928 GT dies on idle
04-03-2016, 06:14 PM
#31
Burning Brakes
Unplug the MAF electrical connector. Does it hold a rough idle? If it does it's the MAF or the electrical connector. If connector contact points are not corroded it's the MAF as everyone is suggesting.
My idle problem cleared up by cleaning contacts surfaces with lightly sanding contacts with fiberglass pencil sander and deoxit.
My idle problem cleared up by cleaning contacts surfaces with lightly sanding contacts with fiberglass pencil sander and deoxit.
The MAF was just repaired (thinking that was the problem - it was faulty) but that resulted in no improvement to the situation.
06-14-2016, 11:40 PM
#34
Burning Brakes
Fixed!
Had a friend come by to help diagnose.
After having MAF rebuild and LH tested and checking continuity and voltage on the connector, assume everything is good between LH and MAF. Starting over:
Car starts and idles fine with MAF installed but disconnected. Hardly runs and dies within 30 seconds or so with MAF plugged in.
Pulled the MAF completely and unplugged. Car fires right up and sounds good.
Plugged in the MAF but did not install. Car fires right up and sounds good.
While car is running, flip MAF over to install in car and car dies.
Short in the connector at the end of the wire plugging into the MAF!
I've ordered new connector from Roger and will be extending the wire harness and adding a new connector. Can't wait to be back on the road!
Had a friend come by to help diagnose.
After having MAF rebuild and LH tested and checking continuity and voltage on the connector, assume everything is good between LH and MAF. Starting over:
Car starts and idles fine with MAF installed but disconnected. Hardly runs and dies within 30 seconds or so with MAF plugged in.
Pulled the MAF completely and unplugged. Car fires right up and sounds good.
Plugged in the MAF but did not install. Car fires right up and sounds good.
While car is running, flip MAF over to install in car and car dies.
Short in the connector at the end of the wire plugging into the MAF!
I've ordered new connector from Roger and will be extending the wire harness and adding a new connector. Can't wait to be back on the road!
08-23-2016, 11:47 PM
#37
Advanced
Thread Starter
MAF back and installed and situation much better, but not perfect.
Stalling at idle is much less often, and generally only occurs after car is well warmed up and after running at highway speeds. When exiting the freeway and stopping at end of ramp, RPM drops and dies half the time unless throttle tickled to keep alive. If engine does die, starts right back up again.
Stalling at idle is much less often, and generally only occurs after car is well warmed up and after running at highway speeds. When exiting the freeway and stopping at end of ramp, RPM drops and dies half the time unless throttle tickled to keep alive. If engine does die, starts right back up again.
08-24-2016, 01:03 AM
#38
Addict
Rennlist Member
Rennlist Member
Join Date: Oct 2003
Location: Gone. On the Open Road
Posts: 16,442
Received 1,609 Likes
on
1,050 Posts
Does your idle switch work? (Does it close the circuit as measured at the ECU pins when there's no pressure on the gas pedal?)
Last edited by worf928; 08-26-2016 at 01:07 PM.
08-26-2016, 12:10 PM
#39
Advanced
Thread Starter
I tested it about a year ago when the problem arose; and I used the 928 Periodic Inspection.pdf to which you referred. Did the Idle/WOT switch test and the Idle Stabilizer test; both good.
I should probably do them again for a double check.
R Mace - 1990 928 GT
I should probably do them again for a double check.
R Mace - 1990 928 GT
08-26-2016, 01:10 PM
#40
Addict
Rennlist Member
Rennlist Member
Join Date: Oct 2003
Location: Gone. On the Open Road
Posts: 16,442
Received 1,609 Likes
on
1,050 Posts
macerl, see step 3 in my post #25 above. Have you checked that?
08-31-2016, 07:43 PM
#41
Advanced
Thread Starter
Thank you. I will check these vacuum lines.
- 3) The manifold vacuum system is sucking-in fuel from one or more broken diaphragms in the fuel pressure regulator or the pressure dampeners.
- Pull the vacuum lines from each of these and see if the ends smell like fuel or drip fuel or if fuel comes out of the vacuum connectors to the regulator or dampeners.
- 3) The manifold vacuum system is sucking-in fuel from one or more broken diaphragms in the fuel pressure regulator or the pressure dampeners.
- Pull the vacuum lines from each of these and see if the ends smell like fuel or drip fuel or if fuel comes out of the vacuum connectors to the regulator or dampeners.
09-03-2016, 04:52 PM
#43
That's normal.
09-08-2016, 03:05 PM
#44
Advanced
Thread Starter
Pulled lines: did not see or smell fuel.
The elbow to the aft fuel dampener was torn (hope not due to my efforts during removal). Replacing that elbow (local parts stores cannot match size of vacuum hoses exactly);
- what size does a 928 use to for hoses and elbows to properly fit on fuel regulator and dampeners, or is any close size that fits snug adequate?
The forward fuel dampener did not have an elbow, hose attached directly but it appeared to have a kink where bent from horizontal to vertical. Replacing that line and getting another elbow as well.
Or I may just purchase the vacuum hose kit and connector kit (however, it does not appear to contain any elbows.)
The elbow to the aft fuel dampener was torn (hope not due to my efforts during removal). Replacing that elbow (local parts stores cannot match size of vacuum hoses exactly);
- what size does a 928 use to for hoses and elbows to properly fit on fuel regulator and dampeners, or is any close size that fits snug adequate?
The forward fuel dampener did not have an elbow, hose attached directly but it appeared to have a kink where bent from horizontal to vertical. Replacing that line and getting another elbow as well.
Or I may just purchase the vacuum hose kit and connector kit (however, it does not appear to contain any elbows.)