irreproducible bucking

My 9000 had the exact same symptoms, car and dealer, when the Direct Ignition Cassette went bad. I found a new mechanic who sourced me a new cassette and the bucking has been gone ever since.

Just curious how much for parts and labor? to replace turbo.

Doesn't sound like a turbo problem to me. Or do you mean for something different? If so, what make, year, model, engine, etc?

I am up against a 'hesitation' problem on my '93 Aero.

I'm having the alternator refreshed and probably adding a modern dry cell battery as it's showing 50amps at the battery while running with 4 volt swings at the dash meter occasionally. I think it should be up around

80-90amps and steady at the dash voltmeter if I understand what the model draws cold once running without any extra devices or audio systems on (although no one seems to actually know exactly).

I had a severe bucking issue on a non-DI '89 CD Turbo and it turned out that is was a fascinating oil triggered ground at the rotor that was tripping the engine management system to cut off fuel in cycles based on an interpreted engine knock. In effect, the engine management computer read the 1 or 2 cycle misfire in the range you describe and would cut the fuel on and off in very rapid succession causing a *very* severe buck at the wheels.

My take is that the knock trigger in the management computer is the culprit in both instances. In the first, the effected plug only showed clear cylinder ignition variation after they had been in for a full service term. In the second, I have a slight pressure variation at #3 which I'm willing to bet is misfire fuel lightly thinning the oil on the rings.

If the system does rely on feedback directly from the plugs (and I think we all agree this is actually the case and not some marketing blipvert for NGK in the owners manual) - the knock algorithms in the chipset must be impacted in some way by operational plug feedback. Therefore - anything that impacts or makes the engine miss might come to be read as a knock and cut back the fuel supply momentarily based on the software trigger. When the system is hesitating or bucking (rather than shutting down to limp mode and holding) - I think it is running a reset check and, finding that the misfire has passed, releasing fuel again.

I have been trying to find some reliable measures to check over the DI on the '93 to see if #3 coil is exactly within specification because I'll wager a nominal coil would be greatly exacerbated by a low amperage situation. I wonder if a swinging voltage situation could cause a coil to heat a little higher over time?

I gather there is a very deep diagnostic factory service manual regarding known voltages and amperages throughout the system. Must keep an eye out for one.

Best wishes for the seasons brother and sister SAAB flagellants. Uncharacteristically clement for December on the story North Atlantic, will no doubt therefore have very severe weather through February for Dunlop DSP2 reports!

About $1500 total. This is > My 9000 had the exact same symptoms, car and dealer, when the Direct

I had the DI cassette replaced recently, too. Don't ask how much that cost. I don't remember, but it was a lot. Maybe it's under warrantee.

What do people think of DI cassettes, conceptually? Clearly, they do not save money over distributors etc. Do they work so much better that they justify the cost?

I'm rather fed up. This is my third and last Saab. I'm sorry to say this.

Tom

You can't do with a distributor what Saab and other makers are doing with DI. It's not just spark generation, it's an integral part of the engine management sensor system.

Tom, to me it sounds like you just need to find a better mechanic.

Dave Hinz

FWIW, Ferrari plans to use DI in upcoming models (from a Dec/Jan. "Automobile"magazine interview).

My mechanics don't cause my breakdowns. I don't understand how a better mechanic would yield better luck for me.

Tom Reingold Noo Joizy

Further to my response:

My engine seems to have ceased hesitation upon the addition of a new regulator today - the dash volt meter is not to be trusted as I suspected. We thought it might be the rectifier bridge, but that checked out fine.

Interestingly, when the electrical shop got the alternator on the bench to test - it was reading fine having been banged around a bit getting it out of the car. They reproduced the problem by heating it up for about 1/2 hour on the bench - then shutting it down and going to lunch. They fired it back up and it was producing only 80amps with irregular voltages.

The fellow working on it pointed out that the very small bosch regulator on the side of the alternator will split a seam once it rusts even a little bit and the circuit becomes untrustworthy and degrades quickly.

When we put it back in the car, we thought we hadn't solved the problem at all as there was still an irregular idle despite having full amps and steady volts across the board.

However, we had knocked one of the three vacuum hoses off the back of the manifold when we pulled the alternator and that produced exactly the same symptoms as low amperage and irregular voltage (slight misfire at idle, hesitation/buck on acceleration or steady driving at 2,500-2,700rpm)

Anyway, I remain convinced that the SAAB engine management system is

*greatly* impacted by aging alternators and I am now wondering how many DI units and Turbo's (both of which were replaced by the previous owner) are being serviced when the real culprit is at the end of the serpentine belt.

The alternator is a cheap fix too - less than $75 Canadian at Rand Electric for the parts and service - about 3 hours at Halifax Autosport (Nova Scotia) to pull everything off and put it back on again with a fresh idler pulley.

Interesting issue regarding rust-proofing application was discovered along the way. There is a very tight space between the front plastic wheel well liner and the steel inner wheel well/strut/spring support proper that remained untreated. I looked at it closely with the plastic liners out and realized that unless a wand is specifically pulled between the liner and the well - there is no way to rust-proofing material to weep in.

I will run it over to Krown on Robie to take a look, I don't see it as a deliberate miss on their part - it's just a spot where gravity works against the weeping action and coats the plastic rather than the metal.

Cheers and good luck.

Dex,

I have only heard bad things about sprayed on (aftermarket) rustproofing material. I know that it was the cat's meow around here (New England) back in the 1960's and 70's, but has since fallen out of favor amongst even the shysters at the dealerships. Some accounts hold that the stuff was merely a ploy for additional profit margin for said dealerships (similar to the magic "poly-gly-cote" no more waxing scams) and others have found that in some cases the "rust=proofing" actually exacerbates the rusting of the subject vehicle by trapping moisture between itself and the sheet metal, and by restricting the drainage holes if appplied improperly.

WRT the untreated spot that you found in the wheel well (behind the plastic liner). Did it look any more corroded than any of the treated area?

of course, YR(ustpoofing)MV

-Fred W

Merry Christmas brother Fred.

Actually, the Krown coating is a sort of weeping oil treatment that I have used for many years to greater or lesser success depending on how badly rusted the vehicle is in the first place. I say this with some measure of confidence given that they pretty much re-pave all the roads in Nova Scotia with anywhere from a sprinkle to a solid couple of inches of rock salt come December, then reapply as needed to maintain depth into April.

You sort of know you are in an black ice zone around here when it suddenly sounds like you are running a freshly graveled secondary.. :/ ..

Anyway, the Krown goop does a pretty good job at coating everything including the harness and has stopped a lot of surface corrosion on most of the metal in my cars. It will blacken and seal surface rust when it finds it and keeps it sealed up over any given year until I have it re-applied.

It tends to make marginal hoses slip a bit and you have to be careful to check around for a month or after application to make sure nothing is moving off a nipple or is changing shape radically. It does tend to spot up the windows when applied, but a little elbow grease gets them cleaned up. Drips all over the under the car - so park it on the street or on some grass for a while after coating. Hasn't killed any lawn I've left it on yet.

I gather, however, that not all independent or chain rust proofing is the same. The good folks at Wally-Mart seem to have a very corrosive material that will most definately seal any open rust solid - but is reputed to eat the plastic off harnesses and the felts off of windows. One local wag has it that they bought up all the surplus Korean war Naval Jelly they could find and thin it with the waste oil they collect as they go along. Not that he knows one way or the other.

I don't know about the dealer treatments as I have only ever used the Krown system (they actually have an old series 9000 showing the coverage points in the flyer and literature locally). The material itself seems like a some sort of thin wax/oil mix and, on the understanding that it works best if applied annually, I have come to trust it given that any SAAB I have applied it to has remained pretty solid in rough local conditions.

I doesn't repair holed panels and does wash out over time if there is a steady flow of water (say through a hole in the top of a wheel arch) - but

- I've seen some pretty rust prone cars that have been annually treated since new that look pretty much like they did when they left the showroom floor.

My 2.cents - all the usual disclaimers and limitations.

I'm beginning to think it's the clutch. It happens more often after I have accelerated very hard from a standstill. I know these aren't good for the car, and I don't do it often. And the clutch (or whatever) feels and SOUNDS different when the problem occurs. If I clutch really slowly, I don't get the bucking, but maybe that's because I am pushing the accelerator very lightly, too.

Could it be the clutch? Remember, this is an intermittent problem.

Thanks again.

Tom Reingold Noo Joizy

Could be oil occasionally dripping onto the clutch I suppose, though I'm not sure where from. It's hard to say without driving it though.

I've been having a similar problem with my car ('87 900S 5-speed, 2.0 non-turbo). I was finally able to eliminate the fluctuating idle at cold start as being related to the "bucking" by cleaning the AIC (twice) as recommended by this group. My symptoms are a little different than yours however, bucks at high rpm's instead of low, sometimes it doesn't even buck it just doesn't have any power (see example below). And it gets even weirder: it completely goes away after about 10 minutes- you can almost set your watch by it. It doesn't matter if I let it idle or if I drive it, but once it's been running for 10 minutes it stops doing it, and it only happens if the engine hasn't been running for at least

4-5 hours.

Another symptom: last week I was driving down a flat road, 3rd gear, about 3,000 rpm's, pedal floored and could not accelerate (no I don't normally drive like this); there was no bucking. This is similar to, for example, being in 5th at say 30mph and trying to pass someone. I have not been able to detect any slipping in the clutch via the tachometer, speedometer, and/or audibly (engine revving). All spark plugs, wires, etc are all new.

Any thoughts on this one?