Malibu #4 cylinder not fireing

[rugby_7]

Hi all Im a new guy but have been working on cars for years. I purchased my 1998 malibu 2.4l two months ago for $400 and had 6000 miles of no problems until yesterday.
I was driving home and hit a bump then my engine started running just on 3 cylinders. I got it home and checked the plugs. The #4 plug was wet with gas. I checked for spark and all 4 cylinders are getting spark (it may be just my imagination but the #4 plug looks weaker). I switched plugs and boots around still no change. Switched the coils around still no change. Switched the injectors around still no change. Checked compression #1-150 #2-150 #3-150 #4-125, The number 4 cylinder is lower but not enough to effect if it is fireing or not.
It is getting a check engine light but Im waiting on my code reader in the mail.
I also had some coils from another 2.4, I put them in still no change.
Sorry for the long post, just wanted to get all the details. Anyone know what could be wrong? Thank You!

[oldblu65]

Sounds like you had a wiring issue that was just looking for an excuse to become a problem ? I suspect that " bump " you mentioned pushed this potential problem into a real - time issue . I'm not an electrical / electronic expert but I would start the engine ( making sure it is secured with the parking brake and wheel chocks ) and look at the wiring in the engine compartment to see if anything is obviously wrong ? If not , try gently moving your hand around on wiring in the engine bay ( making sure to stay clear of any moving or hot engine parts ) to see if it improves the running of the engine as it idles . Also make sure all electrical connections are secure . This would include wiring on the firewall as well . There could even be a connection in the wiring under the dash , that's not quite completely connected as intended , that the bump loosened just enough to cause your problem . Electrical " gremlins " can be a nightmare to track down so don't get frustrated and you'll find your problem - Good luck !

[danielsatur]

1) Reset/clear code and monitor.

[Tech II]

You say:

"The #4 plug was wet with gas. I checked for spark and all 4 cylinders are getting spark (it may be just my imagination but the #4 plug looks weaker)."

Exactly how did you do this?

#4 compression doesn't look bad(slight wash down from fuel?)......

More often than not, the problem is the ignition tower itself.....

[rugby_7]

I checked for spark by running jumper cables to each plug as a ground and had someone turn the key. I know the proper way to do this is have a HEI tester, but this was a quick way to see if it was at all getting spark. I think I am going to hook it up to my multimeter and see what reading are coming from each pole, maybe that one will be showing weaker. I wish my code reader would hurry up and get here so I could read the codes.

A loose connection could be a possibility since it happend the way it did, Ill have to go pull them apart and plug them back in, not something Im looking forward to...

I also read that with these engines the coil housing sometimes cracks or gets carbon tracked and grounds out the current, that could be the problem as well. Maybe also a stuck valve. Just going to have to try different things, Thanks for the input so far guys, Its good to get some different ideas!

[rugby_7]

#4 compression doesn't look bad(slight wash down from fuel?)......

More often than not, the problem is the ignition tower itself.....

What does slight wash down from fuel mean?

The ignition tower is where the coils are housed?

[Tech II]

If no fire to the plug, fuel can wash down the cylinder walls of oil.....

Ignition tower and coil housing are the same thing....

[rugby_7]

Ok yeah that makes sense. Would reading the poles of the housing with a multimeter be the way to see if it is bad?

[rkvons]

You could remove the coil that has the #4 spark plug wire on it, check under it, then swap it with another coil that is next to it. Make sure the wires are moved correctly from one coil to the other. then see if the problem moves to another cylinder.

[Tech II]

Rkvons, this is not a DIS system with external coils and wires......the coils are inside an ignition tower/housing and uses no wires(boots connect the plugs to the housing).....

Rugby_7, an ohm meter doesn't help.....the carbon tracking is inside, and shorts out.....

It's just like wires....you can ohm them and they are ok.....but a break in the insulation causes the spark to jump to ground and cause a misfire....

Like I said, if plugs, boots, compression, injectors and coils are ok.....it's the tower.....very rarely have I seen the ICM(bolted to underside of cover) be the problem, but it has happened....

[rugby_7]

It might just be worth buying the tower, its only like $40 so if its not the problem i have it for if it ever becomes the problem. Well I finally got my code reader in the mail today, came up with two codes. Cylinder four missfire (knew that) and injector circuit

[danielsatur]

Suspect injector # 4, connector, or signal wire going to injector 4.

[Tech II]

yeah, with the injector circuit code, that could cause a P0300 or P0304.....go with what Danielsatur said.....check injector circuit with a noid light....

[rugby_7]

So by process of elimination, I moved the injectors around and it didn't change that would leave the connection??

[slls]

Or driver for #4 injector, noid light check.