2.4 fludding

[kjones755]

I have a 98 Malibu 2.4L that was idling rough but would run ok on the highway the last time I drove it. It set a few weeks and now it will not start but for a few seconds even with the throttle wide open. It will not start again until it has set awhile. I have replaced the fuel injectors, fuel pressure regulator, spark plugs, MAP sensor, fuel filter. I did a crude test on the fuel injectors by removing the injectors with the fuel rail and cranking over the engin with the injectors spraying on a peace of paper. The spray pattern looked ok and they didn't leak under pressure, could not tell if the quanity was ok. Checked the compression, all cylenders 100psi+. Checked fuel pressure (45psi). Checked spark plugs for fireing. Drained the gas out and replaced with fresh gas. No codes showing up. I am out of ideas!

[Tech II]

Exactly how did you check the spark plugs for firing?

[kjones755]

I removed the cover over the engine, removed the spark plugs. Fliped the cover over and pluged the plugs into the boots and grounded the plugs and cover and pluged in the wiring connector then cranked the engine over and watched the plugs fire.

[Tech II]

I am a little suspect of testing it that way.....1 and 4 fire together, 2 and 3 fire together....so when 1 and 4 fire together, one cylinder is under compression, and the other is not.....the one under compression creates more "resistance" and gets the majority of the spark......so your way, you are creating little resistance......the way I do it, is remove the cover and the four boots, and attach four wires....I disconnect one wire, add a spark tester and a smaller wire, so the spark tester is in series and you can see the spark from the tester with the engine running.....

The few things that I have seen happen to these engines is, bad coils, bad ICM(rare), leaking f/p regulator, bad boots, cracked vac line to MAP, and the main culprit is the plastic ignition tower(houses the coils), that can carbon track and cause misfires.....

Is the timing cover creating engine noise? Bad tensioner could cause the chain to jump, but you said compression is ok....

[kjones755]

I am familiar with the coils and the way they fire. And the common problems with the coils and the cover. We have had this car since 1999 and have replaced these parts multable times. Also the timming chain and the wear blocks and tensioner was replaced about a year ago when I replaced the water pump. It should still be good? There has got to be something more.