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DanHoug
Samba Member
Joined: December 05, 2016
Posts: 4791
Location: Bemidji, MN
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 Posted: Fri Dec 08, 2017 6:24 am Post subject: Re: extreme hesitation and loss of power at temp |
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what is the time span between starting/runs great and when the symptoms appear? and where is the temp needle when this occurs?
-dan |
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ohhorob
Samba Member
Joined: September 26, 2013
Posts: 212
Location: Santa Cruz
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| Posted: Fri Dec 08, 2017 8:44 am Post subject: Re: extreme hesitation and loss of power at temp |
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| graystephen wrote: |
cat has been gutted and entire exhaust system is new and sealed well. |
If I were in your position, I'd still double-check the exhaust. New parts and recent labour isn't always as reliable as we'd like..
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"Gundy" - '85 Westfalia
GoWesty 2300cc, Digijet |
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jberger
Samba Member
Joined: November 17, 2003
Posts: 2476
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| Posted: Fri Dec 08, 2017 9:08 am Post subject: Re: extreme hesitation and loss of power at temp |
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| Find a known good ecu and swap it out. I have experienced a bad ECU perform exactly like this. Upon start up you have plenty of go (if you were looking at AFR's then you would see it is running rich when cold) once warm and the ECU has to process the data the O2 sensor is giving it it can not keep up. Call for power under load and the ECU does not increase injector pulse time to supply enough fuel. This equals a very lean condition that manifests in lag and poor power. |
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E1
Samba Member
Joined: January 21, 2013
Posts: 6563
Location: Westfalia, Earth
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| Posted: Fri Dec 08, 2017 12:07 pm Post subject: Re: extreme hesitation and loss of power at temp |
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| graystephen wrote: |
I have not tested injectors but they haven't been changed since it ran well (not ruling them out just not sure they're the issue)
have not checked spark plug color and will probably do that next. |
Mine were fouled by water getting into the evaporation canisters in the front wheel wells.
Running a decent fuel drier may be worth a try.
The telltale for mine was the plug colors were all over the place; two normal cocoa brown, one black, the fourth black and very wet.
Edit: The evidence when my O2 went bad was it would fire instantly, run and rev clean as new, then in one to two minutes the O2 would kick in and it'd run horribly.
_________________
‘84 Westy, 2.1L with Digijet, 5.43 R+P, GT Gears
"Adding power makes you faster on the straights.
Subtracting weight makes you faster everywhere."
— Colin Chapman |
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AceTaylor
Samba Member
Joined: July 15, 2009
Posts: 139
Location: PERKASIE, PA
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| Posted: Sat Dec 09, 2017 7:49 am Post subject: Re: extreme hesitation and loss of power at temp |
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I can only share my experience. I had the same symptoms. I tried all the usual suspects. I tried the voltage test with the air flow meter. I stumbled upon the meter vane slightly binding up and not moving instantly after the throttle was opened. The result going instantly lean until the air flow meter opened up an sent fuel. I took a few seconds to catch up. Made for some really interesting driving when attempting to pull out from a stop in traffic. A new (rebuilt) air flow meter solved my issue.
My recommendation would be to take the air flow meter off and assure yourself that the vane moves freely with out the least bit of resistance. |
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djkeev
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Joined: September 30, 2007
Posts: 32625
Location: Reading Pennsylvania
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graystephen
Samba Member
Joined: January 19, 2010
Posts: 58
Location: Springfield, MO
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| Posted: Sat Dec 09, 2017 9:02 am Post subject: Re: extreme hesitation and loss of power at temp |
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I'll be double checking the afm again and possibly swapping a different one in in the next couple days. I will post results when I can.
DanHoug: it happens as soon as the needle starts to move
ohhorob: I installed it myself and double checked everything, the exhaust was replaced because the old system was rusty and leaking everywhere.
jberger: I swapped the ecu out and the symptoms didn't change at all.
E1: the evap system was disconnected/removed by a previous owner.
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'85 Caravelle GL w/sunroof (temporarily sick) |
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graystephen
Samba Member
Joined: January 19, 2010
Posts: 58
Location: Springfield, MO
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| Posted: Sat Dec 09, 2017 9:06 am Post subject: Re: extreme hesitation and loss of power at temp |
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I may have forgotten to mention that when it's acting up and I open the throttle, if I hold it open, the afm will occasionally snap open with a loud POP. I want to be clear, it is not snapping open as though it were stuck (it is moving with the intake pulses before this) it just lags and then BAM snaps to full open and come back to normal position.
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'85 Caravelle GL w/sunroof (temporarily sick) |
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DanHoug
Samba Member
Joined: December 05, 2016
Posts: 4791
Location: Bemidji, MN
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| Posted: Sat Dec 09, 2017 1:27 pm Post subject: Re: extreme hesitation and loss of power at temp |
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that AFM action seems suspect. never had mine do that and i watch the wiper with the cover off while snapping throttle. the design of the AFM has an air chamber built into the V shaped flapper to act as a damping mechanism to prevent just what you are describing. one leg of the V reacts to the intake, the other leg pushes into a blank chamber to damp motion.
so....
- i'm sure you've swung the AFM back a forth a zillion times. but there is perfect smoothness to a good one with absolutely no catches or sticky points.
- base spring tension on the AFM closes the vane against the stop. if you're at all floppy in the rest position, it will lead to rich running. i've played around with mine quite a bit and like it 1 click looser than stock. mine ran fine with it 3 clicks looser but my MPG dropped. regardless, look for some base tension, but not too much <grin>.
- i would say it probably has never happened in the history of these AFMs but check that the back side leg of the V is present because your action described says there's no damping!
-dan |
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graystephen
Samba Member
Joined: January 19, 2010
Posts: 58
Location: Springfield, MO
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| Posted: Sat Dec 09, 2017 5:10 pm Post subject: Re: extreme hesitation and loss of power at temp |
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So, upon further fiddling, I have realized that the POP that I hear and the afm vane movement is actually combustion being sent back into the intake and the afm slamming shut. (this was hard to see since it moved so quickly.)
I've read that intake backfiring can be caused by improper valve lash adjustment, improper ignition timing (checked), or a super lean condition.
I have checked timing again, it is close enough to correct, and I have even moved it forward and back to see if any improvement can be made to no avail. I'll double check my valve lash tomorrow when it's light out.
I don't know if it's a lean condition because I have checked o2 sensor voltage (hot and running) and it moves between .4 and .7 with some occasional highs and lows.
DanHoug: the AFM movement and return to closed position is as it should be, firm closed and free moving towards open with resistance from the spring.
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'85 Caravelle GL w/sunroof (temporarily sick) |
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djkeev
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Joined: September 30, 2007
Posts: 32625
Location: Reading Pennsylvania
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Howesight
Samba Member
Joined: July 02, 2008
Posts: 3274
Location: Vancouver, B.C.
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| Posted: Sat Dec 09, 2017 6:16 pm Post subject: Re: extreme hesitation and loss of power at temp |
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| graystephen wrote: |
So, upon further fiddling, I have realized that the POP that I hear and the afm vane movement is actually combustion being sent back into the intake and the afm slamming shut. (this was hard to see since it moved so quickly.)
I've read that intake backfiring can be caused by improper valve lash adjustment, improper ignition timing (checked), or a super lean condition.
I have checked timing again, it is close enough to correct, and I have even moved it forward and back to see if any improvement can be made to no avail. I'll double check my valve lash tomorrow when it's light out.
I don't know if it's a lean condition because I have checked o2 sensor voltage (hot and running) and it moves between .4 and .7 with some occasional highs and lows.
DanHoug: the AFM movement and return to closed position is as it should be, firm closed and free moving towards open with resistance from the spring. |
Above are all the clues to suggest that you have sticking intake valves. This vehicle sat long enough for the gasoline to degrade chemically and form varnish, which is then sprayed on the intake valve stems by the injectors. It is hard for most people to accept how incredibly sticky gasoline varnish is, but it can stop intake valves from moving at all, causing bent pushrods, as well as causing intake valves to stay slightly open. The backfiring is a classic sign of intake valves sticking open.
Having said that, it is possible for a seriously lean condition to cause backfiring, but rather rare. What happens is the flame front moves so slowly, due to a lean mixture, that it is still burning in the cylinder on the exhaust stroke at the point when the intake valve opens, as there is a small amount of valve timing overlap when intake and exhaust valves are open at the same time.
As for the poor running when warm, this may simply be connected with partial clogging of the injectors, and it may also be a malfunctioning AFM. The AFM does suffer wear on the shaft at which the flap pivots. A van that has had a hard life on bumpy, dusty roads is more likely to have greater wear on that shaft, but any AFM can get sticky.
So, as I suggested above, a compression test will be very helpful in diagnosing the cause(s) of your engine issues. Also, pics of your spark plugs will be helpful.
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'86 Syncro Westy SVX |
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graystephen
Samba Member
Joined: January 19, 2010
Posts: 58
Location: Springfield, MO
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| Posted: Sun Dec 10, 2017 11:02 am Post subject: Re: extreme hesitation and loss of power at temp |
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Howesight:
If it is an intake valve or valves sticking open, why would it run perfectly before the coolant warms up? I started it this morning and it would run and rev just fine, right up until it got even a little warm...maybe the heads get warm and take up any extra space in the valve guide(s) which holds the valve in place.
I guess I'll have to take the intake runners off and get eyes on the valves or do that compression test.
on a side note, I made a genius move and broke one of the vacuum nipples off of the distributor advance when removing it earlier today...lets hope jb weld holds well enough.
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'85 Caravelle GL w/sunroof (temporarily sick) |
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Wildthings
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Joined: March 13, 2005
Posts: 50351
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| Posted: Sun Dec 10, 2017 12:59 pm Post subject: Re: extreme hesitation and loss of power at temp |
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You could have a bad TSII sender as they will choke the engine out as it warms.
As for valves, if they are tight in their guides then they will just get tighter as the engine warms. Add a quart of Marvel Mystery Oil, 2-cycle oil, or synthetic motor oil to a full tank of gas and see if this will keep the valves moving. |
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E1
Samba Member
Joined: January 21, 2013
Posts: 6563
Location: Westfalia, Earth
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| Posted: Sun Dec 10, 2017 3:19 pm Post subject: Re: extreme hesitation and loss of power at temp |
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I'd add Lucas Oil Treatment to that list. (Edit: to your oil)
Over four years, my valves made noise on start-up, lasting from 30-60 seconds.
With the Lucas, it lasts 0-3 seconds.
The OP's recent comment that it runs perfectly when first fired still points to an O2 sensor. But as we all know, it could be anything else related to what happens when the sensor kicks in, too.
And therein lies the Joy. 
_________________
‘84 Westy, 2.1L with Digijet, 5.43 R+P, GT Gears
"Adding power makes you faster on the straights.
Subtracting weight makes you faster everywhere."
— Colin Chapman
Last edited by E1 on Mon Dec 11, 2017 12:12 pm; edited 1 time in total |
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graystephen
Samba Member
Joined: January 19, 2010
Posts: 58
Location: Springfield, MO
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| Posted: Mon Dec 11, 2017 10:42 am Post subject: Re: extreme hesitation and loss of power at temp |
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put about 5 gallons of new gas into the tank with some MMO last night and drove it for a bit, the low rpm power loss is still present but it was more drive-able than I remember. I'm hoping that if there is varnish build up on the valves that this new fuel will help wash it away.
I was double checking the o2 sensor output and I thought I would watch the voltage while I worked the throttle. I specifically watched what the reading was when I would try to rev the engine and it would hang and stumble....voltage dropped down to almost zero while the engine was stumbling which suggests to me that I'm probably getting spark but I'm definitely not getting enough fuel. I'll be off to buy that fuel pressure gauge in a bit to verify fuel pump and FPR function again (it's been a while.)
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'85 Caravelle GL w/sunroof (temporarily sick) |
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graystephen
Samba Member
Joined: January 19, 2010
Posts: 58
Location: Springfield, MO
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| Posted: Mon Dec 11, 2017 1:19 pm Post subject: Re: extreme hesitation and loss of power at temp |
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Bought a vacuum gauge and the manifold vacuum was 10in. I know the state of the internals so I knew timing was off which means I'm either worthless with a timing light (not true ) or something else, so I decided to time it with the gauge and it's now running fairly well. I haven't test driven it yet but the backfiring has stopped and the idle, while not super smooth, is better. I'll post results of the trestdrive later.
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'85 Caravelle GL w/sunroof (temporarily sick) |
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graystephen
Samba Member
Joined: January 19, 2010
Posts: 58
Location: Springfield, MO
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| Posted: Mon Dec 11, 2017 7:21 pm Post subject: Re: extreme hesitation and loss of power at temp |
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It was absolutely just ignition timing....makes me feel like a complete idiot. I know I set the timing by the ten cent method, the timing marks must be wrong on my pulley. I think I'll be setting it by the vacuum gauge method from now on.
Thank you all for the ideas and guidance. I'm quite sure I would not have thought to look at manifold vacuum, and the ideas brought up here lead me to that.
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'85 Caravelle GL w/sunroof (temporarily sick) |
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E1
Samba Member
Joined: January 21, 2013
Posts: 6563
Location: Westfalia, Earth
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| Posted: Mon Dec 11, 2017 10:22 pm Post subject: Re: extreme hesitation and loss of power at temp |
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Apology not necessary, CONGRATULATIONS!!!
_________________
‘84 Westy, 2.1L with Digijet, 5.43 R+P, GT Gears
"Adding power makes you faster on the straights.
Subtracting weight makes you faster everywhere."
— Colin Chapman |
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Dan57
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Joined: May 20, 2017
Posts: 31
Location: SoCal
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| Posted: Tue Dec 12, 2017 1:00 am Post subject: Re: extreme hesitation and loss of power at temp |
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| Did you have to advance or retard the timing? |
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