86 2.1 idle issue searched & worked - please lend me your ear

[fortheloveofvdub]

‘86 2.1, I have an idle issue I’ve chased for a very long time. Ive searched, I’ve worked, I’ve swapped.
When cold starting it revs up (don’t have a tack’ but enough to make you worry on cold startup) and dies. It does this over and over until it warms up just a tad. The transition period between cold and warm is the only time it half ass idles correctly. Then, once warm it drives well but once at a stop sign in neutral or with the clutch actuated, the idle ramps way up and stays there until you pop the throttle with your foot. At that point it dies way down and hunts right back up and would stay ramped way up until you pop the throttle again.

The only things left in question are the ECU and fuel pressure regulator.
New or re-built parts were:
-new power steering switch
-new distributor (I broke the plug on the old one)/ plugs/ wires
-new fuel lines
-New fuel filter
-new aluminum fuel “rails”
-injectors professionally cleaned re-sleeved and flow checked
-rebuilt idle control module (module master) with each terminal cleaned and dielectric greased

-AFM swapped out with another running van to no avail,
-new air cleaner
-new oxygen sensor
-new “temp 2” sensor
-new breather tower
-go-westy rebuilt throttle body
-idle control valve checked for operation per searched info
-grounds cleaned and dielectric’ed: under dash, in battery box, by ECU, on engine bay wall, on block, on nose of tranny AND an 8ga. wire ran from ground at battery, to ground to battery box, to nose of tranny, to block to ground and to the ground on the engine bay to ensure a strong ground.
-new vacuum hoses with clamps on all
-AFM clamped well with no cracks
I’ve been wrestling with this for years.
Any smoking guns left to check for please? Where should I “go” next?

[4Gears4Tires]

I'd start off with a smoke test for vacuum leaks.
_________________
'87 Syncro Ferric Oxyhydroxide Superleggera Edition
'85 Westy Sciuridae Domus Edition

[Igeo]

Idle control switch on the throttle body adjusted correctly?
_________________
1987 Westfalia 2.1 WBX Manual

[fortheloveofvdub]

Thank you, I’ll search that "smoke test" procedure next.

(later edit to reply: I forgot about that, good call!)

[fortheloveofvdub]

Idle control switch adjusted. I will double check it however. I put it on about 3 years ago.

[DanHoug]

how does it act with the plug to the idle stabilizer valve unplugged?
_________________
-dan
60% of what you find on the internet is wrong, including this post.

'87 Westy & '89 Westy both 2.1 4spd

Past projects can be found at--
www.thefixitworkshop.com

[fortheloveofvdub]

Huh, I have not tried that recently. Will research tonight also, thank you!

[shadetreemech]

I was having to pop the accelerator after coming to a stop. Turns out, I pulled the Throttle Position Switch out, cleaned it up, gapped it per 117 in the Bentley, no more pop the pedal no mo'.

https://www.thesamba.com/vw/forum/viewtopic.php?t=268356&highlight=throttle+position+switch

Dan
_________________
'84 GL 1.9
'01 Volvo V70 T5
'88 Westy - "MZDRTHY"

[SyncroHead]

[fortheloveofvdub]

I read back again about unplugging the idle stabilization valve. I forgot all about that as a diagnostic indicator.
I also read back through several write-ups on the TPS. I need to check the conduction of the switch and make sure it's gapped correctly also. When I put the new one in there it didn't change the idle for the better at all. At that time I did not check the switch too closely except for the "click" at the right time. It was supposed to be all ready to go and thought not to fix what might not be broken. That new throttle body only has probably 1,000 miles on it.
I think I will "start" again there.
During this re-do all new stainless steel coolant lines and hoses were put in. Also a new distributor so it's not in time perfectly yet. It had that same old pattern of idle, however.
I think I will check the rubber hoses and paper gaskets on the intake also. I put them there 12 years ago and they're the only part of that system undisturbed. I forgot about the "smoke test"! BINGO
If this is a vacuum problem I will stand on my head and fart sparks!
Thank you for your input. I first started searching for this problem here 10 years ago.
One new one I found was that not only the PS switch (I replaced) provide input on the idle so does the AC. My AC is not functioning. I wonder what connector the signal comes from and what happens in that signal when there isn't one.
I was so disheartened that after 3 years of multisystem overhaul the same damn idle popped up. You folks of all people know what I mean.