Slightly odd warm start problem

[zhastaph]

Hi,

I have a year 2000 v8 GT, it has a slightly odd warm start problem.

If the car is left for say more than half an hour to cool down but not get completely cold, if I then start the car what I find is that after say half a minute it will either stall, if I've not gone anywhere or have reached a junction at that time, or it will just suddenly run really awful for a few seconds.

If it doesn't stall it's fine after that, if it does stall and i restart it she's also fine.

Suggestions anyone?

Thanx :)

[DAVES_GT3]

Does it have an IAC vale like the 4 cylinder?

Have you reset the ecu recently? If so did you reset it when it was warm?

dave

[zhastaph]

Thanx for you input Dave;

I haven't reset the ECU and am not that keen to unless I know it's gonna sort it, I've read too many stories of these things being a pain with their idles and stalling after an ECU reset.

Yeah, she's got an idle control valve stashed under the plenum - I cant see it being this because if your driving her under say part throttle at about the time when it would normally stall it feels seriously sick for a couple of seconds.

>> Edited by zhastaph on Wednesday 20th July 22:42

[DAVES_GT3]

no problem
im not up to much on the V8 im affraid but maybe the TPS? Had a similar problem on mine. Think you need a V8 guru.

Hope you get it sorted

dave

[kmaier]

I've experience this as well and some other V8 owners I know have experienced the same... car idles poorly, tendency to stall and has near-zero power for a very brief period. I don't think the IAC would cause this as you have no power when you step on the accelerator (which takes the IAC offline) I seriously doubt resetting the ECM would have any real effect on this, although I've reset my ECM numerous times over the years and yes... idle learning can be a painful process alternating between A/C on and off in between stalling at traffic lights, etc.

Some basic questions: Are you losing any coolant? Have you checked spark plugs for any signs of fouling? What is the outdoor ambient temperature when you experience this? Is the Fuel system flowing properly? Any fuel system pressure leakdowns? (which could cause vapor lock). Granted, you would think the ECM would flag a check engine light if things were really amiss, but it never does for this odd condition. Granted, I've checked ALL of these on my car and none of these conditions exist, yet I experience the problem from time to time.

Regards, KM
2000 V8

[zhastaph]

km said:

Some basic questions: Are you losing any coolant?

Yeah, gradually. It's an external leak as I see the little droplets hanging round the bottom of the chassis.

Piston liners were done a year ago

km said:

Have you checked spark plugs for any signs of fouling?

She's recently had a new set of plugs. Also, I recently had a misfire problem and was compression testing her, during this process there was some oily crap on one of the plugs.

km said:

What is the outdoor ambient temperature when you experience this?

It's been doing it through winter and summer, it's definately been worse of recent, so this could be because it's now warmer than before, or it coulda just got worse . It's been like it pretty much since I've had the car, I'm just on to niggles these days as I've sorted pretty much everything else

km said:

Is the Fuel system flowing properly? Any fuel system pressure leakdowns? (which could cause vapor lock). Granted, you would think the ECM would flag a check engine light if things were really amiss, but it never does for this odd condition.

No fuel leaks that I know of. I've also swapped the 2 fuel pumps over recently as the primary pump was making this high pitch "power supply type" of noise. Not a "I'm stuffed" sort of noise, just the type that coils make sometimes, but being right behind your earole {on a RHD UK car} it was really fecking annoying.


==========

The symptons you describe are 100% spot on and exactly the trouble I have - right down to if you floor it when it's like it, there's just nothing there - and it lasts no more than 2 or 3 seconds.

I'm no mechanic {I'm a programmer lol} though I do all my own work on the car, but if I had to say what I thought was the problem I'd say that the car doesn't know what temperature it's running at and is completely stuffing it's fueling for those few seconds or something.


==========

Am I right in reading that you've on and off had the same problem, but never got to the bottom of it?

I do have software for the car, so mayb I should spend some time logging this period and see if there are any clues in some of the sensor readings.

Thanks KM

[kmaier]

zhastaph said:

km said: Some basic questions: Are you losing any coolant? Yeah, gradually. It's an external leak as I see the little droplets hanging round the bottom of the chassis. Piston liners were done a year ago km said: Have you checked spark plugs for any signs of fouling? She's recently had a new set of plugs. Also, I recently had a misfire problem and was compression testing her, during this process there was some oily crap on one of the plugs. km said: What is the outdoor ambient temperature when you experience this? It's been doing it through winter and summer, it's definately been worse of recent, so this could be because it's now warmer than before, or it coulda just got worse . It's been like it pretty much since I've had the car, I'm just on to niggles these days as I've sorted pretty much everything else km said: Is the Fuel system flowing properly? Any fuel system pressure leakdowns? (which could cause vapor lock). Granted, you would think the ECM would flag a check engine light if things were really amiss, but it never does for this odd condition. No fuel leaks that I know of. I've also swapped the 2 fuel pumps over recently as the primary pump was making this high pitch "power supply type" of noise. Not a "I'm stuffed" sort of noise, just the type that coils make sometimes, but being right behind your earole {on a RHD UK car} it was really fecking annoying. ========== The symptons you describe are 100% spot on and exactly the trouble I have - right down to if you floor it when it's like it, there's just nothing there - and it lasts no more than 2 or 3 seconds. I'm no mechanic {I'm a programmer lol} though I do all my own work on the car, but if I had to say what I thought was the problem I'd say that the car doesn't know what temperature it's running at and is completely stuffing it's fueling for those few seconds or something. ========== Am I right in reading that you've on and off had the same problem, but never got to the bottom of it? I do have software for the car, so mayb I should spend some time logging this period and see if there are any clues in some of the sensor readings. Thanks KM

Well, no, I've not yet found the cause of the problem to date as it never sticks around long enough to find it... not to mention I'm usually away from the house when it does happen. In any case, my gut feel is that it's either a slight pressure drop in the fuel system allowing it to bubble and cause vapor lock (hence poor fuel delivery until the pressure builds up and the air is gone from the fuel rails) or that heat is causing an intermittant electrical problem which prevents proper ignition and/or injector firing.

On another note, whatever you do... FIND the coolant leak and fix it asap... this can easily lead to cooling system pressure loss, and you may experience an overheat condition after giving it some serious stick. The turbos will boil the coolant as will the liners from increased temps. Even though the temp gauge will read lower, the temps at the liners can be much higher especially if it boils. The Hylomar sealant becomes suspect and breaks down around the 150C mark.

In the rear of the car, check the two short hoses from the rear of the heads to the heater feed pipe.. they do tend to seep over time. Lotus used hose sections that are too long and clamp them too far back on the engine side. This allows the coolant to get past the ridge on the pipe and it eventually rusts that section and the hose starts to seep (been there done that). Also check the front short hose sections that attach to the alloy downpipes as they can intermittantly leak and cause problems. Whatever you do, correct it now. Use a pressure tester to find the leaks if you have one.

Regards, KM
2000 V8