Another rough runner

[Gilesy]

After replacing the Brake Servo, which had a hole in it causing the engine to run lean, on my 2.9 S2 and a good service changing plugs, leads, air filter etc. the engine has never run so rough. It seems fairly flat at idle, hesitates on accel, hangs on decel and doesn't run smooth at constant speed.

I was going to take it to the local Ford garage for a diagnostic but having read other posts the rolling road seems to be a good idea. Does anyone have views on either of these? Where would I go and how much would it cost?

Cheers

[M@H]

What plugs and leads did you fit ?

Cheers
Matt

[Gilesy]

RC7YCC plugs with 0.032" gap
Hotwires Silicone leads

Cheers
Ian

[M@H]

Err.. gap sounds about right.. think I used to set mine slightly wider.. plugs, cant comment as I used to fit the ford ones as they have the tapered seat.. I know I'll probably get flamed for this, but did you try resetting the ECU to solve the problem.. sounds like a timing issue of some sort to me ??

Cheers
Matt.

[M@H]

Hotwires.... don't understand this at all..

"Nology HotWires are the most technologically advanced ignition wires available. HotWires create the most powerful spark possible. HotWires are engineered with a special built-in capacitor, exclusive only to HotWires. This revolutionary design allows energy from the ignition coil to accumulate in the capacitor until the voltage at the spark plug electrodes reaches the ionization point. At that split second point the entire power of the stored spark is discharged at once, creating a spark 300 times more powerful."

[Podie]

quote:
Hotwires.... don't understand this at all..

Marketing "bumpf"..?

[Gilesy]

Thanks for your help Matt.

Problem is my Gunson ECU tester says that there is nothing wrong, so I guess the ECU is trying to compensate for some maladjustment. Not wanting to get involved in the "white man's magic" of the ECU, as you can get tied up in knots, I thought I would take the car to someone who knows what they are doing rather than cock it up myself??!!

Cheers
Ian

[shpub]

Well it could well be that those advanced technology leads are screwing up the electronic ignition system that I think uses a constant energy approach. These do not like strange things hanging off them like capacitors as they don't expect this and sulk. I have experienced this melancholia on a Rover system but not a Ford one but they use the same approach for the ignition system.

Might be worth fitting the original leads.

Steve

[M@H]

Whats it like without the throttle pot connected.. ?

also same question with idle sensor..?

Cheers
Matt.

I'm betting your service has nothing to do with the fault at all and is just a coincidence..

[John Mac]

Just had my S2 2.9 set up on a Rolling Road by a Specialist Engine Tuner - cost £38.
Doesn't seem much difference to be honest so perhaps it was OK before !!?
One reported item was an air leak on the Brake Servo and a replacement was advised as necessary before further tuning attempts were made, travelled up to South West Breakers in Hanham Nr.Bristol who are the only Saab breakers in the SW (allegidly) and for £25 got a replacement Servo and Reservoir, these are to be fitted in a couple of days.
Can't praise enough the helpful attitude of SW Breakers if you need one (tel.[phone])
Cheers
John Mac

[Heath]

Are you experiencing back firing? Is the car trying to over compensate by dumping more fuel, are you getting lots of fuel spitting from the exhaust?

If so could be the vane air flow meter, are the connections the right way around?