|
|
|
|
| Author |
|
|
Registered
Join Date: May 2007
Location: Oakbank, MB
Posts: 36
|
Severe engine miss at high RPM
I have a 1982 928 (AT) and having an acceleration problem. Starts fine, accelerates from stop fine (although it seems a little low on power). When running at approx 65 mph and step on gas to drop a gear, rpm goes from approx. 3400 to 4000 rpm then starts to miss wildly - tach drops to 2000 rpm and jumps up and down with corresponding engine miss. The car does not do this all the time - about 50% of the time car drops to 2nd and accels very hard and steady. I have replaced fuel filter, fuel pump (after unrepairable leak was noticed). Plugs checked and gapped. Clean air filter. Gas consumption is very high - no exact number as speedo gear is shot (winter project). Suspected valve timing but problem is not consistent. Fuel injection? Any thought as to where to start?
|
||
09-04-2007, 07:43 AM
|
|
|
Network Native
Join Date: Jan 2007
Location: SoCal
Posts: 10,349
|
Lack of fuel doesn't usually feel like a miss, it feels like letting up on the accelerator. My wild guess would be ignition. If it kind of needs it anyway, I would replace coil, rotor, cap, wires and see if that doesn't help.
Maybe first thing is to clean all the ground points.
__________________
US 83 zinc metallic 5 spd, aka the nice car. Euro 85 black, 5 spd, the fast rough track car maybe car. SOLD Euro 84 red, AT, only car in garage in years, my parts car, soon to go last 7 years. |
||
|
09-04-2007, 09:21 AM
|
|
|
Registered
Join Date: May 2007
Location: Oakbank, MB
Posts: 36
|
I had a similar problem with a Saturn and it ended up being the wires, so that may be a good place to start. When it happens, it definately does start to slow down (jerking back and forth as if fuel were being injected on and off), so I don't want to rule out fuel yet. But I'll check out the ignition and see what shoes up.
|
||
|
09-04-2007, 09:53 AM
|
|
|
Registered
Join Date: Jan 2007
Posts: 652
|
What do your plugs look like after this happens?
__________________
1984 928's w/ 5 speed Smoked Quartz Metalic 1982 928's Turbo w/ 5 Speed Platinum Metalic 1978 Euro Widebody w/ 5 speed Guards Red |
||
|
09-04-2007, 10:48 AM
|
|
|
Registered
Join Date: May 2007
Location: Oakbank, MB
Posts: 36
|
Plugs are fine - dry, light gray, not burnt or carboned up at all.
|
||
|
09-04-2007, 07:57 PM
|
|
|
Registered
Join Date: Mar 2005
Location: Ca.
Posts: 137
|
I am a old tune up guy and driveablity specialist, not Porsche however my feeling is anytime you see the tack jumping around I look close at plug wires. Surely it could be a crank sensor or distributor pick up coil but,You may have a burned one or one with a brake in the insulation. On the job I would spray salted water on the wires, this would make the problem worse!
 but makes it much essayer to isolate..
|
||
|
09-05-2007, 03:18 PM
|
|
|
|
Network Native
Join Date: Jan 2007
Location: SoCal
Posts: 10,349
|
How about plain tap water in one of those misting type sprayers?
__________________
US 83 zinc metallic 5 spd, aka the nice car. Euro 85 black, 5 spd, the fast rough track car maybe car. SOLD Euro 84 red, AT, only car in garage in years, my parts car, soon to go last 7 years. |
||
|
09-05-2007, 04:26 PM
|
|
|
Registered
Join Date: Jan 2007
Posts: 11,758
|
Green wire to the distributor. Next it will totally fail, and leave you stranded somewhere. Can look good on the outside while being totally shot.
Educated guess. Plug wires are also a good bet as previously stated. LOL |
||
|
09-05-2007, 04:45 PM
|
|
|
Registered
Join Date: Jan 2007
Posts: 652
|
Run your car and look under the hood in the dark. Alot of times this is the easy way to find ignition shorts whether it be a plug wire or the green wire.
__________________
1984 928's w/ 5 speed Smoked Quartz Metalic 1982 928's Turbo w/ 5 Speed Platinum Metalic 1978 Euro Widebody w/ 5 speed Guards Red |
||
|
09-05-2007, 05:02 PM
|
|
|
Registered
Join Date: Jan 2003
Posts: 93
|
Quote:
__________________
John V. 1990 928GT 1980 928 EuroS (GT2-S) |
||
|
09-07-2007, 04:56 PM
|
|
|
Registered
Join Date: May 2007
Location: Oakbank, MB
Posts: 36
|
Is there a way to test/check the green wire? Looks fine from the outside but that doesn't always tell the whole story.
|
||
|
09-16-2007, 08:37 PM
|
|
