THat's right. Damn near forgot I had the same thing happen to my 93 I had.
Engine would act nuts and the tach would go crazy too.
LArry
"Denny" > wrote in message
...
> This kind of reminds me of a weird one I had a few years ago. Intermit no
> power, pops back thru intake, didn't run worth a **** at part throttle and
> may even die at times. No codes were present. Finally caught it acting up
> and it was the crank position sensor. Never came back for that problem
> after replacing it.
>
> Denny
>
> "maxpower" > wrote in message
> ...
>> its an intermittent secondary misfire, plugs/wires/coil
>> "Ted Mittelstaedt" > wrote in message
>> ...
>>>
>>> "Janne S Sweden" > wrote in message
>>> om...
>>> > Today i discovered that i by pressing the throttle several times could
>>> > get the car to accelerate fully without bacfiring in the aircleaner.
>>> > It worked fine several times. If i press the trottle only one time it
>>> > still backfires.
>>> >
>>> > Does that help anyone to get a bright solution to my problem???.
>>> > Janne S
>>>
>>> Hey Janne,
>>>
>>> What you have described so far isn't possible. Here's what I'm
>>> hearing
>>> you say:
>>>
>>> 1) Backfiring at part throttle, not full throttle.
>>>
>>> 2) Ignition system completely checked out with a friend's scope and
>>> timing
>>> is correct and all parts of ignition system have been replaced
>>>
>>> 3) Car completely within emissions.
>>>
>>> In short, this isn't possible.
>>>
>>> So, let's go back to the beginning and s tartover.
>>>
>>> If this was a spark plug/secondary ignition problem (bad coil, crossed
>>> wires, etc.) then
>>> the misfiring/backfiring would get worse the higher the rpm.
>>>
>>> If this was a spark primary ignition problem (ie: timing) then the
>>> friend
>>> and his scope would have caught it.
>>>
>>> If this was a restricted fuel filter or bad fuel pump then the higher
>>> the
>>> rpm the
>>> worse the problem.
>>>
>>> If this was a compression problem it wouldn't be backfiring.
>>>
>>> If this was a fuel problem then the emissions would be out of wack.
>>>
>>> So I have to conclude that your testing methodology is flawed. If you
>>> are
>>> absolutely
>>> positively positive that the timing is perfect and the ignition system
>>> is
>>> perfect - which means your friend and his scope tested it out
>>> correctly -
>>> then the problem is in the fuel system,
>>> specifically the engine is running too lean - which means that the HC
>> would
>>> be high and
>>> the CO way low - which means the emissions would be off.
>>>
>>> In short, you cannot have it both ways. You cannot have a perfect
>> emissions
>>> report
>>> AND a perfect checkout with your friend and his scope, and still have
>>> this
>>> problem.
>>> One of them has to be wrong.
>>>
>>> Off the cuff the most likely candidate is bad timing at part throttle,
>>> OR
>>> too lean
>>> condition at part throttle. However both the timing and the mixture are
>>> computer
>>> controlled. There is an old saying with computers, garbage-in,
>> garbage-out.
>>> I think
>>> the likeliest problem here is you have one or more bad sensors feeding
>> into
>>> the computer.
>>>
>>> The fact as you say that sometimes it runs fine is even more an
>>> indication
>>> that it's
>>> a sensor-to-computer problem. Maybe a bad sensor that with the
>>> vibration
>>> occasionally "heals"
>>>
>>> Some would say that if it's a bad sensor that the computer would set a
>> code.
>>> Well I
>>> have a '95 T&C with a 3.8 and when I bought it 3 years ago used, the EGR
>>> valve was
>>> shot, and the van wouldn't pass emissions, and there was NO CODE set.
>>> PERIOD.
>>> Replacing the EGR valve dropped the NoX down and it passed emissions.
>>> So
>>> don't
>>> argue with me and tell me that the computer in these things is smart
>> enough
>>> to detect
>>> if a sensor is shot. I know from experience this is just wishful
>> thinking.
>>> Sometimes
>>> sensors will fail in such a way that the computer cannot figure out that
>>> they are bad.
>>> For example, your TPS could have worn out the middle of it's slide and
>>> the
>>> computer
>>> not know where the throttle is, fuel mix is going to be wrong, then.
>>> Car
>>> computers
>>> are notorious for saying one part is bad when it's another part
>>> entirely.
>>>
>>> You say you have already shotgun the ignition system components. Well
>> fine,
>>> great,
>>> quite replacing them. Or better yet keep replacing them and send me
>>> your
>>> old ones
>>> because they aren't broken.
>>>
>>> It's time you put a scan tool on this vehicle, or pay someone to do it.
>> If
>>> you really want
>>> to do it yourself, you can buy an OTC Monitor 4000E off Ebay pretty
>>> cheap
>>> that will do this. You need to scan it and run the engine and make sure
>>> your actually getting
>>> valid inputs from all the sensors. You need to check timing with a
>>> timing
>>> light - yes I
>>> know the factory manual says timing is non-adjustable, but a timing
>>> light
>>> and degree wheel on the crank still work. The cam chain could have
>>> jumped
>> a
>>> tooth and that is going to
>>> shift timing out of wack. You need to put a fuel pressure guage on the
>> fuel
>>> rail and test that. In short, you are past the stage of being able to
>>> fix
>>> it with a $39.99 on-sale Sears Craftsman wrench set, a Haynes manual,
>>> and
>> a
>>> bucket of miscellaneous screwdrivers. You are either going to have to
>>> go
>>> out and buy the tools (and documentation, like the Factory Service
>>> Manaul)
>>> to troubleshoot it properly or pay someone who has the tools to do it
>>> correctly.
>>>
>>> Ted
>>>
>>>
>>
>>
>
>