91' tech acting up

I am hoping someone give me a starting point on tracking down an
intermittent tech problem on my 91' 2.3L Stang. Unfortunately the motor I
have is not included in the Haynes manual I picked up years ago and they
never followed through on sending me the latest additions to the manual. I
have the 2.3L with 8 spark plugs (electronic ignition - 2 coil packs). Any
idea where I should start my search.

Thank you in advance

"Slightly Graying Wolf" >
wrote in newsJxLe.213425$s54.7002@pd7tw2no:

> I am hoping someone give me a starting point on tracking down an
> intermittent tech problem on my 91' 2.3L Stang. Unfortunately the
> motor I have is not included in the Haynes manual I picked up years
> ago and they never followed through on sending me the latest additions
> to the manual. I have the 2.3L with 8 spark plugs (electronic ignition
> - 2 coil packs). Any idea where I should start my search.
>
> Thank you in advance
>
>
>
>

what kind of problem..

if you mean "TACH", then I assume it's the problem where the needle
intermitently goes to about 3 grand or a little more then varies a little
with the engine speed then it's in the tach head itself.

I suspect it's a component (probably internal voltage reg) and it isnt
really fixable... just head to the salvage yard and get a new cluster, then
replace the tach part.

Backyard Mechanic wrote:
> "Slightly Graying Wolf" >
> wrote in newsJxLe.213425$s54.7002@pd7tw2no:
>
>> I am hoping someone give me a starting point on tracking down an
>> intermittent tech problem on my 91' 2.3L Stang. Unfortunately the
>> motor I have is not included in the Haynes manual I picked up years
>> ago and they never followed through on sending me the latest
>> additions to the manual. I have the 2.3L with 8 spark plugs
>> (electronic ignition - 2 coil packs). Any idea where I should start
>> my search.
>>
>> Thank you in advance
>>
>>
>>
>>
>
> what kind of problem..
>
> if you mean "TACH", then I assume it's the problem where the needle
> intermitently goes to about 3 grand or a little more then varies a
> little with the engine speed then it's in the tach head itself.
>
> I suspect it's a component (probably internal voltage reg) and it isnt
> really fixable... just head to the salvage yard and get a new
> cluster, then replace the tach part.

No, sorry I should have specified (and yes I meant tach) the tach drops to
zero while driving or idling for short periods of time - then the check
engine light comes on (presumably because the computer needs to know the
RPMs) as soon as the tach jumps up to the correct RPM the check engine light
goes out.

"Slightly Graying Wolf"

> No, sorry I should have specified (and yes I meant tach) the tach
> drops to zero while driving or idling for short periods of time - then
> the check engine light comes on (presumably because the computer needs
> to know the RPMs) as soon as the tach jumps up to the correct RPM the
> check engine light goes out.
>
>
>

Okay... that's a WHOLE lot different. Does the engine idle quality change?


I think the problems have common source and it shouldnt be in the tach, It
would be in Crank/cam position sensor.. or in the DIS module itself.

It would be very poor engineering for the PCM to look at the tach
Since the CEL comes on, hie thee to autozone to have the codes read out.
Make them give you the code numbers, not just the definitions, and do a
google on the codes and post them here.

Backyard Mechanic wrote:
> "Slightly Graying Wolf"
>
>> No, sorry I should have specified (and yes I meant tach) the tach
>> drops to zero while driving or idling for short periods of time -
>> then the check engine light comes on (presumably because the
>> computer needs to know the RPMs) as soon as the tach jumps up to the
>> correct RPM the check engine light goes out.
>>
>>
>>
>
> Okay... that's a WHOLE lot different. Does the engine idle quality
> change?
>
>
> I think the problems have common source and it shouldnt be in the
> tach, It would be in Crank/cam position sensor.. or in the DIS
> module itself.
>
> It would be very poor engineering for the PCM to look at the tach
> Since the CEL comes on, hie thee to autozone to have the codes read
> out. Make them give you the code numbers, not just the definitions,
> and do a google on the codes and post them here.

Idle quality/ engine performance does not change very noticeably (maybe a
tad hesitant on acceleration).

I will try to get the codes read next week - no AutoZone's around but I have
family friend who owns a garage - just a bit of a haul to get there.

Thanks for the help

Backyard Mechanic wrote:
> "Slightly Graying Wolf"
>
>> No, sorry I should have specified (and yes I meant tach) the tach
>> drops to zero while driving or idling for short periods of time -
>> then the check engine light comes on (presumably because the
>> computer needs to know the RPMs) as soon as the tach jumps up to the
>> correct RPM the check engine light goes out.
>>
>>
>>
>
> Okay... that's a WHOLE lot different. Does the engine idle quality
> change?
>
>
> I think the problems have common source and it shouldnt be in the
> tach, It would be in Crank/cam position sensor.. or in the DIS
> module itself.
>
> It would be very poor engineering for the PCM to look at the tach
> Since the CEL comes on, hie thee to autozone to have the codes read
> out. Make them give you the code numbers, not just the definitions,
> and do a google on the codes and post them here.

The code is #218 "No ignition monitor signal"

The problem did not happen on the way to work today so it made me wonder if
this could be a battery/ alternator problem as it usually happens at idle
under heavy load on the electrical system - A/C, radio, headlights (day time
running lights - Canada).

The guys ****ed around with it for an hour or so discounting anything I
said... charging system was 12.1 Volts under full load - Then it happened
with the tester on the battery (it dropped down to 11 volts) until I revved
the engine and the problem went away again (then the voltage returned to
12.1).

The mechanic then pulled the small plug off of the alternator and duplicated
the problem.

Looks like all I need is either a new battery or alternator (or both).