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Date:         Mon, 9 Feb 2009 20:38:54 -0800
Reply-To:     Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Subject:      Re: Bucking, hesitation between 1500 and 2500 RPM when hot
Comments: To: Jerry <jbvelo@bellsouth.net>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
              reply-type=original

hi Jerry, by now you've probably seen Mark's post on this shielded wire thing. It's quite informative.

I would add..........fwiw........that shields .....like an outer braided covering, should only be grounded on one end ...... according to various electrical guru's........so don't ground the end near the plug connector..... it should be properly grounded in the ECU, and then to the engine block.

you can check that with an ohm meter, and also that the signal wire is not shorted or connected to the shield somehow.

the reason for any shield around any signal wire is to ground out any electrical interference from nearby sources ......... without shielding it might be possible for outside electrical RF to contaiminate the signal .

on engines like subaru's, for example.........lthe cam and crankshaft position sensors have shielded signal wires. Any time the signal is a small current ...........shielding is normal, and needed.

the oxygen sensor system needs to be considered of course. I have suspect that's nor where your problem is. one traditional test is to oerpate it with the oxygen sensor disconnnected. if it runs better then........that would make me think that the oxygen sensor circuit or the sensor itself might be 'the problem' or part of the problem. my standard rule is 'check the basics' ........ even if you have to start over 'checking the basics' 5 times, or 10. I start with compression, then move on to vacuum leaks. I check fuel pressure of course. No one that I've ever heard of considers the fuel itself.....but I find water in the fuel tanks of vanagons, once in a great while, particularily in the winter. Water in the fuel can cause very intermittant weirdness........not that I think that's what you have going on ......but the fuel itself must be considered in all cases of not running correctly. Same is true for cat and muffler........though I doubt you hvae anything going on there , so far.

I have seen plug wires cause real weirdness. I don't think you have that going on especially either ......but plug wires can be an issue that's not readily apparent. And you can't check enough about Air Leaks. I had a 2.1 waterboxer engine that just wouldn't rev out much ........ like you could tell it was taking in air with open throttle..............but the matching amount of fuel wasn't being added to that air. I finally found about a dozen tiny leaks in the whole intake system , and that was 'the problem' . Cracked air boot..........gotta always watch for that , but unlikley on a 2.1.

'It's just a blockage or leakage of fluids or electrons." ( fluids include gases like air and vaccuum, not just liquids. ) but that's all it is ............one, or more than one.........'blockage or leakage of fluids or electrons.' I promise. scott www.turbovans.com

----- Original Message ----- From: "Jerry" <jbvelo@bellsouth.net> To: "Scott Daniel - Turbovans" <scottdaniel@turbovans.com> Cc: <vanagon@gerry.vanagon.com> Sent: Monday, February 09, 2009 7:09 PM Subject: Re: Bucking, hesitation between 1500 and 2500 RPM when hot

> Thanks for the reply Scott. > > I have replaced and tested the Temp II sensor. > I have also adjusted the TPS per the Bentley. > > My green wire to the ECU is not shielded. > How does the shield connect to the ECU? > What effect does not having a shielded green wire > have?? > > I installed the Boston engine. > I cleaned and replaced all the grounds > during installation. I know that the > brown ground wire to the left head is good. > I also installed a new ground cable from > the left head to the left side under the coil. > > Could this new ground be causing a problem > with my 02 ground circuit? They are grounded > at the same point on the left head. > > At this point I'm just guessing. > > > JB 88 GL > > > On 2/9/09 6:56 PM, "Scott Daniel - Turbovans" <scottdaniel@turbovans.com> > wrote: > >> some of my thoughts....... >> you might be getting a slew of emails suggesting your temp sensor >> ........Temp Sensor II ........the one at the thermostat >> housing.......it's >> a critical input to the ECU. >> >> throttle switches are often off........you should at least check that. >> Pretty easy to do. >> >> on your oxygen sensor comments..... >> the green wire goes to the ecu, and is the input to the ecu. >> it's shielded.......and that shield connects to the ECU.........and to a >> ground wire there........that goes back to the engine block. >> The body of the oxygen sensor is grounded to the exhaust system >> ...........as shown by current track 25. >> you should be looking at page 97.89. >> >> looking at my 86 I see the brown ground wire disappears into the main >> harness and it's not easy to tell where it grounds. >> you could just unplug the connector plug and use an ohmmeter to check >> continuity and resistance to ground. >> if it tests OK that way, it probably is all right. >> you could also just add your own ground for that wire if you needed to. >> >> the white wire is power, for oxygen sensor heat, from the main relay. >> that wire should have power on it any time the key is on I >> think.........and >> certainly any time the engine running. >> >> oxygen sensor heat is not absolutely critical to making the engine run, >> or >> run right. Of course you want that system working....... >> but not likely that lack of oxygen sensor heat is keeping your van from >> running properly. >> >> I do read of, from time to time, a shorted out oxygen signal in the >> oxygen >> sensor sometimes, but have never seen that myself......and sort of 'don't >> believe in it.' >> >> oh.....in general..........you should just undo, clean, and tighten all >> the >> Ground Wires by the coil, on the left side of the engine compartment, and >> on >> the engine block, left side, especially that one - I see them quite >> corroded >> all the time. I recommend a general WD-40 spray down , moderately, of >> any >> engine that's showing signs of corrosion. Just don't spray it inside the >> alternator......but everywhere else is good. >> >> that many new parts makes me nervous. >> a part being new is not an automatic guarantee that it's good........or >> that >> it was installed correctly either. >> >> I don't know who installed your new engine ....... >> but I commonly find a few workmanship errors on waterboxer engine >> installations. You'd think anything related this way would do it from >> the >> beginning though. >> Scott >> www.turbovans.com >> >> >> >> >> >> >> >> ----- Original Message ----- >> From: "Jerry" <jbvelo@BELLSOUTH.NET> >> To: <vanagon@GERRY.VANAGON.COM> >> Sent: Monday, February 09, 2009 3:49 PM >> Subject: Bucking, hesitation between 1500 and 2500 RPM when hot >> >> >>> I hope for some much needed advice on this problem. >>> >>> I have an 88GL which actually meets the electrical >>> specs of an 87 by looking at the Bentley wiring diagram. >>> >>> My problem is this: >>> When the engine is cold it seems to run fine. >>> At highway speeds all is well until the engine >>> reaches operating temperature. After the engine >>> reaches operating temperature it begins bucking >>> during upshifts and throttle speed increase. When >>> I push on the throttle to increase speed there is >>> a significant hesitation. The engine speed will >>> finally increase to meet the fuel demand and throttle >>> response. Engine speed above 2500 seems ok. Throttle >>> increase above 2800 RPM seems normal(no hesitation). >>> >>> I am thinking this is an Oxygen Sensor GROUND problem >>> but am not sure. I have read all the posts concerning >>> oxygen sensor grounds and I have questions. >>> >>> Where does the oxygen sensor ground(green wire)? >>> Does it go to ground at the #29 chassis ground by the ECU? >>> >>> I have a three wire oxygen sensor. Where does the brown >>> wire ground from the oxygen sensor(chassis harness). The Bentley >>> indicates >>> a ground at #12 ground in engine compartment(left). The brown wire >>> on my 2.1 02 sensor goes into the engine compartment harness which >>> runs along the front of the engine deck. I cant tell >>> that the brown wire goes to ground from the 02 sensor. >>> >>> I have cleaned and reinstalled all grounds, however >>> I combined some of the grounds at two locations on >>> the left engine firewall. >>> >>> I have a 2.1 Boston Engine installed in MAR 2008 >>> New AFM >>> New Idle Control Unit >>> New 02 sensor >>> New Distributor and Hall sensor >>> New ECU >>> New Evaporative control canister >>> >>> This problem has got me down! >>> As you can tell I've replaced just about all components. >>> I also have the harness installed between the AFM >>> and original chassis harness. >>> >>> Thanks for any advice. >>> >>> JB 88 GL Guido >>> New spark plugs, cap, rotor and wires >>> New fuel injectors and fuel lines >>> New fuel pressure regulator >> > >


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