engine missfiring

[sandylolee]

I have a 2003 turbo auto stick, 19,000 miles,airbox silencers removed, use a K & N. Same a started misfiring when engine is under a load (say just before it would change to passing gear). Dealer has changed plugs and one wire number 3 I think?.
When same starts to miss if you use auto stick and go to 3rd no miss, if you travel at 70 or above no miss. if you accelerate through say 55 to 65 no miss does anybody know what could be wrong[:I]

[skylight]

TSB# 18-029-03
Date: August 8, 2003
SUBJECT: Slight Engine Mis-Fire Above 5200 rpm

OVERVIEW: This bulletin involves replacing the Powertrain Control Module (PCM).

MODELS: 2003 (PT) Chrysler PT Cruiser

NOTE: This bulletin applies to vehicles built prior to January 22, 2003 (MDH0122xx) equipped with a 2.4L Turbo engine and manual transmission or prior to March 18, 2003 (MDH 0318xx) for vehicles equipped with a 2.4L Turbo engine and automatic transmission.

SYMPTOM/CONDITION: Vehicle operator may describe a random or slight engine mis-fire when operating vehicle above 5200 rpm. There will be no DTC logged in the PCM. If there are DTC’s present additional diagnosis should be done to determine the problem. This condition is caused by a internal hardware issue in the PCM.

[im4gzs]

I have an '03 GT autostick, too, with 18k miles, airbox silencers removed and a K&N, and I have a similar problem with misfire under load, but at much lower RPM than 5200 (say in the 2500-3500 range).

It's been that way from day 1. Haven't been to the dealer yet (can't bring myself to leave Zippy with something akin to a black hole (a.k.a. the service department) for a day...)

Zippy doesn't seem to miss at higher RPM, either, only the lower RPM, so I can't see how the TSB would apply. I haven't checked the sparkplugs for fouling or the wires for arcing yet...

[ZZCruzr]

I'm glad to hear I'm not alone...(not that I wish anyone problems, but misery loves company). I have never had a miss until last week. Filled up with Amoco 93 octane (I only run 93). Car was fine...has a little over 8K, running Mobile One with AMX cold air intake...manual tranny, stock injectors/computer/no boost added. Car misses bad, BELOW 5000 RPM - under acceleration. (Not WOT). Car missed so bad last night that it back fired! Going to reset the computer tomorrow morning and hope like hell it goes away. I can't help but think that I got a tank full of garbage gas. First EVER problem with my baby...DRAG!

[PianT]

If the TSB applies (as in, the dates match the car) have the dealer replace the PCM under warranty, they should do it no questions asked. Start from there, if you still have the trouble have them check further.

[sandylolee]

Jody:

Thanks for the info PT is at the dealer now will advise them of this info and see what happens will post results

[Jason_L]

back firing would be a timing issue... is it backfiring through the exhaust, or the intake? I'm thinking, if it's not the PCM, you're timing is being retarded to much. The turbo spools up really fast at partial throttle around 2500 rpm - the intake mods would make it even more so, and the PCM might be retarding the ignition to accomodate a potential lean condition. I'm not sure why this would only effect some cars though.. Have you tried putting the factory airbox back on and seeing if it still has problems?
I'd brainstorm some, try to figure out what scenerios would trigger the pcm to retard the timing.. I'm at work, but I'll think it out some when I get home tonight.

[ZZCruzr]

Jason_l thanks for the info. I was thinking timing also because of the backfire. I reset the computer today and cleaned the air filter. I haven't had a chance to drive it much since then...but it doesn't seem to be as bad. It is more a sputter now, in second around 2500 rpm. Going to work tommorrow, and I'll play with her at different speeds, throttle and see where I'm at. Probably have to go to the dealer next Monday.

[sandylolee]

got her back from the dealer they replaced a bad plug wire, all is fine for now[8)]

[Jason_L]

quote:Originally posted by sandylolee

got her back from the dealer they replaced a bad plug wire, all is fine for now[8)]

wish it were always an easy fix like that, eh?