Another idle issue & cold running

[ashm]

My Elan has developed a new fault recently:

It only starts with the throttle open, and I have to keep my foot on the pedal to keep the car running. If I let the throttle close, the car dies. After 5 mins running it's fine and it'll idle normally. After stopping and sitting for a while, it won't start again, turns over but can't maintain idle. More details:

- secondary throttle works as normal.
- timing is ok.
- oil level is stable.
- fuel pump runs audibly for a while before I try the ignition.
- HES recently replaced, no error codes appearing at all.
- throttle cable adjustment is ok (quadrant against stop when the ignition's off and ElanScan shows 0% throttle).
- If I screw the idle adjustment screw out a couple of turns the car will start properly, but after a few minutes the idle speed gets far too high, unsurprisingly.
- The IAC seems to be moving successfully according to ElanScan.
- I've also got two _very_ slow coolant leaks, one at the header tank (soon to be replaced) and one in some indeterminate location at the O/S end of the radiator

Tonight I'll do a compression test and if that's ok I'll see if I can clean the IAC valve.
I want to check I don't have a HGF between cylinder and coolant circuit, hence the compression test.
Other than the IAC, I guess the list of other suspects includes:

- HT leads
- coils
- injectors
- earthing
- battery
- some random loose connector somewhere

Any advice? Cheers!

Adam

[Specky]

When you say you have the throttle open, do you mean you have the pedal fully floored on starting?

If so that may help the diagnosis...

TTFN

[RayD]

You seem to have most things covered Adam,

Is it worth starting the engine using the idle adjustment screw then put the paper clip in ... adjust the revs ... run it for five minutes hopefully at a constant 950 ... then pull the clip out to see if the revs rise.

Have you checked all the vacuum pipes?

Ray

[GeoffSmith]

CTS?

[ashm]

I knew there had to be things I forgot to mention!

- I start cranking, then floor the pedal. Not sure why, just in case the ECU needs the throttle at zero when I turn the key. However, it also starts if I floor the pedal, then crank.
- I've checked the vacuum pipes, they look intact... and there's a dramatic response from the engine when I create a vacuum leak, so they seem to be ok.
- the battery voltage is around 12.5 before starting, according to ElanScan.
- the ElanScan coolant temperature numbers seem vaguely sensible, I'll do another scan tomorow morning and see if it shows anything up.

I got home too late to tinker tonight, I'll investigate further tomorrow.

Adam

[ashm]

So I cleaned up my IAC valve, and the car seems to be starting normally again. The valve was all coked up, which seems odd as it's upwind of the injectors - surely nothing should be burning at that point?
Unless it's just 60,000 miles of road gunk built up in there.
The IAC is such a nightmare to remove and refit! Even removing the intake pipe, header tank and loads of other things. Hope I don't have to do that again anytime soon.

My next problem is the tendency to run far too cool. It seems like the thermostat's stuck open but it's a brand new stat only installed a few weeks ago, and it was working ok when I installed it.
If I can sort out the temperature issue this weekend, the engine will finally be running properly, more or less. Then I can get back to finishing the new throttle cable!

Adam

[ashm]

Ok, so today I swapped the thermostat for an old one and the running temperatures are much better, if still a bit low.
Funny thing is, I tested both the stats and they open at the same temperature. The new one was opening much wider, and the old one had a rubber seal when closed, whereas the new one was just metal on metal. The only thing I can think of is that the new stat was letting too much coolant past when closed. Any ideas why this would happen?

Anyway, my only remaining problems under the bonnet are the two small coolant leaks, one at the header tank and one at the radiator.
I did a compression test today, results with the engine hot were 170/170/165/165, so it seems unlikely that the cooling system's being pressurised with combustion gases. Do we think I'll be ok replacing the tank and sealing the rad leak?

Cheers,

Adam