Time for engine work, but how much engine work?

Hi TW,

I've got a 2004 tacoma 3RZ-FE 235K maintained miles that started a subtle misfire that lasts about 5-10 seconds on cold starts. Threw a code so I got it checked out. Did compression and leakdown at 2 shops.

Test @ shop 1: Cyl 1 160psi, 11% leak; Cyl 2 140psi, 60% leak; Cyl 3 140psi, 40% leak;
Cyl 4 145psi, 50% leak
Test @ shop 2: Cyl 1 175psi, 30% leak; Cyl 2 120psi, 55% leak; Cyl 3 150psi, 30% leak;
Cyl 4 155psi, 35% leak

I was told at the least will require a valve job, headgasket replace. The concern is doing this work will stress the bottom half and give me grief. The alternative is the full rebuild or a used engine for a swap. Anyone been here and done this and share their results? Work will be done at a shop 3k quote for the valve/headgasket, and close to double for the full rebuild.

 

Buy a reman from a shop with a good reputation and warranty. Turn yours in for the core. It will be cheaper and you will end up with a more desirable result.

 

Where is the leak down occurring? I would determine where the leakage is before I did anything else. Did either shop tell you the leak down test results other than the percentage?

 

What do you mean “stress the bottom half”?

 

first shop said all leaking was going out the exhaust, second shop gave me some more to go on.
cyl 1 test bubbles from radiator
cyl 2 test air coming from #3
cyl 3 test air coming from 1 and 2
cyl 4 test air coming from 1 and 3

 

So, often when its low compression on central cylinders on a motor with EGR, its simply carbon on the valves.

I've seen EFI services clean off this carbon, in person on a few motors. I've seen 90psi to 140psi on an altima that we ended up blocking the EGR on, simply with a can of EFI cleaner.

I would 100% try a hot injection flush prior to a rebuild.

You can also try a simply seafoam clean through the intake, this will clean valves as well.

Edit my post came late. It sounds like HG and valves, I'd still try a flush.

 

I was warned that doing the work to the top half would create a mismatch of sorts and the bottom half could be prone to failure

 

Not really, but you do want your cylinder pressures to be similar.

 

Thank you. I will look into those cleanings. Prior searching I did revealed the valves will actually get burned if not adjusted when they should be. I've never had them adjusted, didn't know that was a regular maintenance item. Seemed like i fit the bill for burned valves.

 

I've only seen a handful of burnt valves on Toyota, its actually really easy to spot with a good camera/boroscope. Typically a burnt valve will be very very low compression, lower than 100psi and will induce a misfire code, even on the older models.

 

What was the code exactly?

A burnt valve would quickly get worse and cause a misfire all the time. Hot exhaust gases leaking past the point where the valve is not sealing will quickly erode it into a bigger leak.

It does sound like something is wrong. Ideally, you'd be fairly confident in any diagnosis before spending all the money/time to pull the head.

 

code was a cyl 1 misfire. Came on a cold start as the truck did its short misfiring ritual. These are subtle misfires at idle rpm. has never missed above idle. It missed just hard enough for the code to be triggered. since having the tests done it has actually stopped its previous cold start misfire ritual.

 

Cylinder 1 seems to be a common place where the head gasket leaks/blows. Near the front left corner if you're facing the engine. I mention that because you said the leakdown test on #1 showed bubbles in the radiator. I'm not sure how to interpret the #3 leaking into 1 & 2 and #4 leaking into 1 & 3. How does the pressure from 4 get to 1 but not 2?

 

Yea I'm fuzzy about how the air leaks are getting around as well. The mech said they use a stethoscope and could listen to the moving air. My mech also did a search for engines and did not come up with much for used engines. I am currently searching for engines as well. Just driving the truck to work today it does not feel much different than it has always felt. Could easily be down some power, but not anymore than it was down 3 months ago or 6 months ago.. Are there more indicators I should be on the lookout for to give more of a hint at what is wrong or what is failing?

 

what they are referring to is that there is a possibility of it consuming oil after the valve job. The theory is that the rings and valves wear together and when you seal the top with a new valve job the increased cylinder pressures will blow past the rings, pressurize the cranckcase and push more oil vapor throught the PCV into the intake to be burned.

The decision on what work to do is a tough one... is the balance of the truck in good shape? Will you be doing the work or a shop?

 

The balance of the truck is in good shape with several mods/upgrades that fulfilled my needs and wants. Work will be done at a shop.

 

It seems like there's still enough bottom left to warrant head work only. Depends what you want out of the truck for future. 2 more years? 5 more years?

 

I burned a valve. I was very obvious as it was missing badly and had no compression. This happened at around 87,000. All due to my negligence - On days when I did not visit a store or go anywhere besides my shop, I drove it approximately 2000 feet round trip. With so many short runs and long over due oil changes I sludged it pretty bad, both valve covers were packed with goop. I took a chance and only did the top end. That was about 70,000 miles ago.

I think the shop that did my heads cheesed on the guides, if it is driven at high speed for 30 minutes or more, it poofs out a cloud of smoke the next time it is started. And I get oil blown back into the air filter box. The pcv valve can cause this when driven at higher RPMs, and that is how pretty much it has always been driven. I know, I'm a dirt bag what can I say?

Given that it is basically only driven within 30 miles of home and still passes the smog test, I'm not worried about it. If yours has always had regular oil changes, and hasn't been through the crap I put mine through, the bottom end has probably got many miles left on it. If all the leaks were between cylinders or at the head gasket, the bottom is probably good. It really depends on how you have maintained and driven it up until now. You never said how many miles are on it. Whether you are planning on towing stuff long distance or just 40 minute drives to work, may be the deciding factor really.

My wife drives mine now. She has a lead foot and that truck is regularly cruising at 86 mph. It uses a quart every few thousand miles - much of it through the intake. At around 130,000 I drove it up the "Grapevine", about a 700 mile round trip, uphill both ways, and it burned a quart. But it ran great, and runs great now. See if that price includes a new timing belt and water pump, as well as all new belts.

 

It's difficult for me to gauge the urgency I need to have in dealing with this. If you lined up 10 taco's all over 200K miles what would the compression/leakdown numbers be like? Have been commuting with it all week and it just plain runs.. like it always has. I think its worth doing the head work and leaving the bottom alone but should it be done this week? this month? in the next 3? or when symptoms develop further?

There must be different levels of "burned valve" do you even notice a 'lightly burned valve"? It seems like if a had a truly burned valve I would not have been able to commute this week in the truck.

 

misfire was prob. a spark wire or boot.

Numbers don't seem bad enough for me to be pulling heads if it runs good. All engines 'leak down'.