Hard bucking, 82 CA Van

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fiftybuckbunny
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Hard bucking, 82 CA Van

Post by fiftybuckbunny » Mon Jul 23, 2012 7:10 pm

Great site here and I'm hoping someone can help. Subject is 82 Van CA l jet, about 20k on full rebuild with mild Scat solid lift cam. It bucks badly in 2nd 3rd and 4th above 3k rpm. Common problem right? So here is what I have done: valve adjust, set timing 26 hoses off n plugged, fuel psi in spec, fuel volume 1 liter in 30 sec, AFM test shows no dropouts on analog meter. Temp 2 ohms out ok, all new ground connectors and added ground from case to body, new o2 sensor, smoke test showed no leaks. It still bucks violently. I got the wife to drive while observed spark with a timing light on lead out of coil, no misfires I can see when it misbehaves. What the heck am I missing?!?!? Throttle response is horrible, never been great but now it's really bad. Is there any way to test the ecu itself to rule that out? Bentley says nothing on that. Getting desperate as this is the wife's kid hauler and I won't let her drive it in this state. Almost ready to give up and go buy some carbs. Any suggestions appreciated

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SlowLane
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Re: Hard bucking, 82 CA Van

Post by SlowLane » Mon Jul 23, 2012 9:11 pm

Wow, you've really done a lot of diagnostics. Hard to think of what else to check. Don't despair and succumb to the carbs, though.

Long shot here: the CA-spec ignition system has an "OXS relay" wired into it which trips at 3000 RPM and does "something" with the WOT switch setting feeding into the ECU. I can't recall what the "something" is right now, as I'm not at home to check the Bentley. I think it's supposed to protect the O2 sensor under certain over-rich conditions.

I'm only bringing it up because you identified 3000 RPM as the trouble point, and that's the speed at which the OXS relay trips. Pretty circumstantial, I know.
set timing 26 hoses off n plugged
Not sure what you mean by "set timing 26". :scratch:

PS. The test for the OXS relay is on page 24.14 of the Bentley, under Speed Limit Switch, checking. Seems Bentley can't keep their naming conventions consistent.
'81 Canadian Westfalia (2.0L, manual), now Californiated

"They say a little knowledge is a dangerous thing, but it is not one half so bad as a lot of ignorance."
- Terry Pratchett

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Amskeptic
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Re: Hard bucking, 82 CA Van

Post by Amskeptic » Tue Jul 24, 2012 9:25 am

SlowLane wrote:Wow, you've really done a lot of diagnostics. Hard to think of what else to check. Don't despair and succumb to the carbs, though.

Long shot here: the CA-spec ignition system has an "OXS relay" wired into it which trips at 3000 RPM and does "something" with the WOT switch setting feeding into the ECU. I can't recall what the "something" is right now, as I'm not at home to check the Bentley. I think it's supposed to protect the O2 sensor under certain over-rich conditions.

I'm only bringing it up because you identified 3000 RPM as the trouble point, and that's the speed at which the OXS relay trips. Pretty circumstantial, I know.
set timing 26 hoses off n plugged
Not sure what you mean by "set timing 26". :scratch:

PS. The test for the OXS relay is on page 24.14 of the Bentley, under Speed Limit Switch, checking. Seems Bentley can't keep their naming conventions consistent.
Excellent follow-through, SlowLane. Bunny, please unplug the ox sensor IF it is a single wire sensor, and drive. Is it better?
You can adjust AFM with ox sensor unplugged, then replug it in. Do symptoms recur? Test ox sensor.
A "mild" cam on a CA emissions engine is a disaster, the damn thing needs every bit of airflow it can get at the lower end. You must richen mixture to compensate. Catalytic converter does not like this fact, but you and I are more interested in happy exhaust valves. I would run the car without the ox sensor for now if the symptoms go away when you test unplug it.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

fiftybuckbunny
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Re: Hard bucking, 82 CA Van

Post by fiftybuckbunny » Tue Jul 24, 2012 3:38 pm

Just to be clear, I meant 26 degrees total advance. This thing does not have a cat, just a 4-1 header and a glasspack. It has never had on O2 sensor until I installed one Saturday evening in an attempt to rule out possibilities. This thing used to run like a scalded cat, as scalded as a Van gets anyway. I have actually given up for now and am letting a shop take a look at it. The tech I spoke to on Saturday is a long time VW guy and sounded knowledgeable about the l jet system. Perhaps a pair of fresh eyes will have some fresh insight. I've spent far too many hours with zero results. Only spent $75 on it so far for a fuel psi regulator that was out of spec but not the problem. I'm curious about the speed limit switch also. I did put my meter on it and got weird readings, jumping all over asi raised the rpm. Could be it? What does it do? Can it be jumpered around? I read on that "other" site van will not run without it and they are obsolete. They haven't done anything to it yet so if I see a rePly I can experiment tonight

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SlowLane
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Re: Hard bucking, 82 CA Van

Post by SlowLane » Tue Jul 24, 2012 4:30 pm

I'll have to check again when I get home, but I think that the OXS relay simply sits in series with the WOT switch and only supplies the switch with +12V when engine speed is more than 3000 RPM. I believe the intent was to only allow full-throttle enrichment over 3000 RPM so that the catalytic converter wasn't flooded with unburnt fuel.

Since you apparently don't need the cat and O2 sensor where you are, you might consider converting to a Federal-spec L-Jet system, or alternatively, a Megasquirt system. Of the two, I suspect the Federal L-jet will be the most straightforward and the least hassle for you. It should be a bit more forgiving of non-stock cam profiles.

I've also heard of people adapting K-jet to their type 4 engines. You should cruise over to ShopTalkForums if you're curious about any such misadventures.

If you do convert to a Federal L-Jet, I'd recommend keeping the CA-spec ignition (distributor, ignitor and coil) and just use the vacuum advance side of the vacuum can. The factory Hall-effect ignition provides nice, strong consistent sparks. I was running with just this configuration for several months, and it works really well.
'81 Canadian Westfalia (2.0L, manual), now Californiated

"They say a little knowledge is a dangerous thing, but it is not one half so bad as a lot of ignorance."
- Terry Pratchett

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Re: Hard bucking, 82 CA Van

Post by fiftybuckbunny » Tue Jul 24, 2012 8:01 pm

I know several MS people, all on turbo VR Corrados. It works very well if you know what you are doing and are willing to work at it and dont mind being without wheels for days or weeks at a time. I'd consider it if I had time and money to burn. This thing needs to run. I'll see what the shop says tomorrow. They may pick up on something I missed. After that I'll search for a 49 state setup. Maybe I can find one locally and soon! Just need the harness and ecu. Piece of cake!

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SlowLane
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Re: Hard bucking, 82 CA Van

Post by SlowLane » Tue Jul 24, 2012 10:13 pm

Just need the harness and ecu.
Also:
  • Fed-spec AFM (they are calibrated differently than the CA-spec AFM)
    decel valve (the CA-spec decel valve opens at a lower vacuum level, which can upset your attempts to get your Fed-spec system to idle correctly)
    double relay
    injector resistor block
    pull the grounding terminal off the Fed-spec junker engine. The Fed-spec harness ground wires terminate in front of the plenum, not underneath it.
You said that you were running a collector exhaust, so I'm assuming you have the 49-state heat exchangers. If not, you might consider picking those up as well, or at least the left-side one.

It's also prudent to strip any junker engine you find of its FI parts for spares: injectors, regulator, CSV, AAR and AAR elbow, TTS, EGR valve, S-boot, even the fuel rail pipes. If you come across a 1980 model, get the air plenum, because it doesn't have the mounting holes for the EGR valve or the EGR plumbing inside. Grab the distributor, too. Its internal springs and weights can be used with your CA-spec dizzy if you need to re-curve it.

If the OXS relay is defective, you should be able to safely bypass it by jumpering terminals 4 and 8. This will provide +12V to the WOT switch under all running conditions, just like the Fed-spec system does.

Good luck.
'81 Canadian Westfalia (2.0L, manual), now Californiated

"They say a little knowledge is a dangerous thing, but it is not one half so bad as a lot of ignorance."
- Terry Pratchett

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Re: Hard bucking, 82 CA Van

Post by fiftybuckbunny » Wed Jul 25, 2012 9:39 am

Verdict from the shop is in! Bad afm is the cause of all my heartache. Ohms ok on the bench but not under load on the road. No dropping out but high ohms causing it to go full lean. Now, where can I get one? None locally available from my contacts. I have a week to get it together.

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Re: Hard bucking, 82 CA Van

Post by fiftybuckbunny » Wed Jul 25, 2012 5:09 pm

I just went out and did the reposition, bend, tweak, clean of my afm. Worked great... Until the van got good and hot and it promptly started its bucking routine, although not nearly as severe. It's almost tolerable but not really. When I drive I hammer on it a bit harder than the wife, so it may be ok for her to run around in for now. I know it's not going to strand her. Not for that reason anyway. I'll take the plunge and just order a rebuilt unit as used ones are probably just as crappy as what I have now. Thanks for all the help. I'm a long term Split, Bay, T3, Mk1 rabbit owner and do all my own work but this had me stumped and totally rattled. Usually just clean up grounds and away you go. More experience for my VW resume.

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SlowLane
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Re: Hard bucking, 82 CA Van

Post by SlowLane » Wed Jul 25, 2012 6:04 pm

Nice going. Just out of curiosity, you might want to bypass that silly OXS relay anyways. It's not really doing the job it was intended for, and it's just one more thing that can go wrong.

You might also want to re-visit the amount of total advance your distributor is giving you. You should be seeing 28 - 32 degrees with the stock distributor at 3600 RPM. A quickie dis-assembly and refresh of your distributor's innards can make a world of difference. Just make sure you have a clean area to take it apart where you can easily hunt down tiny parts that go sproingggg!
'81 Canadian Westfalia (2.0L, manual), now Californiated

"They say a little knowledge is a dangerous thing, but it is not one half so bad as a lot of ignorance."
- Terry Pratchett

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Re: Hard bucking, 82 CA Van

Post by fiftybuckbunny » Wed Jul 25, 2012 6:30 pm

28-32 sounds like a bit much but I'll turn it up a bit and see how it responds. No temp gauge to stare at and worry about so i may just go for it. This little affair has just lightened my wallet to the tune of $400 and I'm not happy about that. Just had to rebuild my 88 Cabby engine to the tune of about $500 after all was said and done. Was really hoping to buy some new sneakers for that or do the desperately needed front end rebuild on the van but all that will have to wait. If I had to pay someone else to do all this work it would be thousands, so I suppose I'm ahead. It's all for the love of the VW marque. Can't be seen in anything else.

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SlowLane
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Re: Hard bucking, 82 CA Van

Post by SlowLane » Wed Jul 25, 2012 7:06 pm

fiftybuckbunny wrote:28-32 sounds like a bit much but I'll turn it up a bit and see how it responds.
From the Old Volks Home distributor page for your engine:
Old Volks wrote:Timing Set At:: 5deg ATDC @ 800-950 rpm (Manual Trans), @ 850-1000 rpm (Auto Trans) w/strobe, vacuum hose(s) connected. Idle Stabilizer must be disconnected and it's plugs directly connected together (bypassing the Stabilizer) for accurate timing with strobe. Reconnect Idle Stabilizer when timing is set.
Advance/Retard Range: Vacuum: 9-12deg Adv @ 8.2 In. Hg, 11-13deg Ret @ 8.2 In. Hg; Centrifugal: 9-13deg @ 1600 rpm, 12-16deg @ 2800 rpm, 21-25deg @ 3600 rpm
Assuming that you time per the specs and set your timing to 5 deg ATDC at idle with hoses on, then the combination of allowable vacuum retard and full centrifugal advance values will net you a target range between 27 (11+21-5) and 33 (13+25-5) degrees BTDC at 3600 RPM (no vacuum advance in this equation). 30 degrees would seem to be the sweet spot.

But I'll defer to Colin's expertise on this. He has strong opinions on ideal timing.
'81 Canadian Westfalia (2.0L, manual), now Californiated

"They say a little knowledge is a dangerous thing, but it is not one half so bad as a lot of ignorance."
- Terry Pratchett

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Re: Hard bucking, 82 CA Van

Post by fiftybuckbunny » Wed Jul 25, 2012 8:34 pm

If that is where it belongs then that is where it will go. Great help, fellas!

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Amskeptic
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Re: Hard bucking, 82 CA Van

Post by Amskeptic » Fri Jul 27, 2012 12:17 am

fiftybuckbunny wrote:If that is where it belongs then that is where it will go. Great help, fellas!
I have strong opinions on ideal timing. I use the factory detent on the scale which yields a 25-28* total centrifugal advance at 3,200-3,400 rpm. This helps high speed cooling.

I do not trust big indictments of AFMs. They are rugged and simple and repositioning the board is a snap if you have resistance readings acting weird.

If you have no cat, by all means play with the mixture! A new AFM will be lean most times.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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Re: Hard bucking, 82 CA Van

Post by fiftybuckbunny » Fri Jul 27, 2012 4:11 pm

Ok, so $230 worth of rebuilt afm, $150 worth of another shop diagnosing it and guess what? Still a bucking bronco! Only thing left is computer! I shoulda just got carbs.

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