running issues after removing from storage

[philbert]

I recently gotten in my possession a '76 914 after it had been in storage for a number of years. It's an extremely clean car.

The issue I'm having is keeping it running and obviously being able to drive it. It starts right up with no issues at all and runs pretty darn well for about 60 seconds. Then it can stall or when you try to rev it up and stalls. If you can get the rpms up, to 3000 or so, it will oscillate between 3000 and 1500 rpm. I don't know the previous history...if it did this before going into storage. I kinda doubt it though.

Plugs good, gas drained and fresh, points clean, new cap, no obvious vacuum leaks.

What should I be looking at to figure this out?

[Mike Bellis]

The old fuel may have dried in the injectors and turned to varnish. You can clean them by soaking in lacquer thinner.

[philbert]

The car has been driven about 50 miles like this. It's not easy to drive but it can be done.

[Mike Bellis]

If your injectors are gummed up, driving it may not clear them out. You need to remove the injectors from the engine to clean them. You could first try some Sea Foam (auto parts store) and see what happens.

[philbert]

I'm having difficulty thinking it might be clogged injectors given that it runs pretty darn good for 60 seconds when you first start it up. It revs and idles fine (a bit higher than normal), it's after that 60 second time period when it all goes to crap.

[Griffinroydonal]

I would check the fuel pressure to see if it is a constant delivery to the engine. I would blow the lines and drain and clean the tank and replace the fuel filter before I went any further. Fresh gas and clean goes a long way to a happy drive.

[philbert]

As I said earlier, fresh gas and it does have a new gas filter. Even dropped in a bottle of injector cleaner (Seafoam).

I am thinking it must be a sensor or something that is not right because of how it starts to run really bad after that magic 60 second mark. I will check fuel pressure though...good idea.

[Dave at Pelican Parts]

The stock injection doesn't have any 60-second timers in it. There are things that change based on temperature (e.g., the head temp sensor circuit, the intake air temp circuit). There are two things that get heated up to change behavior--the Auxiliary Air Regulator and the Thermo-Time Switch. The AAR makes the idle higher when the engine is cold, and takes several minutes to close. The TTS controls the cold-start valve, which can only ever spray while the starter is cranking. So neither of those is likely to have anything to do with your 60-second timer.

Gunk in the fuel tank is still the likeliest cause. Also look for fuel hoses that might be kinked, especially under the fuel tank.

--DD

[philbert]

So...it looks like I might be eating humble pie and quite frankly it doesn't taste very good.

Fuel pressure is right around 30 psi...cold or warm engine, so that looks good. I was told it had been flushed and had fresh gas but I gotta tell ya, when I did the fuel pressure test the stench of the gas told me otherwise. I dropped in a bottle of fuel injector cleaner and after about 10 minutes of driving it progressively got better. It still stumbles but I don't fear the engine will die at any moment. I will drain the tank and I'm guessing that will take care of most, if not all of the problem.

[Dave at Pelican Parts]

Don't worry about the taste--I find one gets used to it after a while. (My wife will tell you that I'm always wrong any way. )

The 60 second thing did sound suspicious, especially after dealing with lots of modern cars which do have a lot of electronics.

The important thing here is that the car is running better!! Keep at it and you'll have it behaving nicely before you know it.

--DD

[Griffinroydonal]

Humble pie is ok once you get used to the taste. I have been through the same problem and found after I removes the tank and blew out the lines everything cleared up. I am glad the tanks are easier to remove than most cars. The filter thing comes from having to rebuild carbs that actually had sand in them from a nasty tank. I don't deal with the F.I issues because the past owner pulled that long ago

[seventythree]

Hi Dave,

The AAR supplies extra air to a cold engine; please remind me, where does the extra fuel come from to elevate the idle speed?

I have a verified to be functional AAR, but as of late, the cold start RPM doesn't go to 1600 like it used to. It idles poorly at around 600. All is well once the engine is warmed up. I am trying to isolate the problem.

Thanks

[Dave at Pelican Parts]

The extra air is detected by the manifold pressure sensor, which more or less sees it as a very slightly open throttle. (The throttle position sensor doesn't, of course, because the throttle is closed.) So the MPS sees the extra air, and causes fuel to be added to go with it.

--DD

[seventythree]

So, if the extra air is going in (verified by pulling the supply hose to the AAR) but the idle stays low, what would you guess is the problem? If the MPS doesn't add the extra fuel, it is sensing higher vacuum, so a vacuum leak in the hose can't be the problem. A bad MPS? Or, could it be some sort of a electrical problem?

[Dave at Pelican Parts]

Could be too much fuel? That can bog down the idle RPM. Or it could be that it just plain needs more air than it's getting.

--DD

[racer]

Have Dwell/Timing been set properly? Would failing FI trigger points be causing a problem?

Or, as mentioned, first guess would be krud/rusting fuel tank. May need to get it cleaned and sealed.