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
>>
>>
>
>