Loose Spark Plug!

Well, I just joined today and would like to relate how I fixed an engine (3.4 liter) problem with my 2002 4runner. About two months ago I noticed a slight change in the driving of the truck. It felt like slight bumps were occuring as if I was travelling across the black cracksealing lines on the black top, but this "bumping" feeling became more frequent with time. The engine was missing at all driving speeds (hardly noticeable around town) but not missing at idle or when revving the engine past idle in "Park". So I found this Forum and started trouble shooting. The CEL never came on (steady) until one day I revved it up to near redline in second gear. I made an appointment with Toyota, explained the problem as I saw it and took it in. A few hours later I got a call and was asked if I had cancelled the CEL and said that I had when I removed the ground wire from the battery to safely work in the engine to clean the MAF sensor. Toyota told me that their "Technician" would not work on it as no CEL or other lights were showing! I asked where to go from this point and I was told to drive it until the CEL came on again then bring it back in with the light showing!? When the CEL lit up I called Toyota and the soonest they could look at it was more than week down the road. That did not sit well with me so I bought a set of DENSO plugs from Toyota, gapped them to 0.043" and got started replacing them. First plug was for cylinder 2 and the plug was worn with the central electrode no longer round, but oval. The gap between the central and ground electrodes was noticeable greater than that of a new plug. Next plug to do was that of cylinder 4. When I slipped the socket over the plug it somehow felt loose and I simply backed it out by hand - did not have to use the ratchet! The plug ceramic insulator was dirty with carbon and yellowish deposit at the base. Also it looked like a 1/16" wide carbon "track" had formed along most of the length of the insulator. I hoped that this was an "Ahah!" moment and it in fact was. Finished the plug change (and cleaned the carbon from the throttle body). Engine fired right up and test drive was perfect. Gained over 100 RPM on cold idle. Bought an Innova 3030RS code reader on sale at Crappy Tire and checked the CEL code. It was indeed for a cylinder 4 misfire.
I thought I would post this, as I never found any existing posts about loose spark plugs and had never found a plug to be loose in any of the myriad vehicles I have owned over the last 54 years.
Bill

 

Welcome Bill

 

Sounds like maintenance was deferred. Never seen a spark plug come loose.

 

I got the 4runner 2 years ago with incomplete maintenance records and no indication of when the plugs had been changed (or if they had even been changed). I suspect that they were changed and for some reason #4 was never properly tightened/torqued. I torqued the new plugs to 13 ft/lbs with moly paste on the threads.

 

Curious why the vehicle was even taken to the dealership if you could work on it yourself.

As for a loose spark plug anything, yeah I had that issue once. Probably don't hear about it because the fix is super simple.

For me it was both the spark plug and the boot wouldn't go back on.

Replaced all plugs and wires in less than an hour's time and was good to go.

 

Welcome to the forum.

I once had 1978 Oldsmobile Cutlass that developed a miss and I found the same issue... Had one plug practically flopping around in the cylinder head. Tightened it up and good to go, Until the timing chain stripped. This was the 4.3 Liter, 260 CI V8.

 

Hi Kwikvette,
I'm not very good (yet!) at working on my 4runner and could not figure out why it was missing AND I live on Vancouver Island and I was not keen on working outside in near constant rain/drizzle with temps just above freezing. You are certainly better than me in doing plugs and wires in less than an hour! Took me more than 2 hours just for the plugs.

 

Ah, freezing outdoors yeah that would put a damper on things. Did mine outdoors as well, but in 100 degree heat.

The only thing I found painful was the order of the wiring with the use of those "combs". Always take plenty of pics before disassembly so that assembly goes back together easily.

 

Do NOT gap modern plugs.

Just check the gap.

If you actually "gap" them and bend the electrode, you have ruined the plug.