Shaking when idle and throttle not idle

[Carrmonkey]

Guys
Im after a bit of help on a problem with my S3. Recently I started the car and it immediately raced to 2000rpm and fluctuated quite a lot for about 2 minutes then settled down. The car then almost cut out after about 5 minutes of driving but managed to settle again but idling is still inconsistent between 1200-1500 then back to 900 rpm.

The car shakes when idling and I can smell fuel at start up.

I've cleaned up the air intake, idle control and plugs as well as cleaning the carb but running is still rough and I can now kangaroo at low revs in second gear

Its all a bit strange

Any Ideas?
Thanks
Mark

[ketvrin]

ISCV valve is where I would start but look here too...

http://www.fordscorpio.co.uk/faultfinds.htm

good luck

K

[orange_dodo]

Does your car have air flow meters?

Dodgy AFMs could cause over fuelling which would mean rough running and the petrol smell but it should idle fine so that's confusing. A check of throttle pot, AFMs/Lamda sensors, ISCV may reveal something.

The article kev linked to is a good read

[GreenV8S]

Over-revving and misfire makes me think perhaps you have an air leak. Are all the vacuum hoses into the plenum sound and securely attached at both ends? Especially check the brake server hose. If the servo itself is leaking, that might account for it.

[Carrmonkey]

Thanks for the tips guys
Ive just come in from tinkering and the ISCV was loose and there was no gasket. I have made a gasket and refitted and ensured the iSCV works which it does. This has caused a slight improvement but will check the air flow and lambdas next
Thanks for the tips
Cheers M

[Barkychoc]

Sounds like a misfire to me.
Pull the leads off the distributor one by one and refit them loosely.
Start the engine and pull them off and replace one by one - hold the cable a little way up when pulling / replacing it.
When you replace the lead just push it gently into the top of the dizzy - push them back in properly when the engine is stopped.
If you find one thats misfiring it won't make any difference when you pull it off.
When you pull a good one it will get worse.

Be careful you don't get a belt off the HT system - doing it this way and holding the wire a little way up means the spark jumps to the HT lead when you put it back in the dizzy. Hopefully.

[ChrisGadd]

Sounds to me like the throttle pot has gone ?

[Roy C]

Carrmonkey said:

...will check the air flow and lambdas next

S3 (air flow meters) or S3C (lambda sensor)?

ChrisGadd said:

Sounds to me like the throttle pot has gone ?

Easy to check.

[Gerald-TVR]

GreenV8S said:

Over-revving and misfire makes me think perhaps you have an air leak. Are all the vacuum hoses into the plenum sound and securely attached at both ends? Especially check the brake server hose. If the servo itself is leaking, that might account for it.

^^^+1^^^

[King Fisher]

Carrmonkey said:

Guys
Im after a bit of help on a problem with my S3. Recently I started the car and it immediately raced to 2000rpm and fluctuated quite a lot for about 2 minutes then settled down. The car then almost cut out after about 5 minutes of driving but managed to settle again but idling is still inconsistent between 1200-1500 then back to 900 rpm.

The car shakes when idling and I can smell fuel at start up.

I've cleaned up the air intake, idle control and plugs as well as cleaning the carb but running is still rough and I can now kangaroo at low revs in second gear

Its all a bit strange

Any Ideas?
Thanks
Mark

Your car has a carb???

[Carrmonkey]

Guys
Thanks for your tips

The car is now idling OK at 900rpm but as soon as I pull away and stop to do the necessary 3 point turn to exit the road, when I depress the clutch the car idles at 2000rpm this continues for about 15 seconds aand then settles to 900rpm. I have just disconnected the throttle pot and the car idles at 2000rpm. Is that normal
Thanks
Mark

PS Always called the throttle air flap and housing the carb hangover from my Karmman Ghia days
Cheers

[Gerald-TVR]

Carrmonkey said:

Guys
Thanks for your tips

The car is now idling OK at 900rpm but as soon as I pull away and stop to do the necessary 3 point turn to exit the road, when I depress the clutch the car idles at 2000rpm this continues for about 15 seconds aand then settles to 900rpm. I have just disconnected the throttle pot and the car idles at 2000rpm. Is that normal
Thanks
Mark

PS Always called the throttle air flap and housing the carb hangover from my Karmman Ghia days
Cheers

Air leak!!!!!!!!!!!!!

[Carrmonkey]

Ok that makes sense. I'll check all the hoses and see how I get on
Thanks

[Roy C]

Carrmonkey said:

I have just disconnected the throttle pot and the car idles at 2000rpm. Is that normal

No. Sounds like the TP was trying to cope with the real problem.

Air leak?

[Carrmonkey]

Thanks for your help on this guys

I've checked the pipe work from the air housing to the plenum and made sure all are tight and sound and all is the good. The pipe at the head end of the plenum going in the servo was split and ripped so I have re-terminated. This had a mild effect but I have noticed as I turn the engine off their is a hissing sound (Air escaping) from some where and I cant bloody find it.

Im sure this hissing could be the source of the problem and It appears to be coming from the lower near side at the front of the engine bay but I cant identify were its coming from.


Do any of you have a hissing noise from your engine when you turn it off? It last for about 3-4 seconds

Thanks M

[Barkychoc]

Sounds like knackered brake servo. It will be rotten at the bottom and hissing when you turn the engine off.

If you block the hose off see how the engine runs then.

BE CAREFUL IF YOU DRIVE IT - YOUR BRAKES MAY BE MUCH LESS EFFECTIVE.
I wouldn't recommend it.

Edited by Barkychoc on Wednesday 6th July 21:26

[Carrmonkey]

BINGO!!!

Thanks a lot Barkychoc

Just had a route around the bottom of the brake servo and it is corroding and is the source of the leak

Another job to add to the list

Thanks to all for your help
Cheers
M

[Barkychoc]

Another beer in the bank :-)