medipedicman

I have a couple of symptoms that may be related to air-fuel mixture, and I need your help. I have had a handfull of no starts after driving for a while. The first one I attributed to weak alternator. After sitting 20 minutes I got a jump and it started right up. After experiencing that a few more times it seems the 20 minutes is more significant than the jump because the charge is fine and it cranks fine. It wants to catch, but it doesn't.
The other symptom is extremely hot exhaust. REALLY HOT.

Could these two things be related and could they be fixed with a simple adjustment to the air-fuel screw.

As a side note, I discovered last night that the cars bogs down at 4500 rpm under full throttle. It the mixture too rich?

Any ideas or advice would be appreciated.
Thank you

Jadz928

Pull spark plugs... black/rich, white/lean

medipedicman

Thanks Jim- I will check that today.

medipedicman

Well I guess I was hoping too see something really obvious.
Any ideas?

BTW I have a new set of plugs, wires and cap to be installed soon. I have an Adj tool on order that will be in next week. Anything else I can try?

IcemanG17

those plugs aren't that bad...... How about the infamous "green" wire that goes from the dist to the ign brain on pass fender? I know those are serious achilles heel of all 16V 928's

On my race 928 I have a fully adjustable fuel-spark system....with a fuel adjustment **** on the center of the dash that goes +/- 50% fuel.....with the system set for WOT fuel (Race car) it does run a bit rough the rest of the time, since its set far too rich at 12.5afr.....so I lean it out to simulate 14.7 afr with the ****....and it runs much better at light loads-putting around the paddock....

medipedicman

Hey Brian
I have inspected the green wire and the PO has said it was changed when the new fuel lines where installed. I hope to play around with the mixture next week.
I had read a thread at some point about a burned up catalytic converter because of a mixture that was too rich. Because my exhaust is so HOT I thought it might be related.

Thank you

Jadz928

Man, if you were that rich, you'd know it. Eyes would be burning...

Dean_Fuller

Could this be a clogged catalytic converter ? That was my first "hot exhaust" issue.

medipedicman

I just passed emissions.?.?
Would that be effected?

Hilton

If the exhaust is that hot, I'd suspect unburnt fuel passing out the exhaust ports into the cats. Be very careful - the cats can cause a car fire.

medipedicman

What would cause that and how would I fix it?


Thank you all for your help. Combustion is way outside my comfort zone.

vze2jshn

IMHO, I think if you passed emissions your air/fuel mixture is probably in the correct range. If you plan to fiddle with it, you need to close off (pinch) the air pump hose and then have a shop with an accurate exhaust sniffer read where you are in the acceptable range and slowly adjust, then rev engine to clear and see where the reading has gone. It is not advisable to try and adjust by ear.

medipedicman

Thanks Greg.

medipedicman

Could the issues no start issues in the original post be related to the regulator?

https://rennlist.com/forums/928-foru...ggestions.html

https://rennlist.com/forums/928-foru...-shut-off.html

I was trying to tie the no starts with the hot exhaust and they may be unrelated.
The flooding described in the posts above resemble the issues that I am having.

Jadz928

Do you have any sense where your idle adjustment is? If it's CCW from center, you may be really close to where the fuel meter barrel (in the FD) is about to crack. When it cracks, you can hear it dumping fuel in the cylinders. This is VERY rich!