2-for-1 and possibly related: Bucking and unstable/nonidle

Bus, Microbus, Transporter, Station Wagon, Vanagon, Camper, Pick-Up.

Moderators: Sluggo, Amskeptic

Post Reply
User avatar
SlowLane
IAC Addict!
Location: Livermore, CA
Status: Offline

Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by SlowLane » Sat Feb 21, 2015 7:34 pm

If Washington State doesn't require you to keep the L-Jet system, you might want to consider installing a Mega-or-micro-squirt system like luftvagon's. Since the megasquirt system is infinitely tweakable, and doesn't rely on a AFM or MAF sensor, you will likely be better able to dial in the behavior you desire from your non-stock engine. Be less drastic than an engine tear-down anyways.
'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

User avatar
Ronin10
Getting Hooked!
Location: Columbia City, Seattle, WA
Status: Offline

Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by Ronin10 » Mon Feb 23, 2015 8:39 am

Apologies for the late response, I spent all my spare time this weekend doing project around the house to get it ready to sell.
Amskeptic wrote:I have to rewrite the AFM article. You have read elsewhere I hope, that we can set the wiper pretty specifically for 10.9-11.3 full throttle at 50 mph, should lean out to 11.5-11.7 full throttle at 65-70 mph.
I hadn't read that. Will hunt for it to get more details.
You can't be all the way over to the rich side on that wiper adjustment AND have a bottomed out mixture screw. That is crazy compensated and would lead to horrendous fuel economy, do you have horrendous fuel economy?
Believe it or not, I am indeed set there since I pulled the prior, now deceased AFM. I double checked this morning before heading out for work. I'm getting about 13.5 MPG with city driving and some AFM tuning and timing adjustment sessions/experimenting. It's pretty bad, but I knew it would be bad while I chased down these idle mixture and timing questions to see if a stable idle with a good A/F ratio is achievable. I feel like that exploration has just about run its course though, so backing off everything to get good A/F ratios throughout the 1500+ RPM range (whatever my idle mixture is so long as it doesn't die) is right around the corner.

I did have an interesting thought though this morning, that the mixture readings I'm getting at idle may be bogus due to using the tail pipe clamp for the O2 sensor with the curved tailpipe itself, placing the opening of sniffer port either up against the tailpipe wall where there is very little exhaust air flowing or certainly at a substantial angle relative to the exhaust flow that there's not enough velocity in the exhaust to get an accurate reading. I do have a bung for the O2 sensor so I may revisit this at a later date once I get that welded into the tailpipe.
Do you have a CHT gauge? Please note, I know you would love to bias all adjustments towards rescuing the idle, but that leaves everything else compromised. Your lean idle is because the engine is sucking exhaust at the beginning of the intake stroke from that considerable cam overlap instead of getting clean sucks (good vacuum) down the intake. The AFM just is not getting adequate airflow to signal a sufficient mixture.
Understood. I do have a CHT gauge (a lowly VDO), just no way to mount it at the moment. I could rig something temporarily though I suppose. Anyway, since I have a stable, warm idle now, I'm inclined to let the science experiment fade (especially with selling the house coming up) and focus on getting the A/F ratios at the higher RPMs sorted as well as my cold idle (within about 5 minutes of a cold start)

Programmable fuel injections setups are incredibly appealing to me, but perhaps down the line. I like the notion of getting my stock setup working and fully understood before deviating at this time. Likewise, since I drive Greta to work everyday and can limp along for the moment, tearing her engine down and swapping the camshaft isn't too viable. I actually feel that now that I can idle warm, everything getting the rest of the system dialed in isn't too far off. If the need arises to tear into my engine, you bet I'll swap the camshaft back for stock.
Oscar: 1976 Sage Green Bus, Stock Motor, Solid Lifters, Manual Transaxle

User avatar
Amskeptic
IAC "Help Desk"
IAC "Help Desk"
Status: Offline

Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by Amskeptic » Mon Mar 02, 2015 9:14 am

SlowLane wrote:If Washington State doesn't require you to keep the L-Jet system, you might want to consider installing a Mega-or-micro-squirt system like luftvagon's. Since the megasquirt system is infinitely tweakable, and doesn't rely on a AFM or MAF sensor, you will likely be better able to dial in the behavior you desire from your non-stock engine. Be less drastic than an engine tear-down anyways.
Let's ask luftvagon how his launch torque vs. cam profile is . . . luftvagon?
Colinvagen
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

luftvagon
Old School!
Location: Little Rock, AR
Status: Offline

Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by luftvagon » Mon Mar 02, 2015 6:22 pm

I'm running stock cam with bit bigger valves. My launch torque is same as stock, if not better. Now, my microsquirt install also depends on manifold vacuum, and it will not help his performance cam issue. With performance cam you will have to raise your idle.
1981 Volkswagen Vanagon Westfalia - air-cooled Type4 1970cc CV (hydraulic lifters, 42x36 valves, stock cam, microSquirt FI with wasted spark ignition)
1993 Ford F-250 XL LWB Extended Cab 7.3L IDI

User avatar
Ronin10
Getting Hooked!
Location: Columbia City, Seattle, WA
Status: Offline

Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by Ronin10 » Tue Mar 03, 2015 8:06 am

Thanks for the heads up, luftvagon. I also have the oversized valves and don't want to go throwing good money after bad. My bus is old enough now to where I don't have to do any inspections in WA so this was a consideration for me.

I found a local shop to re-curve a spare 205P distributor of mine. I asked them to restore it to stock specification. That should be done tomorrow. I figure to swap that in later this week and see how that affects performance. Depending on the result, I'll have them re-curve the distributor I have installed now to match my camshaft better. Regardless, I want to have a distributor on hand that matches stock as closely as they're able to make it. I'll make use of that someday, I'm sure.

Any recommendations or reading assignments for matching distributor timing to camshafts? I figured on calling Webcam and seeing what their thoughts were on the subject, but beyond that, I don't know a whole heck of a lot about it.

Making little adjustments to the AFM as time allows to adjust for driveability. I've also had a hard time with cold start the last couple weeks that's taking up mental real estate as well.
Oscar: 1976 Sage Green Bus, Stock Motor, Solid Lifters, Manual Transaxle

User avatar
Amskeptic
IAC "Help Desk"
IAC "Help Desk"
Status: Offline

Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by Amskeptic » Tue Mar 03, 2015 1:53 pm

Ronin10 wrote:Thanks for the heads up, luftvagon. I also have the oversized valves and don't want to go throwing good money after bad. My bus is old enough now to where I don't have to do any inspections in WA so this was a consideration for me.

I found a local shop to re-curve a spare 205P distributor of mine. I asked them to restore it to stock specification. That should be done tomorrow.
Any recommendations or reading assignments for matching distributor timing to camshafts? I figured on calling Webcam and seeing what their thoughts were on the subject, but beyond that, I don't know a whole heck of a lot about it.

Making little adjustments to the AFM as time allows to adjust for driveability. I've also had a hard time with cold start the last couple weeks that's taking up mental real estate as well.
On Monday February 16th, I wrote:
If you can narrow the advance range, great, 10* to 12*BTDC at idle increasing to only 28* would be good for that camshaft set up.
Colin
(ask Air-Cooled.net if they have a SVDA with that artificially narrowed range)


So, REALLY NOW, I think a stock curve is going to be just another missed opportunity, though, as ever, hope springs eternal. Try at least talking with John at AircooledNet.
The reason we are at Page 6 here is that we are retreading over the same old information with inadequate retention of both concepts and potential execution of the many helpful suggestions herein, such as this unanswered gem from Slow Lane, January 7, 2015:
"Finally, getting back to the valves and camshaft question: has this engine ever run smoothly at idle for you with this valve and camshaft combination? That is, do you know for a fact that it can run smoothly at idle, or are you simply assuming that it must be able to?"
Colin
(this topic has meandered into so many different corners, that I am moving it to Type 2, where it shall be your personal diary, rather than a Troubleshooting Forum "resource". There is nowhere near enough specificity left within this epic here that could help another soul work out their troubleshooting "problem > solution")
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

User avatar
Ronin10
Getting Hooked!
Location: Columbia City, Seattle, WA
Status: Offline

Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by Ronin10 » Tue Mar 03, 2015 3:24 pm

Point taken.

This has evolved into something of an experiment now in an effort to fully understand the relationships within my engine in particular the fuel injection system. It is clear to me now that the bucking and idle issue is tied to the interplay between the Webcam 107i camshaft, my AFM setting, and the ignition system setup. I did discover some incorrectly functioning parts along the way, but by and large, the components just need to be setup in order to match better. I sincerely apologize if this is no longer helpful to other readers.

I do take issue with the suggestion that I'm not addressing issues and questions as they arise. I am by no means perfect, but some suggestions aren't pursue-able due to time, cost, practicality (it's not feasible to replace my camshaft anytime soon), or simply the availability of an investigative path that might narrow down the scope of the problem. Unfortunately, my investigations are limited to what time I have on my hands and with the requirement that the bus needs to be driveable again each morning.

I agree that the stock setup distributor may very likely not help this specific situation, but it will help me understand the differences timing curves can have driving performance and fuel economy. Additionally, I have spare engine sitting aside in my garage that will be built up as a stock engine down the line. I'd like to have this distributor available for that, might as well have the correct springs in there. I left that information out, because it didn't seem pertinent to the discussion. But using that stock curved distributor in my current engine is strictly for reference, my personal education, and as a stopgap so I don't have a bus that's down for a week while I wait for the distributor to be recurved. I consider it an investment in the future.

Please don't think that I forgot or disregarded your statement you made about the advance curve endpoints, but I took that to be a starting point for the curve. Two data points do not make a complete curve so it seems like a lot could happen with the way the curve behaves between those limits and how the vacuum signal from a nonstock camshaft could alter that curve. I appreciate the help so far and will discuss any further curve requirements with John and the folks doing working on my spare distributor.

Also, I did respond to Slow Lane in the very next post where I said that I had an acceptable idle when I had carbs installed a couple of years ago. Maybe that was insufficient, but it didn't come up again until now so I let it be. To expand on that point, I don't recall the fuel economy I was getting at that time though. It may indeed have required an awful jetting setup. I was new to carbs then as I'm pretty new to FI now (understanding more each day). At the time, I did not have an AFR meter and I was driving my bus about 20-30 miles/week, if that. I wasn't worried about tracking fuel economy. It ran well enough so I moved onto what I felt where higher priority items.

I think I have enough information to be going onward from here and get my engine more or less setup correctly (with a bit of time). Again, I apologize if my way of thinking and pursuit of broader understanding instead of just pushing direct to a solution forced the readership down a more circuitous route than necessary. Unless some new information arises to undermine the current state of things, I consider the diagnostic part of this closed.
Oscar: 1976 Sage Green Bus, Stock Motor, Solid Lifters, Manual Transaxle

luftvagon
Old School!
Location: Little Rock, AR
Status: Offline

Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by luftvagon » Wed Mar 04, 2015 6:08 pm

The trick is, you are now the engineering, R&D, testing, and a customer at the same time. It's up to you to tweak this non standard configuration. I don't think ignition timing is going to make any difference. You have other issues on top of L-Jetronic tuning.

Anyway, I lost track what's your issue -- random bucking on cold engine? random bucking on cold engine?, bad hot idle or bad cold idle?
1981 Volkswagen Vanagon Westfalia - air-cooled Type4 1970cc CV (hydraulic lifters, 42x36 valves, stock cam, microSquirt FI with wasted spark ignition)
1993 Ford F-250 XL LWB Extended Cab 7.3L IDI

User avatar
Ronin10
Getting Hooked!
Location: Columbia City, Seattle, WA
Status: Offline

Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by Ronin10 » Thu Mar 05, 2015 8:58 am

Hi luftvagon, thanks for sticking with me.

Here's my current status and what I'm trying to address:
  • * Bus will not idle when first started. I have to stay on the gas pedal for a few minutes first. By the time I get out of my neighborhood, it will idle, but it's not that smooth. After 10 minutes or so of driving, it idles fine, around 800-850 RPM. After a long time of driving, it seems to be more around 1000 RPM.
    * During driving, I have intermittent bucking issues. This morning, on the drive into work, not a single buck, but other times I'll get an occasional hiccup, and still other times, I'll get a 20 or 30 second period where it's really hard to keep the bus going.
    * The A/F ratios aren't set correctly across the RPM range.
My current plan of action is this:
  • * Continue to adjust the AFM to get the best compromise between drivability and fuel economy. My last tank of gas was 14.5 MPG. This is slow because I have to burn sufficient gas to measure fuel economy, assessing drivability in the meantime.
    * Getting my backup distributor set to meet stock specifications for reasons given above. (Calling on it today to see if it's done)
    * Put this backup distributor into my bus and get my currently installed distributor custom curved for my 107i camshaft.
    * Compare the drivability of the two different distributors and learn something.
    * Once happy with the driveability / fuel economy / distributor setup, install my CHT gauge to verify that I'm not going to run into issue down the line.
FYI, the other day, I installed my Pertronix module in lieu of the points, since I couldn't seem to get the points to stay adjusted. Instantly increased power (although it still feels off a bit from what I've had previously) and reduced bucking, although it still sometimes occurs, particularly when I tromp down on it (as a test, I don't normally drive that way).

So, I'm hesitant to dink around too much more until I get the AFM set satisfactorily. It seems to me that this is the biggest variable out of whack at the moment. With the adjusting I've been doing, I'm learning a lot about the engine, and it seems to me that dialing in the upper end of the RPM range upsets some of the sensitivities around idle just enough to be unsatisfactory and vise versa. My sense is that I'm spiraling into an acceptable setting, just need continue adjusting and put in some time behind the wheel to verify.
Oscar: 1976 Sage Green Bus, Stock Motor, Solid Lifters, Manual Transaxle

User avatar
satchmo
Old School!
Location: Crosby, MN
Status: Offline

Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by satchmo » Thu Mar 05, 2015 9:59 am

I still think the bucking is likely related to a faulty electrical connection somewhere in the AFM wiring or the harness/double relay block connector. These intermittent disconnects will also cause fouling/pitting/etc in the points for some reason, so you end up chasing several variables at the same time when the engine bucks: bucking causes points to go out of adjustment which causes poor running which causes you to continue to suspect other components which causes you to change things like AFM settings, and on and on.

This has been my experience. That, and I'm trying to drum up more support for 'satchmo's theorum' ;-)
By three methods we may learn wisdom:
First, by reflection, which is noblest;
second, by immitation, which is easiest;
and third, by experience, which is bitterest. -Confucius

User avatar
Ronin10
Getting Hooked!
Location: Columbia City, Seattle, WA
Status: Offline

Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by Ronin10 » Thu Mar 05, 2015 11:24 am

Satchmo, let me get the AFM to a spot with decent A/F ratios and driveability (no bucking, if possible, & decent accel) so we can eliminate that as a consideration. I had it there at one point - to the expense of my idle - so I'm trying to rediscover an operating setup that might sacrifice the idle a bit, but not so much that it dies at stoplights and such.

At this point, my preference is to eliminate known problems before pursuing the unknowns. If the bucking persists after that, it seems plausible to reinvestigate the electrical system. I do get what you're saying though. Intermittent behavior is a classic electrical failure mode. Stay tuned. I'll update with the results of my adjustments over the weekend.
Oscar: 1976 Sage Green Bus, Stock Motor, Solid Lifters, Manual Transaxle

luftvagon
Old School!
Location: Little Rock, AR
Status: Offline

Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by luftvagon » Sun Mar 08, 2015 7:47 am

My Vanagon had a bad case of random bucking. I've literally done everything to troubleshoot it. One time it turned out to be a loose TSII, the second time, I couldn't find it. The bucking , I ripped the entire L-Jet out, and cracked open the ECU. The ECU was (still) wet and was rusting, and shorting-out. Nothing is impossible at the moment. I bought another L-Jet ECU and put it back into the van, and no more bucking.

However, I hated the black AFM magic, and replaced it with some more advanced black magic which allowed me more adjustability right from the drivers seat.

The poor idle, is just that poor idle. Even with a wildcam it should still idle erratically, as if it had an air leak. You are either dealing with not enough air volume or wrong A/F mixture. Is your AAR working? New TSII? Vacuum hoses good? How many turns on the idle a/f screw?
1981 Volkswagen Vanagon Westfalia - air-cooled Type4 1970cc CV (hydraulic lifters, 42x36 valves, stock cam, microSquirt FI with wasted spark ignition)
1993 Ford F-250 XL LWB Extended Cab 7.3L IDI

User avatar
Ronin10
Getting Hooked!
Location: Columbia City, Seattle, WA
Status: Offline

Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by Ronin10 » Mon Mar 09, 2015 7:41 am

I think this might be another hit to Satchmo's Theorem, but I think I've cured my bucking issues with a correctly adjusted AFM. I don't have the precise A/F ratio numbers with me at the moment, but they were in the 12 1/2 - 13 range from just off idle up to about 2500 RPM or so (which seems fine as those are the accelerating RPMs). From there, the ratios ramped steadily from 13 to the upper 14s/low 15s at 4000 RPM where I stopped checking as I don't drive beyond that RPM. Driveability-wise, I don't know if the bus has had a better overall setting since I rebuilt the engine a couple years back.

Idle still isn't great, but it's manageable. Like you say, luftvagon, it acts as if there's an air leak, but only at idle. The air-fuel ratio blows up at idle so the setting I've arrived at keeps it in the upper teens to low 20s. Just after a cold start, I still have to stay on the gas a bit to keep it alive. On cold-running (thanks for correcting my terminology, Colin), the engine will idle rough around 750 - 800 RPM. By the time I'm fully warm, it settles into an 800 RPM okay-ish idle, but other times it'll idle very nicely around 1100. I haven't discerned what the trigger is for the difference in idle RPM yet, but will keep thinking and investigating, just a bit more casually.

For the record, my wiper is set as far as it'll go towards rich, the mixture screw is 3/4 turns out. AAR functions correct, TSII is a couple months old and was replaced, though my original tested fine (and was kept as a spare).

I'm still burning through my current tank of gasoline, but by the end of the week, I should be far enough into (almost done, in fact) that I can see what my fuel mileage is with this current setup. If that checks, I'll verify that the engine is running at decent temps via my CHT.

Long story short, things are looking pretty wrapped up. I still wish I could clean up that cold-running idle, but it's at a point that I can live with.
Oscar: 1976 Sage Green Bus, Stock Motor, Solid Lifters, Manual Transaxle

Jivermo
IAC Addict!
Status: Offline

Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by Jivermo » Mon Mar 09, 2015 9:45 am

Man-this post has some legs!

User avatar
Amskeptic
IAC "Help Desk"
IAC "Help Desk"
Status: Offline

Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by Amskeptic » Mon Mar 09, 2015 11:19 am

Jivermo wrote:Man-this post has some legs!
I can barely walk at this point, my sneakers have holes in them.

Ronin10, I am nervous about your reported leaning out at high rpm, it is deadly to the exhaust valves.

"From there, the ratios ramped steadily from 13 to the upper 14s/low 15s at 4000 RPM where I stopped checking"

Your engine's torque peak with the performance cam is likely to be higher up than the stock system. Stock peak is just about 3,000 rpm, it is here that the mixture must be correct. With your engine, you need adequate fuel from 2,500 to 4,000, which is about 40-70 mph. If you are on a long uphill run with a floored accelerator, the engine will be dropping from 3,800 down to about 2,800 before you downshift.
A max of 12.5 would be best for that circumstance.
A Dakota Digital CHT gauge would provide you some driving-based protection, but it could also give you a whole new universe of anxiety . . .
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

Post Reply