08-07-2022, 07:29 PM
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Renaissances Dude
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Join Date: Dec 2004
Location: Redwood City, CA
Posts: 34,130
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You put your finger on a problem with keeping these old vehicles running. There are all sorts of small items that can become corroded, loose, just less than optimally functional. I’ll look for the thing you speak of.
I found a post from 2015 on another site on this topic, he raised an interesting point that I hadn’t heard before. I’ll cut and paste about half of the post here:
Quote:
From you description, it Seems the 02 sensor is a likely culprit, and hesitation under acceleration is usually a running lean issue.
I have a similar vintage Van, but a Dodge, and my engine power and MPG went up after I cleaned the sensor connectors with Caig Deoxit d5 spray.
The TPS, MAP and 02 sensors, despite their contacts swathed in Dielectric grease their whole lives, had oxidized badly. I used a bunch of Precision Swabs and Caig Deoxit d5 spray to clean the actual contacts.
Flush out the old hard dirty crusty dielectric grease from the connector with a normal, less expensive electronic cleaner product, and then use the Den tek mini bottle brushes to help remove grease. Then spray on the Deoxit d5 spray and work it around with clean mini bottle brushes, and let is dissolve the oxidation for a while.
Then come in with those tiny precision swabs, drug stores might sell something similar for removing make up, and clean the insides of the sockets and the pin exteriors. The swabs will get all tore up at first and turn black. Then less so and turn grey. Use more D5 and swabs until they do not get shredded and remain Pink from the d5. I was using between 3 and 5 swabs per socket before they remained unshredded and pink, and gleamed like oiled chrome.
After I cleaned every sensor contact I could using this method, it felt like I removed 500 LBs from the Van. Around town MPGS I thought forever lost due to taller heavier tires, returned.
My hypothesis is that the computer sends 5 volts out to the sensors, and then makes Air fuel trim and spark timing adjustments on the return voltage from the sensors. When the sensor contacts are all oxidized, too low a voltage returns to the ECM and the AF and timing is not where it should be.
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https://www.vanning.com/threads/ubbthreads.php/topics/693506/all/help-with-my-g20-tbi-problems
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1986 300SDL, 362K
1984 300D, 138K
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