Hesitation just off idle (and only in gear)

[ckuske]

Which reader do you have?

Hi Dane,

This is the one I have. I’ve had it for a few years but have been using it more lately trying to get these last things closed off:

https://a.co/d/bi62gOr

I’m conflicted whether this is a valid theory since the KOEO seems to work well. It’s less traffic to analyze than KOER though. I’m almost wondering if there is a maybe a grounding issue on the EEC?

As a person at my work says, I am starting to look to “moonbeams” as theories…

[grumpin]

Hi Dane,

This is the one I have. I’ve had it for a few years but have been using it more lately trying to get these last things closed off:

https://a.co/d/bi62gOr

I’m conflicted whether this is a valid theory since the KOEO seems to work well. It’s less traffic to analyze than KOER though. I’m almost wondering if there is a maybe a grounding issue on the EEC?

As a person at my work says, I am starting to look to “moonbeams” as theories…

That’s the one I have and I’ve been happy with it.

I agree, could be a grounding issue, the EEC or the reader. This is aggravating.

I don’t remember, have you checked the wiring from the reader hook up to the EEC?

Does anyone you know have the same era Ford that you could check the reader on?

I use the reader on my Bronco and the 94 F250 I used to own.

[Gary Lewis]

That’s the one I have and I’ve been happy with it.

I agree, could be a grounding issue, the EEC or the reader. This is aggravating.

I don’t remember, have you checked the wiring from the reader hook up to the EEC?

Does anyone you know have the same era Ford that you could check the reader on?

I use the reader on my Bronco and the 94 F250 I used to own.

That's a bummer to have the reader seemingly go bad in the middle of reading. At that point I'd use a test light to read the codes, as explained on the page at Documentation/Electrical/Electronic Engine Control (EEC).

But, I'd drive it a bit to see if it learns something, like it seems to have done this time. You've fixed a vacuum leak so maybe it takes it a bit to forget that?

[ckuske]

That's a bummer to have the reader seemingly go bad in the middle of reading. At that point I'd use a test light to read the codes, as explained on the page at Documentation/Electrical/Electronic Engine Control (EEC).

But, I'd drive it a bit to see if it learns something, like it seems to have done this time. You've fixed a vacuum leak so maybe it takes it a bit to forget that?

Yep, back to basics! Hopefully things are clearer with a test light.

A test light is coming tomorrow, but I’ll be on a work trip this week. (First one since COVID, and I was flying home on my last trip one day before international flights got shut down!)

I hope to post findings again next Friday or Saturday.

[Gary Lewis]

Yep, back to basics! Hopefully things are clearer with a test light.

A test light is coming tomorrow, but I’ll be on a work trip this week. (First one since COVID, and I was flying home on my last trip one day before international flights got shut down!)

I hope to post findings again next Friday or Saturday.

Hope you have a good trip and then you are fresh when you get home and can sort out the problems.

[ckuske]

Hope you have a good trip and then you are fresh when you get home and can sort out the problems.

Thanks Gary, I'm back. It was weird to be back out into the world after three years at home... (mostly)

I fired up the truck in the garage and let it run for a good 10 minutes or so, just to give everything a little "stretch" and confirm the problems were still there.

I didn't take it on the road, but the stumble at high idle is there still. I confirmed also that if you kick the idle down, the problem is "gone". If you give some gas back to around 2000 RPM, the problem appears again.

It occurred to me that normally when I run the KOEO, the engine is cold. So, I ran a KOEO again after it was warmed up.

I got one code: 31. I had seen this before a couple years ago, but I replaced the EVP sensor and it went away. I ran the test multiple times - same code every time. There were a few continuous codes also, but I'll gloss over those for now. I also ran a KOER and got 31 on there first, along with a few others. I'm surprised that all of the sudden I have KOEO codes again, but if the ECM is going bad, then maybe it is not a shock.

I verified that there is 5VDC on the VREF line. I then backprobed SIGRTN to EVP, and it was tough to get a reading. At one point, I got .21VDC, but I have read it should be at least .25VDC. I then jumpered VREF to EVP, as I read that the code should change from 31 to 35. It didn't, it stayed at 31. So, I think this means I have more bad wiring all of the sudden (and I didn't touch that portion of the harness), or the ECM is on its way out.

The next recommended step is to take off the ECM connector and check for (lack of) continuity between pins 27/40, and 46/60. If there is, then it indicates an wiring issue. If it checks out, it means my ECM is bad (most likely?).

My ECM is behind the I/P, between the radio and instrument cluster. It looks like I can take the connector off to check the pins, but if that passes, how do I remove the ECM? Do I need to take the dash pad off? Or the whole thing () It looks like a bear to remove, and I think I remember some screws on the side between the frame that holds the ECM and the ECM itself?

[Gary Lewis]

Thanks Gary, I'm back. It was weird to be back out into the world after three years at home... (mostly)

I fired up the truck in the garage and let it run for a good 10 minutes or so, just to give everything a little "stretch" and confirm the problems were still there.

I didn't take it on the road, but the stumble at high idle is there still. I confirmed also that if you kick the idle down, the problem is "gone". If you give some gas back to around 2000 RPM, the problem appears again.

It occurred to me that normally when I run the KOEO, the engine is cold. So, I ran a KOEO again after it was warmed up.

I got one code: 31. I had seen this before a couple years ago, but I replaced the EVP sensor and it went away. I ran the test multiple times - same code every time. There were a few continuous codes also, but I'll gloss over those for now. I also ran a KOER and got 31 on there first, along with a few others. I'm surprised that all of the sudden I have KOEO codes again, but if the ECM is going bad, then maybe it is not a shock.

I verified that there is 5VDC on the VREF line. I then backprobed SIGRTN to EVP, and it was tough to get a reading. At one point, I got .21VDC, but I have read it should be at least .25VDC. I then jumpered VREF to EVP, as I read that the code should change from 31 to 35. It didn't, it stayed at 31. So, I think this means I have more bad wiring all of the sudden (and I didn't touch that portion of the harness), or the ECM is on its way out.

The next recommended step is to take off the ECM connector and check for (lack of) continuity between pins 27/40, and 46/60. If there is, then it indicates an wiring issue. If it checks out, it means my ECM is bad (most likely?).

My ECM is behind the I/P, between the radio and instrument cluster. It looks like I can take the connector off to check the pins, but if that passes, how do I remove the ECM? Do I need to take the dash pad off? Or the whole thing () It looks like a bear to remove, and I think I remember some screws on the side between the frame that holds the ECM and the ECM itself?

Glad you are back.

I don't know about the error codes, but I do know something about the ECU bracket. I posted about them in this post, but have copied some of the pictures over here.

There's a tab that holds the ECU in the bracket, which you can see in both of the pictures. In the left pic you can see the tab on the lower right of the right one. The left pic shows the front of the bracket and the right pic is the rear of the bracket. So you should be able to pull that bolt, remove the tab, and slide the ECU down.

[ckuske]

Glad you are back.

I don't know about the error codes, but I do know something about the ECU bracket. I posted about them in this post, but have copied some of the pictures over here.

There's a tab that holds the ECU in the bracket, which you can see in both of the pictures. In the left pic you can see the tab on the lower right of the right one. The left pic shows the front of the bracket and the right pic is the rear of the bracket. So you should be able to pull that bolt, remove the tab, and slide the ECU down.

Thanks, I got it pulled out no sweat.

There is something small rattling around inside - maybe not a screw, but probably something that shouldn't be there!

If the wiring checks out, it looks like the Cardone reman unit is the most common/available. Any reason I should go somewhere else? Recommendations?

The ID number on it is E43F-12A650-Z1A

[Gary Lewis]

Thanks, I got it pulled out no sweat.

There is something small rattling around inside - maybe not a screw, but probably something that shouldn't be there!

If the wiring checks out, it looks like the Cardone reman unit is the most common/available. Any reason I should go somewhere else? Recommendations?

The ID number on it is E43F-12A650-Z1A

I haven't found that # in the MPC. But I do agree that you shouldn't have anything rattling around in the ECU. I'd pull the cover and see what you can find.

[ckuske]

I haven't found that # in the MPC. But I do agree that you shouldn't have anything rattling around in the ECU. I'd pull the cover and see what you can find.

Yep, that’s the plan tomorrow!

In the Fuel section of the parts catalog, my truck is either Calibration 376 or 409 (not sure which, the label on the valve cover is long gone)