[Si_J]

I have searched and followed previous advice posted here and on other forums but I'm still stuck with my misfire.

The car when cold idles erratically (as do all c900) when warm its fine but still does the odd drop in revs which on the odd occasion stall the engine.
However my main grief is when driving the car will misfire/hesitate/splutters (whatever you want to call it) briefly then carry on as if nothing has happened.
This scenario usually occurs when pootling along in traffic say in 3rd gear, then when a bit of space opens up you put your foot down, now rather than the car pulling and upping the revs it misfire/hesitate/splutters then carries on.
I can get it to do this in any gear, it seems to happen between 2000 ~ 3000 RPM, maybe 1500 ~ 2500 if in 2nd.
I've spoken to various people about it, it was though that the hall effect sender on the dizzy was dying.
Not that, swapped out the dizzy (keeping the Group9 vac capsule) and I'm still in the same boat.
Next, tried the AMM as that made sense with the jittery idle when cold. No luck still the same after swapping out the AMM

I've replaced a dodgy looking king lead - rest of the leads are fine (Magnecor KV85)

I've replaced the plugs (thats another story in itself!) and rotor arm - haven't yet changed the dizzy cap.
All the APC gubbins look fine and look pretty new so I haven't ventured down that path just yet.
For those that don't know the car has a 91 engine & gearbox with the Lucas stuff replaced with the "simpler" Bosch gubbins, (probably 2.2) It has the 30Lbs Red injectors and a custom written ECU (by Mr. Faulks) and a chip written by "unknown" so the APexi S-AFC is redundant, just use it as a rev counter as the one in the car dies once over 3000 RPM -- if that's of any consequence.

Need ideas of where to look next, or more importantly what to hit! :roll:

 

[pda]

Fuel starvation, whats the A/F ratio like has it been checked lately

leaking/dodgy FPR just a thought

Paul

___________________________________
Sleeper baby, no show & all GO...............

 

[Si_J]

Fuel starvation, whats the A/F ratio like has it been checked lately

leaking/dodgy FPR just a thought

Paul

___________________________________
Sleeper baby, no show & all GO...............

Wouldn't know where to start on the "A/F ratio"

I was starting to think about the fuel filter though, but as the condition only exists when quickly changing revs and not constant I've put that one to the bottom of the pile.

 

[Matt88S]

I’m having similar problems with one of my cars, an 88 900S. Interestingly enough it also has had an engine transplant, 2.1 from a 1992 900S.

I don't think the transpant had anything to do with it though as it ran fine for the better part of a year after the transplant. It seems like just as the weather warmed up it started to have issues with loosing power while going down the road. RPM’s would drop to about idle and flooring it would have no effect whatsoever, although pumping the accelerator would sometimes work. Usually within a 5-10 seconds it would be fine and take right off. And some days it runs fine, other days you can't get it out of the driveway. Diagnosing intermittent problems like this is the ultimate nightmare. Its almost as if it simply not getting fuel. So far I have replaced the fuel filter, pre-pump, fuel pump, injectors, AMM, air filter, O2 sensor, the list goes on and on.

I WILL get that car running again though.
It was my first Saab, her name is Birgetta.

So I'm vary interested in what your problem turns out to be.

 

[Si_J]

I have no issues with power as such and I'm still inclined to think it has something to do with the retard/advance as the hesitation is only there when changing revs quickly.

I have found that if the needle on the standard boost gauge is in the top quarter of the white (not the little white block which = ~0 Bar) then I can get the car to kangeroo constantly - very easily in 4th and @ ~2500 RPM

So it's kind of specific to vac position maybe advance etc at a fairly small rev range.

There is a rolling road day being organised down my way on July so if I haven't cracked it by then, I'm going to take the car along and get it on the rollers and see what the RR operator has to say about it - if they have time and are in a friendly mood.

Until then it's step at a time fault finding again :roll:

 

[fliptopbin]

Si, did you get this sorted in the end?