Idle Flare on start up

[M100TURBOFR]

Hi
Have already posted re this problem and read most of ther recent posts on vacuum problems. Have changed the vacuum hoses, checked the accelerator cable, but problem still persists. The engine races away on start up (2500/3500 rev) and does not die down to idle.
Any ideas as I'm truly at a loss.
Thanks David

[tb10]

Have you checked the temperature sensor? Not sure if this was discussed but it will think the engine needs fuel as it may read -40

[Brit-Car-Nut]

Don't know if this will answer it, but I got this from a Google search:

many cars automatically increase the engine's idle speed until the engine is warmed up. ...
If there is an issue with this system, such as an intake leak, or faulty IAC (Idle Air Control) valve, there could be too much air getting into your engine causing a fluctuation in idle speed.

A100E6505S - Description: Valve, Idle Air Control (IAC)... Price (each): £20.06

I ordered some recently at a lower price but they got lost in shipping and I didn't bother trying again.

[Simon_P]

Can you post an elanscan?

[M100TURBOFR]

Hello
Thanks for all your suggestions. Will check out the IAC.
No I do not have Elanscan.
The problem is that I am frightened to let the engine rev so high for a long period of time until I could, for example, get the paperclip installed.
David

[marvic]

I recently cured a similar issue. Car flared on startup and then a lumpy idle. There was one leaky vacuum pipe and no cap on the mixture adjustment - sucked my finger when engine running!

Main issue was the throttle position sensor though. Once adjusted using Elanscan, all sorted. Making Elanscan cable was both cheap and easy thanks to the Youtube video which also covered the software and drivers.

[M100TURBOFR]

Marvic
Thanks for input. Always good to have a few suggestions. However, I think I've found the culprit. I think it must be the IAC as on taking it out I see it's jammed solid (spring portion fully extended and jammed open. Now looking for an identical aftermarket one. On searching with the number stamped on it (A1679) have come up with Magnetti Marelli 820003354010 which appears to be identical. Can anyone confirm this?
Thanks David

[Brit-Car-Nut]

I found this one while I was searching for other parts:

https://www.carparts.com/details/Isuzu/ ... 13205.html

I searched for Isuzu Impulse RS which is the Turbo Impulse.

I will try to find time to compare one to a used one from a spare engine I have and let you know.

This is not the best company as far as shipping goes. On another order, they screwed up my address and it took a while to get things sorted.

I do have a history with them now.

I also have a few used engines and intakes around if you want me to try to find a decent used one from an M100 engine.

[M100TURBOFR]

Thanks John.

[Simon_P]

However, I think I've found the culprit. I think it must be the IAC as on taking it out I see it's jammed solid (spring portion fully extended and jammed open.

if I have understood your description "fully extended" is jammed closed (as it extends it blocks the hole), which makes sense as it can't keep the revs down. Also it is a stepper motor so it isn't actually jammed.

You can test its operation by connecting it and switching the ignition on/off.

Have you checked the vacuum hose to the servo?

[Brit-Car-Nut]

Sorry for the delay, but I did finally dig out the new IACs I bought and they LOOK just fine, BUT, the plug socket is not indexed correctly and the connector will not clear the intake manifold. It needed to be 120 degrees clockwise from where it is pinned now. I was able to get 2 pins out, but the 3rd is pressed in too far to get a "bite" on it. I may try to "stick something to it using the small mig welder, but I am not sure it will survive any heat.

So, Do NOT order it

It's too bad. Everything else looks just fine and the price is stupid cheap.

I have a couple of used IACs from the engine core I have collected, so if you want one of those at no charge, I can get you a shipping quote.

I am sorry for not getting to this sooner today.

[Simon_P]

No I do not have Elanscan.

There are a number of things that could be wrong which are easily detected with elanscan.

The problem is that I am frightened to let the engine rev so high for a long period of time until I could, for example, get the paperclip installed.

I wouldn't consider that particularly high revving or a long period of time, you might annoy the neighbours though.

Have you checked the temperature sensor?

A good piece of advice

Have you reset the ECU after checking the hoses?

Have you checked the idle screw? And checked the tickover in service mode?

[Brit-Car-Nut]

I found a fairly OLD post that provided some insight into the IAC discrepancy: IAC Discussion: read the entire topic...

It appears that Lotus used the IAC from VAUXHALL Astra MK3 MK4 & Nova Tigra Mk1 because the more standard version puts the plug socket in the wrong place.

You can look at GM: 17108187 or 17111946 and according to the pictures, the plug socket is around 180-deg away from the Isuzu version.

Drilling the pins is possible, but they are around 2mm in diameter and have a partially rounded head, so a difficult project.

[M100TURBOFR]

Hi there
New IAC valve fitted but exactly the same as before. Engine races away on start up.
Perhaps I'll have to invest in Elan Scan.
David

[Alan M]

This could be the sign of a decent vacuum leak - I’ve just sorted one on mine which was the PCV valve. It appears a previous owner had removed the innards which I believe should contain a spring loaded valve that controls how much air is passed into the manifold. As there was nothing inside mine it was allowing a large amount of air into the manifold at idle. I narrowed my search to this when I clamped the hose from the oil separator to the cam cover and this made a big difference to engine speed at idle.

[M100TURBOFR]

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