- Thread starter
- #61
Power outage will reset the ECU which results in a super low idle. I'm guessing that's why you had a low idle. Ill give it a try though. Nothing to lose here.
No More High Idle on Cold Start
- Thread starter harrydunn
- Start date
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Power outage will reset the ECU which results in a super low idle. I'm guessing that's why you had a low idle. Ill give it a try though. Nothing to lose here.
- Thread starter
- #63
Updating this so hopefully I can help somebody else out someday. With the 100's of posts I've read trying to figure this out, the main thing I notice is that most posts just stop! I've adjusted the TPS a bit and used some Techron and I don't get the little start-up stumble as shown in my videos any longer. I'm not sure if that is a coincidence or not. I did not use the FSM this time as that didn't make any changes. I just used the butt dyno while turning the TPS clock-wise a bit. When the shift points started getting funky, I backed the TPS off a bit and tightened the two set screws.
It still will not idle high when cold and still idles low at idle when warmed up. In park, about 575 and in gear about 500-525. I'm thinking vacuum leak all the way but I have checked over and over with a can of starting fluid and can find nothing. I'm tempted to just bump up the RPM by adjusting the throttle cable and living with it at this point. I do realize the ECU sets the idle RPM and that I should not have to adjust the throttle cable.
Just an FYI...
It still will not idle high when cold and still idles low at idle when warmed up. In park, about 575 and in gear about 500-525. I'm thinking vacuum leak all the way but I have checked over and over with a can of starting fluid and can find nothing. I'm tempted to just bump up the RPM by adjusting the throttle cable and living with it at this point. I do realize the ECU sets the idle RPM and that I should not have to adjust the throttle cable.
Just an FYI...
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- Thread starter
- #64
Hooked a smoke machine up. Smoke present at the EGR valve diaphragm. Would that indicate a torn diaphragm or a stuck open EGR valve or both? I'm still a little green when it comes to the EGR system. I suppose I will pull it off this weekend and stick a block-off plate between the valve and the upper intake to see if that improves things. Just keeping this post updated...
Hi,
I would try and pull vac on the valve with it disconnected from the system and see if it holds, or hook up a vac gauge, check the reading then disconnect the valve, block off the vac lines to it and see if it moves higher.
I once had a FI 280z drive me crazy with a vac leak, after hours of searching it turned out to be the diaphragm on the charcoal canister.
I would try and pull vac on the valve with it disconnected from the system and see if it holds, or hook up a vac gauge, check the reading then disconnect the valve, block off the vac lines to it and see if it moves higher.
I once had a FI 280z drive me crazy with a vac leak, after hours of searching it turned out to be the diaphragm on the charcoal canister.
bloc
SILVER Star
The start, stumble, and recover is exactly what mine does any time I reset the ECU.
I'm wondering whether your ecu is still seeing the constant +12v. Or maybe voltage on that wire running too low when cranking. Or your truck not seeing the cranking signal which does have an impact on what the truck does with regard to learning.
Personally I'd move on to verifying the voltages are as they should be at the ECU. Particularly all grounds, "+b" which is your constant 12v, the start signal, etc
I'm wondering whether your ecu is still seeing the constant +12v. Or maybe voltage on that wire running too low when cranking. Or your truck not seeing the cranking signal which does have an impact on what the truck does with regard to learning.
Personally I'd move on to verifying the voltages are as they should be at the ECU. Particularly all grounds, "+b" which is your constant 12v, the start signal, etc
- Thread starter
- #67
Interesting. I'll have to search for some threads on how to test those items. I've got an FSM.
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- Thread starter
- #68
Soooooo, I've been looking at the EWD in the FSM and I'm a bit lost--electric troubleshooting is not my strong point. More of a wrenches type of guy. Little help? I've got the ECU out and disconnected with mulitmeter in hand.
bloc
SILVER Star
if you have the ECU out remove both main covers and give the circuit board a good look for leaking capacitors. Caps will be cylindrical objects with a colored shrink wrap.. these can leak their guts onto the circuit board which will corrode it. Unlikely that this second ECU (IIRC?) has the exact same issue, but since you have it out it is easy to check.
The rest of what I'm thinking of needs to happen to the harness where it goes to the ECU.
There are 4 gray plugs that go into the ECU. The one notated as "D" on the EWD is called E7, and it is 22 pins. It is one of the two big connectors. The other large one is 26 pins, E10, for the record. If you look VERY closely there are tiny numbers printed on the back side of the connector where the wires go in. If you can't see these, Write out a list of the 4 corner wire colors and what pins they correspond to via the EWD (there is an index of each connector and which slots will have wires or an X to show no wire) to map out which pin is what.
If you look at your EWD You'll see the EFI main relay just to the left of the ECU, and a R-Y (Red/Yellow) wire going from the power source 15A EFI fuse to the EFI MAIN RELAY. It also jumps off of this and goes to page 4, where it drops down and into the ECU at E7 (22-pin connector) pin 2. Basically what this means is this wire/pin should see +12v constant via the EFI fuse.. even when the truck is off. This is what lets the ECU "remember" the idle and fuel trim settings, and also what gets voltage cut when you pull the battey or EFI fuse to reset the ECU.
Also on E7:
Pin 13 Black/Blue should see +12v when ignition is ON
Pin 11 Black/Red should see +12v when ignition is in START, ONLY when shifter is in Park OR neutral. Nothing in R,D,2,1
Pin 22 Black/White should see +12v when the ignition is in START, whether it is in Park/Neutral, or not
Personally I'd be checking pins 2 and 13 with the ECU out AND in.. and pins 11/22 with the ECU in only (to minimize cranking). You'll probably need help with the start circuits. You can push the multimeter probe into the back of the harness connector slots while they are plugged into the ECU.. just be careful not to damage anything by going bananas.
The start circuits may not be super relevant, but I know for a fact that on my toyota diesel swap with an electronically controlled denso fuel injection system, if the ECU didn't get a start signal, the timing would be WAY out. Clearly toyota/Denso thinks the start signal is important enough to run a wire and let it impact some parameters of how the ECU runs things.
On E10 (26-pin):
Pins 13 & 26 will be Brown, make sure these both have a very good ground.
Pin 24 is Brown/Black, also should get ground. Note that there is another Brown/black on this connector, but it is a ground from the ECU to a few sensors, it shouldn't show a clean ground unless the ECU is plugged in. (even then, it is unlikely to be your problem)
Hope this helps..
If it doesn't change anything, we can start moving on to oxygen sensors, IAC circuits, etc
The rest of what I'm thinking of needs to happen to the harness where it goes to the ECU.
There are 4 gray plugs that go into the ECU. The one notated as "D" on the EWD is called E7, and it is 22 pins. It is one of the two big connectors. The other large one is 26 pins, E10, for the record. If you look VERY closely there are tiny numbers printed on the back side of the connector where the wires go in. If you can't see these, Write out a list of the 4 corner wire colors and what pins they correspond to via the EWD (there is an index of each connector and which slots will have wires or an X to show no wire) to map out which pin is what.
If you look at your EWD You'll see the EFI main relay just to the left of the ECU, and a R-Y (Red/Yellow) wire going from the power source 15A EFI fuse to the EFI MAIN RELAY. It also jumps off of this and goes to page 4, where it drops down and into the ECU at E7 (22-pin connector) pin 2. Basically what this means is this wire/pin should see +12v constant via the EFI fuse.. even when the truck is off. This is what lets the ECU "remember" the idle and fuel trim settings, and also what gets voltage cut when you pull the battey or EFI fuse to reset the ECU.
Also on E7:
Pin 13 Black/Blue should see +12v when ignition is ON
Pin 11 Black/Red should see +12v when ignition is in START, ONLY when shifter is in Park OR neutral. Nothing in R,D,2,1
Pin 22 Black/White should see +12v when the ignition is in START, whether it is in Park/Neutral, or not
Personally I'd be checking pins 2 and 13 with the ECU out AND in.. and pins 11/22 with the ECU in only (to minimize cranking). You'll probably need help with the start circuits. You can push the multimeter probe into the back of the harness connector slots while they are plugged into the ECU.. just be careful not to damage anything by going bananas.
The start circuits may not be super relevant, but I know for a fact that on my toyota diesel swap with an electronically controlled denso fuel injection system, if the ECU didn't get a start signal, the timing would be WAY out. Clearly toyota/Denso thinks the start signal is important enough to run a wire and let it impact some parameters of how the ECU runs things.
On E10 (26-pin):
Pins 13 & 26 will be Brown, make sure these both have a very good ground.
Pin 24 is Brown/Black, also should get ground. Note that there is another Brown/black on this connector, but it is a ground from the ECU to a few sensors, it shouldn't show a clean ground unless the ECU is plugged in. (even then, it is unlikely to be your problem)
Hope this helps..
If it doesn't change anything, we can start moving on to oxygen sensors, IAC circuits, etc
- Thread starter
- #70
Thanks for the helpful reply.
Here are my results:
ECU looks good internally, no blown capacitors, etc.
E7 Pin 2: +12v
E7 Pin 13: +12v
E7 Pin 11: +9v (EWD says 9-12v is acceptable for pins 11 and 22 unless I'm reading the EWD incorrectly?)
E7 Pin 22: +9v
E10 Pin 13: .9 ohms
E10 Pin 26: .9 ohms
E10 Pin 24: .6 ohms
Here are my results:
ECU looks good internally, no blown capacitors, etc.
E7 Pin 2: +12v
E7 Pin 13: +12v
E7 Pin 11: +9v (EWD says 9-12v is acceptable for pins 11 and 22 unless I'm reading the EWD incorrectly?)
E7 Pin 22: +9v
E10 Pin 13: .9 ohms
E10 Pin 26: .9 ohms
E10 Pin 24: .6 ohms
bloc
SILVER Star
EWD is to be trusted over me concerning 11 and 22.
Did you check how much Pin 2 drops during cranking?
Did you check how much Pin 2 drops during cranking?
- Thread starter
- #72
Drops to 10.5v
bloc
SILVER Star
That doesn't seem excessive.
Ok.. so all of this means that your ECU shouldn't be getting reset.
You said you get the AC idle up.. I see four coils on the IAC valve.. I'm not sure how this thing operates but with four coils it is possible that there are different "steps" of idle up.. maybe small ones for things like the a/c and PS, and big for cold start?
When you had the IAC apart, did you notice any Orings or weird stuff that didn't seem factory?
According to the EWD it gets +12v from two Y/R wires, and actual control inputs (assume modulating the negative of each circuit) on E10 pins 4 6 5 and 7. I'd verify continuity from the ECU connector E10 to the IAC plug itself on the engine harness. Since you have the EWD I won't bother listing out wire colors and IAC pins. Also verify continuity for the positive side.. For this you can either use the Y/R wire in the EB1 connector.. it is gray, ~3 wires, and right behind the distributor.. or pin 22 Y/R on IH1 which is the large white 24-pin connector behind the glove box. Now that I think about it, to help isolate things I'd personally unhook both EB1 and IH1.. and check between EB1 and the IAC plug.
The EWD shows resistance values for the pins of the IAC valve itself. You can disconnect EB1 and check how close these resistance values are at the actual ECU/IH1 connectors are as well.
Ok.. so all of this means that your ECU shouldn't be getting reset.
You said you get the AC idle up.. I see four coils on the IAC valve.. I'm not sure how this thing operates but with four coils it is possible that there are different "steps" of idle up.. maybe small ones for things like the a/c and PS, and big for cold start?
When you had the IAC apart, did you notice any Orings or weird stuff that didn't seem factory?
According to the EWD it gets +12v from two Y/R wires, and actual control inputs (assume modulating the negative of each circuit) on E10 pins 4 6 5 and 7. I'd verify continuity from the ECU connector E10 to the IAC plug itself on the engine harness. Since you have the EWD I won't bother listing out wire colors and IAC pins. Also verify continuity for the positive side.. For this you can either use the Y/R wire in the EB1 connector.. it is gray, ~3 wires, and right behind the distributor.. or pin 22 Y/R on IH1 which is the large white 24-pin connector behind the glove box. Now that I think about it, to help isolate things I'd personally unhook both EB1 and IH1.. and check between EB1 and the IAC plug.
The EWD shows resistance values for the pins of the IAC valve itself. You can disconnect EB1 and check how close these resistance values are at the actual ECU/IH1 connectors are as well.
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- Thread starter
- #74
Nope. No o-ring mods or anything like that. I'll have to find some time to test the IAC but when I had it out a month or so ago the stepper motor worked fine. I was able to fully open/close it. The reputable shop I use hooked up an OBD1 device to all four IAC pins and found nothing amiss there or at the ECU. I will go through the tests you recommend however. If that checks out, where might you go from there. This whole thing is baffling! I'm surprised there aren't more 80 owners that have reported this.
bloc
SILVER Star
Honestly I'm not sure where to go other than verifying everything else works as it should. Not knowing how the ECU maps IAC use means it is hard to point at any one thing as a cause.. Which also means it could be just about anything.
And personally I prefer testing pinouts and checking wiring before throwing parts ($$$) at the problem.
What we do know is your truck doesn't seem to want to act like the vast majority of rigs like it.. so time to burrow down and figure out exactly what is different?
One thing I did think about.. fuel? Maybe if it's not building pressure quickly enough that will cause the stumble and the ECU's reaction is to bypass the high-idle? OTOH a quick way to look into this would be to start the truck cold, then shut it off quickly, then immediately start it again. Fuel pressure shouldn't bleed off substantially in that time. Though giving 12v directly to the fuel pump even before starting would be a more effective way of assuring you have fuel pressure.
And personally I prefer testing pinouts and checking wiring before throwing parts ($$$) at the problem.
What we do know is your truck doesn't seem to want to act like the vast majority of rigs like it.. so time to burrow down and figure out exactly what is different?
One thing I did think about.. fuel? Maybe if it's not building pressure quickly enough that will cause the stumble and the ECU's reaction is to bypass the high-idle? OTOH a quick way to look into this would be to start the truck cold, then shut it off quickly, then immediately start it again. Fuel pressure shouldn't bleed off substantially in that time. Though giving 12v directly to the fuel pump even before starting would be a more effective way of assuring you have fuel pressure.
Try checking your voltage on the ecu pins THW and E2. Check the voltage b4 you start it when cold and as it warms up with ign on. The voltage should raise as.it warms up. Will be a low voltage- 1 and below
ppc
M Go Blue
In post #1 you indicated you cleaned the throttle body and the IAC. Did you make sure the ports in the TB that route to and from the IAC opening were actually clear from any blockage or restriction? If there was any type of resriction then the fuction of the IAC could be nulified.
- Thread starter
- #80
I'll have to check that out. What is that looking for? Thanks.
EDIT: Disregard. Looked in my FSM and saw those were the ECT pins on the ECU. Thanks.
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