1981 Euro Intermittent Rough Running
Thread Starter
Three Wheelin'
Joined: Mar 2011
Posts: 1,831
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From: Columbus, OH
1981 Euro Intermittent Rough Running
My 1981 Euro 5 speed w/ CIS fuel distribution and single distributor INTERMITTENTLY runs rough and is very noticeable at or above 3,000 RPMs. It doesn't happen all the time, but when it's running rough and the revs get to 3-4K RPMs the whole damn car starts to shake & vibrate very roughly. So, I take it easy all the way home and kill the ignition, let it sit for a while. Come out after she's sat for a bit and she starts up with no issues and runs VERY smoothly from 1,000 to 6,000 RPMs and in ALL gears. Somehow it "CURES ITSELF"... (which we know doesn't happen).
Needless to say, I'm stumped. To date, we've calibrated the CIS air/fuel mixture via a tail pipe sniffer; replaced the plugs (nice & tan), new spark plug wires, rotor & distributor cap; replaced transmission mounts. We have not replaced motor mounts, but they appear serviceable and since it doesn't happen ALL the time I'm guessing the motor mounts are not the problem. Maybe I'm wrong?
Any expertise, insights, thoughts, opinions, experiences to determine the cause would be GREATLY appreciated. Thanks!!
Joel
Needless to say, I'm stumped. To date, we've calibrated the CIS air/fuel mixture via a tail pipe sniffer; replaced the plugs (nice & tan), new spark plug wires, rotor & distributor cap; replaced transmission mounts. We have not replaced motor mounts, but they appear serviceable and since it doesn't happen ALL the time I'm guessing the motor mounts are not the problem. Maybe I'm wrong?
Any expertise, insights, thoughts, opinions, experiences to determine the cause would be GREATLY appreciated. Thanks!!
Joel
Former Vendor
Joined: Feb 2005
Posts: 15,228
Likes: 2,530
From: Anaheim
Check the fuel pump/strainer in the fuel tank.
These can get so restricted that there isn't enough fuel flow to support higher rpms.
When you shut the car off, the pump/pumps quit sucking and the "loose" dirt will float away.
Then the problem will not occur until the "loose dirt" plugs up the strainer again.
Becoming more common on 928s.
These can get so restricted that there isn't enough fuel flow to support higher rpms.
When you shut the car off, the pump/pumps quit sucking and the "loose" dirt will float away.
Then the problem will not occur until the "loose dirt" plugs up the strainer again.
Becoming more common on 928s.
Last edited by GregBBRD; Mar 22, 2022 at 05:06 PM.
Thread Starter
Three Wheelin'
Joined: Mar 2011
Posts: 1,831
Likes: 547
From: Columbus, OH
Greg,
Thanks. My bad, I failed to mention we replaced the leaking fuel tank with a used / cleaned tank & new strainer, pump, filter, hoses, accumulator & rebuilt FD. It could be fuel restriction but I think we’ve covered those bases and I would imagine it would happen with some regularity. This issue is very intermittent.
Would a bad motor ground cause an intermittent condition like this? It has an aftermarket long woven engine ground installed with long tube headers (Not by me). Or, perhaps the FOE harness / 14 Pin as they are original?
I just hate throwing parts at intermittent problems with no confirmation of cause ☹️☹️☹️
Thanks. My bad, I failed to mention we replaced the leaking fuel tank with a used / cleaned tank & new strainer, pump, filter, hoses, accumulator & rebuilt FD. It could be fuel restriction but I think we’ve covered those bases and I would imagine it would happen with some regularity. This issue is very intermittent.
Would a bad motor ground cause an intermittent condition like this? It has an aftermarket long woven engine ground installed with long tube headers (Not by me). Or, perhaps the FOE harness / 14 Pin as they are original?
I just hate throwing parts at intermittent problems with no confirmation of cause ☹️☹️☹️
RL Community Team
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From: Clemson, SC
Turn the mixture screw a hair richer, test and repeat until the cutout at full load and higher RPM doesn't occur. That's how I tuned that car to eliminate that full load stutter.
Thread Starter
Three Wheelin'
Joined: Mar 2011
Posts: 1,831
Likes: 547
From: Columbus, OH
Hmmm… If that’s the issue, wouldn’t it happen all of the time? On most days it’s not an issue and the engine runs smooth as silk.
Thread Starter
Three Wheelin'
Joined: Mar 2011
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From: Columbus, OH
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RL Community Team
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From: Clemson, SC
Also, make sure the timing is set right. Think it may be higher for the Euro and think I had it set around 28 degrees with vacuum disconnected at 3k rpm.
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Joined: Jul 2010
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From: As - Belgium
My 1981 Euro 5 speed w/ CIS fuel distribution and single distributor INTERMITTENTLY runs rough and is very noticeable at or above 3,000 RPMs. It doesn't happen all the time, but when it's running rough and the revs get to 3-4K RPMs the whole damn car starts to shake & vibrate very roughly. So, I take it easy all the way home and kill the ignition, let it sit for a while. Come out after she's sat for a bit and she starts up with no issues and runs VERY smoothly from 1,000 to 6,000 RPMs and in ALL gears. Somehow it "CURES ITSELF"... (which we know doesn't happen).
Needless to say, I'm stumped. To date, we've calibrated the CIS air/fuel mixture via a tail pipe sniffer; replaced the plugs (nice & tan), new spark plug wires, rotor & distributor cap; replaced transmission mounts. We have not replaced motor mounts, but they appear serviceable and since it doesn't happen ALL the time I'm guessing the motor mounts are not the problem. Maybe I'm wrong?
Any expertise, insights, thoughts, opinions, experiences to determine the cause would be GREATLY appreciated. Thanks!!
Joel
Needless to say, I'm stumped. To date, we've calibrated the CIS air/fuel mixture via a tail pipe sniffer; replaced the plugs (nice & tan), new spark plug wires, rotor & distributor cap; replaced transmission mounts. We have not replaced motor mounts, but they appear serviceable and since it doesn't happen ALL the time I'm guessing the motor mounts are not the problem. Maybe I'm wrong?
Any expertise, insights, thoughts, opinions, experiences to determine the cause would be GREATLY appreciated. Thanks!!
Joel
I have exactly the same problem. Was your problem solved ? And if so, what was done to solve the issue ?
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From: As - Belgium