Re: 1255 code on 164LS & rough idle

["Colin Verrilli" <verrilli@domain.elided>]

Here's an update on this problem.
It seems that the 500 ohm reading on the cam sensor is OK. The manual is
wrong.
The 1255 code was stored and when cleared, it did not re-appear.
But the rough idle still remained...
I decided to check the timing. Following the manual, this involves
removing
the air intake box, intake runners, coil covers, 6 coils, cam covers,
timing
belt covers (the engine has to be tilted to access these). After about 2
1/2
hours of removing stuff, I discovered that one of the right hand cams
had
slipped one tooth. The timing belt also appeared loose. I spend another
1 1/2
hours pulling off the accessory belt, 6 pulleys, 2 tensioners, the PS
bracket
and finally the timing belt. During this process, I discovered that the
timing
belt tensioner would not retract. I removed it and tried to push in on
the
plunger on the workbench and still couldn't get it to retract. I assume
that
the plunger should go in fairly easily (at least with a vise!). Can
anyone
confirm this?
Anyway, I plan to order a new tensioner, put on a new belt and spend a
few
hours putting the whole thing back together. I think I must have about a
hundred bolts that need to find their homes!

Colin Verrilli wrote:
>
> My 164LS has a very rough idle. Before I investigate a skipped timing belt,
> I want to eliminate other possibilities. The check-engine readout says 1255
> which is a bad cam position sensor. The shop manual says that to diagnose this
> you should check for 1.5V at pin 2. If that fails, then check for 20ohms between
> pins 1 and 2. If this fails, replace the sensor. When I checked these, I found
> ..15V at pin 2 (when connected) and 550 ohms resistance between pins 1 & 2.
>
> Before I spend $120 on a new sensor, does anyone have any experience diagnosing
> a 1255 - cam sensor? Is this a valid test?
> - --
> Colin Verrilli           <verrilli@domain.elided>        IBM Raleigh, NC
>
> ------------------------------

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