QuickdomesticRacer

iTrader: (4)

On cold start, until 180* the car noticably is misfiring, Its substantially low on power, even WOT and the SES light flashes.

More recently, the light continues to flash, and you can audibly hear the misfire still at 180*, but some of the power seems to come back.

I have taken it to a tuner to have it tuned, and he ran Diagnostics on it, and both of my o2s were giving seemingly accurate readings(he claimed everything seemed normal). My MAF, my injectors, etc all checked out also.


There are no vacuum leaks.

About 1.5 years ago, a slightly similar problem happened, where it would randomly misfire/run like crap, but it would only do it between 2,000, and 4,500RPM and go away on either side of that. Random Misfires was what the SES light said(but it never flashed), and replacing the o2s then fixed the problem.

Any suggestions on what to do here? The o2s in it, are BOSCH, purchased new a year ago.

lw.jordan

iTrader: (16)

I recently dealt with a problem having many of the same symptoms. Have you changed your spark plugs recently? Another possibility is fuel pressure.

twelver12

iTrader: (3)

a flashing SES light means there is a catalyst damaging misfire i would start by checking all ignition components plugs, wires, coils could even be a possibility. It seems here you have fuel pressure but no spark somewhere so you dumping unburnt fuel into your cats. If you leave it alone long enough you will be replacing your cats, and possibly O2 sensors also as they will be ruined from all the raw fuel which will coat the insides and render them useless. Try checking the temp of each of the exhaust outlets while the car is running, the misfiring cylinder should be running quite a bit cooler than the non misfiring cylinders. If you find it through this test then pull that plug and wire and check each, a DMM will help here for the wire, then obviously replace faulty parts.

QuickdomesticRacer

iTrader: (4)

I replaced the plugs w/ NGK TR6s about 6 months ago, before that they were in (TR6) for a 1.5yrs. When pulled out, the plugs still looked good, but I replaced them anyway.


Fuel Pressure... Hmm. I should have also said, it is temperature dependent. The colder it is (water temp and ambient) it seems to be worse.

JonCR96Z

iTrader: (33)

Not saying that it is your problem, but next time you buy o2s, buy ACdelcos. Bosch's have had problems with short lifespans

QuickdomesticRacer

iTrader: (4)

Really.. Ok. Thanks. I will be purchasing some this weekend.

CamaroSS22

iTrader: (1)

Which tuner did you take your car to? If its not the o2s then it is your tune. There are 4 random misfire tables that need to be adjusted for cammed cars to avoid this problem, one being in the middle rpm region. If he didnt adjust those then your shooting yourself in the foot. Check the o2s and let me know.

QuickdomesticRacer

iTrader: (4)

I will. thanks again for suggestions.

QuickdomesticRacer

iTrader: (4)

Replaced both o2s brand new. Didnt do a thing.

Does that temperature sensor that goes to the PCM effect misfire, if the unit is faulty and not sending the correct engine water temp sensor to the computer?

I will be checking plugs this weekend. Wires are also new/last year MSD 8.8MM. No damage to these at all.

How do you check the coils?

Mastif

Did you ever get the problem solved? If so, what was the culprit?

QuickdomesticRacer

iTrader: (4)

Somewhat. My #3 cylinder was slowly dieing. By the time we diagnosed the problem the coil wasnt firing at all. It was something to do w/ the coil wiring harness, and we got it to work again, but I believe I still have intermittent misfires, b/c my Knock Sensor low input light is on, and every once in awhile, I can hear a very slight sputter. I also thought I still had low RPM misfire, but I will associate that to slight cam surge.

I still dont know how to check to see if the coil is actually in a proper efficiency range.