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Date:         Sat, 17 May 2008 12:56:22 -0400
Reply-To:     pickle vanagon <greenvanagon@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         pickle vanagon <greenvanagon@GMAIL.COM>
Subject:      Re: hesitation/bucking (was: Re: tested Oxygen Sensor, and...)
In-Reply-To:  <001701c8b7e8$a8f2a8b0$6401a8c0@DJZL7KF1>
Content-Type: text/plain; charset=ISO-8859-1

Thanks again for the replies! I'm going to go out and check my air flow meter and throttle switch resistances according to bentley.

I've seen some older posts about problems with the AFM that were fixed by wiring in a resistor (or by using the VW repair harness). Does this apply to 1.9's as well, and if so, how would I found out whether or not I had that problem? It seems to me that most people with that issue had much more severe symptoms. I've never had really bad bucking, or cutting out. I just have this very occasional, very slight, forward backward surging/hesitation, when driving at low constant speeds.

Any other suggestions are welcome!

Thanks again, Wes

On Sat, May 17, 2008 at 2:38 AM, Scott Daniel - Shazam < scottdaniel@turbovans.com> wrote:

> > Just make sure the engine is up to full operating temp - your t-stat makes > it run fully up to temp, right ? > Rev it a time or too........ > It'll be warm enough. > At this time of the year it is completely unlikely that it won't be warm > enough to produce a good output. . > > I see, it's new. > Bosch ? > You had it connect into the circuit during your measurements, yes ? > And .4 to .7 volts is not bad. > It's what a working one looks like. > > Air Flow Meter - can cause uneven running, very easily. > Regarding idle speed - > There's nothing that can be hurt by turning the big screw out on the > throttle body to increase idle speed. > It's not a mixture screw or anything critical. > You've checked that the idle switch is making contact, and at about the > right time ? see Bentley > Nobody - evidently - every checks those and they get off slightly over > time. > > Except for smog check reasons, the idle just has to be 'nice.' > Slightly higher keeps oil pressure up, and coolant circulating better. > You do not say if manual trans or auto and idle is a factor there. > > Yes, my list of things to check does run 30 to 50 items. > One of these days I'll list all the things I check in about 5 systems that > affect engine running. > Not a 'how to' but a 'what to check' list. > Takes me a long time to get 'em just right sometimes. > But I'll tell you this...........when a manual trans equipped 1.9 > waterboxer > engine is REALLY right - they just rip ! > > As for just running really nicely.........and CO. > Yes, officially it must be set to the correct CO reading, measured before > the cat - as per Bentley. > > If smog check is a factor, yes, needs to be right. > Otherwise.........you can fake it a bit on that one, heresy though some may > think that is. Mixture screw at AFM affects only idle mixture. > Remove the anti-tamper plug. Leave it out. Turn it with a 5 mm allen screw. > The effect is minimal. > > Oh yes, as I said, gutted cat can not really run right. Either good cat or > straight pipe to replace it. > > Once running down the road, mixture control is all ECU from inputs, and > oxygen sensor. > I actually can get 1.9's to run better and smoother than 2.1's > Takes me a bit though ! > And AFM...........there is no test for a weak or dead spot or uneven AFM > other than a known good unit, or a new or rebuilt one. > > I just ran 5 AFM's back to back on a fresh valve job 1.9 ........they were > all dodgy or weak or ........UNEVEN - especially 'uneven' in how they ran > and accelerated, except one of them. > They all ran, but only one was really even and smooth. > I'm saving that one for myself or for a good test unit. > > Where electrons and mechanical movement meet - that's a fundamentally weak > and challenged spot - as in the sweeper contacts in the AFM. > > The AFM is so crude compared to good modern systems - it's like a lawn > mower > engine part. > Scott > www.turbovans.com > > > > -----Original Message----- > From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of > pickle vanagon > Sent: Friday, May 16, 2008 10:48 PM > To: vanagon@GERRY.VANAGON.COM > Subject: hesitation/bucking (was: Re: tested Oxygen Sensor, and...) > > Thanks for all of the responses, guys. > > I think maybe the first time I hadn't let the van heat up enough. (The > engine was already warm, but maybe I didn't actually let the sensor heat up > enough?) > > When I measured again, I did get fluctuation, but the swing wasn't as large > as .5volts. I'd say ut swung between around .4 and .7. I guess its > possible that there was actually a greater swing than was showing up on my > digital voltmeter. I should mention: the oxygen sensor is only about 4000 > miles old. > > Anyways, the reason I was checking the oxygen sensor voltage in the first > place, is that I've noticed recently (since my head job...) that the van > occasionally exhibits some slight hesitation symptoms when driving at a > constant speed (usually low speed, so low load). The van surges slightly > forward and back, maybe at a rate of once per second or so, kind of like > very minor bucking. It only has happened occasionally, so I can't say for > sure when it seems to happen the most. But it has never happened when > accelerating or otherwise when under load, and it has never caused any > problems idling. It idles very smoothly, although it seems to me that it's > idling at lower rpms than before. Of course I don't have a tach so I can't > say for sure. > > What should I look for with these symptoms? The only things I've done are: > looked around for any obvious vacuum leaks, checked the oxygen sensor as > above, rechecked my valve adjustment, checked my Temp 2 sensor, and > replaced > the engine compartment ground strap (the one that goes to the head). I'm > guessing that with a problem like this, there's a list of 50 things to > check. > > I guess I should really be checking the mixture properly in a situation > like > this, but I don't have an co meter or anything for the exhaust. > > Thanks for any pointers, > Wes > 1.9l westy > > On Fri, May 16, 2008 at 11:25 PM, Dennis Haynes <d23haynes57@hotmail.com> > wrote: > > > A steady reading of .5 to .6 volt is a sign of an open sensor or one that > > has not heated up enough to function. The voltage is due to the leakage > at > > the ECU input. Measure the voltage at the sensor lead with it > disconnected > > to see if you are really getting a signal. > > > > Dennis > > > > > > -----Original Message----- > > From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf > Of > > pickle vanagon > > Sent: Friday, May 16, 2008 5:53 PM > > To: vanagon@GERRY.VANAGON.COM > > Subject: tested Oxygen Sensor, and... > > > > Just for fun, I decided to go out and "test" my oxygen sensor today, by > > which I mean I warmed up the car, and then checked the voltage coming off > > the sensor wire with the van at idle. I got readings of around .52 > volts, > > which maybe seems okay (?), but the voltage was steady, not oscillating > > (it > > stayed between .51 and .53 volts always). Does this mean my engine is > > never > > entering closed loop operation? If so, what are the standard things to > > check, since the O2 sensor seems okay? > > > > Thanks, > > Wes > > > > > -- > No virus found in this incoming message. > Checked by AVG. > Version: 7.5.524 / Virus Database: 269.23.16/1446 - Release Date: 5/16/2008 > 7:42 AM > > >


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