If you can figure it out I’ll donate to a charity of your choosing!

So:
Transit Connect 2005
1.8L petrol/LPG

Engine idle very low when cold and stalled at junctions- Previous owner cut IAC connection! I replaced the IAC and rewired (couldn’t tell the polarity but issue below happens when plugged either way).

Engine idles high – 12-1400rpm
When driving if you put the clutch in the revs climb slightly then fall and settle at 2000rpm.
As you come to a stop (clutch in) at 5mph the revs suddenly shoot up to 3-3500rpm and only fall to idle after 10 seconds of being stationary.
No codes when plugged in. All self tests complete without issue including IAC self test which raises idle as it should.

Possible causes:
-IAC wiring issue? If I leave the IAC unplugged the engine drives fine without issue but idles slightly high. IAC self test raises idle and releases as it should.
-PCM sending wrong signal to IAC?
-EGR vacuum solenoid had a slight perforation to the diaphragm but issue remains after repair.
-MAF issue? Symptoms remain the same without the MAF plugged in (so not MAF issue?)
-Previous owner – could he have somehow set the idle higher to counteract cutting the IAC wiring? and now it struggles to close throttle body?
-Throttle body very clean, sensor attached.
Just had cam belt kit done- engine mount removed and engine moved up/down to fit – possible damaged connection?

No idea is a bad idea!

No fault codes – What are you using to read the codes?

I’d put a scope on the IAC and look at the pulse width/control wire signal maybe?

Previous owner – could he have somehow set the idle higher to counteract cutting the IAC wiring? and now it struggles to close throttle body?

Yes. Good call. Is there a base setting procedure on ETIS?

Is this an aftermarket LPG conversion? I can’t see a dual fuel model listed by Ford.

Hope that confuses helps the issue 😆

Has this got the electronic throttle pedal?

If so, that ^

(Random guess 😉 )

I gave up on car mechanics when I couldnt fix things by adjusting the points or twisting the distributor body.

Marko- using OBDII and ForScan software
I can post oscilloscopes after work but from memory IAC ‘vibrates’ between 24-70% depending on throttle pressure/idle on/off

What is ETIS?

Ford LPG factory system (rare so very little online help), separate ECU for each fuel, same issue in petrol and in LPG

Tillydog- mechanical throttle cable from pedal to throttle body, intake is very clean, cable is free moving

Could it be because I haven’t let it idle/relearn long enough after resetting the PCM settings?

Lots of vans increase rpm when clutch goes in. I think its part of antistall features. could that be related?

The ford transit forum would be the place to ask.

It’s just super odd how when the (new) IAC is left unplugged the issue goes away completely? surely an unplugged IAC should throw a code/engine light

I have asked on transit forums but no reply yet

Ford Tech:

ETIS

You need to register and pay up – cheap enough at less than £10 and hour.

I can’t find any ref to an LPG version. If I’m on the correct wiring diagram it looks like the IAC feed is shared with the injectors from the main relay, so I doubt you have a power supply problem.

surely an unplugged IAC should throw a code/engine light

I would have thought so. But 2005 might be too early for full EOBD coverage. Does your scan tool show freeze frame data? Can you see any misfire counts (or at least an option to display them?)

Is the engine code EYPA?

Marko – muddying the water since for ever.

It’s not the MAF!
Just put a new one on, made it rev even higher when it surges! balls

mechanical throttle cable from pedal to throttle body

Does it have an idle position switch then?

If so, that^

😆

Have you tested the Vac lines and all gaskets in the system

You say it runs ok without the IAC plugged in. IAC should fail to closed no – so if your engines still running then it’s getting air else where

You plug in IAC and it opens too it’s getting more air…

Not familiar with the system just thinking out loud about where I’d probably look based on what’s been said.

tillydog- no there is not idle position switch just a rubber block the recoil spring sits up against at idle

then it’s getting air else where – Hmm good point, maybe a leak around the throttle body??

I have checked by spraying an aerosol around the vacuum hoses and no change to idle speed, only poss leak I found was in the diaphragm of the EGR solenoid which I have repaired (ordered a new one)

Found this, describes my problem almost exactly!
Revs hang high, then you hear a ‘pop’ and they drop the rest of the way…going to clean my TPS

I’ve test fitted the 2.0 one, the throttle will hang open for a few seconds, before a slight pop is heard from the throttle body, as if something is closing, and only then will the car return to idle speed. Is the position sensor on the 2.0 likely to be faulty?

http://www.talkford.com/community/topic/240071-1820-throttle-body-differences/

—><><WINNER><>— TRAIL_RAT —><><WINNER><>—

pick a charity mate, been pondering that thought about how it’s getting in

previous owner snipped faulty IAC cables AND improvised a bodge to hold the throttle body open slightly at idle to counteract!
Air sneaking in from this + when now working IAC kicked in meant loads of air in causing a surge of RPM

All sorted and super smooth idle at about 800, perfect!

finally can relax been poking around for days, cheers bud and all who commented

I wish I could say it was my skills but it was just going back to basics – balancing the fire triangle.

If you really want to donate – dundonnal mrt in lieu of some chuffing bampot Robbin their hq last night .

done, cheers again