My 1986 9000 suffuers with misfire at around 3500 revs and the turbo starts working hard this is even on medium acceleration . If I accelerate hard, then misfire is severe and will not get up speed back off and it will accelerate slowly but smoothly. reach 70 odd and maintain it then I get the feeling of drag coming on and the check engine light comes up . I have replaced the DI unit (red) as the last one packed up completely however being on limited funds I got it from a scrap yard , is the problem still likely to be the DI unit or something equally sinister and expensive........Help!

Off the top of my head, the lambda sensor could be duff - if you have one.

I thin kmy DI unit is on it's way - judders badly when one of the coils doesn't perform.


Phil.

Hi, I recently traded my 1989 T16, and have had a missfire on Turbo Boost with that car. I eventually replaced the rubbers in the DI Unit where they enclose the spark plugs, I think in my case they were corroded and encouraged breakdown of the spark. Oh, and I tried the hugely expensive platinum plugs from Bosch just before I sold the car as the NGK plugs I used (Reliably) were out of stock.

Forgive my ignorance but ehat is a lambda sensor

The lambda sensor is positioned in the exhaust either in the manifold or in the pipe close to the manifold. It produces an electrical signal when it is heated which varies with the amount of oxygen in the exhaust gas. This signal is fed back to engine management ECU which uses it keep the fuel mixture at the optimum ratio for minimum emmisions. A duff lambda sensor can cause variable symptoms but mostly affects the drivablity of the cars due to an incorrect fuel mixture.

Is this the unit that sits in the middle of a thick plastic flexible pipe ,is a square device with a round red button and multiway cable coming out of it? if so I have had problems with that and found that wiggling the plug has had a temporary effect on performance. e.g. the turbo started to behave itself etc.

Hi Tim,
The unit you describe sounds like the air mass meter. This measures the volume of incoming air to the engine. (It will usually have the BOSCH tradename on the side)

By the way, I believe that only catalyst equiped cars (from approx '90 on) have lamda sensors. So as you have a '86 9000 you probably won't have one. As Derek states it would be near the exhaust manifold in the side of the exhaust pipe, if you did.

I would go with Kevins' idea of checking/changing the spark plugs.
The more pressure there is in the cylinder the harder it is for the spark to be ignited and the likleyhood of a misfire is far greater on-boost than off.

Cats are std on all petrol engined cars after 1/1/93 (I believe). I am sure that Saab were fitting cats to 9000 cars on the UK market prior to 1990. I distinctly remember the sulphurous smell (bad eggs) eminating from some cars in the late 80s, particularly Saab 9000s, due to the catalytic converters. NB All US Saabs have been fitted with Cats since 1974 or thereabouts.
/john