914 newbie --idle problems

[jeff91418]

I just purchase this 1975 914 1.8 fuel injected. The car had been sitting for 7 yrs and the previous owner bought it to restore and never moved it once, also i realized he didn't know much about mechanics after a few brief questions.... I got it home, changed oil, plugs, cap & roter, fuel lines, filter, & pump and she fired right up....

I drove it for about a mile and it died.... would start up intermittently and it appeared as though the throttle was wide open, even though i wasn't touching the pedal.... after getting it in gear i was able to make it home... the problem has evolved so that now when I start the engine (no foot on the pedal) it rev's up so much that i have to turn the key off.... Try it a second time and it will barely idle, backfire and die after about 3 seconds.... and then repeat the process again... (throttle wide open, i turn the key off... 2nd time it sputters and dies.)
Before the problem evolved to the state i described, i was able to start it and run back to the throttle cable butterfly valve and manually operate it and the engine sounded great, but leave it to the pedal and bad thins happen.... I have a sneaking suspicion it is the butterfly valve attached to the throttle cable. However now that the throttle appears to be stuck wide open, i can't even manually keep it running.... Any suggestions? A little direction? Should i look into replacing the throttle valve? it seems to abrupt to be caused from a vacuum issue but I could be wrong... the vacuum lines need replacing and several components are not connected (Decel valve, egr, etc) not sure which ones are important and which ones can be eliminated....
As harry Karry says..... "Your thoughts?"

[jeff91418]

So today i replaced all the vacuum & air hoses according to a factory diagram. My 914 had abandoned the decel valve and a few other air lines were plugged.... I hooked everything back up stock (the best i could determine). Now the problem looks like this:

Turn the key and start the car (foot off the accelerator) The car surges to about 7,000 rpm and then dies.... Turn the key a second time and it sputters for about 5 sec (i assume it is burning the excess fuel from the previous start).... It sounds like it is running on all cylinders when it surges so that would tell me that each individual injector is functioning properly.... but something is either causing too much fuel/air in the manifold.... I'm assuming the problem is fuel related since it makes more sense with the 2nd start scenario. but i could be persuaded.

[Dave at Pelican Parts]

Check if there are any hoses connected directly from "upstream" of the throttle body to "downstream". In stock form, all of those hoses have some component in the middle of them, and most of those components block air from going through them.

7K RPM is a rather good-sized air leak. If it were just a vacuum leak from the outside getting in, the air leaking in would be unmetered air ("false air") that the fuel injection doesn't know about and would result in a lean mixture. The engine would likely not idle or would run really very poorly. So chances are that there is a leak of metered air, so something from "downstream" of the air flow meter.

Either that, or you have a ton of extra fuel going in, like your head temp sensor is unplugged, and you do have lots of "false air" going in.

--DD

[jeff91418]

The Temp sensor is intact and plugged in traced the wire over to the relay board? on the left side of the engine compartment... seems like most people say if that is faulty it will just run rough.... any other ideas? what component would cause fuel to dump straight in the cylinders without accelerator manipulation?

[jeff91418]

could you articulate a little about upstream vs downstream? which compoants run off upstream and which one run off down?

[Dave at Pelican Parts]

The air going into the engine all follows the same path, pretty much. It gets sucked into the snorkel on the air cleaner, goes through the filter, passes through the air flow meter, goes down to the throttle body, into the manifold, and then out to the intake valves. "Upstream" in this case means closer to the intake snorkel on that path, while "downstream" means closer to the intake valves.

Components like the decel valve and the aux air regulator act as a way for air to bypass the throttle body. They are intended to raise the idle RPM by a certain amount under specific circumstances. So they have one hose connected to the rubber boot between the air flow meter and the throttle body, and one hose connected to the manifold. But those two components are normally closed, especially in steady-state operation.

If you have any hoses directly from the intake boot (the rubber thing upstream of the throttle body) to the manifold, those are wrong. Those hoses should be removed and the openings plugged.

--DD