dayrunner

I guess I will say that just a day ago I drove 200+ miles with no check engine light and enough chevron techron fuel addative for up to 32 gallons with a full tank of gas (18.5gal).
4 months ago my engine felt real rough like it was missing w/ no check engine light I only thought to throw a fuel addative to it. I ended up using the lucas oil little bottle and no noticeable improvement and not knowing that the Chevron techron was the way to go I waited till a light would come on.
3 weeks ago a Check Engine light came on with a misfire code in the 3rd cyl. After swapping the coil pack and rechecking code it came up still the 3rd cyl. PRIMARY AND SECONDARY. At 116,000 miles I wasn't happy to have issues with the motor. I did a compression test that showed that the bad cyl. was @ 130lbs and the others were @155 & (2)@ 150lbs. Without getting to do a leak down test and an injector service thanks to a friend who's a Rover mech I don't know where the issue was.
After running this tank of techron I will be curious to find out that I am getting more compression in the 3rd cyl. I put good gas in I thought shell/76 were good? I'm no mechanic but think simply but is this a red flag for something that might be in the future? To do an injector cleaner where is the valve to hook up the injector cleaner system?

KrashDH

I had a very similar issue to you a bit after I bought my 99 tacoma 4x 2.7, w/ 120k. It had no power (not like the 2.7 has a lot). Changed out most everything possible for a misfire first (plugs, wires, etc) and that was no help whatsoever.

I then had it taken to a shop to have the compression checked. If I recall I had low compression in my 3rd as well. I believe it was less than what you listed for yours. I consulted a buddy and he suggested that I had a bad valve.

So we took a gamble and tore everything down, and behold I had a burnt exhaust valve. It was pretty bad, it wasn't circular anymore, hence there was a void, which in turn created the bad compression. It seemed that that particular valve was out of adjustment (maybe over tightened) from the factory.

While I had everything apart I had the head re-surfaced and I replaced ALL if the valves (intake and exhaust) for good measure even though the others looked ok. (local machine shop, very good rep) As well, because I was in there, I did all of the timing stuff as well (chain, guides, belt, etc.) and new gaskets.

I now have 161k and she runs like a charm. No issues whatsoever. It was scary for me as this was my first real project on the truck. thankfully I had my buddy who helped a ton.

To answer your question, I would say treat it as something that if not taken care of could get worse in the future. Hopefully though it may be something simple.

dayrunner

I wonder if the valve is gummed up and just needs a good dose of techron fuel addative for 4 or 5 tanks? I also had it smogged about 2 months ago and it passed like it was brand new. With the compression being just a little lower than the others as well as only haveing 116k miles it seems like a valve is gummed up. I heard that ethanol is no good for your valves??????

KrashDH

certainly worth a try for starters. If that doesn't work then i guess ya gotta dig a bit deeper. I'm not sure if compression would be directly related to smog or not...May just make your cat work harder to burn every thing up...

Stick_Figure

start w/ the leak down to determine where the problem actually is. You could have a burned valve, you could have some carbon stuck to the valve, not letting it seat 100%, you could have a bent valve, you could have a bad ring, you could have a leaking head gasket, i could go on, but you need to determine where the lost compression is going. Once you figure that out, you can move on to figuring out the best course of repair.

sseaman

You might try seafoam before your complete tear down

tlo86

id rather use water

hross14

Stick_Figure--is Spot on. There is no cure in a can (for the most part)

Leak Down!!! and listen to see where the leak is coming from. Air out the intake--bad valve. Air out the exhaust=bad rings.

You can also squirt some oil in the hole during the test and see if that improves the PSI reading (NOT ALOT either). If it does your rings and probably the problem. No easy way around it.

dayrunner

Valves were out of spec. My mechanic adjusted 5 exhaust valves for being tight and even though there are 16 different shims, only four are for when they get tight. I know on at least one that there is no more adjustement after this. I wonder why they are wearing so fast for as much as I take care of the truck? How much longer till I need a valve job?, maybe another 80k?
I'm bummed out that I'm having to think of when to sell the truck before a valve job or just do it and keep the truck? A newer truck with maybe a V6?

hross14

motorcycles have this same problem (valves being tight). I have only seen this on a 22RE with over 500k. Not sure of the exact factors that cause it though..... theory suggestest either the valves stretch or the seats are beaten further into the head???