2.1 bogged down in traffic

[djkeev]

I have a 90 2.1 with an Automatic.

I've got 2,200 miles on the engine "refresh"..... head gaskets, rings, rod bearings.......

It has been running great though the fuel mileage isn't what I'd like to see, only about 16 on the last fill.

I noticed the idle will hang up about 1200-1400 rpm if I gently remove my foot from the throttle, if I kick the pedal and it will drop to 900 or so.

The linkage or the throttle body itself is hanging up.
I need to fix this but it is running very well (until today) and life is insanely hectic right now so I've put it off.

Today it was in the 80’s and I got stuck in a long line at a very short light.
A good 10 minute crawling forward idling wait.

The closer I moved towards the light I noticed I was losing power and when I finally got the green, I barely crawled through the intersection.

I know the throttle hangs up at idle.
I know the TPS doesn't close when this happens.

I'm thinking with the TPS open, I'm getting too much fuel at idle and after a prolonged period of idling, I was flooding out, hence the bogged down lack of power.

Once moving again, after a few miles my normal pep returned. The plugs burned off the crap from idling.

With my understanding of the Digifant system....
Would I be correct on this diagnosis?

I'm thinking that I better be fixing that sticky throttle sooner rather than later!

Or is there another possible cause?

Thanks!
Dave
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[Abscate]

I don’t like that diagnosis. I would idle it for 19 I the driveway and see if that reproduces. Maybe even pull the plugs and see if they foul.
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[DanHoug]

how smooth was the engine idling during this time? if the mixture had gotten bad enough foul plugs, you'd be running rough.

but it still could be mixture related.. how old is your O2 sensor? a smooth idle with little power also acts like a disconnected AFM. you don't have any green weenies in the plug at the AFM?

but Occam's Razor would say it is a heat related problem... idling 10 minutes at 80F spikes crazy high temps under the lid.

- how low was your fuel level? if rilly low, the fuel could have warmed up from engine recirculation to cause suction side cavitation. low fuel pressure would give a smooth idle with no reserve for when load increases. any restriction on the pump intake side, like from a prefilter or tank screen plugging will increase this chance. you running a prefilter?

- other heat related guesses are free too!
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60% of what you find on the internet is wrong, including this post.

'87 Westy & '89 Westy both 2.1 4spd

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[MarkWard]

I have an owner's auto van on the lift at the moment for an automatic trans replacement. I noticed that the underside of the rod between the throttle plate and the transmission has been dragging across the throttle body linkage for some time. I assume at some point the rod must have been bent out of alignment. For it to work it needs to pull square to the throttle plate.

This could affect how the throttle closes from time to time and that would affect the TPS function. Kicking the throttle, might let it completely return. You may want to inspect the underside of the rod where it attaches to the throttle body.
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[danfromsyr]

also the ball socket connection for the front throttle cable and the transmission relay lever gets buggered up with age and doesn't allow that last little bit of return motion.
it's apain to deal with it up on the lever. but the lever can easily be taken off the input shaft of the transmission and brought down/twisted to a better working position.

a little grease or anti-seize in the ball socket will give years of smooth action.
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[dabaron]

do you have gas in the tank

dragging throttle linkage was an issue i had when i put this engine in the Westy. the throttle would hang open just enough to not close the TPS. it would bog down after a bunch of stop lights, i had to use my foot to flip the pedal up and close the TPS.

resolved with some filing of the barrel to make it not bind in the throttle lever.
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1991 Vanagon GL Camper
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[AceTaylor]

I had like symptoms once upon a time. Chased down all the usual suspects. Long story short, it was the AFM. The door would bind and not open properly with throttle. Opening the throttle would allow more air, but the AFM door wouldn't properly correspond making the engine go lean until the AFM caught up and would drive fine. A rebuilt AFM not a "known good used one" which is nothing more than a worn part made the car drive like new.

[djkeev]

Thanks for the replies!

Yes, 80+° it was hot!

The front cooling fan operated as designed and the gauge remained steady just below the LED

Filled tank in NJ and had only put about 40 miles on when I encountered the traffic.

Oxygen sensor has 2,200 mikes on it. It has the proper plug on it, not the universal kit.

TPS was adjusted to spec with feeler gauges off the engine.
Shaft wear exists but not horrible, though a little wear just may be my issue.

Thanks for the "where to look" ideas!
Much appreciated.

Now to actually look at it!

I'm thinking my sticking TPS is my poor mpg hog. It isn't doing the fuel shut off while coasting as speed.

Dave
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[djkeev]

[djkeev]

[MarkWard]

The manual throttle cable has a lot more flexibility than the auto. When you examine closely how it works, it’s actually surprising it does. The ridged rod is not forgiving. Any misalignment can cause resistance as the barrel rotates as the linkage moves through its arch. Add to that the rod is spring loaded against the barrel.

A spring loaded cable like Audi and vw ended up using would be a much better solution.
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[Blakesinclair]

Any chance you can post a link to the 10c AFM test? My 1.9 has a similar issue. Once my engine is running a little hotter than normal, like on a hot day in some stop and go traffic it'll find it's idle closer to 1100 rpm. Doesn't over heat, radiator fan kicks in at both levels, but it has that same funky higher idle.

Does the AFM use temp sensor data to make mix adjustments?

I talked to my mechanic one day about this, and he didn't seem alarmed as long as it's not wildly high idle or over heating. But I would like to pin point or at least rule out the AFM.
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1985 Weekender Vanagon 1.9L - Manual

[dabaron]

[Abscate]

Dave , I don’t think an incorrect idle will lower your mileage to the 16 mpg on a country trip like your NJ to PA trip. You should be getting near 20 mpg fir that cruise, unless you are in a lot of traffic
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[djkeev]

[Abscate]

It does, but none of that will Cost you 20% of your fuel efficiency on a town drive, with presumably very little idle or full throttle operation

I’m just pointing out that after you get your TPS and linkage sorted, I think more work orders will be issued

Luvya! ❤️
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[Howesight]

Hey Dave:

Since you are in the part of the world where the roads are salted and Vanagons can just melt away with rust, I think it might be a good idea to check the wiring between the Temp 2 sensor and the ECU and also the wiring between the AFM air temp sensor and the ECU. These sensors are both Negative Temperature Coefficient designs and any resistance in the circuit will cause the ECU to add fuel. I have seen the Vanagon wiring corrode from a terminal up to 1/2" under the wire's sheath. That adds resistance.

Also, the mechanical function of the AFM can be a problem if the flap hangs up on its shaft. This mechanical issue is not easy to observe. Perhaps some lubricant on that shaft would help. If this flap hangs up, then you can experience an over-rich AFR if it hangs up open too much and you can have problems with accelerating gently if the flap hangs up nearly closed. The '80s to '90's Toyota Bosch EFI AFM's were the same design and occasionally the flaps hung up in this way.
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'86 Syncro Westy SVX

[djkeev]

[zimflux]

[djkeev]

Well, I didn't pull the throttle body yet but I did lubricate the rod and pivot assembly at the throttle body.

It moves more freely after the lubrication but it still hangs up and doesn't return fully on gentle de-acceleration.

I'm thinking I need to follow the whole accelerator assembly up to the pedal.
Grease and lubricate.

On the Initial depression of the gas pedal there is a hard spot before it starts moving, like something is jammed or over rotated and needs to be over come.

Once over come, it works smoothly.

On the list of 100 other things to do this week!

Dave
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https://www.thesamba.com/vw/forum/viewtopic.php?t=482968&highlight=74+super+vert