I have an '89 Carlsson, which is hesitating when under hard acceleration between 3500-4000rpm. From previous threads, i have looked in the DI unit, the inside of which looks fairly clean with no obvious signs of corrosion. One obvious problem is a loose plug/sensor unit with a rubber hose that leads from the large bore rubber hose coming from the right hand end of the turbo, spliting into two tubes to the throttle housing and the top left hand end of the timing head. Is this some sort of exhaust gas sensor similar to the later Lambda sensor? Would it be contributory to the acceleration problems i'm experiencing.
Any other suggestions?

More info....hesitancy is worse when engine is warm, virtually no problem at startup.

Just been into Buckingham and Stanley In Cambridge. They suggest the hesitancy is due to Turbo overboost and the turbo should be recalibrated. But because the turbo is a Mitsubishi one fitted by Abbott they could only rest the boost to Saab standard..which is kinda counterproductive! They say I gotta go back to Manningtree.

Ed

Sounds like a cop out from Buckingham and Stanley. Abbott supply their kit to others for installation aswell as doing it themselves. Saab City sell Abbott modified Saabs.

I suggest you go back to B&S and tell their Master Tech chap (if they have one) to pick up the phone to Abbott and get instruction to recalibrate it.

Otherwise, try another Saab dealer.

A UK dealer list can be seen at http://www.saabs.org/dealers/

HTH
/john

I think if i got it done locally I would trust my local specialist Saabmaster or a trip down the A14 might not be the worst hardship in the world...I think the phrase is kid in a candy store!

Short term remedy to Turbo overboost,... Standard Unleaded fuel. I have been using 4 Star until now. B&S in Histon said the overboost was just on the cusp, (it not bad enough to slam you into the facia yet!) So presumably dropping down the octane scale has brought the problem that bit further from the point of overboost.

I was reading in Bjorn-Eric Lindh's 40 years of Saab that the difference in performance between 91 and 98 octane fuel can be as much as 20% - generally for each drop in Octane value you will lose 1.5 to 2%

APC enables the engine to run on a range of octane grades b/w 91 and 98 octane and maintain optimal performance whilst ruling out possibility of engine knocking.

/john

Right...back to square one...taken the car to the local specialist who has temporarily bypassed the sensor that checks overboost...and the problem is still there so i guess we can discount overboost....has anyone got any other suggestions?

I was curious too that when attached to a calibrated boost gauge the turbo only showed a maximum boost of 0.9 bar....which is less than the saab standard 1 bar...bearing in mind that the turbo is a larger mitsubishi unit fitted by abbotts, i would guess i have some boost going awol...Would this have any bearing on the hesitancy problem?

If you have a leak, which opened up under presure, you would lose boost, and would also get a very rich mixture, as the ecu would think that more air is going into the engine that actually is, but you would probably hear a leak like that.

Hi Ed,
Not sure that I can help, but I have a problem with a general lack of power through the rev range. The next thing I'm going to try is a new DI cartridge as mine is leaking oil from one of the coils.
On the subject of boost, I believe that the 'Standard' boost setting for the 9000 range varied from year to year and also from model to model. For instance my '90 CD Carlsson has a basic boost of 11.5 psi, note that this is nowhere near 1 bar (14.5 psi) even though it is a Carlsson.
Your larger Mitsubishi unit does not necessarily require higher boost to give greater performance. As it acheives this (the greater performance) by 'flowing' larger quantities of air at the engines higher rpm therefore (with an appropriate increase in fuel) giving more bhp at the top of the engines rev range.
On another note, does the apc/boost indication needle 'flick' back momentarily when the engine is hesitating? This may indicate that the knock sensor is picking up some trouble. Certainly 3500 - 4000 rpm is around the point of max torque when knocking would occour, but lowering the octane of your fuel should exacerbate this problem not cure it. This is assuming LRP (4 star) has actually still got a higher octane than standard unleaded.
My guess ( and it most certainly is a guess) would be a missfire on the plugs, are the gaps correct?

Right, gonna change the plugs and take that potention defect out of the equation. Willing to buy the best possible. Any suggestioms as to which make and type? ('89 2l carlsson)

Hi Ed,
An update on my car...
The engine started to hesitate (missfire) when on full accelleration at around 3000 rpm. This was during the very cold weather we had recently. As the car was due for a service the chaps took a look and pronouced that the DI unit was leaking and put a new one in with the extra loom required. Total cost £125 for the DI plus £18 for the loom, all plus vat.
The car is back to its old self ;-)
Apparently the origional DI units seldom last much past 100k miles.
By the way the hesitation was quite obvious, unlike when I've noticed the APC cutting in and knocking the boost back a touch (much more gentle).
Hope this helps.

Was the DI unit from saab main dealer or from spares company, ive been quoted £200 from my local specialist, but i suspect thats supplied from the local dealer. He likes to use original spares but my guess is he wont mind looking for parallel suppliers.

Would still change the plugs so any suggestions out there.

Hi Ed,
The answer to your question is......
I don't know!
My garage is a long time Saab specialist who normally uses origional parts from a main dealer, but uses other sources when the Saab part is priced unreasonably.
In this case I didn't ask.

Hello chaps. Only use NGK plugs in your Saab.
Please feel free to contact me with details of your car if you would like a quote for the required parts.

Thanks.
Regards,
Julian
email: julian@elkparts.com<br />website: www.elkparts.com (http://www.elkparts.com)

Went to Two Stroke to Turbo today, and i can now say its not overboost, it isnt the plugs (got them changed), it isnt the DI rail (ditto). Infact the change of these made things worse, so the air mass box was changed, (no improvement) and then the APC solenoid was replaced with modest improvement with standard U/L fuel. I then filled it with 4 star and the hesitancy came back. So where do i go from here?

Hi Ed,
Sorry your still having trouble.
Is the hesitancy due to a missfire? Or is it due to the apc dropping the boost off?
If the latter you'll notice the boost/apc gauge needle flicking back towards atmospheric pressure as the apc solenoid cuts the boost back. If this is happening then the knock sensor is picking up the beginings of knock and protecting the engine. This is usually a gentle hesitancy.
However if it's a missfire, the hesitancy will be much more pronounced and the apc/boost gauge will stay at the same position.
HTH
Nick

The needles stays where it is.

Sounds like a missfire then. Which would usually lead me to think it's the DI cartridge, but since you tried another one at Two Stroke....
Was it a new one? I believe they do used parts. Even if it was new, I know from bitter experience, parts can be faulty from the off. The best bet is swapping with a known working part. Also are the plug gaps correct? And a quick compression test while the plugs are out, but the readings would have to be way down to be a cause for a missfire (about 50% of normal).
HTH

The DI unit was new, but the air mass box was used. i will presume at this stage that they are ok. The oil gauge shows a good level of pressure. One suggestion they did make was that the narrow tubing from the dump valve to the throttle body was too soft through age, which it is, and was collapsing at highest boost. Anyone else heard of this?

I haven't come across the dump valve tubing going soft but I note that in your earlier postings you mention changing the spark plugs. Have you done so? If not I seriously suggest you do, I have had hesitation problems and flat spots with a previous 2.0L Turbo which were cured when the plugs were replaced. Use NGK BCPR7ES gapped to 0.039"

Just done a high speed 350 mile round trip on shell super U/L fuel and didnt get a shimmer of a misfire, so i guess the main culprit has to be LRP petrol.

I believe most Europeanm countries are withdrawing it on technical grounds so i wont be using it again!

Anyone else had any bad experiences with LRP?

Never used it. Why use LRP in a car that was designed to run on unleaded/super-unleaded?

From my understanding it was the other way round, as a pre-cat car, it was originally designed for 4-star, that was able to run on U/L fuel.

Nope, I agree with Derek.
All 9000's ,since their introduction in '85, have been able to run on unleaded, hence the green petrol filler cap.
4 star used to have a slightly higher octane and therefore potentally giving greater performance. But as for its' replacement (LRP), I'm not sure. From your findings it seems that its octane rating may be lower, leading to your missfire problem.

Hi
When I had my '89 Carlsson I ran it for 46,000 miles on Unleaded (with A Brocquet fuel catalyst in the tank)with no problems whatsoever. The car flew. I saw no point in bothering with Super U/L or 4* as 4* was going to disappear.

Gavin
'89 9000 CSE 2.3 Turbo Auto lpg

I have had a problem fixing the miss on my 9000CDE.I finally got round to trying a different DI rail, unfortunately this did not resolve things. I will try and add as much information as I can, hopefully without clouding the issue.
This missing occurs in all gears, but it can only be provoked in first by revving it to about 5000rpm, where as other gears its usually 2750 - 4000rpm. Going up hill it will occur at lower rpm than going down hill. Backing off and trying to accelerate more gently can allow revving to go past this range but trying to accelerate hard again will cause the miss to reoccur. After filling the card up on one occasion the problem got briefly worse but then cleared, and the car was a delight to drive, but this didn't last, more's the shame. This tank of fuel was obtained during the fuel shortage and I felt that the fuel may have been of dubious parentage (this is possibly a red herring). In case of the problem was being caused by low octane rating I have tried octane booster with no effect. My experiences have lead me to believe the problem is load/ boost related. The last thing I have tried, this evening, was to disconnect the pipe that goes from the inlet manifold plenum to the bypass valve (?)( positioned between the battery the engine) which connects the inlet duct before the turbo to that after the turbo. Low and behold the problem cleared. I must say I did not seal the pipe and therefore it was allowed to vent which could have effectively reduced the boost, but I have disconnected one of the other pipes on the plenum with out any change. Is this any help?

Note: When I describe the problem as a miss, it is not just a hesitation under acceleration, it is like the ECU is performing a violent cut in the power, if you attempt to keep the power on the engine will kangaroo.