924 Surging & power loose

[Roger Hall]

1981 924 loose's power and surges under acceleration at low RPM's. Also small backfires, happens when A/C is on but doesn't go away when A/C is turned off. I thought the car was running rich because of the backfires. Someone suggested it was running lean. I have had the fuel mixture checked 3 times in the last eight months. Could it be the electric supply to the fuel pump or the fuel pump? I'm just looking for suggestions.

[thamlin000]

When my cars do that, I just tune it up. New plugs, plug wires, distributer cap, rotor, air/fuel filters are cheap and easy to install. Then I cross my fingers and hope it goes away. If that doesn't work, at least you'll improve performance and fuel economy.

Good luck.

[Roger Hall]

Done all that and more. The car was sitting for about 10 years. Ive replaced injectors, cold start valve, timing belt, and exhuast system. Your right car runs much better now. I have to figure this out though its annoying.

[Eturbo924]

Have you checked the timing?
Sounds like you might have to much ignition advance. Mine will do that exact same thing if I advance the ignition timing to much. Check it and or just play with it a bit to see what your engine and driving habits like the most.

Eric
www.geocities.com/eturbo924

[JonA]

If you have replaced all the usual ignition parts and are sure that that is not your problem, I would look at the fuel. Get out the Haynes and systematically eliminate everything it ain't. The pressure test might be a good starting point, you need to cobble together an adapter to get a pressure gauge into the line. Best bet is to take it somewhere and have a competent mechanic (with Jetronic experience) check it. There are two pressures to check, the system pressure and the control pressure. This test can give you a lot of information. Most everything else can be done with a multimeter.
All that being said, here are a few random thoughts:
Check all along the intake for air leaks. The big rubber boots can move out of position and pull away from the housings or they can develop cracks where not easily seen. Check all the vacuum lines for the same thing.
Check the fuel injectors for proper spray pattern and equal flow. This is an easy test and will tell you if an injector is bad or, more importantly if your fuel distributor has gone south (uneven flow). The old fuel distributors can be a problem, maybe especially where your car sat for 10 years.
Does the car start and warm up properly? If so you can be less suspicious of the injection components that control these functions.
Let us know how you make out. With more information there are many on this board who can be very helpful. There is a wealth of experience and knowledge.
Good luck,
Jon

[Roger Hall]

Repalced on of the boots it was cracked near the aux air regulator conection. Replaced most of the vacum lines, but didnt check for vacum leaks. Lots of ruber dried out and cracked over the 10 years.

I am going to have the fuel pressure checked at my mechanic (Foriegn Affairs in Pompano Beach FL Father & Son outfit I really like these guys eventhough they take lots of my money). I will be interested to see what the result of the pressure test is.

Car starts great warm.

Timing should not be the problem. Had the basic shop tune up and had it checked twice in the last eight months. I will put a timing light on it though just for my own satisfaction.

Replaced the injectors a few months ago. Never performed the tests just felt like they needed to be replaced.

Thanks for all the help JohnA and ETurbo924

[drew1]

Have vyou adjusted the valves. Maybe one is too tight or maybe warped out. Taking a reading with a vacuum gage or a compression test might show this, if not a leak down test will.

drew1

edit: Checxk distributor advance, too.