1971 Volvo P1800 TPS

So I’ve been having an issue with the throttle on my p1800. It starts right up, but to keep it running I have to feather the throttle for at least 10 mins. To make the engine rev higher I have to feather it harder. It has a Bosche injection system on it mostly original.

I have replaced the fuel filter, pressure regulator, had the pump serviced, replaced the fuel pump relay, and had the computer control looked at by a mechanic, who said it looked fine but seemed unsure.

The only thing I can think of is the Throttle Position Sensor, but I cannot find them for sale anywhere.

Any ideas would be awesome.

Thanks Garrett

Does it have a TPS? I’d have thought it has Bosch Jetronic (of some vintage) FI, which is largely mechanical. If this problem goes away once it’s warm check if there’s a cold start injector, maybe something wrong with that.

Also, that’s a very popular car with Volvo folk, I bet you’d get a quick answer on one of the P1800 forums (google it).

It does have a TPS attached to the Throttle body which regulates the amount injected. I changed the cold start sensor, and cleaned the cold start injector, which is a small port in the air intake.

OK. But is it only a cold start issue? If it is, I have trouble seeing how the TPS would be the problem.

No, I have to feather it for at least the first 10 mins even if its a warm restart.

I believe the TPS functioned only to indicate that the throttle was released, signaling the computer to take over the idle speed.

So the issue may be in the idle control. Okay I’ll check that out.
Another thing is that if I disconnect the temp sensor for the injection system the problem seems less sever.