DonS

Email/PM me and I will send you the write-up on cleaning and adjusting both the sweeper and spring.

King James

Update:

Symptoms - Starts right up, but dies immediately if not floored. Once floored, it chug-chug-chugs barely running, then roars up to 3000-4000k. Runs great at high RPM, but I can't maintain, feathering gas will keep revs (and smooth running engine) between 2k-4k, once I let off gas, it dies.

I've checked vacum and all parts of the diagram check out ok
Valve timing correct
Ignition timing correct
fuel obviously good as it revs great (with above method applied to get good revs)
AFM checks out aok - thanks Don for all the info!

And thanks to all for the suggestions, but I'm rapidly running out of ideas! I'm at the point where I'm considering getting this POS towed to a shop to pay someone to try and fix it...

I'm wondering if anyone has any ideas I may not have tried and/or the name of any reputable 928 mechanics in Milwaukee area?

Thanks again for all the help/suggestions so far, it feels close, but I can't find anything at fault!

King James

PorKen

Did you check the TempII resistance at the ECU connector?

Here's the L-Jet service bulletin, scanned and zipped - (2.3MB, right click, Save Target As...)

King James

Thanks PorKen for the reply.

I have checked the TempII resistance at the ECU and it is within the correct range per the WSM. The zip file is great, I've never seen it before. It has some excellent troubleshooting tips, I've done most of them, but I will try anything that I have not done.

It really seems like I'm chasing a vacum leak/air issue, but I've swapped all vacum lines for new, and checked all places I can think of for leaks...I've heard an old trick is to use propane (or carb cleaner) as a leak chaser, car runs better when it gets a whiff...any experience chasing leaks this way?

King James

DonS

Hang in there; as you check things out you're also eliminating them and the culprit is being smoked out.

What about the Cold Start Valve and throttle switches?

King James

Don,

I am assuming that since it fires up right away (then doesn't stay running w/out flooring it) that the cold start is doing it's job...does this sound correct?

I've also checked both idle and rich throttle switches, they both check out ok (as far as the manual goes)...

I hate to do it, but I'm starting to re-do things already checked, maybe I pull the spider, pull the throttle body and AFM, re-assembling and re-verifying that all vacum hoses are connected...BTDT though...

Any suggestions - shout out, I'll report back as I go

Thanks all!

KJ

DonS

What were the results with the scope? Good patterns?

Check all the values on page 18 of the Porsche AFC file at the ECU connector. This is how I traced mine. Even if BTDT have you done all the diagnostics per their procedures in that file?

If you're not finding anything out of spec then back to the AFM or else !WAG! cam timing? Your description of the running condition seems to have all three requirements but something's WAY off?

kiwiokie

I had similar symptoms on my '82 due to a massive vaccuum leak caused by a plastic blanking plug falling off the throttle body. Its been some time since I looked at it but there was a half inch plastic cap on one of the unused ports coming off the throttle body. Might be worth checking.

hacker-pschorr

Jim Page @ Page Auto, 27 years experience working on 928's (his first 928 customer was in 1980) is in Green Bay. He has his own personal collection of 928's. PM me if you want his contact info, he is a Rennlist member

Reading thorugh this thread I'm a bit confused myself as to what could be wrong. Sounds like a massive vacuum leak.