Date: Thu, 29 May 2003 01:29:54 -0700
Reply-To: zampano <matthias.k@ATTBI.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: zampano <matthias.k@ATTBI.COM>
Subject: rich bad mileage syndrome miss stall
Content-Type: text/plain; charset=US-ASCII; format=flowed
You guys can ignore this. I just want to post it with all the keywords
in the subject line so it might help someone in the future from the
archives. The new AFM and OXS from BD cured it and it's back to normal.
Normal in my case means dealing with a dismal rebuild once again. I am
going to paste all my posts and useful responses from everyone. Thanks
a bunch!!!
Start quote(s):
Here's what's going on (aside from the coolant issue in my other post):
She's been getting 15 mpg in mixed driving over the last month. I
checked around her and saw that the J-pipe in the exhaust, the one that
houses the OX sensor, had a hairline crack. So I disconnected the OX
sensor. Now, 11/2 weeks ago the J-pipe got replaced. I reconnected the
OxS and went to have her smogged. Passed (in California). But I kept
on getting poor fuel mileage, about 15 mpg. No other problems except
coolant whizzing out of the water pump. Ran beautifully and powerful.
So I went and exchanged the OxSensor, checked visually for all the
vacuum hoses and tightness, all connectors, all ignition wires etc.
Went for a ride with the new OxS yesterday and she ran worse, poor
idling, would not go past 4000 rpm once warm, in any gear, accompanied
with some occasional bucking.
I now just replaced the rotor and cap, but that only worked until she
was fully warmed up again. Needless to say I don't have the OxS
connected anymore at all.
This is a rebuilt/resealed motor with about 3000 miles on it.
My plan is to
- check and replace spark plugs, do compression test
- check coil
- check ignition wire resistance
- try to perform a test on the AFM (per Bentley)
- try to test distributor
- call Autotrader :(
I am pretty sure it is a ignition problem vs. fuel problem Not 100%
though. The fuel filter is about 18 months old, the air filter is 6
months old. The fuel pump and fuel regulator are 3 years old. How would
I be able to check the injectors, apart from taking them out and see
that the spray is cone shaped??? Could my exhaust be blocked from a
disintegrating cat??
She runs perfect when cold, say for about 2-3 miles in city traffic,
and she'll happily rev past 4000 rpms. Once warmed up this is no more
so.
I am gonna go and piss off into the archives for couple hours,
meantime, any and all help is greatly appreciated.
Matthias
'84 WBX Man Wolfy in Los Angeles, CA
m
> From: zampano <matthias.k@attbi.com>
> Date: Wed May 14, 2003 3:03:06 am US/Pacific
> To: "John McMahon" <jfm@nts-online.net>
> Subject: Re: Vgon syndrome on 1.9 WBX
>
> Hi John, evrybody
>
> Anything like tire pressure and brakes binding etc can be ruled out.
>
> I know that on CIS injectioned engines there's a separate injector
> just for warm up. The Digijet just has an auxiliary air valve which
> pumps air into the intake. Or might I be wrong?? Is it an actuall
> injector?? But there's no fuel line going to it.
> If I squeeze that hose from past the AFM to this valve at idle, the
> idle drops. Since she idles really poorly, I don't know for sure
> though.
> That aux air valve is really hard to get to. I'll try and disconnect
> it and see what happens.
>
> Cheers
>
> m
> On Tuesday, May 13, 2003, at 11:33 PM, John McMahon wrote:
>
>> Matthias,
>> Thanks for the rapid reply. What about the Cold Start Valve? Does
>> the
>> Digijet system have a Thermo-Time Switch? In my 1975 VW Beetle with
>> L-Jetronic (AFC),
>> I once had a injector stick wide open dumping raw fuel out of the
>> tail pipe.
>> Since I believe that the orifice on the Cold Start is likely to be
>> smaller
>> than on an injector, it could be that you have a Cold Start Valve
>> that isn't
>> shutting off, or the needle can't/won't seat properly and you are
>> leaking
>> fuel continuously. That might explain the
>> rough idle when warm. The Thermo-Time switch could be faulty or the
>> wiring
>> harness shorted/crimped/pinched telling the Cold Start Valve to spray
>> constantly.
>> I am leaning away from ignition, and toward fuel system.
>> My other thought: a combination of "problems", maybe?
>> Front-end misalignment, low tire pressure, wrong tire/wheel size,
>> overloading, a/c usage, dragging brakes, clutch? slippage, all
>> contributing
>> for the increase in fuel consumption.
>> Good luck...you'll find it!
>> John M
>> ----- Original Message -----
>> From: "zampano" <matthias.k@attbi.com>
>> To: "John McMahon" <jfm@nts-online.net>
>> Cc: <vanagon@GERRY.VANAGON.COM>
>> Sent: Wednesday, May 14, 2003 12:18 AM
>> Subject: Re: Vgon syndrome on 1.9 WBX
>>
>>
>>> ok you guys,
>>>
>>> The spark plugs I just changed as well. They were beyond fouled, no
>>> surprise at 8 mpg. There is no fuel leaking anywhere visible. The
>>> possibility of the exhaust being blocked seems ruled out, since I
>>> removed the cat altogether, and the muffler seems fine, as in: I can
>>> blow air thru it if I blow real hard. . Easy now. Seriously, I got
>>> the
>>> muzzie to prove it. It's maybe 2 years old as well. I had the
>>> J-exhaust pipe replaced at a shop, and the trip home (80+ miles) went
>>> fine. Although I only got 15 mpg.
>>> I did all the resistance/continuity checks in the Bentley, in the
>>> fuel
>>> injection group, they all checked out fine. Even did all the checks
>>> involving the throttle valve/full throttle enrichment valve. Check.
>>> My
>>> air filter is rather clean. Fresh spark plugs now. New OXSensor from
>>> ShmAutozone. Resistance is fine on my spark plug / ignition wires.
>>> Coil
>>> checks out ok. My injectors spray in nice cone fashion. Checked
>>> resistance on Hall sender, fine. Only things I can think of is the
>>> AFM
>>> and the ignition distributor, or maybe the ignition distributor.
>>> Have
>>> not checked fuel pressure regulator reliably, but it is maybe 2 years
>>> old, as is fuel pump. Fuel filter is 3 years old. Fuel delivery is
>>> according to spec (Bentley). Timing seemed fine, although maybe a bit
>>> jumpy, to the tune of 1-2 degrees maybe. All vacuum hoses are
>>> connected
>>> and tight, heck, they have mostly been replaced when they put my
>>> motor
>>> back together under warranty.
>>> Maybe my cold start auxiliary valve is shot, but all the test per
>>> Bentley worked out, though she idles real poorly.
>>> Have not done a compression test yet. Have not been able to really
>>> check AFM, though I did all the checks in the Bentley, and the
>>> results
>>> are spot on. (But what is the tolerance when I move the flap, Bentley
>>> and Haynes are rather unspecific...). All my grounds are wired
>>> afresh,
>>> and they contact the motor (rebuilt 2 months ago) outstandingly, I
>>> should think. It seems insane that I should be getting 8 mpg.
>>>
>>> I bet the farm it's got to be my AFM. It;s been my daily driver for
>>> the
>>> last three months, and the bad fuel economy only started 1 month ago
>>> (15-16 mpg city/mixed).
>>>
>>> If anybody knows of an accurate way to test the AFM while moving the
>>> flap, let me know, please.
>>> It idles poorly once it's warm, and dies at times, stays around
>>> 400-600
>>> rpms when warm, normal (900 rpms) when cold.
>>> I can smell that the exhaust is too rich.
>>>
>>> Why am I doing this to myself???
>>>
>>>
>>> Cheers
>>>
>>> m
>>> On Tuesday, May 13, 2003, at 09:30 PM, John McMahon wrote:
>>>
>>>> Matthias,
>>>> Has there been a noticeable change in the idle speed, or idle
>>>> smoothness?
>>>> Do the spark plugs appear black, sooty, fouled, wet? Accelerator
>>>> pedal seem
>>>> to be in the same position per mph?
>>>> I am supposing that you've checked the cleanliness of the air
>>>> filter.
>>>> I am guessing here, but it seems that it has to be enrichment
>>>> related.
>>>> However, without other symptoms
>>>> showing themselves, that doesn't make complete sense.
>>>> If your calculations are correct, and you are not leaking it
>>>> somewhere, the
>>>> spent fuel has to be going out the tail pipe one way or another.
>>>> An interesting problem. I will be watching for the answer.
>>>> Good luck!
>>>> John McMahon
>>>> Abilene, Texas
>>>>
>>>> ----- Original Message -----
>>>> From: "zampano" <matthias.k@ATTBI.COM>
>>>> To: <vanagon@GERRY.VANAGON.COM>
>>>> Sent: Tuesday, May 13, 2003 10:07 PM
>>>> Subject: Vgon syndrome on 1.9 WBX
>>>>
>>>>
>>>>> Hi all,
>>>>>
>>>>> So,
>>>>>
>>>>> I checked all the FI sensors and other peripherals. The idle valve,
>>>>> full throttle enrichment
>>>>> switch,
>>>>> checked
>>>>> all the voltages and resistance per Bentley. All checked out good.
>>>>> Checked the ignition timing. Swapped out the ECU, removed the
>>>>> catalytic
>>>>> converter.
>>>>> All didn't make a difference. I just filled her up and calculated
>>>>> I'm
>>>>> getting 8 mpg. This NEVER happened. Seems insane. Maybe she's
>>>>> starting
>>>>> to behave like her possible Detroit replacement.
>>>>>
>>>>> I am going to order a new AFM from Busdepot. Seems like a very
>>>>> good
>>>>> deal actually.
>>>>>
>>>>> It's the only thing I can see being bad, though I can't tell for
>>>>> sure
>>>>> that my AFM is bad. The spec in both Bentley and Haynes don't
>>>>> specify
>>>>> exactly whereabouts the resistance would be if you move the flap.
>>>>> It
>>>>> just says" varying voltage", but no more. As I move it around I get
>>>>> fluctuations between 1100 and 1600 ohms, but it doesn't steadily
>>>>> increase in either one direction. While it idles, the potentiometer
>>>>> arm
>>>>> vibrates, when I open the throttle, it gets steady again.
>>>>>
>>>>> I'll keep you all posted on what happens, hopefully the new AFM
>>>>> will
>>>>> make a difference.
>>>>>
>>>>> Happy Trails
>>>>>
>>>>> matthias
>>>>>
>>>>
>>>
>>>
>>
>
yes.
I think I checked out pretty much all the bugs by now. TaTam. Even
swapped out the ECU.
Better be that $300 AFM I ordered next day air.
Cheers
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