No acceleration Running on 2 cylinders

I just purchased a 1988 BMW 325i Convertible from a private party who told me extensive work had been done on it (rebuilt motor, hydrolics, exhaust, etc.). I drove it for 2 days without any problems and then on the 3rd day it had problems starting. Once started, it has very low acceleration (foot to the pedal 20MPH). The max speed I could get was 70MPH.

We thought it was the catalytic converter so we cut the pipes to see if it made any difference. It didn’t. We welded the pipes back on and drove it to a local mechanic for a diagnostic. 1 hour of his time and $90 later, I was told that it would take him at least another hour to complete the diagnostic. I chose not to pay him for another hour and drove the car home putting 20MPH. It’s running rich and sucks gas like it’s air! I swear it uses 1 gallon a mile!

The mechanic was able to determine that the mass air flow sensor had been tampered with (opened up and silicone applied to it???) and that the car was only running on 2 cylinders. Is the problem with the fuel injector and the mass air flow sensor?

BTW, I LOVE your show and always get a good chuckle listening to you 2 guys!



My money is on the the mass air flow sensor.

Good Luck

Now, the spark plugs are fouled. Look at them and decide if they need replacement. There might be other things wrong, also. Such as: fuel pressure; dirty air filter; engine coolant temperature sensor; MAP Sensor; etc.

1988…The Dark Years… Rebuilt…Terri…BMW…Money Pit…This thread is NOT going to have a happy ending…

Any engine running on two cylinders is going to suck gas like it’s air…unless the cause of the poor operation is fuel starvation. If the engine is only burning part of the gas being fed to it, it’ll need to use a lot more of that gas to get the energy needed to get you home. The unburned portion just gets blown out the exhaust.

Did the mechanic actually check the MAF sensor signal?
Did he check any other sensor signals?
Since he said it’s running on only two cylinders, did he check anything in the ignition system to see if there was a high voltage signal being sent to the other spark plugs?
Did he check the shape and amplitude of those signals?

Did he check the operation of the fuel injectors?
Did he check the operation of the fuel pressure regulator?

Is the reason he didn’t check these items because you wouldn’t allow him more time?
Why wouldn’t you allow him the time?

I’m going to guess that you have a failing ignition system component, perhaps a coil, perhaps a distributor, but without checking a few things it’s just a wild guess. You need to give someone the time to do a proper diganosis. The vehicle is 22 years old, has had an unusual amount of work done to it, and it’s just going to take the time for someone to check things one by one.

Yeah, you should replace that MAF sensor. But I think you have a lot more going on here than just that.

Sorry, but I can’t offer a simple “replace this and the car will be fixed” solution.

Kaaa-Ching, Ka-ching, Ka,ching…

You will not get Tom and Ray on this forum; only an assortment of people offering advice as to the problem.

A MAF sensor is not going to pick on 2 cylinders. It will go after all of them.

If the car were mine I would run a compression test as a first step. You state a private party told you extensive work had been done including an engine rebuild and statements like this should be considered puffing at best or utter BS at the worst.
Maybe it’s running on 2 cylinders because a head gasket gave up; or the goop someone used to patch a head gasket waved the white flag.

I’m an optimist. I’d look at the ignition system first.

But I agree emphatically with your post. This isn’t just a MAF sensor. There’s something much more going on here. My guess is that the MAF sensor signal might even be good, even if someone gumped it up with silicone silastic. It needs replacing anyway because of the silicone’s affect on its function, but it’s not the core problem.

I really appreciate the series of questions you fired out. These are things I just don’t know and can now go back to the mechanic and ask. I’ll keep you posted to his response. Thanks again!

You believed what the private seller told you regarding this vehicle. That was your first mistake.

You’ll spend more money to fix what’s wrong than the car will ever be worth.

Good luck.

I hate to say it but I believed all them - husband, wife and son! I bought their story and drove away thinking I had a great car.

You really think it will cost too much to fix?

Thanks for the response and I’ll be talking to the mechanic on Monday to ask him more about his diagnostic. I’ll update any new info as I get it. Thanks again!

This would be a GREAT car for a back-yard mechanic with access to a salvage yard full of retired BeeMers… A week of tinkering and parts swapping and happiness might be found. But I don’t think you are that person and happiness will take a miracle and or a lot of money…