Idle issue has me stumped

chadly

Registered
I have been getting a high idle, around 2K in park, 1200 in drive. My first thought was a vac leak, went through everything but couldnt find any leaks.

On a hunch, I disconnected the battery for a few minutes and it ran fine for a couple days, then the high idle returned. I checked for codes but couldnt find any. Now whenever it starts doing this again I either reprogram the ecu with my X3, or disconnect the battery and it "fixes" it for a while.

I am thinking its a sensor, but which one? Any ideas or suggestions are greatly appreciated.
 

Venti Dragon

Registered
Same in here. Changed the IAC , TPS , higher and lower gaskets on intake manifold, new air and fuel filters , new spark plugs. No leaks.... when I slightly open the tube after the air box it runs as it is supposed to be. Will try to put K@N air filter hopefully will help with air flow... :( any help would be appreciated.
 

driller

El Presidente
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Did you clear the KAM when you replaced the IAC valve?

Whenever you replace an IAC component it is recommended that the KAM (Keep Alive Memory) be cleared so the idle strategy does not use the previously learned adaptive values. Erasing DTCs does not clear the adaptive idle table.

To clear the KAM, disconnect the negative side (only) of the battery for a minimum of five minutes. When reconnected the idle strategy will need to be relearned and that may take several drive cycles.
 

Venti Dragon

Registered
Yes. I did. Actually I disconnected both ( - and + ) terminals and put jumper cable between for about 5 minutes. Everytime after that it starts perfect and runs for about 15 -20 miles and at some point of driving goes again with rpms about 1100 at low idle at park or neutral... :( if I press the pedal to 3500 rpms and step out of it.... it drops very quickly to arround 1500 rpms and it takes about 30 seconds to go back to 700 rpms. If I disconnect the air tube right between the air filter box and the plastic tube that goes to the TB It runs great. ( meaning rpms drops fast to where are supposed to be. ) what that should point to? And is there software for live diagnostic on my 1995 mark viii that I can use? It's obd-I ? Thank you for your fast reply. :)
 

driller

El Presidente
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Yes. I did. Actually I disconnected both ( - and + ) terminals and put jumper cable between for about 5 minutes.
According to the PCM troubleshooting and diagnostic manual, the specific instructions are to disconnect ONLY the negative battery terminal (to clear the KAM). I am not certain but I theorize the PCM senses the presence of the positive voltage and recognizes the negative terminal has been disconnected and internally starts a 5 minute "countdown". This is specifically different from disconnecting BOTH terminals (as when "resetting" the PCM or even simply replacing a battery).

Realize the disconnect of the air tube is allowing unmetered air (air that has NOT been "measured" by the MAF). The results of such a response you describe indicates to me a fault in the MAF circuit such as a dirty or faulty sensor or some type of issue with the circuit wiring (open, short, etc...).

Yes, there are live diagnostic tools available that you can use but they are limited to specialty service tools of the era such as the Ford Rotunda STAR tester and the FLM 'breakout-box' for the PCM interface. Some earlier third party tool vendors such as Snap-On and others were able to run live diagnostic scans to varying degrees.
 

Venti Dragon

Registered
Wow... thank you soo much for the info. Will try all of your concerns this Monday. I'm out of states... would be soo easy to have someone check my car out there.... but here in EU. sucks... :( have to do all of my work by myself... thank's again and God bless you !!! :)
 

Venti Dragon

Registered
Update: tried all of concerns. Nothing. Besides 4 days ago shifting into 2-nd gear takes long... about over 2000 rpms. Have power not grinding noises. Just takes long to go into 2-nd gear. After that it goes smoothly into 3-rd and 4-th. Decided to change today VSS, OUTPUT SS, CRANKSHAFT SENSOR AND CAMSHAFT SENSOR. That fixed the high idle, and now when I let out the gas pedal at 80 km/hrs I get down to 1 l / 100 km. Which it's great. Before I was happy to get 5 L/ 100 km.
Now I'm worried about that 1-st to 2-nd gear delay. Any help would be appreciated. Thanks.
 

driller

El Presidente
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Paid Member
Sounds like you possibly have a stuck 1-2 shift accumulator. Is this something that has just started abruptly or has it been ongoing for some time?

If it is the 1-2 shift accumulator, you would need to drain the transmission fluid and remove the pan to access. Replacement is not major surgery. YouTube has several videos...
 

Venti Dragon

Registered
Sir? I've been looking all arround. Can't find a place where I can get that whole assembly. Need help. 1995 lincoln mark viii - 1st to 2nd shift accumulator set. I don't feel comfortable with jmod as advertised on most sites. Any links to part number's sites etc. Would be greatly appreciated... just wana do a swap of the broken parts. Thank you in advance...
 

driller

El Presidente
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Paid Member
HERE you go!

The 1-2 accumulator springs, piston, retainer and retaining ring are universal across the 4R70W transmissions. There are spring options and deletes for varying modified applications, but for a stock vehicle you are best advised to use both standard upper/lower springs (Factory Direct Replacement for F75Z-7F284-AA upper and F7AZ-7F284-BA lower springs).
 

Venti Dragon

Registered
How about the piston stock number? Is there a shop where I can order the whole set? Piston, seal and both springs. I'm abroad... not in the usa... :( I wish could be there. Thank you tons. I really appreciated your kindness received.
 

driller

El Presidente
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Click the link I posted above or go to bcawebstore.com for the 1-2 accumulator spring kit($22). You can add option for the "1-2 accumulator kit with cap"(piston with retainer cap) for $19 and even the "1-2 accumulator retainer ring" for an additional $4. All together should be no more than $45 plus shipping.

Very likely you only need the springs, but if you have the OEM 1-2 accumulator piston which was an aluminum body with o-ring seals - you want to upgrade to the new piston with the bonded rubber wiper style seals, part number F7AZ-7F251-AA. See the link below from the tech pages for details...

https://www.lincolnsofdistinction.org/lincolntech/modrepair/accumulatorupgrade.html
 

Venti Dragon

Registered
I'm lost... :( springs were NOT broken it was original orange top and purple on the bottom. As well with aluminium piston. I replaced all the kit with white-blue on top and purple on the bottom plus new ( upgraded) piston and new cap... oil was clean. No debris... tapped with new mercon V and new filter. Same difference. Have power but long delays from 1-st to 2-nd. It changes to 2-nd at about 3000+ RPM'S... HEEEELP MEEEE 😭😭😭
 

driller

El Presidente
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So... I was thinking about this.

This shifting issue appeared before, during or slightly after the idle issues? The idle issue appears to be resolved now?

Either the malfunction is in the 1-2 shift or when it is commanded to shift. The usual suspect (1-2 shift accumulator) did not appear to help so we can assume it is functioning as it should and either the shift physically cannot complete for some reason or the shift is yet to be commanded when it should be.

If it is a physical problem in the shift, I tend to believe it could be due to low pressure. That would likely manifest itself in other ways besides just the delay in the 1-2 shift. You could seek a transmission shop and have the pressures checked.

The more likely explanation is the shift is not being commanded properly, possibly due to a faulty input. The first thing that comes to mind for me is the throttle position sensor.
 

Venti Dragon

Registered
It start slightly after replacing all sensors. VSS, Output SS, Crankshaft SS, and Camshaft SS in order to fix high idle issues that I had. High idle issues are gone now. I pushed the car after replacement of those sensors ( car went to about 6000 RPM changing into 2-nd gear and the problem occurred right after. It has the same symptom like on the video you pointed to me about 1-2-nd gear accumulator spring broke. So I thought I broke the spring. But in my case I was not lucky... :( how about solenoids etc. Nobody have that scan tool in Bulgaria... 😭 I HATE THIS COUNTRY!!! 🤬🤬🤬 BTW I still don't have my cruise control working and prior changing all the sensors I had rpms increase while stepping on the brakes while driving ( if that helps on diagnostic) .After changing all the sensors that issue is gone now. Thank you for your support . Respect!!! :)
 

driller

El Presidente
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...how about solenoids etc. Nobody have that scan tool in Bulgaria...
IF you could find a scan tool that could datalog the shift, that would truly help. I'd have to dig back in the manuals but there is a way to tell when the shift command is electronically given and you can monitor rpms, VSS and OSS to determine when it shifts relative to the command as well as torque converter slippage and lockup. Lacking that we have to rely on logic and intuitiveness to ascertain the cause of the problem.

Shift solenoids rarely fail and if they do it usually just will not shift, so that would be far down the list of potential suspects in my mind. I have personally witnessed strange shifting due to a faulty TPS however. And I suppose if there was a fault with the VSS/OSS that could cause a problem in shifting as well. What is odd to me is the fact that it appears to only influence the 1-2 shift and not the other shifts. Ford diagnostics involve a lot of special tools and specific procedures not readily available to the layman but I like to refer to the troubleshooting charts to help pinpoint the path forward.

When it comes to the automatic transmission, it becomes even more involved as we are now adding hydraulics to the customary electrical and mechanical issues to diagnose. Shift concerns span all three; electrical, hydraulic and mechanical. When it comes to improper shifts or no shifts, we start with the electrical aspect of the Powertrain Control System.

The electrical components responsible for input/output controls of the powertrain control system include the electrical harnesses, the PCM, shift solenoids, EPC solenoid, TFT sensor, OSS, TPS and MLPS. Ford's testing process involves testing of these components with special tools and pinpoint tests.

The hydraulic/mechanical concerns span from fluid level (as well as condition), 1-2 shift accumulator, line pressure, stuck solenoids, stuck valves and blocked or damaged solenoid valve screens (in the valve body).

This all gets even more specific when addressing the 1-2 shift (only). Electrical: harnesses, PCM, shift solenoids and OSS. (Note TPS omitted). Hydraulic/Mechanical: damaged/misadjusted MLPS, intermediate clutch pressure, line pressure, 1-2 shift valve, 1-2 accumulator valve, shift solenoid malfunction(SSA/SS1), gasket damage(valve body), number 8 ball not seating, hydraulic pump (damage, cross leaks, porosity, balls missing), intermediate clutch assembly (seals, piston or friction components), intermediate one-way clutch (not holding or damaged) and finally the planetary one-way clutch (not holding or damaged).

I find it interesting that the TPS was omitted in the diagnosis of the 1-2 shift but I found that to be the case for each specific shift, 2-3 and 3-4. I conclude that if the TPS was at fault it would interfere with ALL the shifts and not just a specific shift.

If you have followed along this far, maybe you see something I see as well. If it were me, I'd be asking what did "I" change that could have possibly caused this? You mentioned replacing all the sensors... I'm wondering if there could be some issue with the OSS? Is it the correct one? Is it faulty (even though it is new - it happens)? Is there an issue with the harness connector?

It may be worth giving the OSS another look. Maybe even backtrace and replace the new OSS with the old one?

Easy enough and worth a shot? :unsure:
 

Venti Dragon

Registered
Thank you again. I'm tired of guessing without proper scan tool. May you point me for tools that will give me options to look at live data table? I'd rather spend money on it so I can see what the heck it's going on. Mechanics in this country don't wanna spend money on equipment for American cars. Such a jerks... I really like my 95 mark viii. I wana fix it. I will appreciate if you give me tips on what kind of equipment I need for this specific car. Thank you in advance...
 

driller

El Presidente
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Paid Member
I understand your frustration. One of the reasons I converted my '93 Mark VIII to OBD2 was to be able to more easily datalog for tuning purposes. There were very few systems able to do so and even fewer now. The best advice I could give you currently would be to look into the Moates Quarterhorse product. https://www.moates.net/quarterhorse-for-fords-p-199.html

You could get an EEC-IV code reader but that wouldn't give live data, just generic diagnostic codes.

iu


You can actually pull codes without one... http://www.thorssell.net/hbook/eectest.html

If you have any codes, a quick google search will tell you what they are.

The Ford Rotunda SuperStar II diagnostic tool is another option, but again it is not useful for live data.

iu


There is also a EEC-IV 'breakout box' which is used to give you access to all the pins on the PCM.

iu


It piggybacks between the harness connector and the computer and has a test port for each wire going to the PCM. You would need to know all the respective pin numbers and their circuit descriptions to successfully probe with a multimeter to test varying circuit outputs and sensors.

Snap-On had a diagnostic scanner (MT 2500?) from that era that could pull live data, but I don't have any details for it. I'm sure you could find a used one on eBay, but be aware you need specific dongles/modules/adapters for different makes/models of vehicles.

The first thing you should invest in is the '95 Mark VIII factory service manuals, including the Electrical and Vacuum Troubleshooting Manual. You can usually find them on eBay pretty cheap. They are definitely helpful troubleshooting the specific problems you'll likely encounter with your Mark VIII.

Good luck and I hope this helps! :)
 
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