit. Voltage is sent to the AFM, that voltage is modified in amount by the varying resistance in the signaling board, and sent back to the ECU telling it how far open the flapper is. That may not make sense as it is a crude way of putting it, but really the only way to test the AFM is by metering it so you can see how the signal is behaving and if it's behaving correctly according to the flapper movement. Run a search on testing the AFM or see the FSM.
I can tell you this; whenever I've had a bad AFM, it's never had any bearing on brake actuation. Only the idle, sluggish performance, and poor mileage.
I've been told that i could have an air leak at the plenum, but haven't had a chance to check it. If anyone has any idea what it may be it would be VERY helpful. If y'all think posting a video might help diagnose it, i would gladly do that. Thanks in advance and sorry for the long post.
It's possible...an air leak at the plenum, but that's such a consequential place to have leak you ought to be able to track it down with ether if there's one in that area. Spray all around the plenum mating area with ether before the engine gets hot. The engine will race a bit if a leak is found.
04-11-2012, 09:24 PM
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Airflow and incorrect signals aren't the problem with the VAM disconnected. The fuel pump relay switch is in the VAM. When no air is flowing through it, the vane is completely closed, thus turning off the fuel pump.
Did you replace those parts in order to correct this problem, or did the problem surface when you replaced them? Is the TPS adjusted properly? Is it from the same era truck?
It sounds like your baseline idle speed is too high and/or the TPS setting is off. Pushing on the brake makes the ECU think the engine is in an overrun(engine braking) situation and it shuts off the injectors until RPM drops below the minimum set point. The injectors then come back online, the RPM rises, fuel is cut, and you get the surging idle. When everything is working correctly, it knows that brakes applied at idle speed ≠ engine braking.
It sounds like your baseline idle speed is too high and/or the TPS setting is off. Pushing on the brake makes the ECU think the engine is in an overrun(engine braking) situation and it shuts off the injectors until RPM drops below the minimum set point. The injectors then come back online, the RPM rises, fuel is cut, and you get the surging idle. When everything is working correctly, it knows that brakes applied at idle speed ≠ engine braking.
04-12-2012, 04:58 AM
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Thanks for the replies! So, i guess the order i should check things is
1)Brake Booster
2)Compression
3) TPS (checked a few times since installing so it should be good)
4)Plenum leak.
I'll keep you guys posted on the progress.
Dirt Driver- The TPS and ECU were brand new parts, and i checked and rechecked the adjustment on the TPS. AFM was from another truck. They were purchased to fix a separate problem involving the fuel pump relay you mentioned in your last post.
1)Brake Booster
2)Compression
3) TPS (checked a few times since installing so it should be good)
4)Plenum leak.
I'll keep you guys posted on the progress.
Dirt Driver- The TPS and ECU were brand new parts, and i checked and rechecked the adjustment on the TPS. AFM was from another truck. They were purchased to fix a separate problem involving the fuel pump relay you mentioned in your last post.
04-13-2012, 05:14 AM
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Ok, the only thing i was able to check yesterday was the brake booster. When removing the vacuum line from the booster and blocking it off i depressed the brakes and it still had the surging idle, although it was not as severe and rapid as before. When i increased the throttle, the surging still occurred, but at a faster pace and increased with the engine speed. It has also started surging at idle without the brakes being used. I'm still confused as to why this is happening and i plan to do the compression test this evening. Is there another procedure to test the brake booster or is the only way to test it by blocking off the lines?
Thanks
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04-13-2012, 11:28 AM
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The booster alone can be checked with a portable vacuum source of some sort. It should hold steady vacuum(like an A/C system) with no assistance from a pump. Disconnecting it from the engine and sealing the vacuum lines rules it out as the sole cause of your idle problem, though. It may or may not be contributing, but there's something else going on too.
04-17-2012, 04:51 AM
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ok, finally got the chance to do the compression check.
-First test with normal conditions
1. 150
2. 130
3. 138
4. 110
-Second test i added a little oil to the cylinders and tried again.
1. 160
2. 180
3. 230
4. 135
I guess they don't look to low, but that cylinder 4 kinda worries me. Now that i think about it, cylinder 4 is where the rod is knocking if that has anything to do with it. i guess maybe 2 and 3 have some carbon build up. i examined the spark plugs and they look perfectly fine, no rich or lean burn. The gap was a little off on 2 of them, so i adjusted them all to .031in. I'm really not sure what to do now. When pulling the plugs, i realized that 2 of the clips on the end of the wires had come loose and came off when i pulled the wires. Just before i did the test i drove it around to warm it up and it started missing REALLY bad. I'd get the gas pedal about 1/4 of the way down and it starts spittin and sputtering and it doesnt want to accelerate. I don't know if this has anything to do with it, but i'm kinda starting to get a little ticked off with all these problems. Although, i guess if you're driving a 23 year old truck you'll have to deal with the problems.
-First test with normal conditions
1. 150
2. 130
3. 138
4. 110
-Second test i added a little oil to the cylinders and tried again.
1. 160
2. 180
3. 230
4. 135
I guess they don't look to low, but that cylinder 4 kinda worries me. Now that i think about it, cylinder 4 is where the rod is knocking if that has anything to do with it. i guess maybe 2 and 3 have some carbon build up. i examined the spark plugs and they look perfectly fine, no rich or lean burn. The gap was a little off on 2 of them, so i adjusted them all to .031in. I'm really not sure what to do now. When pulling the plugs, i realized that 2 of the clips on the end of the wires had come loose and came off when i pulled the wires. Just before i did the test i drove it around to warm it up and it started missing REALLY bad. I'd get the gas pedal about 1/4 of the way down and it starts spittin and sputtering and it doesnt want to accelerate. I don't know if this has anything to do with it, but i'm kinda starting to get a little ticked off with all these problems. Although, i guess if you're driving a 23 year old truck you'll have to deal with the problems.
04-17-2012, 08:02 AM
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May want to do a leakdown at this point and/or check the coolant for exhaust byproducts. 110psi dry actually is on the low side, 135 wet isn't that great either, and the variation is really wide. The high mileage 8:1 turbo engine in one of my 'Stangs makes 145-155psi cold and dry and I know that it has cracked valve seats.
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