Stumbling when hot

[shnazzle]

We're slowly getting through each little issue on Jack the SP240.
I have a couple theories but looking for the expertise of the group again;

Some of you will have remembered from the Holy Island run that Helen's car was absolutely fine, until it was nice and hot and we slowed down. Then parked at the restaurant it kept doing fast idle, then very slow to the point of stalling.

We thought an ecu reset sorted this at the time, but it didn't.
I've had the pleasure of using it as a daily driver the past week while my car is getting work done and I've noticed this effect after every time it gets nice and hot. After that, it stumbles and wants to stall when  you're trying to park or tootling in traffic.
I park it at work, and when I come back, it's back to normal.
Same thing when I get home. Next morning, it's absolutely grand.

So... It's something to do with it being hot.
Thermostat reads fine on the dash.

My next steps are to replace the throttle body with my old one. That replaces the IACV and TPS in one go for a know good set.

Any other ideas?

[Call the midlife!]

On my old Capri I had a problem with the coil when it got hot, some component inside moving due to heat expansion and causing it to stutter and cut out.
Different ignition system I know but possibly a failing coil pack?


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[shnazzle]

Entirely possible. I guess an easy way to check is to swap mine in. Will do when I get my car back

[Call the midlife!]

Entirely possible. I guess an easy way to check is to swap mine in. Will do when I get my car back

At least you've got some at hand to play with!
We've just been for a "forest experience" in Mk2 Escorts that still had old school ignition with distributors etc. The first one they used died after 10 minutes due to the points closing up, they ran on LPG too! But while we were all throwing our suggestions in it seemed like the coil.


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[Gaz mr-s]

Spark plug?

[shnazzle]

Spark plug?

Nah. Been tried. Twice

[jonbill]

Sounds like an air leak to me

[Carolyn]

Sticky idle air control valve, my suspect.  But air leak is also possible -

[shnazzle]

I'm going to swap over the entire throttle body soon so that will take care of that. It's my guess to be honest. It was my best guess on the Holy Island run  as well. It did a "click" when the engine went into higher revs and then another "click" when back down. So, some kind of switch is causing it.

[shnazzle]

Throttle body swapped. Clamp came undone and p***ed coolant everywhere. Epic.
Topped that up and took it out for a spin. It's always very different after an ECU reset (battery out) so it's hard to tell at the minute.
It felt smooth. A hell of a lot of burbling on overrun though.

Idling far too high at the moment. Not sure why. It does this when we've reset the ECU though.

See what it's like tomorrow after a day's commute. Fuel trims should settle and give a good picture

[shnazzle]

Think I'm just writing to myself here but who knows  s:) s:)

Went for another drive and the high idle is not just the ecu. It's the throttle body  s:) s:)
Joy!
After thinking about it and confirming with a fellow member, it's very likely the (then working) IACV on my old throttle body has become a bit stuck while sitting in my garage for a few months. I did clean up the bore and butterfly, and lubed up the spring, but didn't take off the IACV.

Going to see if it unsticks on the drive to/from work tomorrow. If not..back off it comes. At which point I will be no closer to a resolution.

So, can't confirm if the stumbling is gone, because the car won't rev under 2k  s:) s:)
Drives lovely though!

[shnazzle]

Nope. IACV on my old TB is stuck. Quite embarrassing in traffic revving at 2000 rpm constantly.
All that unmetered air is not helping either. Sending cylinders 3 and 4 massively lean.

[Carolyn]

I would suggest that you do your magic to the throttle body you just took off and give the IAC a good going-over.  Then you'll have one ready willing and able for a 'quick' swap?
It seems these valves do not like being idle for very long, which now motivates me to do the one on the engine I'm about to put in the blue car, while it's easy to get at, and no coolant to dribble...

[shnazzle]

Dribble... I had a spout going.

Yes that's the intention. I'll ask Helen if she intends to drive the car soon. If not I'll order a gasket and another 5 point security torx bit (wrecked my last one) and clean her original one up.

[ChrisGB]

Nope. IACV on my old TB is stuck. Quite embarrassing in traffic revving at 2000 rpm constantly.
All that unmetered air is not helping either. Sending cylinders 3 and 4 massively lean.

Air coming in through the IACV will be metered. High idle, no load may well lean things out a lot though.

[shnazzle]

Nope. IACV on my old TB is stuck. Quite embarrassing in traffic revving at 2000 rpm constantly.
All that unmetered air is not helping either. Sending cylinders 3 and 4 massively lean.

Air coming in through the IACV will be metered. High idle, no load may well lean things out a lot though.

I thought the exact same thing today on the drive home. For some reason, at the time of writing, I thought the IACV took air from atmosphere.
Hadn't woken up yet.
Also, the fuel trims indicate a rich mixture, not lean, so all in all I wasn't compos mentis this morning.

What is flippin annoying is that high idle. It's embarrassing. And the little trickle of air is leaning out overrun and making it burble soooo much.