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

Reply to
Howdy
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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?

Reply to
TNKEV

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.

Reply to
Howdy

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')

Howdy wrote:

Reply to
Bill Putney

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.

Reply to
David

Reply to
mic canic

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?

Reply to
Howdy

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

Reply to
maxpower
[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

Reply to
Howdy

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

Reply to
maxpower
[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

Reply to
Howdy

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.

Reply to
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

Reply to
maxpower
[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!!!!!

Reply to
Phil

Reply to
tim bur

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?

Reply to
Phil

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

Bob

Reply to
Bob Shuman

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?

Reply to
Phil

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...

Reply to
Phil

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