Yet Another "Help, my car doesn't run" Thread, '75 2.0 Options

[poorsche914]

I haven't touched the car in a couple months but it was nice today so I thought I'd see what happens.

It is a Cali '75 2.0 that when I bought it last summer, ran OK. It did have the stumble at around 2500rpm or so typical of the problem TPS. I backdated the exhaust with SS exchangers and a ??? muffler. Still ran OK.

I then decided to remove the smog stuff. The pump was already missing. When I pulled the air injection pipes, they were clogged with ???. I used JBWeld and caps to seal them and reinstalled. Removed the other pipes and plugged the connection point on the air breather. Started it and did not run too well. I checked and double checked to be sure I had all the vac lines connected in the right spots. Looked OK.

I then checked the gas tank. Pulled it and looked inside. Some rust but not too bad. I cleaned the sock and put in new fuel lines and fuel filter. Put it all back together and still not running right. Even swapped out two other fuel pumps. Same result all three.

Today the weather is beautiful so I decided to give it another try and pay more attention to what is happening...

1. Starts right up and idles fine. Freely revs without much issue. Some backfiring.
2. Drove down the road (less than half a mile before turning around) Some hesitation and bucking at the 30-3500 range under acceleration.
3. Drove home and let it idle for about 5 min to warm up then back on the road. Under acceleration, MAJOR bucking/hesitation at just over 2k and up. Backfiring. Limped home and shut it off.

Any suggestions on where to start would be appreciated. Nice weather is here and I really want to start driving my 914! (IMG:style_emoticons/default/driving.gif)

Thanks.

[pbanders]

As always, hard to diagnose these kinds of problems over the internet, but we'll give it a try. From the backfiring and bucking you describe, it sounds to me like it's running lean. I'd check the following items:

1. CHT resistance
2. Fuel pressure
3. Injector spray patterns

To really diagnose it properly, you should use a gas analyzer to check your mixture under part-load. You can do this in a number of ways, including getting your own AFM that can mount to the exhaust, or going to a dyno shop and having them do a run while it's on the analyzer. Anything over 14:1 is too lean, it should be about 13.7:1 under part-load and about 12.5:1 under full load.

[poorsche914]

As always, hard to diagnose these kinds of problems over the internet, but we'll give it a try. From the backfiring and bucking you describe, it sounds to me like it's running lean. I'd check the following items:

1. CHT resistance
2. Fuel pressure
3. Injector spray patterns

To really diagnose it properly, you should use a gas analyzer to check your mixture under part-load. You can do this in a number of ways, including getting your own AFM that can mount to the exhaust, or going to a dyno shop and having them do a run while it's on the analyzer. Anything over 14:1 is too lean, it should be about 13.7:1 under part-load and about 12.5:1 under full load.

Yes, I realize it is difficult to analyze over the internet but at least I can get some ideas of what to check. Thanks for the suggestions. I did mess with the adjustment on the ECU so may have got it too lean.

[pbanders]

The mixture knob on the ECU only affects the idle mixture. Once you open the throttle at all, that circuit in the ECU is opened and has no effect. It shouldn't have any effect over the running problems you've had while driving.

[underthetire]

Stuck open AAR ?

[ME733]

..........CHECK the point gap......should be .016 ths inch.............m.m.