1989 740 'pings'

Tigermoth · Post by **Tigermoth** » 21 Dec 2007, 07:43

Hi everyone, I have a problem with my car in that when you accelerate it tends to ping inside the engine, it doesn't do it when driving or accelerating once your moving. any ideas?

Also does anyone know how much hp a '89 740 wagon has?

Cheers

waynej · Post by **waynej** » 22 Dec 2007, 11:07

How long have you had the car? Has it just started pinging or has it done it since you got it ? The auto trans cars and the manual trans cars have different
engine control units. If someone has installed the wrong one it will ping at very low RPM and not at higher speeds. If you are in a warm climate a bad air box thermostat will cause the same problem. You can get a new one from Eeuroparts.com or rprusa.com or fcpgroton.com.

Kmaniac in California USA · Post by **Kmaniac in California USA** » 22 Dec 2007, 11:23

Something else you should look for is a vacuum leak, either at an intake side gaskets, with rubber vacuum hoses or the vacuum reservoir tank.

My 740 used to ping occasionally when I first bought it three years ago. At the same time, my vent controls and heater control valve didn't function. I soon discovered a crack more than half way around one end of the plastic vacuum reservoir tank (located under the car and in between the front wheels). Once I replaced the vacuum tank, the pinging stopped and the vent controls and heater control valve started working again. What surprised me most is that the engine idled and ran well, even with this severe a vacuum leak.

By the way, it looks like you got your car to start now. Let us know what you find and what you do.

Tigermoth · Post by **Tigermoth** » 23 Dec 2007, 05:28

Thank you, I hadn't thought of that, this puts me in a whole new direction! sorry about the late reply, yes the car started being good but knock on wood it stays that way. I'll check out your ideas, thanks. Is it possible that an over machining of the head could cause this problem?