Our purpose is to support owners in their use and maintenance of the Porsche 928 and to foster camaraderie among owners throughout the world.
Welcome, Guest
Username: Password: Remember me

TOPIC: Running rich, way too rich

Running rich, way too rich 23 Apr 2021 19:51 #21851


  • Posts:4
  • What Personal Text?
  • HCDawg's Avatar
  • HCDawg
  • New Forum Member
  • Offline
  • Karma: 0
Hi everyone, my 928 is a 1980 Euro S with the 4.7 (all fresh) and 171,000km on the odometer, the engine management is done by MegaSquirt X3, COP coils, fresh plugs (gapped at .29) and 24lb injectors. I have a readout that shows me air/fuel ratio as it happens and it should be 15.7 as optimal.
I bought the car a few months back and it drove onto the trailer just fine, got it home and took it down the street and back (750m) and it was idling rough, readout says 8.0. The car runs so rich that fuel is spitting out of the tail pipe. When I start it cold it runs at 1500rpm for a few seconds then seems to idle okay at 900rpm, if you touch the gas pedal it stumbles and dies.
I never imagined I was going to get this intimate with my engine, first I checked for spark using a timing gun and found #1 not firing, I took the plug off the coil and the grounds and voltage were right on, put the plug back on the coil and the plug now fires, now #6 isn’t firing, same thing, now #5. Probably a bad ground, I took the wiring harness apart and found nothing unusual, I removed the engine/chassis ground, cleaned, pasted and re-installed, no difference. I bought 8 inline plug testers, I put dielectric paste on all the coil connections and they all fire properly, I tested the injectors with a NOID light and they all work. When I remove an injector plug or 2 the engine just keeps running the same.
I don’t know anything about the MegaSquirt, I’ve had it plugged into the computer and watched things happen but I’m leery about touching anything and the manuals are a university course, (I read proficiently at a grade 3 level). I know I’m going to learn this monster soon whether I like it or not.
There is gas dripping out of the exhaust fittings at this point and I’m wondering if the 02 sensor plays any part in this and will it survive this?
When I saw my first 928 30 some years ago I couldn't stop staring, I was in love
The administrator has disabled public write access.

Running rich, way too rich 25 Apr 2021 08:24 #21853


  • Posts:4
  • What Personal Text?
  • HCDawg's Avatar
  • HCDawg
  • New Forum Member
  • Offline
  • Karma: 0
it came to me at 3am, i sat up in bed and said to myself "I have a stuck injector", it helps when you write it all down, gives you perspective and the old phrase "Let me sleep on it" works.
When I saw my first 928 30 some years ago I couldn't stop staring, I was in love
The administrator has disabled public write access.

Running rich, way too rich 28 Apr 2021 10:51 #21854


  • Posts:348 Thank you received: 22
  • Rich928's Avatar
  • Rich928
  • Moderator
  • Offline
  • Karma: 4
An upgrade to MegaSquirt is turning the old 928 engine control electronics into modern technology. It is universal and highly programmable, and that is the problem. Bosch and the automakers spend years and 10s of thousands of miles testing and tuning. For the MegaSquirt customer, you become the automotive engineer.

Porsche was using the best technology at the time, however technology has greatly improved. Today, our 928s would produce at least 50% more power with the latest engine control technology.

You are breaking new ground. Keep us informed. I find it very interesting.
Rich
Membership Chairman
Charter Member
1993 928 GTS Cover Girl
1987 928 S4
1979 928 5-speed rescue
1979 928 5-liter track beast
The administrator has disabled public write access.
Moderators: Rich928, mm928, billvvOC
Time to create page: 1.178 seconds