9000CSE at 2200rpm

Ramsey Frist 22 years ago

I have had my 1998 9000CSE for almost two years. Its a 5 speed with the Aero engine. I would like to know if it is normal for there to be a slight discontinuity when accelerating through 2200 rpm. I would not call it a dead spot but just a slightly noticable change in output as the engine revs through 2200 rpm. It is most noticable in 2nd gear but is detectable in all gears. I think it has been that way for the 30,000 miles that I have put on it but I just notice it more of late. I did not experience such with my 1994 9000CSE (now my son's work car) but it had an automatic transmission. I am more curious than worried about it.

Any comments would be appreciated.

R. Frist

98 9000CSE
94 9000CES
85 900 Turbo 5 sp. (now belongs to my grandson with 220,000 miles)

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SAABurger 22 years ago

Ramsey, I posted to this group yesterday (see thread "2.3 liter hesitates on acceleration") explaining how an exhaust leak was causing my problem, and how a new front section of exhaust cured it.

What I didn't say in that post was that the hesitation was strongest when accelerating through about 2000 rpm. The difference between your 2200 and my

2000 rpm could be accounted for by our engines being turbo and non-turbo respectively. For me, the discontinuity was very marked just before I had the exhaust replaced, but gone completely as I drove home from the exhaust-centre.

It is my guess that there's a discontinuity in the fuelling logic at about

2000 and that this normally unobservable artefact becomes imperfect when the lambda sensor (which monitors oxygen level in exhaust gasses) is confused by a leak.

From my experience I would have to recommend having your exhaust and lambda sensor checked. I would also advise that my car passed two MOT tests whilst exhibiting this problem, so your leak (if you have one) may not necessarily be observable on the ramps.

Adrian

1992 9000CS 2.3-16i

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Ramsey Frist 22 years ago

I will check it out. I replaced the front Oxgyen sensor (post 94 CSEs have one before and one after the catalytic converter) about 3 weeks ago. That cured the "check engine light" but had no effect on the 2200 rpm discontinuity.

Best regards, Ramsey

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