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High/Odd Idle...; I didn't mess with anything!!
Topic Started: Jan 4 2013, 05:32 PM (2,184 Views)
sarguy01
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Okay, I did mess with some stuff....!

I did some searching and saw that Metros have a few issues that can cause a high idle. I drove the car and it was fine. I unhooked all of the plugs going into the junction box under the dash to rewire the headlights. I also replaced the air filter, did a compression test and checked the EGR pressure transducer. I popped the top of the transducer, looked at the little filter and popped it back on. As soon as I started it back up it had a higher than normal idle. My calibrated ears tell me the idle is steady around 1500 or so (no tach...) It did this morning as well. Warm or hot, it idled high and after it sat for a minute or so it would go to normal.

I am going to check the vacuum lines, EGR system, TPS, Idle Control Whatever and the other things listed in the various threads searched with the term "high idle".

But, does anyone know off the top of their head that by unhooking the junction box, the high/erratic idle can be caused by ??? Or, since I popped the top off the transducer I could have ____(fill in the blank). Yes, I hooked all of the vacuum hoses back up to the transducer and they aren't visibly cracked.

I really think it has to do with me unhooking the junction box/EGR Pressure Transducer and not a sensor going bad at the same time. Any thoughts??

Edited by sarguy01, Jan 4 2013, 05:39 PM.
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sarguy01
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I went out and checked to see that I had the pressure transducer hooked up correctly as I took it off the car. I switched the top two vacuum lines and the idle is still high, then drops after a few seconds. I wonder if one of the pressure transducer vacuum lines is leaking and causing a vacuum leak.
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sarguy01
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Went out and bypassed the transducer, still no change in idle. I hooked up my tach and it sits around 1550 and drops to 970 after 5-10 seconds. I checked everything I messed with and am really stumped on this one.
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sarguy01
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Idle still hangs. I am clueless.

I checked all vacuum lines and sprayed carb cleaner through all around the intake and lines, with no change in idle.

This started as soon as I fixed the headlights. I cut and spliced the correct wires and now the idle hangs. Any thoughts?
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snowfish
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Basic GearHead

Quote:
 
I hooked up my tach and it sits around 1550 and drops to 970 after 5-10 seconds.

To me, it sounds like it's acting the way it should. :hmm My snowmobile, Jeep, and Metros, will "hang" for a little while. Then come back to normal idle. ^o)

The fact that it Does come back to 970rpms, after being at 1550, means all should be tight. :news No vacuum leaks. :thumb

I think your asking to fix something that really is not broke. :hmm

You should be able to fine tune, the idle, with the idle air screw. :hmm But I wouldn't mess with it until it's Really up to temperature. :shake Meaning after a 10, 15, or even 20 mile run. :drivin

There's a number of members who purposely raise the idle, to around 1000rpms, to reduce engine shaking that many have at lower revs. :gamerz
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sarguy01
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snowfish
Jan 24 2013, 11:11 AM
Quote:
 
I hooked up my tach and it sits around 1550 and drops to 970 after 5-10 seconds.

To me, it sounds like it's acting the way it should. :hmm My snowmobile, Jeep, and Metros, will "hang" for a little while. Then come back to normal idle. ^o)

The fact that it Does come back to 970rpms, after being at 1550, means all should be tight. :news No vacuum leaks. :thumb

I think your asking to fix something that really is not broke. :hmm

You should be able to fine tune, the idle, with the idle air screw. :hmm But I wouldn't mess with it until it's Really up to temperature. :shake Meaning after a 10, 15, or even 20 mile run. :drivin

There's a number of members who purposely raise the idle, to around 1000rpms, to reduce engine shaking that many have at lower revs. :gamerz
Hmmm...acting the way it should? Okay, maybe I will leave it as is. I was not going to change anything, but keep looking for grounds to clean and for unhooked connectors.

Here is what gets me though... the idle dropped normally before I fixed the headlights. Now, it takes longer to drop.

It could be something like the temp outside. Before I fixed the headlights, it was still warm outside, as in above 50. Now it is 20-40 degrees. Maybe it means I need to verify that the coolant lines are clear and to check what temp thermostat is in it. Maybe the ECM thinks the engine is cold and keeps the idle up. I am not sure.

I am not going to mess with the screws on the throttle body or throttle lever. They are both still set from the factory. I think the TPS is still factory set as well and don't want to move that, either.
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snowfish
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Basic GearHead

Quote:
 
Before I fixed the headlights, it was still warm outside, as in above 50. Now it is 20-40 degrees.

:congrats We have a Winner! :congrats

Mine hangs much more, when it's cold, (try -10 :cold) than when it's warm. :coffee

Good idea to keep any eye, on everything, like you are. :thumb Great job. :cheers
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sarguy01
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snowfish
Jan 24 2013, 12:00 PM
Quote:
 
Before I fixed the headlights, it was still warm outside, as in above 50. Now it is 20-40 degrees.

:congrats We have a Winner! :congrats

Mine hangs much more, when it's cold, (try -10 :cold) than when it's warm. :coffee

Good idea to keep any eye, on everything, like you are. :thumb Great job. :cheers
Yes, it is a warm 25 degrees in Virginia Beach.

I know how cold it gets in your neck of the woods. I went to college at Iowa State...!

I am not going to worry as much about the idle, as long as nothing else changes.

I also have a DTC 31, MAP sensor low. I am on my second replacement (pick and pull) MAP and before I replaced it I checked the voltages as per the FSM. It still throws the 31, but the check engine light isn't on. I am stumped on this one too. No other codes, just a 31. Checked the grounds, added some direct grounding wires, still have a code. It could be some of the screwy wiring that one of the last owners did to the ECM wiring harness. I wonder if this adds to the higher idle.
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clarkdw


@ snowfish: If this is on his 95 there is no idle air screw to adjust. It is upgraded emissions.

@ sarguy 01: snowfish is right, the idle on your car is acting quite normal. My 94 with upgraded emissions acts exactly the same.

That being said you do still have some issues. Does your MIL (Malfunction Indicator Light) come on when you turn the key on before you start the car. A DTC 31 should turn on the MIL. If the light doesn't come on when you key on that needs to be addressed. Possible burned or removed bulb. Time to pop out the dash and check it.

DTC 31 is low manifold pressure indicated. It sets if the MAP sends a output to the ECM indicating lower than 27"HG pressure for more than 0.2 seconds. Since we know for sure that the pressure is not actually that low we can begin troubleshooting for wiring problems.


The Factory service manual says: (Please note that this is from a 94 manual. The system is identical and it will apply but I am not positive the color code will be the same)

Turn ign off.
Disconnect MAP sensor connector.
Connect voltmeter from connector cavity 3 to ground.
Turn on ign switch.
Voltage should be 4-5V.
Is it?

Yes
Connect voltmeter from connector cavity 2 to ground.
Should be 4.5-4.9V
Is it? If yes- replace MAP sensor. If no- check for short to ground in Lt grn/red wire.

No
Check for an open or short to ground in Gra/red wire.

This problem will not necessarily make the car run badly but your mileage will be :shit
Ask me how I know. :thumb
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sarguy01
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clarkdw
Jan 24 2013, 12:48 PM
@ snowfish: If this is on his 95 there is no idle air screw to adjust. It is upgraded emissions.

@ sarguy 01: snowfish is right, the idle on your car is acting quite normal. My 94 with upgraded emissions acts exactly the same.

That being said you do still have some issues. Does your MIL (Malfunction Indicator Light) come on when you turn the key on before you start the car. A DTC 31 should turn on the MIL. If the light doesn't come on when you key on that needs to be addressed. Possible burned or removed bulb. Time to pop out the dash and check it.

DTC 31 is low manifold pressure indicated. It sets if the MAP sends a output to the ECM indicating lower than 27"HG pressure for more than 0.2 seconds. Since we know for sure that the pressure is not actually that low we can begin troubleshooting for wiring problems.


The Factory service manual says: (Please note that this is from a 94 manual. The system is identical and it will apply but I am not positive the color code will be the same)

Turn ign off.
Disconnect MAP sensor connector.
Connect voltmeter from connector cavity 3 to ground.
Turn on ign switch.
Voltage should be 4-5V.
Is it?

Yes
Connect voltmeter from connector cavity 2 to ground.
Should be 4.5-4.9V
Is it? If yes- replace MAP sensor. If no- check for short to ground in Lt grn/red wire.

No
Check for an open or short to ground in Gra/red wire.

This problem will not necessarily make the car run badly but your mileage will be :shit
Ask me how I know. :thumb
Thanks for the reply.

Yes, I already tested the MAP as per the 95 FSM. Both wires have the correct voltage. A while back it threw a 31 and 32 at the same time. I followed the 31/32 troubleshooting procedures. After replacing the MAP with 2 different used sensors, it still has a 31.

The MIL does work. I had to take the dash apart to put the light back in when I first got the car. It was on all the time with a 31, 51 and 13 (Whatever the O2 sensor is, replaced it, code gone). Cleaned the EGR, now just a 31. At first it would come on only when I was in gear, moving and took my foot off the gas or was on at idle. Now it doesn't come on when I decel/idle. Pop the fuse in to check codes and get 3 blinks, long pause, 1 blink, so I know the light still works.

In another thread I started, I show a pic of some splicing of a few wires in the ECM's harnesses. But, I untaped a little and it looks to be a ground wire that runs with the wires, not spliced into them. The only wire that has insulation cut with this wire spliced is the green/blk sensor ground. I think this was the last owner's solution to the MIL illumination. I am guessing he ran parallel ground wires. I am going to tear into the harness after I get home from work today. I already told the wife to not expect me inside the house for a few hours!

The wires he ran the bare wire in the following pic were red (C2, O2 Sensor input), orange (C2, Ign Ref Low), white (C2, Ign Ref High) and green/black. The green/black (sensor ground) has the bare wire in the pic soldered on. The bare wire then splits and runs up the red, orange, and white wires. Where the bare wire ends, I have no idea. I would hope that they are not spliced into those sensor wires, but am not for sure.

Here is the wiring...
This is a bare wire that is taped onto some other wires.
Posted Image

This is a quick splice and there is another one on a different harness. This was the blue/red (C3, A/C Idle Up circuit) spliced into the blue (C1, Rad Fan Relay Control). I think this was done to raise the idle when the rad fan kicked on.
Posted Image


Mileage has been 32-35. I only filled this thing 3 times since I bought it. I thought that was pretty good for not trying, 200K miles and 100 PSI on cylinder #3!

Tonight I am going to rip into these harnesses and find out where that bare wire goes. I seriously doubt it is factory wiring. Since it is wired into the sensor ground, I think it might be causing the 31 to be stored. But, that sensor ground also goes to the TPS, O2 sensor, Coolant sensor and IAT sensor. If it was spliced into those other sensors' wires, I don't understand why I am not getting a bunch of codes.
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sarguy01
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Took out the junction box. Checked all the wires and verified I cut the right wires for the headlight fix. Put it back together. Idles high.

Unhooked ISC. Idle was at 700, didn't move for headlights. Must work. Normal idle was around 950 and would change with headlights and heater fan.

Took off ISC. Took apart anyway, looks okay, put back together. While it was off, I set the TPS. It was at 1.62 volts. I adjusted it back down to .986 volts. Put ISC back on. Start car, goes to 2500 rpm, then slowly drops to 950-1000, still cold. Rev it, headlights on, off, heater fan on, off, all combinations, idle drops like normal! Yeah!! But, start car again, shoots to 2500, slowly backs down to 950-1000. Granted, the garage is about 40 and the outside air is about 25. Maybe normal.

No MIL, but now codes 21 and 46. Rad fan also comes on while engine is still cold. Troubleshoot fan first using FSM. Using FSM, either blue wire is shorted to ground or I have a bad ECM. Remember, that blue wire was spliced into the A/C idle up signal going into ECM... I cut the wire, but am wondering if that ghetto splice fried the ECM?? Troubleshoot code 21 next. I only have 1.97 volts on Lt Grn/Wht wire. Supposed to be 4-5 volts. FSM says the Lt Grn/Wht wire could be shorted, if not, replace ECM. I checked the wire, can't see where it can be shorting. Next, 46, ISC. It works as per FSM, no need to go further on chart, but is still throwing the code. FSM also says that if 21, 46 and 22 are stored, the Lt Grn wire could be shorting. I didn't see the 22, but maybe I missed it. 2 out of 3 codes could mean an open Lt Grn wire.

It could be the ECM, but I have never heard of a car that needed an ECM that still ran. Usually, the car won't run at all, though this car could be different.

Any thoughts??

Wait, "Ah Ha" (light went on in head) moment. Just checked the TP wiring in FSM. Lt Grn is a 5V reference wire from ECM. I had a 31, MAP voltage low before this. I didn't see it, but maybe I missed it too. Need to check again. Even if I don't have one, maybe that Lt Grn wire is not supplying the 5V it should be supplying. Need to check the MAP sensor harness for 5V. If it is there, than I can assume the wire is damaged between TPS connector and splice to MAP supply.

Is anyone reading this still???
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clarkdw


Keep posting. I am trying to work through it as you are testing. :thumb
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sarguy01
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Fan was easy fix. I didn't remove the ghetto splice. The end found a ground and completed the circuit. I removed the splice wires and it is fixed.

Lt Grn is at 5 volts, both at MAP and TPS.

T-Pinned the Lt Grn/White at the ECM and it shows 1.97 volts. It says to check for a short/ground in that wire and a bad connection at the ECM. At the ECM, the wire shows a steady 1.97 volts. Okay, this might be the ECM, but I am not convinced. Need to make sure the ECM is getting full power. Time to read some more schematics...

clarkdw, thanks for following!
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sarguy01
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Went to drive it, get it warm, idle was crazy. Shot up, came down, stayed up (2900 rpm, came down, etc).

If I ground the ECM body, the 1.97 goes to a 1.5...clueless...
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sarguy01
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Disconnected the plugs at the ECM and the TPS. Ran a wire from B+ to Lt Grn/White at TPS plug and then tested voltage at ECM plug. It was a solid 12.5, so there are no shorts in the wire.

I cannot think of anything, aside from the ECM being bad, that is causing this. I have no idea why the TPS wasn't throwing codes before tonight and now is. What changed that would cause this low voltage?? No clue, unless I shorted the ECM out when I was messing with the previous owner's ghetto splice...
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