Flashing CEL / misfire

[emedlin]

04 Envoy with 199K on it started flashing the CEL. My wife had said it seemed to lack some power when starting off a month or two ago. I added some techron then to clean it out some. Didn't seem to help much, but the car still accelerated OK. It is not like a night and day difference in acceleration. But yesterday the CEL started to flash when starting off while going up hill. No codes though. The plugs and fuel filter were changed at 147K. Could the AC Delco Iridiums be dead after 50K? The originals actually made it to 147K before it start having issues.

One other thing is the when the AC is on you can hear a wining sound that comes and goes, but mostly at lower to mid rpms when starting off. This is not a normal sound and I think it started over the summer sometime. It made this sound all three times I saw the CEL flash yesterday. I saw some other posts about vibrations like bad motor mounts causing a flashing CEL. It isn't vibrating like bad motor mounts I have had to have those replaced before. Could the bearings in the AC compressor being going out and vibrating something to cause a fake misfire flashing CEL?

So much easier when something just breaks or gives an error code.

 

[Mooseman]

Lets start with the misfire. Any codes?

 

[emedlin]

No codes. Wish there was.

 

[Mooseman]

If it's got a flashing CEL, there has to be a code for the misfire, either hard or pending. If you have a bluetooth OBD adapter, use that with Torque to watch the misfire counts along with other stuff like MAP, MAF and fuel trims.

 

[emedlin]

I use a bluetooth ODB adapter and it doesn't see any codes logged or pending. I will have to connect it and drive around to watch the misfire count, MAP, MAF, and fuel trims. I have never watched those before. I didn't even know there was a misfire count in Torque. Mainly just use it for pulling codes.

 

[Mooseman]

I think you need Torque Pro. For a couple of bucks, it's money well spent.

 

[emedlin]

It may be in Torque Lite also. I had to add the GM / Opel / Vauxhall set of PID's now I have the options to add dials with Misfire current and history along with a lot of other stuff. Which should I watch the current or history? Is current the current drive session and history 'x' drive sessions?

I added all the displays for misfire, MAF, and fuel trims. I don't see MAP though. What does MAP stand for?

Just have to wait until this afternoon when my wife gets home with the car to see if the new dials tell me anything. If not I will get the Pro version.

 

[Mounce]

The history is only history of since the scanner has been monitoring usually on torque. Like if you leave the app and come back another day the history will be back at zero. I usually just watch both to be sure not to miss an event.

Oh and MAP is Manifold Absolute Pressure. It monitors the vacuum in the intake.

 

[emedlin]

I have an intake manifold pressure. So, I will add that display also. Thanks.

 

[emedlin]

Got a 301 from it when my wife got home. She said it had done it several more times. Looks like I need to check that plug and/or swap the coils on 1 and 2 to see if the code moves. 301 is the one up at the front of the car right?

Also, no missfire counts in the lite version. Always blank. Same with MAF. Intake pressure is 4.2psi at idle. Fuel trim only shows on fuel trim bank 1 sensor 1. It moves from 3 to -7 at idle. The others are blank. Fuel Trim Bank 1 Short Term shows -7 to 2. Not sure what that is, but it said fuel trim, so I looked at it.

 

[Blckshdw]

301 is the one up at the front of the car right?

Correct, #1 is up front by the radiator

 

[Mooseman]

If you're not getting misfires during that particular Torque session, it will show 0 or possibly it doesn't work in the Lite.

There is the Long Term Fuel Trim and Short Term Fuel Trim for bank 1 only since it's an inline 6. As long as it stays between -10 and 10, it's good although -7 is a tad high but could be because of the misfire.

 

[emedlin]

I am guessing misfires doesn't work in Lite as I had it running when I got it to blink the CEL again. Plan to work on it tomorrow and see if the code moves with the coil pack.

 

[fletch09]

check the plug. I had misfire on #2, turned out to be a bad plug. replaced original plugs at 98K.
new plug lasted 22K. one on top is at 98K, one on bottom is 22K. both 41-103

 

[emedlin]

Found the problem. Spark plug is missing the ground electrode. So this iridium plug lasted 52K. Any clue why it would have died an early death. I am going to replace it and put the same coil back on it. Question though. Why is the number one cylinder that is misfiring so much dirtier than the number two? Do I need to clean it out any?

 

[Mooseman]

It's dirtier due to incomplelete combustion. It might fire sometimes but mostly not. New plug and you should be good to go.

 

[I_Shoot_Back]

looks like #1 plug wasen't seated proper and you had a bit of combustion getting into the cavity where the coil sits. That or the top seal of the coil didn't sit proper against the valve cover and allowed dirt into the cavity,hard to tell from the picture

 

[emedlin]

Running good now. Interesting thing though. For about 2 years the car has had a tapping sound. Thought maybe it was a valve tapping or something. Could hear it at idle, but much above that and normal engine sound would drown it out. I couldn't figure out what it was, and it didn't seem to be causing a problem. So, I didn't worry about it to much. After changing the plug the tapping is gone. Seems they were related.