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Date:         Wed, 2 Jan 2002 22:55:44 -0600
Reply-To:     John Clavin <jc@AUSTIN.RR.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         John Clavin <jc@AUSTIN.RR.COM>
Subject:      Engine Cutout
In-Reply-To:  <200201022050.g02KoCll011338@txmx01.mgw.rr.com>
Content-Type: text/plain; charset="us-ascii"; format=flowed

After continuing to work the usual cures for my persistent problems with engine stumbling or hesitation, the problem has only gotten worse with my 1985 Vanagon during the past two months. The latest episodes, which now occur daily, involve the engine completely cutting out. The tach crashes *hard* to zero and the engine is *dead*, only to mysteriously revive a good one or two seconds later. Here is the status of my anti-stumbling efforts to date:

AFM - reconditioned unit just installed (did wonders for overall driveability, eliminated surging, and smoothed out the idle - but no effect on the cutout problem)

Throttle Plate Switch - installed new cam, adjusted correctly, switch tested ok

Temp Sensors - resistance measures within limits per Bentley

Idle Stabilizer - new, but bypassing it seems not to make any difference with respect to the cutout and stumbling problem (in fact, with the new AFM, the van runs just as good without this thing, so I have left it bypassed)

Ignition Coil - resistance checks ok per Bentley (are there other tests?)

Hall Control Unit and Sender - pass all voltage and operating tests per Bentley

Cap & Rotor - good condition, relatively new, rotor ohms out ok

Plug wires - good condition, resistance ok per Bentley

Plugs - W7DTC, relatively new - replacing them did not help.

O2 sensor - relatively new, replacing it did not help.

CO screw setting - 1-3/4 turns from bottom (remanufactured AFM came set this way). Checked setting against O2 sensor readings and concluded after some adjusting that this was a good setting - O2 sensor readings oscillate, crossing over 0.5 volts, during "normal" warm idle.

Idle setting - who knows? Most of the time it idles 900-1100. but then some times it revs back and forth from 1000-1500+, other times it stays at 1500+ and only slowly comes down. I don't know how to set the idle adjust screw under these conditions.

Timing - running approx 3-5 deg ATDC (spec for '85 is 5 deg ATDC) - have experimented with settings from 5 deg BTDC to 5 deg ATDC, some differences in driveability but no setting seems to eliminate the cutout or stumbling.

Grounds - all grounds coming off the left side of the engine ohm out ok

ECU - visually inspected the circuit board - all solder joints look good, no signs of any overheating

Vacuum lines - all in good condition, all vacuum devices tested for leaks and checked out ok

Fuel pressure regulator - measured a few pounds higher than Bentley calls for (both with and without vacuum)

Fuel filter - will change it this week (but gut feel and past experience tells me this is not going to make a difference)

After doing some lengthy searches on the archives (again!), it appears there are lots of reasons for stumbling, but some people who have had the severe engine cutout as I described ultimately traced it to a bad ECU or Hall Sender. Is this true? Anyone have a different experience? Anyway, I am concentrating my next efforts on these plus the cabling and &$#*& plug on the distributor that connects the Hall Sender. Other opinions, suggestions, and guesses are eagerly solicited. I am getting desperate -- at this point I am even willing to replace the front bumper if there is the slightest chance it could help. However, funds and patience are becoming exhausted.

Are there any other tests (besides Bentley) to perform on the Hall Sender? Can this thing become intermittent and still test good per Bentley? Any ideas regarding the likelihood of it being the Hall Sender vs. the ECU? Is there a kind soul out there in the Central Texas area with a known, good ECU spare I could borrow for substitution testing with mine?

I don't deserve this... really. I still have the original German air in my Continental spare! I need my life and my van back. Help...

John Clavin 1985 Vanagon GL Austin, TX


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