"Howdy" > wrote in message
...
> Hey All!
>
> Kind of a long story here so I'll try to shorten it up as much as
> possible... sorry if I miss a crucial detail... just ask if you need
> more info...
>
> 1999 Chrysler Sebring Jx Convertible - 2.5L V6 with 102,000 miles. I
> bought the car used at 65,000 miles for my teenaged daughter.
>
> When purchased the car got around 17 mpg. I had a tune-up and the fuel
> injectors cleaned and mileage went up to 24 mpg.
>
> Mileage stayed stable for awhile then started dropping around 95,000
> miles. I had another tune-up with plug wires replaced (this past
> January). Car ran fine but at only about 21 mpg.
>
> In April the engine started missing horribly and I took it to a new
> shop (I had moved from Fort Lauderdale to Atlanta, car was trailered
> up). New mechanics said the wrong plugs were put in and the plug wires
> were oil soaked and needed replaced. I did new plugs, wires plus a new
> distributor cap and rotor button (another $450).
>
> Car ran great for about a week and then started missing again, I took
> it back to the shop and they found a defective plug, replaced it and
> the car was running good again.
>
> Now, three weeks later the car is missing horribly, backfiring
> especially at low rpm's. I took it back to the shop and they said the
> plugs, wires etc. are fine but that the oil is not draining from the
> heads back to the oil pan and the hydraulic lifters are not
> functioning properly so the valves are not opening and closing when
> they should and this is causing the engine to backfire and miss and
> that I need to have the heads reworked. (I'm no genus but this sounds
> like utter BS to me.)
>
> I believe the car has always had a barely perceptible miss... at idle
> you can watch the rpm guage jump (and not just when the fan comes on).
> Mechanics who've hooked the car up to a scope tell me I'm nuts.
>
> There is no check engine warning light. The one time it came on it
> was reset when the mechanics in Atlanta replaced the plugs and wires.
> It has not come on since. (I have run the diagnostic on the
> instrument panel and the check engine light (all lights for that
> matter) works great.
>
> This problem does not occur when the engine is cold. After the engine
> warms up however its very noticible on acceleration and when the RPMs
> is under 2000. At 50 mph, and 1800 rpms up a slight hill with no a/c
> you'd think you had a transmission problem the way the car jerks and
> lunges. Dropping the gear down or accelerating and the missing and
> backfiring goes away... once the ride stabilizes out to crusing speed
> (70 mph) you can feel the missing again but you can't detect (hear)
> any backfiring.
>
> So, now I have a car who's engine misses so much its hardly driveable,
> new plugs, wires, cap and rotor.
>
> Suggestions?
>
> Phil
>
Well first of all you need to find out what cylinder is causing the problem,
it sounds as if the adaptive numerator needs to be relearned in order for
the engine controller to determine what cylinder is causing the problem.
Take vehicle on a test drive and get it up to operating temperature, in
second gear go about 40 mph and then let go of the accelerator pedal and
let the vehicle coast down to about 25mph. This will cause the computer to
learn the crankshaft values and be able to set a fault code for which
cylinder is misfiring.

Glenn Beasley
Chrysler Tech