Sudden Intermittent High Idle

[brokencase]

Here is the big collection of Merkur TSB's... They are up there for Brad (or somebody) to place up on the Merkur resource page. Remember? I am pretty sure I sent you a PM with a list of files to add to the resource page.
https://www.mediafire.com/file/1o9z21or ... s.pdf/file

It is ocr'd and text searchable. Go to page 279 in the pdf. It says drill out to 3.5mm
But I would not drill the plate unless you have the EECIV to go with it. Also it mentions this is for vehicles built before 9/01/87 - which was very early on. So, like I said, I'll bet most cars have had this issue addressed and the later EECIV's were revised to accommodate.

Also don't assume that if your throttle plate does not have a 3.5mm hole that your car was not updated. This was a running change for early cars and the issue may have been addressed through software change only in later cars.

You should solder the A/C diode in because that area is impacted by moisture.

[DPDISXR4Ti]

Here is the big collection of Merkur TSB's... They are up there for Brad (or somebody) to place up on the Merkur resource page. Remember? I am pretty sure I sent you a PM with a list of files to add to the resource page.
https://www.mediafire.com/file/1o9z21or ... s.pdf/file

Yes, I do remember. I think I may have already forwarded that along but I see now it hasn't been added to the resource page. I will follow-up - thanks for the reminder.

It is ocr'd and text searchable. Go to page 279 in the pdf. It says drill out to 3.5mm
But I would not drill the plate unless you have the EECIV to go with it. Also it mentions this is for vehicles built before 9/01/87 - which was very early on.

That's basically the cut-off for the Model Year 1987 cars vs. 1988. Keep in mind, our "early 1988" cars are really MY 1987 cars in the rest of the world.

[DPDISXR4Ti]

Regardless of whether or not 21 & 24 are responsible for the high idle, I want to address that issue. Looking at the schematic, I need to tear into the harness and inspect splice S111, which is shared across a bunch of devices. Then I need to check Connectors C1935 and C1936, which seems to be located behind the instrument cluster, if I'm reading things correctly. Lastly, I need to check the proper operation of diodes WOT Cutoff Relay Diode and Throttle Air Bypass Valve Solenoid Diode.

The random high idle has returned lately, as have the typical 21, 24, & 52 error codes (they have probably been there all along). The high idle seems to act a little differently with the '89 PCM installed (vs. original one). I actually watched the idle gradually increase from ~1500 to ~2500 while stationary. I think it even dropped down once before going back up. In hindsight I should have popped the hood and disconnected the IAC while running, but I'm pretty confident it would have dropped right back down.

Looking at the EVTM, the location of splice S111and S112 are indicated as "Near EEC takeout". What do we think that even means? For splice S113 they use the location term, "In EEC takeout" and S122 is "Near EEC module takeout". My best guess is that "EEC Takeout" means the big 60-pin connector.

[zxr250cc]

Hi all,

I am not looking at the file mentioned but have worked with PCB and circuits in consumer electronics. Is there an access point shown that could be described like that for a probe or multi meter test?

Cheers

[Ed Lijewski]

The return of SSHIS; I'm loving it.

YMMV

[Ed Lijewski]

'89 EVTM reads "near tape out to ECA (EEC Module)". "Takeout was a typo.

YMMV

[andyofcolumbusmerkur]

The return of SSHIS; I'm loving it.

YMMV

This is the thread that never ends......
I just goes on and on my friends......

[DPDISXR4Ti]

'89 EVTM reads "near tape out to ECA (EEC Module)". "Takeout was a typo.

Yea, I've got the '89 EVTM in front of me now and see they indicate "Near tape out to ECA (EEC IV) module" for all the splices I mentioned previously and more (S110, S111, S112, S113, S122, etc). But what the hell does "Tape out" mean!? I see they use that term extensively in the '89 EVTM.

Regardless, I decided I'd actually try doing something about this issue last night and I swapped in the IAC from the '89 parts car. Just now back from a 20-mile trip with 3 stops and the engine ran flawlessly. I realize that given the highly intermittent nature of this problem that doesn't mean much - time will tell.

I also took a look at the TB currently on the car and it's got the 3.5mm hole on one butterfly as does the spare TB I have from an unknown car. Interestingly enough, the TB from the '89 parts car has no hole at all and there's a channel between the two openings. But, keep in mind, this is a 5-speed car with no EGR from the factory, so that may be the reason for the different TB.

[Bob Weir]

"Tape Out" using tape instead of a plastic connector. My best guess

If interested, I can email you this,
1988 Mercury Merkur Scorpio V6-179 2.9L Copyright © 1997, ALLDATA Corp. 1-888-968-3494 C2.00
The schematics are in reverse white lines on black background
Its similar to the EVTM manual with addition of lists showing locations of:
Components, Connectors, Grounds, & Splices

No, I won't sell mine
If you don't have it, a helpful item is “1988 Car Vacuum & Wiring Diagrams” Scorpio FPS12136-88P
the 11” wide by 17” unfolds to 36” wide by 17” high
Tri-focal glasses or magnifying glass suggested

[brokencase]

'89 EVTM reads "near tape out to ECA (EEC Module)". "Takeout was a typo.

Regardless, I decided I'd actually try doing something about this issue last night and I swapped in the IAC from the '89 parts car. Just now back from a 20-mile trip with 3 stops and the engine ran flawlessly. I realize that given the highly intermittent nature of this problem that doesn't mean much - time will tell.

I also took a look at the TB currently on the car and it's got the 3.5mm hole on one butterfly as does the spare TB I have from an unknown car. Interestingly enough, the TB from the '89 parts car has no hole at all and there's a channel between the two openings. But, keep in mind, this is a 5-speed car with no EGR from the factory, so that may be the reason for the different TB.

I don't have much confidence in the old, used IACs. But if it is working for you then I guess it is fine.

If you want to check the in cable diodes you should be able to do so with a DMM.

Interesting regarding the 5 speed TB.

[Bob Weir]

While doing research on a much newer Ford, I was a little surprised to see comments about Ford still having problems with vacuum hoses. I remember testing the vac hoses with a MityVac, but not necessarily when the Scorpio was having "high idle issues". Why would I want to do that?

Of course, all of you [not me] have checked and replaced every hose and connection and been extremely careful about working near the hoses while ripping out suspect parts and wiring.

34 year old rubber hoses and plastic connectors - in a temperate climate = of course they're ok.

[DPDISXR4Ti]

If interested, I can email you this,
1988 Mercury Merkur Scorpio V6-179 2.9L Copyright © 1997, ALLDATA Corp. 1-888-968-3494 C2.00
The schematics are in reverse white lines on black background
Its similar to the EVTM manual with addition of lists showing locations of:
Components, Connectors, Grounds, & Splices

Does it actually SHOW the location of the splices, etc, or just list them? The EVTM lists the locations with the aforementioned cryptic language. If it's not too much trouble I wouldn't mind taking a look.

If you don't have it, a helpful item is “1988 Car Vacuum & Wiring Diagrams” Scorpio FPS12136-88P
the 11” wide by 17” unfolds to 36” wide by 17” high
Tri-focal glasses or magnifying glass suggested

I know I have the schematics for the XR and probably have them for the Scorpio. I suspect in this case it won't tell me any more than what's in the EVTM, but I've been wrong before.

[DPDISXR4Ti]

I don't have much confidence in the old, used IACs. But if it is working for you then I guess it is fine.

The one that had been on the car was an after-market replacement. It certainly LOOKED better than the 34 year-old one that's on there now, but that one performed flawlessly today as I ran around in the bitter cold for 35 miles with 5 different stops. I did pull codes before leaving today and 21 & 24 had already returned. I would have been surprised if they had not.

If you want to check the in cable diodes you should be able to do so with a DMM.

Good idea, but it would be nice to verify first if they actually are buried in the harness or somewhere else.

[Bob Weir]

< Does it actually SHOW the location of the splices, etc, or just list them? The EVTM lists the locations with the aforementioned cryptic language. >

Unfortunately, neither show the exact location of the splices. However, the "-Scorpio Electrical Diagrams 88.pdf" does provide a little information that might help. Splices index starts on p 134, for example, S110 Near takeout to ECA module, S111 Near EEC takeout. I presume "takeout" means a taped splice rather than a plastic connector. I'm emailing you the 3.2 MB file.

From my 1988 Car Vacuum & Wiring Diagrams FPS-12136-88P is a pic showing a few of the splices you mention. It "appears" to show relative placement of splices. Splices are shown at a location such as p# Letter,# coordinates. As an example Splice 112 is on p2, E - 13. Other pages will show splices in specific locations [p# Letter - #] that are on a line the spans multiple pages. There are on eBAY $35 + $5 SHIP.

Thanks for going through the trouble to "diagnose & cure" the intermittent high idle. This needs an acronym. We should do a contest! I'm sure a few others will have numerous suggestions. Some not for children's' eyes. I'll start with "IHI".

[Bob Weir]

Ken Kiser hopefully still has his home made breakout box that he loaned me to use on my Scorpio. I don't remember if it was pass through or single connector. This could help you determine what circuit and/or component is malfunctioning.

I suggested to the board for MCA to buy it because he was willing to sell it. MCA could loan it to members to use.