Itinerant Air-Cooled

I have an 82 vanagon with California emissions. The van runs great until you reach 2800 to 3000 rpm's and try to accelerate heavy. It then starts bucking and loses power unless you back of the peddle and then it runs fine. According to my Bently manual I started trouble shooting. I replaced the fuel enrichment relay, the double relay had the
AFM rebuilt to no avail. Recent tune up alternator replaced, fuel tank removed and resealed with all new lines replaced. Also had a used ECU known to be good. So far nothing is working. What am I missing? This happens in all gears engine can be hot or cold it doesn't matter. Even took it to a local Vw shop and he informed me that the AFM was bad, which it wasn't.
I just checked my speed limit switch according to my Bently manual page 24.14. At idle I had 10 volts between terminals 8 & 6. When I revved the engine up the voltage dropped out. Not exactly sure of my RPM'S. Is this correct? Oops wrong terminals. Between 8 & 6 at 3000 rpm'S zero volts. Bought this relay used but tested good according to seller.
Thanks

Bucking...check thoroughly your ignition system, especially timing at 3400 rpms, after a proper valve adjustment, then consider fuel flow. If you get to fuel flow, check your injectors carefully. Others here will offer better advice, but if it idles well and cold vs.hot is not an issue, then it should be something silly. Consider Vanagon Syndrome, if you do not have the modified wiring into the AFM.
Oh, and clean your grounds, especially the ground prongs below the air plenum.

Check the temp sensor II, or just replace it...not one to throw parts at a problem, but this one can act wonky as the engine warms.
Spent almost two years trying to diagnose a bucking problem; turned out to be this.

Does (did) the TSII cause intermittent issues, or was it consistent bucking? Seems that a device creating resistance should be all or nothing, but I do not understand the science behind the thing...

The problem starts around the 3000 rpm range according to my tach. It is not rpm related. This bucking will happen cold engine, hot engine and in every gear.

Fuel pressure regulator?

Mountainhide, I posted this on thesamba as well. I had similar symptoms with my 81 Federal. It turned out to be damaged FCU (ECU). It had water intrusion, and it damaged part of the circuit that got activated at that higher RPM.

Does the engine not want to rev-up past 3000 in Neutral? Mine acted as if I hit a rev limiter .

As far as the Temp II ... sometimes it was consistent (happen at certain RPMs) other times it was all over the place. In my case I was fighting two problems that were causing erratic / inconsistent electrical connectivity.

- My threads are slightly stripped in the head, and it was coming loose. light application of blue loctite solved this.
- I suspect the way the factory connects the wire lead is suspect - noticed the shrink tubing at the base was always loose when the engine was warm..however firmed up after it cooled. When loose, the connection felt iffy.

When I had a bucking issue it was the TSII. It just wasn't staying 'seated' (connected) probably through all of the vibrations of the engine. When I would get to a higher RPM and the natural vibrations of the engine kicked in, I would get bucking. At idle and sitting in the driveway it would always test fine. I simply removed it and reinstalled it. It was getting caught up a little on a piece of tinware so I ended up trimming a bit of the tin away to give it enough space to seat all the way against the head and it finally stopped. It took a few tries, which threw me off looking for other sources but that's all it was in the end.

Mountanhide, you have two threads here and at least two threads over on TheSamba covering this one issue, with much repeated advice being given amongst all four threads. It is becoming a royal pain to monitor all those threads to track what you have tried and what has been recommended to you. I can't speak for others, but I'm not much inclined to put in the time to try and keep up, much less help out.

I suggest you pick one thread on one site and stick to it. Ask the moderators to lock or delete other threads to avoid any more scatter in the responses.

Pretty much everyone here is also on TheSamba, so you're not really getting a wider audience by going to both forums. The S/N ratio tends to be better here, but the volume is less.

And plug your ruddy vacuum leaks. Don't forget to check the AAR elbow. Don't just look at it where it's installed. Pull it out of the car. Inspect under good light.

WOW not a problem. Consider it done. Parts on order

I feel your pain Mountainhide.... do a search... I too posted both here and the Samba (albeit 1 post per forum) as I was at my wits end. One other piece of wisdom....make sure the copper washer doesn't get wedged against the tin and is sitting flat on the head.

Where's RandyinMaine's chime in here? :)

i think 1 post here and 1 on the samba is useful for those tough issues.

get 20 yahoo responses and a couple good ones on the samba and then vet them against the more thoughtful responses here

I don't even know if a vanagon has one, but most of our buses have an EEC valve that draws vapors out of the charcoal canister right at around 2,000-3,000 RPMs. Could you just put a Golf T in yours to rule that out?

Randy in Maine wrote:I don't even know if a vanagon has one, but most of our buses have an EEC valve that draws vapors out of the charcoal canister right at around 2,000-3,000 RPMs. Could you just put a Golf T in yours to rule that out?

My 82 Vanagon has one, the hose to the air filter is about ½" inside diameter.

Tim

That's not tied to RPM. The only thing that can count RPM is the FCU. The other thing that would come into play are vacuum, and mechanical advance. Does your van "kick" in Neutral at ~3000 RPM?