az-dave

So I have a crazy random and consistent misfire. It all started 2 months ago when the CEL and VSC lights came on. The car mostly sat as I have a truck to drive and I did all the usual troubleshooting.
The Scanner Pulled up 2 codes: P1349 & P1656 - Both VVT and OCV codes pertaining to the Variable Valve timing.
I checked out this thread: https://www.clublexus.com/forums/per...ml#post6154316

And I inspected the OCV Filter, it was clean. I then moved on to the Procedure Lexus lines out to test the OCV Valve itself, which failed, and I replaced the OCV Valve. The Car drove fine for 2 days no CEL lights, perfect idle, and then all the sudden it started sputtering randomly. No Lights, no codes. I decided to pull the spark plugs, which looked a bit fouled from the rough running, I replaced the plugs, and the wires. Drove the car 50-60 miles and drove perfect, then Wednesday as I was almost home the engine started knocking loud (louder than bad gas, not as loud as a piston rod)...I was literally 1/2 mile from home, as I pulled in the knocking stopped, and has never returned. No CEL light came on. But now there is a very noticable misfire which causes the idle to be horrible, and you especially feel it on light acceleration, and when cruising at constant speed. There is no apparent loss in full throttle acceleration, but a slight hessitation when going from a dead stop.
There are no CEL lights or Codes, but my car feels like a 1978 camaro with a cam...not a GS300.

Im afraid a valve was sticking and possibly did damage, but then I would expect to feel that under WOT, which I dont, at all. And before doing the VVTi OCV valve my WOT accel sucked big time, as in sometimes the car wouldnt move.

Anyone with any experience? Im at a complete loss on this without ripping the head off. I have a hard time believing Genuine Lexus spark plug wire and new plug could be bad...but maybe ???

az-dave

Let me throw a twist into the problem:
When I changed the spark plugs One of them, Cyl #5 had a bent ground electrode on it, almost touching the platinum tip. I thought perhaps I dings it somehow. Put the new spark plugs and wires in as I described above, and I then ripped the TB off and checked the spark plugs over the weekend. Low and behold the brand new plug in Cyl #5 has abent ground electrode on it. Something in that cylinder has hit the spark plug. The top of the piston looks fine. Im at a loss, I dont think the valves can touch the plug...which leaves the possibility of something hard metal inside that cylinder...or maybe a broken valve. I cant think of anything else that could get inside that would cause the spark plug electrode to become bent.
Anyone ever had anything like this happen?

az-dave

Ive taken apart the intake chamber and exhaust and intake valve covers. All the Cam Lobes and valve lifters are in perfect condition, you cant tell there are any miles on them. There is no Oil Sludge on anything, in fact its so clean in both sides when I touch anything with my finger it only has clean oil film, Its rather amazing, and a testament to Valvoline Full Synthetic.

I did compression tests on all 6 Cylinders. They all ranged from 185psi to 220 psi, I tested each cylinder 3 times, and the readings would vary on all 6 cylinders by that range. In other words Cyl 5 would read 210 one time and 185 another and 200 another, same for all other cylinders.
This is leading me to believe the valves are seating, and the rings are good. So...How is it that a Spark plug electrode gets bent twice? The Spark Plugs are the same Brand and Plug # Ive used for 9 years, Ive never seen any with bend electrode until last week. Now 2 of them?
Maybe Im dealing with a bad fuel injector? Maybe the knocking sound was really bad pre-detonation? But it really sounded mechanical, not like fuel knocking.
Im going to re-assemble everything, test drive it and let everyone know the results.
I found one vacuum hose with a small crack, I believe it goes to the Charcoal Canister, perhaps that is causing the miss...hard to believe.

entryspeed

iTrader: (3)

Ok az dav onto this thread, regarding you losing something or bending a valve to cause this its highly unlikey. If you look at the head design there is no way that a valve even slightly bent can hit the spark plug. Also say something did go through the combustion chamber and out the valve train. Your compression check would have shown even a slightly bent valve resulting in very low compression numbers. I still say either plug is seating to deep for some reason or piston is hitting it especially if you put a new plug in after today and it does it again. then try if only for 30 sec or so leaving the plug slightly backed out (you wont be able to drive this way as the plug will eventually back all the way out). If you fail to bend the plug grounding electrode by backing it out and you dont hear a rod knock then for that 30sec. I say you try to space the plugback out of the cylinder head 1mm or 1.5mm and find a new head or even motor.

Again see below the valve would literalll have to have a 30* plus bend in it to reach over and hit the electrode in the middle of the head. Its not possible! My mind make me think some how your upper spark plug threads are worn out maybe even wollered out to where the plug can go in deaper. But untill you pull the head. I say give it a try and figure out a way to run the plug backed out as described above. GL man



The only other idea i have is detonation. try getting a temp reading on the number 5 cylinder exhaust port and on the one next to it either 4 or 6 will do and compare, maybe just maybe you have a lean issue in that cylinder causing extreame temps heating the electrode/sparkplug so much that the metal is bending simply from the compression/combustion stroke.

az-dave

entryspeed: Its Awesome to be able to discuss something like this with someone like you who is knowledgable and critical thinking, Thank you!

I agree the valves themselves cant ever hit the spark plug...what Im wondering is if a valve-guide maybe broke-off came down into the cylidner and then rattled and bent the electrode...but there are no metal parts I found in any of the cylinders, and the tops of all the pistons as best I can see thru each hole dont look beat up.

The knocking I heard happened 2 times, the first time it stopped and the car still ran perfectly smooth, the second time it happened was louder and when it stopped is when the new miss started. To me it sounds like either 1 valve is not seating 100%, or a fuel miss. I exchanged out the coils and no difference. Thats when I ripped the valve covers off last friday, and in the process discovered the bend electrodes...to my shock.

I got another compression tester last night and I still got readings ranging from 175 to 215psi, none of the cylinders read super low. I went to the dealer to compare my plugs threads and electrode lengths, and they match exactly, so the plugs are definitely not the problem. I cleaned all the plug holes, and I dont see anything on any of them that would allow the plugs to seat lower, no galling no wear-outs. I re-installed all the plugs again and cranked the engine over 4 times for about 30-45 seconds each. Removed all the plugs, and none were bent.

Would a Valve that is very slightly bent, or a very small chip on it still allow a decent compression reading, or would the slightest seating problem cause a cylinder to show a really low reading? Thats what Im not certain about...None of my cylinders are obviously low...thus my confusion at this point.

Im going to pull the fuel injector rail today and inspect/test each injector.
Maybe one of the piston rod bearings is bad, and there is enough oil pressure to keep it in check most of the time, but the last time I saw an engine with a loose rod it was a disaster, and the oil had metal flakes in it. My Oil is clear as Honey after driving it for those 2 days.
After taking off the injector rail Im gunna put at all back together and if it makes the knocking again Im gunna pull the head. At that point my old GS will become a project car, and I will probably pull the entire engine and do a lower-end rebuild and then install the Garrett Turbo I purchased last year.

az-dave

I also pondered extreme lean detonation causing the electrodes to heat and bend...but is that really possible?

And, I had an experience on a fairly built 327 about 20 yrs ago where my carburator float got messed up and ran very-lean and caused extreme pre-det, it burned a hole in the top of 3 pistons after only 1 minute of driving (I pulled over and shut it down once I realized what was going on, but was already too late)...

If I was getting extreme pre-det, do you think I would see other signs such as the top of the pistons, or something else? Or do you think this could be a very intermittent thing where it just didnt have time to damage the engine? But then how could it damage a spark plug so quickly?

Also, no CEL lights at all...and before I fixed the VVTI OCV valve the CEL light would come on after running the engine for 30 seconds. I tested the old OCV Valve and it for certain was bad.

az-dave

Ive been reading some other forums...I just hope I dont discover this:

az-dave

Me wants to get some type of fiber-optic scope...and peer inside each cylinder..easier than removing head. Prior post was from a person in the UK that discovered a bent electrode...car was still running fairly good. But not 100%. They finally sold it at auction, and person who bought took engine apart to discover Cylinder sleeves were um...trashed. I doubt mine could be like this because compression would presumably be hosed, but if the sleeve is damaged near the bottom maybe?
http://www.sears.com/shc/s/p_10153_1...7&blockType=G7 ??? me wants to rent it...not buy it!

entryspeed

iTrader: (3)

Your not going to like this but I have torn a 2jz apart and look at it. There is absoultly only one thing causing this and my friend you do have a spun rod bearing and the piston is hitting the plug. you see we tested the drebris theory from a valve guid and what we saw was the sparkplug had significant impact marks on it not just a bent electrode. however when we placed a 2mm plate ontop of the piston and cranked the motor over it clearly bent the plug electrode. I hate to be saying this but it would have to be some act of god for it to be something simple and not as I desribed. Me and my uncle tested this for you and he happen to have a blown is300 motor that we used. He has been a mechanic ASE certified for 26 years. he doesnt believe there is any other way possible.

az-dave

Entryspeed: Ive found the problem and its not a Spun Rod Bearing. Its something much simpler, and probably never reported before.

Here it goes:

After the throttle body is a Horizontal Aluminum Air Chamber part that is about 8" long and goes from 1 large diameter air channel into 2 rectangular openings. This part bolts onto the upper portion of the 2-piece intake Manifold. Inside this upper intake manifold is a butterfly valve separating the rear 3 lower manifold intake tubes and the front 3. I remembered seeing this butterfly valve about 7 yrs ago when I did my first plug set change on my own. Back then I removed the TB with that Air chamber.

As I explained in my previous posts, Ive suspected something broke off and got inside the cyliders somehow. I suspected a piece of aluminum casting or a chipped valve somehow. What I discovered is when I pulled the intake Air Chamber off that butterfly valve was missing, and the heads of the 2 little screwed that held it on were broken off with the thread of the screws still in the shaft that the butterfly attaches to.

Upon seeing this I knew I needed to rip the entire upper and lower intake manifold off. I did so, and Voila, 2 pieces of that brass butterfly valve are sitting inside the head next to where the intake valves are.

Here are the Pics of the pieces as I found them laying inside the Head:

az-dave

Here is the entrance to the Upper Portion of the intake Manifold. With the Butterfly valve missing from the shaft, I was able to pull it out. Not sure that this valve does except maybe equalize the vacuum between the front and rear 3 cylinders. The actuator I know works because before I ripped everything apart when you rev the engine you can see it rotate the shaft...that once had a valve on it.

az-dave

With all this being said, Now for the good news!!!

Something completely slipped my mind, and Im glad it did, or I may not have decided to pull intake parts off after the TB.

When I pulled that last bent plug again after replacing plugs last week, it was Not the same cylinder as the first bent plug was (how I missed that fact is probably just cuz I was getting worried that the valves were broken). It was the #6 cylinder. One of the electrodes is touching the center electrode. It literally just hit me that the new Miss I started feeling wasnt due to a broken valve or anything, it was due to the newly bent spark plug being completely shorted out!!!

The Butterfly valve is made of brass...far softer than the hardened steel intake valves. Much of the brass valve is indeed missing, its been chewed up probably over the past few months, or even years.

To test my intake valves ability to seat fully & properly I sprayed WD-40 onto both intake valves per cylinder (was able to do 4 at a time, then the final 2). I sprayed enough to create a puddle that submerged the entire valve seat. After 2 hrs I checked and all 8 valves still had the pool of WD-40, I repeated on remaining 2 cylinders with same results. This means the valve are fully seating so good that thin WD-40 cant even leak thru.

I will be re-assembling everything over the weekend, and will probably test drive her pretty hard. The good thing is with all this cleaning and testing, Ive removed a heck of a lot of old carbon from the valves and pistons.

I wonder how much this would have cost me at Lexus...especially since there was no code after replacing the VVTi OCV Valve.! Much hunch: With 250K miles on it, they would have told me bearings had spun and the engine was a junker...which I now know not to be the case.

entryspeed

iTrader: (3)

Well that surely would not be thought of to be the culprit but as i described when me and the uncle put a plate on the piston and spun it over it did exactly what happen. And your butterfly is almost exactly the plate thickness. Not knowing about that me and the uncles only conclusion had to be a rod bearing. good find on your part and gratz for not having a crap motor should be an easy fix and off you go. Props to ya again

az-dave

These pieces were too big to fit thru the intake valves, they were laying on the
intake ports just infront of the valves, and were being bangs by the valves.

I suspect small pieces broke off and got sucked in.

Im amazed there is no damage to the cylinder walls, valve seats or piston tops, but I used HD scopes, and was able to seat the valves and hold WD-40 overnight, indicating a complete seal of the valve to the valve seat.

Again, if someone else told me this story, I would tel them their heads, valves and pistons are done...we will know in 6 months if there is any damage that was too small to be detected, bit at this point I suspect its fine.

Thanks for your input, this is a 1 in a million problem I suspect. Probably a microcrack on that brass disk from the mfgr...too 250,000 miles for it to break apart.

Ive driven about 100 miles with no probs, and a heck of a lot more power. No Misses or rough idle.

az-dave

4th day running fine. The increase in power is pleasantly noticable, now that there are no bent electrodes.