Date:         Tue, 5 Nov 2002 09:17:35 -0800
Reply-To:     Doktor Tim <doktortim@ROCKISLAND.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Doktor Tim <doktortim@ROCKISLAND.COM>
Subject:      Re: hesitation, bogging, rough idle
Comments: To: James <tornadored@HOTPOP.COM>
In-Reply-To:  <B9ECCB70.B57%tornadored@hotpop.com>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 01:12 AM 11/05/2002, you wrote:

>The archives have been helpful in pointing me in the right direction, but I
>though I'd ask about my specific symptoms ('90 2.1L):
>
>Rough idle (occasionally will barely stay running when cold)
>Hesitation/loss of power/bogging under acceleration (sometimes need to back
>way off on the throttle to accelerate w/ out bogging)

In order not to waste money on guessing, verifications have to be made in a
distinct order. Mechanicals come first. Compression balance must be known.
One weak cylinder will fool the oxy control and all bets are off until
resolved. This may be only part of a synergy of issues which when all are
corrected will result in cure. If compression balance is off, do try
resetting the valves per Boston Bob's/Bentley's recent update. Then try
compression again.

I have recently seen a motor with 150/123/134/149, just within the min of
118 and 44 max difference. The system goes to hunting because the oxy is
reading only the combined exhaust of 1 poor cyl and 3 good ones. This feeds
false data to the ECU. Result, hunting idle and wide oxy swings
continuously adjusting mixture up and down up and down full rich to full
lean. Also, 3 cylinders running average lean and one cylinder just pumping
excessive hydrocarbons (poor combustion) most of the time but especially at
idle. At higher rpms the ratios are such that they do run along fine, but
at idle not too stable, when the whole of FI system is responding per specs
and not a single part there is the issue.

There are a number of other things that can add into the equation, but if
you skip the compression test by assumption you could well go on to throw
money at things not needed. Let us know the compression figures, then we
can go on to the next step of diagnosis. You must make the proper knowledge
available in the proper order to insure that all daemons are exorcised.