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When you said "shuddering", it made me think of what happens when you get the engine wet and a spark plug well has water in it. Assuming there's something else at play here though. Check to see that your spark plug wires are all clipped in properly anyway.
Could you post a video or some pictures of the engine bay with the cover/louvres raised? Maybe one of us will spot something out of place for you.
Sept. 81, auto, black interior
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Senior Member
I did not see or hear anything out of the ordinary on your video.
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One of those purists you keep hearing about.
Originally Posted by
Bitsyncmaster
I did not see or hear anything out of the ordinary on your video.
I couldn't get sound but the idle looked fine.
If the WOT switch and unplugging the FV did nothing to affect idle i bet his car is tuned to run open loop.
Dave
Here, somewhere.
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Originally Posted by
sdg3205
I couldn't get sound but the idle looked fine.
If the WOT switch and unplugging the FV did nothing to affect idle i bet his car is tuned to run open loop.
Which raises the question, "Was the Lambda system working BEFORE this problem?". We don't know. Sounds like it wasn't. Maybe you suddenly developed a vacuum leak? Is the plug there over the mixture screw? First order of business would be to get the frequency valve to buzz. Then check the duty cycle and if necessary adjust the mixture screw.
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One of those purists you keep hearing about.
Dave
Here, somewhere.
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Originally Posted by
Bitsyncmaster
Does the FV buzz? The "lambda" relay switches power to the FV and the lambda ECU with separate pin outputs. If the FV does buzz, both the FV and ECU are getting power.
Well, I thought it was buzzing all along, but it turned out to be the idle speed regulator humming!
I can't seem to get it to buzz by turning key to 2. Zero voltage going to either pin on its connector.
But... When the engine is running it gets just over 14V on one pin and the other fluctuates up to 2V.
When I pull the Lambda ECU connector I see that it is receiving no power until the engine is actually running (13.9V).
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Senior Member
Originally Posted by
klaatu42
Well, I thought it was buzzing all along, but it turned out to be the idle speed regulator humming!
I can't seem to get it to buzz by turning key to 2. Zero voltage going to either pin on its connector.
But... When the engine is running it gets just over 14V on one pin and the other fluctuates up to 2V.
When I pull the Lambda ECU connector I see that it is receiving no power until the engine is actually running (13.9V).
The lambda relay gets turned on my the RPM relay. So just like the fuel pump, the lambda system only gets power when the engine is running.
You need to get a dwell or duty cycle meter onto the FV to verify your mixture is set correctly.
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For troubleshooting purposes refer to D:04:12 for a simplified schematic of the wiring of the Lambda system. A good place to start would be the ECU module. Pull the plug and verify power, grounds, switching and wiring. Also refer to D:04:15 5 A-E. By applying power (1.5 DCV) or grounding the O2 sensor lead you should see the correct values on your dwell meter. Read the system repair notes, specifically #3 to power the Lambda system for testing purposes. The Lambda system isn't going to work till you can make it do what it says under "Pulse Ratios #5 A-E. If you can force the readings but it won't fluctuate as it should under A, the O2 sensor is probably no good.
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Originally Posted by
David T
Which raises the question, "Was the Lambda system working BEFORE this problem?". We don't know. Sounds like it wasn't. Maybe you suddenly developed a vacuum leak? Is the plug there over the mixture screw? First order of business would be to get the frequency valve to buzz. Then check the duty cycle and if necessary adjust the mixture screw.
It wouldn't be like me to find an issue that is causing a symptom so I'm sure you are right... It likely wasn't working and was tuned to run open loop without bothering to physically disconnect anything. There is a plug above mixture screw. I'm probably chasing my tail going down the Lambda route.
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Originally Posted by
sdg3205
I couldn't get sound but the idle looked fine.
You can only hear the issue. It's a seemingly completely random fluctuation, not all all like seeking. I'm editing together an updated video with some driving. Should illustrate things better.
It's so intermittent and random that it must be electrical. I can pull away from a stop with no trouble whatsoever and at the very next one, less than a minute away, I can barely get moving, then the next fine again.
The hotter the engine gets, the worse/more pronounced it seems to be. In fact, when I took it out just now to shoot the video, at first I thought that something I had done had fixed it, but it just got progressively worse the further I went.
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