Running poor when engine is hot

[JEL91Westy]

91 Westy

So here is the not so short story.

Replaced the fuel lines, filter, regulator and injectors. Short test run and it all seemed good. Sat for a couple of days and headed up the road on a ski trip and it started to run rough right away, to the point I thought the trip was off. Figured it could be air in the fuel system (if that is possible), and it went away in a minute or so. All seemed good but then I noticed that if I floored it it ran very rough, but otherwise seemed fine cruising at 3500. Ran for 6hrs and camped in sub freezing temps all weekend. Started fine after three nights and idled okay while I let it warm up for 15 min. ( 10F that day), but after driving for just a couple min. Idled very low and rough at a stop. Headed home, and again found if the pedal was fully depressed it ran very rough. Then after 5hrs on the road it started to run rough off throttle and at low RPMs - like extreme sick vanagon syndrome, to the point that if I was off throttle it wanted to stall if I didn’t keep the RPMs up.

Started doing research yesterday and decided to start exploring the grounds, I also pulled the dist cap to find a very slight amount of condensation in the top. Found the ground to the tranny looks pretty good, but the ground to the engine is gone. Ordered some new ground wires, but decided to take it out today to see how it ran after the cap was dry, and before starting down the electrical path. It ran well, idled fine and I could not get it to buck under full throttle.

This all leads me to believe it may be temperature related and will only replicate after the engine is hot ( hrs of running like SVS), and I did not let it run long enough to replicate the problem. Any ideas on where I should go first to resolve this would be much appreciated. I obviously intend to address the grounds regardless, but did not want to introduce too many variables until I had an idea what was causing it.

Several other things I will post about in other threads related to my experience installing a CDH, thinking about installing a insulated headliner in the roof, trying to minimize the impact of road salt etc. This is our Covid Ski assault vehicle this winter.

Thank you in advance.
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91 Westy
85 911

[0to60in6min]

I'd think that you're running lean or very lean..

remove the spark plugs and see what color are they and take a pic and show us.

[Wildthings]

If you had ANY condensation inside the cap that could well have been your only problem.

[JEL91Westy]

Pics of the plugs as requested.

Thanks for the help.
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91 Westy
85 911

[0to60in6min]

your spark plugs are borderline on lean - not too bad, better if there is some brownish color on it, specially on the center ceramic.

I am working on the same issue on my van and my plugs are whiter than that. An ongoing job...

The mechanic suggested the following
- check the O2 sensor using a voltmeter - replace if needed.
- check the Temp2 sensor - replace if needed.
- check the throttle body switch (the click noise when it's open).
- adjust the AFM to enrich the fuel/air ratio (a big job).

btw... you may want to replace the spark plugs with NGK(1263) BP6ET.

Make a search on the internet for how to do those.

good luck

[JEL91Westy]

0-60
Thanks for the insight and suggestions. The hell of it is I don’t think this was happened in before I messed with the fuel system.
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91 Westy
85 911

[Wildthings]

Your #1-3 spark plugs look right on, while your #4 cylinder may be running a bit lean, you might be able to fix this by adding fuel injection cleaner to your gas tank. #1-3 have nice sharp edges to the center electrode which is what you want while I can't really tell for #4.

[mikemtnbike]

I'm still learning to read spark plugs, I really appreciate threads like this one. Thanks!
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1991 Vanagon GL 2.1 AT Westfauxlia. "Frankie" Totaled https://www.thesamba.com/vw/forum/viewtopic.php?t=764510&highlight=carnage
1995 Eurovan Camper "Marzivan"
2020 GTI SE manual

[JEL91Westy]

Wild Things, many thanks for the advice. I didn’t think I would need to add fuel injector cleaner with new injectors. Could I have a bad one?
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91 Westy
85 911

[JEL91Westy]

I went and scrutinized the plugs again, and you are correct #4 has a slightly rounded / worn edge on the one side of the electrode. I installed the following injectors which I bought probably 8yrs ago and never got around to. At the time I researched this these were thought to be an acceptable substitute for the very expensive Bosch.

Maybe they are crap, but the more I look around the engine the more other potential culprits I see.I cannot hear a click in the throttle switch when I move it above idle, but can clearly hear it approaching wide open. I suspect the throttle body is probable shot as well. I plan to take that apart this weekend. And then I have the missing engine ground.

I have until Thursday to get it straight before we head north again in search of Snow.

Thanks again for the help.
I am hell with wood, but mechanic I am not!
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91 Westy
85 911

[Wildthings]

How many miles are on your new injectors? Plug color changes take some time to happen.

If that plug is more worn, maybe it has many more miles on it than the others, or maybe it is a different heat range.

[JEL91Westy]

The injectors were just replace, 700mi.on them when I took the photo.
The plugs have less than 5k on them.
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91 Westy
85 911

[Wildthings]

[Abscate]

[JEL91Westy]

Yep, all the plugs have the same numbers. I did notice the injectors were all numbered the same on the boxes , but one had a different 2nd number on the body. Not sure which cyl that is in at this point, but I will pull them and check.

Anything I can do to prevent moisture in the cap? The cap has less than 10k on it.

Thanks
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91 Westy
85 911

[0to60in6min]

Does your distributor have this dust cover?

https://www.jimellisvwparts.com/products/Volkswage...05241.html

[Igeo]

For another data point: Here are Bosch WR7CC plugs with 7,000 miles on them. Marco's injectors and AFM screw about 2.25 turns out from seated. Timing set at 45 degrees BTDC. Fuel mileage on the highway is about 17-19 mpg.

Left bank

Right bank

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1987 Westfalia 2.1 WBX Manual

[JEL91Westy]

Yes, I have the dust cover under the base of the cap. Why not sealant or dielectric grease around the mating surface?

Thanks for the plug pics. Those are the same plugs I have, and honestly I don’t see a difference. What am I missing?
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91 Westy
85 911

[JEL91Westy]

Yes, I have the dust cover under the base of the cap. Why not sealant or dielectric grease around the mating surface?

Thanks for the plug pics. Those are the same plugs I have, and honestly I don’t see a difference. What am I missing?
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91 Westy
85 911

[Abscate]

Guys, you cannot read subtle plug colors on internet pictures.

Camera...software....internet....monitor all impact the rendering.
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.ssS!