99 Malibu 2.4 Ignition Troubles

[jlm2664]

My son has a '99 Malibu 2.4, automatic with 131K on it. I've read all the posts but believe I need some additional help. Stated out with a clogged catalytic converter, had that replaced last week. Problems continued, car will idle rough and as soon as it's put into drive, it dies. I pulled the codes, only one, P0300, multiple cylinder misfire. Here's what I have done since: Replaced both coil packs, new plugs (AC) and gapped correctly and new plug boots and springs. New air filter, new fuel filter and also tested the fuel pump pressure, 41 lbs, so that should also be ok. After all of this, cleared the codes and computer and after the car runs for about 2 minutes, CEL comes on, check then codes again, same one P0300. Cannot rev the engine over 4000 rpm, just wont, starts sputtering and once it drops back to idle, it dies. Will start right back up. I've even replaced the rubber connection hose between the throttle body and the resonator (part of the air cleaner assembly), throttle body is clean. Engine oil is clean, no water in it and gas is good. Can anyone point me to another direction with this one, I'm generally pretty good with this sort of thing but right now I'm stumped. Thanks for any help in advance.

[Speedy_1234]

What About the wiring are you putting the right way one-withone two-with two 3-with three and 4- with four

[jlm2664]

It's a 2.4, does not have plug wires, plugs have a boot that connects to the coil packs, no way to miswire them.

[taillight]

Get a scan tool with live data and read the long term and short term fuel trim, O2 sensors, MAP,MAF and coolent temp. Also get a fuel pressure guage and read the pressure. From that someone might be able to tell.

[jlm2664]

Thanks for the replies, guess I wasn't clear about how I tested. I have already checked the fuel pressure with a gauge, bought one last year when I was having a issue with another vehicle, I'm getting 41lbs which is right on the money for this engine. I also have a scan tool, very good one, only receiving the single code P0300, nothing else. I can erase it, let the car run for a couple of minutes and it comes right back. Temps are well within operating range and no ood noises or rattles from the engine. Just sputters when it's reved and will die once it's dropped back to idle. I appreciate all of the suggestions but still working with it.
Thanks

[taillight]

Some scan tools will let you have live date which is what the computer is getting from the semsors. It is a lot more helpful.

[stratford_boy]

How old is the coil insultaor. (White plastic piece that sovers the coils.) It is known to cause ignition problems. I think it's about 100 bucks. How dirty is the throttle body, make sure its clean.

[jlm2664]

Thanks for the advice, I replaced that in July and the throttle body is clean. I'm taking a break for a couple of days and start again.

[jonnik]

Have you checked to see if the fuel pressure holds after you shut the ignition off? If the pressure drops quickly, you may need to replace the fuel pressure regulator. A leaking diaphram in the regulator will dump fuel into the intake manifold and bog the engine down. I've had this happen on 2 different cars ('96 Aurora and '97 Tahoe) and the symptoms were the same as you are having.

[eewizard]

check the map sensor and idle control valve. also check the vacuum line connected to the map sensor. I had the same problem on mine and it ended up just being a bad vacuum line connected to the map sensor.

[brian 1]

you might want to recheck fuel pressure.41psi is just low enough to run lean.the correct spec is 52-58 psi.anything below 52psi will cause a lean condtion and cause vehicle to stall and missfire.fuel pressure is just high enough to run.possible bad fuel pump.

[ottoman]

I have the same troubles with my 99 Malibu, and it was a bad "coil insulator" plastic white piece that hold the spark plugs