When I let off the gas before a stop, idle drops to 0 and the inside of the exhaust pipes are coated with black soot (running rich). Sometimes it will catch itself and try to keep running, sometimes it stalls. Could this be the ISV (idle stabilzer valve) stuck open?

Searching the forum reveals a tip for freeing up the ISV by spraying WD-40 or a carb cleaner down a vacuum line, starting at the brake booster and follwing it as close to the engine as I can get before openning it up to spray. How much spray should it take? 5 secs or 30 secs? Do it while its running? ( I guess yes)

This is my daily driver, so I need to get it fixed ASAP

Thanks for any help

KK

 

Could be your MAF sensor is going bad. If you have a 928 buddy near by, all the LH MAFs fit the all LH cars, try swapping MAFs. A gross test is to unplug it and see if the car runs better.

 

Idle stab, sounds like it...

if the idle hunts a bit and bobs up and down it sounds like the IS... I think that some cars used to call this an aux air valve..

on my 86 it was doing this... if I let off the gas the idle would plummet and bounce off at about 200 rpm then it would catch go to 1200 and then back to about 600 then it would be stable..

The best way is to try and lubricate it is to remove the passenger side air plenum then you should be able to see a hole in the tee shaped peice (from the inside with a flashlight)... spray the lube into that hole which... a rubber hose connects the Tee to the ISV.. the idle stab acts as an electronically activated mini throttle... to add or take away air as needed... The hose I mentioned actually bypasses the throttle body...

I used liquid wrench (about the same as wd 40 and it seemed to help... my ISV was working well but I took the intakes off and was messing around for quite some time.. I think that the intakes are usually so wet with oil that these things usually stay well lubed... but sitting for 5 months exposed to air and moisture may have caused it to start to stick.... I have a major oil leak that is keeping me from driving it but the 5 or 10 miles since i sprayed it with wd 40 suggest that this helped... it still if swaying but not stalling...

LO

 

Oh yeah and the soot... that could be a maf or maybe o2... or probably a lot of things....


If you are trying to lube your idle stab from the brake booster vac line I think you will have to flood the intakes with wd 40 ( two or three cans haha).... the brake booster on your car hooks to the driver side plenum and the air tube under the throttle body the

line I spoke to you about is the only direct line I know of...

Here is a pic

take the passenger plenum off.
Spray where the red arrow is...
it should drip down to the ISV.... (the hose takesa u-turn unter the tee peice)

maybe this will get you running temporarily....

LO

 

Having just gone through this myself, i would pull the intake and check not only the idle stab but also all the hoses under there...mine were literally rotten..while there you can inspect the MAS...air leaks fool the injection brain and can lead to rich.

87 euro auto
silver/black

 

Yeah if you have the time and $$$ it is not too hard to pull it all...

All the rubber sleeves, vac lines, injectors, and hoses cost me like $1000

You will need a lot of hoses and the easiest thing is to make good notes and take the PN off the hoses as you go.... Some of the hoses on the 85-86 cars were not in the pet or not easy to find in the pet... Like the cam cover breather lines... If you run into a snag then let me knopw maybe I can look thru the receipts...


youll need...
Intake gaskets, o rings for air tubes and t body, 8 small sleeves, 2 big, tbody and MAF sleeves, a bunch of hoses (easy), May as well replace your tstat and seals there, polish your coolant elbow, vac line and connections, injectors (maybe try the ford ones from summit - 24 lbs for yoiur car)...I will let everyone know how mine goes after next week...

Just call devek or your favorite big vendor and get it all... it does not make sense to just do it peacemeal... it will just bite you in the **** anyway and the peace of mind it good...

just remember to take notes etc.. and even when you do that mistakes can be made... I made a couple of big booboos...

LO

 

Make sure there isn't a raccoon plugging your ports

 

I did check for racoons, none found. I have an MAF on order from JDS Porsche, will update y'all if that solves it. 5 days wait for shipping, I would really appreciate it if together, as a nation, we could convince John Speake to forgo his Imperial citizenship and join us rebels on this side of the lake!

Update in 5 Days!

KK

 

I copuld have sent it 1-2 day FedEx if you paid a little extra.....:-)

Regards