DANdeMAN

Hey guys, I'm in the Ottawa area, I need to borrow a known working ignition distributor for an 84 928 to confirm / infirm that my distributor is or isn't the cause of a recurring misfire. Will pay for shipping if out of the area and give you any guarantee of return that you request. Thank you. Daniel

Note : cross post in the Canadian forum

DANdeMAN

Some additional info. Maybe someone will have a "AHA" moment from reading this. Thanks.

Here is the short of it : New injectors, plugs(the old ones looked good), rotor(cap looks good) and connectors. All donne last week. Coil, wires, both coolant bridge sensor in 2008/9 when I did water pump timing belt job but low milage since. For whatever reason, some time after that the misfire started. Had the alternator rebuilt, no change. Started a thread and checked all that was suggested and after some time playing with this and that, I said f*ck it and drove it as is but it wasn't as bad as now.

Here are the 3 WTF symptoms that may help you help me.
1) No misfire during the engine cold running cycle. After the cycle, about 2 minutes, the engine revs go down and misfire starts.
2) Often after changing the timing (advance or retard) the problem goes away for that day but the next time ( can be a day, a week or whatever) its back. When the alternator was rebuilt and nothing changed, I went back to the shop. The tech came outside, turned the distributor and the car ran perfect but you know the story... The cat came back.
3) Misfire are at idle and low RPM only. There is no starvation or miss when pulling hard... For now.

So you can see how baffling it can be. I was so pissed off, I went to an import garage who seems to know 928s for some help pinpointing the problem. He(the owner) confirmed my suspicion about the distributor and said : "if it is a high milage car(my car as 250,000KM) the bearings may be worn inside and the play from that may be the cause for the misfire".

Now, I have checked the play and it is very small. But from what he said, it does not have to be big. Is it that, is it not that? May be may be not, but I'm getting desperate and will try about anything except blindly trowing more money at it.

Daniel

z driver 88t

Dan, I have an '84 distributor but have not confirmed if it works. I bought a complete used engine a couple years ago from 928 INTL. It came with the a distributor, but I reused my original distributor since mine was known to be working. I saved the one from the used engine as a spare in case I needed it, but have never tried it to confirm if it works.

So it may be a crap-shoot but you are welcome to borrow it if no one else closer has one. I'm in Florida and shipping to and from Canada MIGHT cost more than just buying a good used one up there and rolling the dice.

If you're interested PM me and I'll check on the shipping cost to Canada this weekend.

It does sound like somethign is a miss with the timing. Just out of curiosity when you are adjusting the distributor are you still setting it close to the factory spec. I presume you're checking it with a timing light?

Here is an unlikely cause but may-as-well check to see. Is your timing belt tension set correctly? I could envision a scenario where under load everything tightens up and it runs OK, but at idle or low RPM there could be some slop allowing the passenger side camshaft to deviate slightly and cause an issue. I know it's a long shot, but I'm trying to think outside the box.

Guy

So odd. Going thru this exact same problem which I also believe to be distributor related. My play was small but really showed up under a dial indicator. Now, I am not outta the woods yet but I will tell you that I had some difficulty timing the car at 3000 rpm as the timing seems to flutter. Installing a different unit has cured that issue. Final tune is tonight for me

DANdeMAN

Sorry guys for the delay in responding, I forgot to activate my email notification.

Chris : I have two members from the Toronto area who as offered to send me one. Thank you for the offer.
As for the belt tension, I was thinking about that exact possibility last night. Must be a cosmic thing. Note that I have a Porken conversion installed... So it should be self correcting.

Guy : Odd is an understatement... Now that you mention it, I DO have a flutter at idle after the cold cycle, misfire or not. Anyway, have you solved the problem after final tune? Please share your result. Thanks

I have a couple of things to check today. If I can get someone to rev it to 3000, I will do the light but it is highly unlikely that a few degrees off will cause those symptoms. On my first run after installing the new injectors etc, the miss was still there. After about an hour, I stoped and adjusted timing by ear + throttle body screw and had 4 hours of pure pleasure. It ran perfectly in any situation i.e. at stop light, take off and rolling. But you know the story, a few days later...

DANdeMAN

Update :
I replace the distributor cap with the old one and it ran good.
Then I checked the timing @ 3000rpm and it was off by 2-3 degrees only.
After the cap and timing, I did two test drive; One 0.5h and 2h later, a 1.5h drive with no noticeable miss.
It may be the cap that was defective after all, but I will know for sure in the days/weeks to come.

Daniel

DANdeMAN

Double post...

Guy

[QUOTE=DANdeMAN;14295181]Sorry guys for the delay in responding, I forgot to activate my email notification.

Guy : Odd is an understatement... Now that you mention it, I DO have a flutter at idle after the cold cycle, misfire or not. Anyway, have you solved the problem after final tune? Please share your result. /QUOTE]

The only change I noted was that the car is easier to time at high rpm and the light isn't jumpy. Besides that, no change however I have discovered other issues with my engine

Glad you got this sorted!!