Engine shuddering, only during idle - tried few things..
 

Hey guys,

I've been experiencing what I describe as a engine shuddering/misfiring problem. This is very noticeable during idling but not any other times. Engine acceleration is very smooth, fuel consumption hasn't changed for the worse. However, under load during idling, like the A/C on, the engine stutters fairly bad.

Now this is going to sound strange but I seem to hear a "tick" precisely a moment before the misfire/engine shaking commences. This "tick" sound was very strong on the driver side of the engine, near the valve cover area. Again, this is not a rhythmic tick, just a random tick before the engine shudders. However, today, I followed the sound to the passenger side of the engine, around #1 spark plug.

During the first startup of the day this morning, this ticking sound, followed by the engine shuddering was intermittent and erratic. I'd say, about once in ten seconds to about once in 20 seconds. However, after returning home from a "spirited" driving, this phenomenon was occurring more frequently, I'd say about once every second to once every three seconds. Sometimes even four or five seconds in a row.

I'm leaning toward an ignition related issue over air flow or vacuum leak because ALL vacuum hoses were replaced last week! I have no CEL and the intake air hose seems to be in fine shape. Also, I just did the engine re-seal project at the same time.

Just as a reminder, I have NO engine issues once the car is driving. No acceleration hiccups, stalls or strange RPMs. Can I assume that the MAF is fine since I have good performance past idle? Battery is strong and the tank is full of 91 octane.

I took some videos and going through them now but the quality isn't the best (using a digital camera for video). I'll add a link once this is completed.

I unplugged the injector connector one at a time and this makes the engine shudder far worse than what I'm experiencing currently. Each injector is making a rhythmic ticking sound as confirmed by the mechanical stethoscope.

As of now, I need to figure out what item is getting hot and electrically misbehaving. I'll look at the igniter and clean up some grounds for starters. I'll pull the spark plug on that cylinder for inspection. If there is something else I need to focus on, please let me know.

Thanks.

Re: Engine shuddering, only during idle - tried few things..
 

Do your valve covers leak? Its possible some engine oil has seeped into the coil to plug connection..... this can also cause the coil to ground through its casing. Id remove the plug and clean thoroughly to eliminate that as a cause first.

Re: Engine shuddering, only during idle - tried few things..
 

Hmm, valve cover used to leak years ago until new valve cover seals and bolt washer seals so it's been dry for some time. That's a good point though, I'll tear into it when the wife returns tonight and after everything cools down. I'll check out the coils per FSM.

Update from this morning, first startup:

Well, this morning the ticking sound was coming from #4 and #6 spark plugs but no ticking sound from the passenger side of the engine (#1,3,5). The frequency of the missing was very high this morning for some reason.

Now, where in the heck is the igniter?

You can see the shaking of the engine, the sound is a little hard to discern but hopefully you get the idea.

Video:

http://i127.photobucket.com/albums/p...h_MVI_5583.jpg

Re: Engine shuddering, only during idle - tried few things..
 

The video seems to indicate a good size vacuum leak, your idle seems pretty unstable. The ignitor is on the firewall, by the throttle body. I couldnt discern the ticking from the video..... it could be a spark jump from the coils, but its most likely the hydraulic lifters making the sound.

Re: Engine shuddering, only during idle - tried few things..
 

Yeah, I had a hard time recording the ticking sound with less than ideal video equipment!

The vacuum leak is a possiblity but this ticking sound seems to be moving around AND all vacuum lines and intake gaskets are brand new.

Spark jumping sound plausible that's where I'm going to look around. I'll pull the coils off and test them tomorrow if time permits. I'll check out the ignitor too.

Thanks for the info.

update
 

Well, I made some progress today so it's time for an update for y'all.

As you may recall, the engine miss was preceded by a "tick" sound that I thought was coming from one or two of the spark plug coils. I was able to confirm this and began by replacing the igniter first then the coils on the driver side (#2, #4, #6).

I started by warming up the engine this morning and waited until the missing started. Then swapped the igniter and the missing still continued.

Next, I proceeded with testing the coil primary and secondary circuit per the FSM. Interesting thing is that the three coils on the driver side checked out OK but I bet one or two of them acted up when hot. Due to the PITA factor of accessing the coils, I replaced all three on that side of the engine. Started up the engine and waited for a miss and nothing, nada. At this point, things were looking up and I went for a drive.

Upon returning home, there was a miss and my "tick" sound is back. This time I tracked it to the #2 spark plug coil, on the passenger side of the engine. So, tomorrow, I'll swap it out and see what happens.

In summary, the missing sound is just about 95% gone but I'm still not satisfied until it's ALL gone! On another note, I was able to make sure that the cruise control pump/valve checked out while the battery was out and I had all that room.

Later.

** update **
 

Well, I swapped out the #1 coil (first one on the pass side) and the wife went for a spin yesterday. She states no engine miss or shuddering took place while driving around on local roads. I haven't verified this myself but hopefully things are looking up :D

One thing I forgot to mention that spark jumping is not a likely scenario as there was no evidence of oil inside the spark plug boots. Every spark plug boot so far has been bone dry. However, a little carbon buildup was apparent on the surface that touches the head of the spark plugs. That's normal for the age of the vehicle.

Will update after I go for a spin.

Re: ** update **
 

It won't be oil that shorts out the spark. It is more likely that the rubber boot has carbon tracks running down the side, shorting the spark.
These can be scratched out, and sprayed with Silicon oil.

Harvey.

Re: ** update **
 

Excellent info, thank you.

Went for a drive today and no missing! Yipppeee!