Engine misses & backfires

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

 

Sounds like the valve cover gaskets and spark plug tube seals need to be
replaced,did they suggest that you do that when they pulled oil soaked spark
plugs?

 

Yes and they did that too.

One thing I forgot to mention was that last week I let the car idle
for about 30 minutes and it started smoking very badly from the
exhaust (grey smoke). After driving the car for about 2 miles the
smoking cleared up and it has not smoked since.

I am not suffering any loss of oil or coolant. The coolant shows no
signs of a cracked or damanged head gasket nor does the oil show the
milky white that you see.

 

I think you've not found all the bad ignition parts they put in. Start
over, and get quality parts. There are some real crap aftermarket
electrical parts out there and some shops get whatever off-brand is on
the shelf.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
adddress with the letter 'x')

 

Same thing happened to my lincoln Continental. Gassed up. Turned on the car
heard a loud pop and headed home. Looked like the space shuttle with the two
white smoke trails from the back of the car. Got home opened the hood.
coolant level was fine. Next day started it no problems at all. The day
after the car overheated from lack off coolant. Blown headgasket. So you
might have one.

 

more than likely the dist. is failing

 

I was back to my shop with it and they could induce the miss by
"romping"on the accelerator from idle. It occured almost immediately.
'
This shop does not have an ODB-II diagnostic machine they simply have
a code reader... and since there are no codes to read this one is
difficult.

Again, they want to replace the heads but logically it just doesn't
make sense to me and I'm not one for playing "swap-the-part" until the
problem is found.

I was putting something in the trunk this morning and I noticed that
that the inside of the tailpipe is covered in black soot... which
would indicate to me a too-rich fuel mixture and that has me thinking
O2 sensors.

Any other thoughts?

 

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

 

[snip]

Glen,

Thanks! That got me a check engine light... is there any way to do a
manual PCM code check on a 1999 Sebring?

Phil

 

I would have all codes read by a scan tool along with all freeze frame
data., but take it to someone that is familiar with the vehicle

 

[snip]

Glen,

The code is P0305 (misfire on #5 cylinder). The garage said this is
the same cylinder that had problems before and "its because the oil is
just sitting down there because the heads are so plugged up the oil
can't be pumped away from the plugs and theres not enough pressure to
power the lifters". "You need to spend about $900 and have these
heads reworked to solve this problem".

Their argument for further proof is that when the engine is left
idling for 20 minutes or so it begins blowing clouds of grey smoke out
the tailpipe but when driven for a mile or so the smoke goes away.
They say thats an oil pressure issue and at high rpms the oil gets
pumped away from the lifters.

The absolute lack of logic in their argument has me seriously doubting
their diagnosis.

Your thoughts?

Phil

 

It is possible for the drain holes in the heads to get clogged up
causing the oil to collect in the valve cover area. I have only seen
this happen on very sludged up engines or some older GM stuff where
the rubber valve stem seals got brittle, broke and then got stuck in
the drain holes.

In any case you shouldn't need head work to cure an oil draining
problem. Take off the valve cover and check the drains. If they are
clogged clean them out. Very easy to see if this is really the
issue.

Steve B.

 

I have no idea what they are telling you, Only you know if the vehicle has
been maintained properly. sure if you don't change the oil and perform the
routine maintenance the heads could get stopped up and sludged up.
Do you smell strong odors of fuel when this happens? With out looking at the
adaptive fuel memory on the scan tool it would be hard to tell what is
actually going on. Have you taken this vehicle to a dealer with a good
reputation or another independent shop that knows the system? Because what
they are telling you doesn't make any sense to me

 

[snip]

I my shop read the codes from the PCM and it was a P0305. I replaced
all the plugs, checked the plug wires, rotor and distributor cap and
everything was fine...

Problem is, it still misses and backfires!!!

ARGGGHHHHH!!!!!

 

wrong plug wires or a failing dist.

 

Three more questions:

Does anyone know where I can "borrow" a code reader? I'm unemployed
and a single dad and I can't afford to take this thing to a shop (and
I'm in north Atlanta).

Second, what is the sensor which is located on the upper intake
manifold just in front of the MAP sensor?

Tim bur suggested that I replace the plugwires, this is the second
set... also suggested I replace the distributor... how do I check out
the distributor to see if its faulty?

 

Autozone reads engine codes from OBD-II equipped vehicles for free.

Bob

 

AutoZone read the PCM codes... came up with two more than my FORMER
garage. The three codes are:

P0113 - Input from the Intake Air Tempurature sensor is higher than
expected

P0108 - Input from the MAP sensor is higher than expected for the
current engine operating conditions.

P0305 - miss on cylinder 5.

The autozone guy said it sounded like a short was causing the IAT &
MAP sensors to misbehave.

How can I test the MAP and IAT circuits?

 

Doesn't make sense... otherwise why would the engine run fine at high
RPMs or when the engine is cold?

See the other posting on the new codes...