928 GT, accelerates fine, misses when cruising
#31
Rennlist Member
Before you toss more money please research how to bypass the exhaust sensor relay (assuming you haven't already). Last year while driving Kevin Wilson's GTS it would feel like it was missing at cruise going up slight inclines. This was an issue with the exhaust temp sensors sensing a problem on one of the banks. The result was the relay would trigger the 4 cylinder mode transiently - not fully going into 4 cylinder mode.
#32
Addict
Rennlist Member
Rennlist Member
Join Date: Oct 2003
Location: Gone. On the Open Road
Posts: 16,572
Received 1,690 Likes
on
1,099 Posts
Before you toss more money please research how to bypass the exhaust sensor relay (assuming you haven't already). Last year while driving Kevin Wilson's GTS it would feel like it was missing at cruise going up slight inclines. This was an issue with the exhaust temp sensors sensing a problem on one of the banks. The result was the relay would trigger the 4 cylinder mode transiently - not fully going into 4 cylinder mode.
#33
Rennlist Member
#34
Pull your caps and see if you are missing the center button.
#35
Addict
Rennlist Member
Rennlist Member
Join Date: Oct 2003
Location: Gone. On the Open Road
Posts: 16,572
Received 1,690 Likes
on
1,099 Posts
—^ And check the housings for cracks.
I ran into that once two decades ago: dropped a cap on the shop floor. Didn’t think anything of it at the time. The 928 went straight to limp mode. Wasted a lot of time finding that.
I ran into that once two decades ago: dropped a cap on the shop floor. Didn’t think anything of it at the time. The 928 went straight to limp mode. Wasted a lot of time finding that.
#36
Shameful Thread Killer
Rennlist Member
Rennlist Member
Remove plugs and note if they are oily around the base and ceramic. Once the plugs are out, vac out the oil from the well, and install new plugs. Ultimately replace the seals on the cam cover. Worked for my 90GT.
#38
This was a funny one. Car ran fantastic but as described in the OP there was a slight miss at cruise and you could hear a "burp" at idle that happened every 30 seconds or so. Drove the customer nuts and one day we took the cap off to see that. Problem solved.
#39
Advanced
Thread Starter
I checked my relays and I already have the bypass relay (928.615.175.00) instead of the real one (928.618.175.00). Must have been installed by previous owner or his mechanic.
#40
Addict
Rennlist Member
Rennlist Member
Join Date: Oct 2003
Location: Gone. On the Open Road
Posts: 16,572
Received 1,690 Likes
on
1,099 Posts
Yup, Used the wrong coil wires. Of course, you know why there are four coil wires in a set.
#41
Advanced
Thread Starter
So, since I already have a bypass relay installed:
1) this indicates that my current issue is not with the ECU detecting a problem with the exhaust temp sensors (although I do need to get the correct relay; which appears to be pretty expensive).
2) I need to proceed with the injectors.
1) this indicates that my current issue is not with the ECU detecting a problem with the exhaust temp sensors (although I do need to get the correct relay; which appears to be pretty expensive).
2) I need to proceed with the injectors.
#43
Advanced
Thread Starter
Before the LH rebuild, it was right away.
After the LH rebuild,on the first time I drove it, it took about 30 minutes.
On the second drive, it was apparent as soon as I got to cruising speed on the nearby freeway; 5 minutes.
After the LH rebuild,on the first time I drove it, it took about 30 minutes.
On the second drive, it was apparent as soon as I got to cruising speed on the nearby freeway; 5 minutes.
#45
Pro
When you accelerate it goes away because the LH adds more fuel and it is not as detectable at warm up as the LH is adding more fuel as standard.
I had the same symptoms when the sealant provided by Carl (928 MS) failed on my intake manifold spacers. Small air passages formed through the sealant resulting in a lean running condition providing the same symptoms you are describing.
I diagnosed the problem and source quickly and replaced the sealant for something more suited to the job. My problem is fixed and the car has been running fine since.