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
Staff member
Paid Member
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
Staff member
Paid Member
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
Staff member
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
Staff member
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
Staff member
Paid Member
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
 
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