328 - raving up is same as horse back riding

Hi all!

I experienced a strange behavior with a '87 328 GTS when I quickly push the car to higher speed (RPMs). Once the engine is warm (~25min driving, ~15 km) and ready to be pushed I experience the following:

If I push it quickly, the car will rave up - speed increases until I touch around 5.500 RPMs. Than the car starts stuttering / shaking as if I had not enough fuel or as if the ignition does not work for a fraction of seconds. Lowering speed, and then pushing it again it will show the same behavior at much lower RPMs(4.000, etc.).
(This does not happen when not having a gear)

If I push it slowly it will pass the 6.000 rpm before starting to stutter again at higher RPMs.

Background story:

1st time occurrence:
I had oil refilled (10W60). I take the car to a drive and the moment I raved it up, it started stuttering. When this first happened – the car would stutter later at even lower RPMs until the engine will go off. Like: if it stutters at 6.000 rpm, it will then stutter at 4.000, than at 2.500 then it will go off. The moment I reach an RPM where it stutters it goes down this path (lower and lower and off). I had it then in the garage and they thought it is a fuel problem. They changed spark plugs and cut the exhaust-engine-feedback loop as they thought that it disturbs the fuel-pressure department, etc. (Swiss version has this in contrary with the European version). They said it was fine.

Not even the day later - 2nd time occurrence:
The same symptom appeared again. Once I touch a certain rpm (i.e. 5.500 the car was having problems at lower RPMs and lower and lower). But this time the car at least was somewhat drivable (not like a Ferrari but like a much slow car). I had the car in the garage and they found “it’s the cables to the spark-plugs”. They changed ONE side only of the cables (the other they say was o.k.).

3rd time occurrence:
I take the car – and again – same symptoms… But this time slightly better. The car did not stutter / shake so terribly at touching high RPMs. So I thought perhaps it is something with the cables as problem was - not solved - but at least ½ way better. But the garage was convinced it is something around fuel. The garage changed all spark-plug-cables with an other 328 GTS (which they had there). It seemed not to be the cause. Then they changed the Bosh-“Potentiometer” (which coordinates the engine fuel ignition and my level of pressing the pedal ?). And they believed it was fixed. I tried the car. It seemed almost fine (very little shaking at higher speed). I thought: well, it should be gone with a complete proper service. But then after driving it again and again, it stutter/shakes just like before. I am about to bring it again to this garage – although I am not convinced that they know what they do. But as I have not paid any bill yet I am still in ‘discussion’ mode that they should do their job.

Anyone with experience / tips on that what I could tell them where to look?

Thankful for all input!
Kind regards,


STC

 

hm, sounds very interesting. Now as you say so , I remember:

> filling up the tank always takes time because the fuel nozzle of the gas station behaves as if the tank was full already and disconnects.

> the fuel level indicator varies during driving from filled to low unevenly and sometimes goes up again (after indicating low).

Can I check this by letting air in (opening the gas lid) for a moment, closing it and see difference in driving behaviour?