Hard Start When Cold

[Howard L Tan]

I've been searching through the website, and reading through the troubleshooting guides in the Haynes Manual. But no matter how hard I look I can't seem to find the answer to my problems. Can anybody fill in the blank?

Trouble:
Engine idles badly when cold, then evens out when warm.

Solution:
????

Thanks,
Howard.

[Howard L Tan]

I forgot to mention, I have a 914 72 1.7.

Howard.

[Dave at Pelican Parts]

You probably need some FI tweaking.

First step in any FI diagnostic is to check your ignition system. All the pieces in good shape? Timing and dwell OK? Nice fat happy spark? Good, on the the FI!

If by "idles poorly" you mean that the idle goes up and down and up and down, then you have what's called an "idle hunt". This is symptomatic of a lean fuel mixture. You can richen the idle mixture a bit by turning the knob on the ECU ("brain") clockwise a few clicks. See if that helps.

If by "idles poorly" you mean that it idles very unevenly, you may still have a spark-related problem, or you may have a rich mixture. Try re-checking the ignition, and then try turning the ECU knob a few clicks counter-clockwise.

If by "idles poorly" you mean that it runs relatively smooth but at a too-low RPM, then you might still have a rich mixture, or your Auxiliary Air Regulator might be dead. You can try the ECU knob (try all the way CCW, but count the clicks so you can set it back). Then check the AAR. Pull the hose from it to the air cleaner off the air cleaner. When the motor is cold, air should get sucked into that hose. When the motor is warm (5-10 minutes, maybe less) there should be no air going in there. It is possible to fix a dead AAR.

You can check Kjell Nelin's D-jet article on Tim's 914 Fan Page--[www.estinc.com/porsche] under the Tech Refs section.

If you'd like more help from people on this forum, please describe more completely what the symptoms are. Otherwise, we're just taking blind guesses.

--DD

[L Sjoberg]

Having just bought a '74 1.8. I'm not sure if this'll help, or not, but what the hey, it's free advice : ) A lot of the D-jet Bimmers have the same problem - rough idle at cold, smoother idle once warm. They have a cold-start system that manages the air/fuel mixture until the engine gets warm, when the FI kicks in. If there's a vacuum leak, the cold start system is unable to "adapt" - once the FI kicks in, however, it adjusts the fuel flow to compensate for the air leak. I'm not sure if the early D-jets on the 914's have this set-up, but you might check your intake manifold hose. These can crack pretty easy, especially around the clamps. Like I said, it might not help but it won't cost you anything : )