Hey all,

I've got a 2002 3.0/v6 with 186k miles on it. Recently have had worsening gas mileage before my truck threw a cylinder 4 Misfire code and started idling insanely rough. Next time I drove it I could tell piston was constantly misfiring. No knocking or pinging.

I ran my own diagnostics and found that cylinder's compression to be less than half of all the others (60 psi). Ran a wet compression test using oil and it boosted the readings to 95 psi in that cylinder. I'm assuming this means a bad Piston Ring? I did a "glove test" on the radiator, which came back negative, meaning it shouldn't be a head gasket (no oil in antifreeze either).

Anyways, I'm exploring my options now. Taking it to a professional is out of the picture financially. I've never opened an engine before so what I'm trying to figure out is the following:

1. Can the rings be replaced without pulling the engine?

2. Should I do a complete overhaul/rebuild or simply replace rings and maybe glaze/hone cylinders?

Any help or advice is much appreciated. Thank you guys!

 

Its a valve issue not rings, exhaust valve is most likely

If it was a ring issue the WET test should have raised test number ABOVE the other cylinders DRY test numbers

A WET test will always raise compression in any cylinder, metal rings on metal cylinder walls are NOT a good air seal, lol, sealing it temporarily with oil helps it hold air longer so higher compression pressure

You can just do the one head, valve job, but it would be better to do both heads at the same time, since valves are all the same age and from the same "batch" when head was assembled at the factory


You can do the Dollar Bill test
Google: Exhaust valve dollar bill test

Been around 100 years or so and still works just fine

 

Im sure Ron is right, but do the other test too. I just finished replacing the heads on my 3.0, the passenger side is a snap, driverside a little harder because of AC and power steering. Also good time to replace water pump and more if you wanted. Let me know if you need advice.

 

You are both correct. I did the dollar bill test and the bill was sucked into/blown out of the exhaust back and forth. Definitely air being sucked in there.

With that being said, is it most likely the valves or the valve seals? If I replace the valves, should I lap each seat/valve? Are there any special tools or tips you recommended for this replacement? Lastly, is there anything else I should do in this process?

Thanks again!

 

Look around you can find rebuilt heads for good prices, even rock auto. how long do you want to keep this truck going? you really don't know if you have a cracked head in the exhaust or ? its kinda a lot of work for a quick fix. heads are out there.

 

I really just need to keep her running for six more months or so. I'm in college and graduate in May. Just trying to find a cheap but effective solution to get me through another semester and then sell the truck.

 

Call a local machine shop and ask them how much to do the 3 exhaust valves in one 3.0l head
You need specialized tools to grind valves and valve seats so they seal correctly, also ask TIME FRAME, this is where a rebuilt head may be better, once you have the new head you can do the job in a day, so short down time, vs waiting for machine shop to do the work, which can be 3 to 5 days

Pull off the one head that has the low cylinder, or BOTH if the cost to do one head is reasonable, as said its best to do both, but money is money

You need the head gasket, 8 new head bolts(per head), exhaust manifold gasket and intake manifold gaskets, coolant and an oil change(just after its running again), the old oil will have some coolant and bits of old gasket in it so has to be changed
You can reuse spark plugs just clean them up


Why exhaust valves?
because they run HOT, really really HOT
Intake valves are cooled by the air fuel mix coming in
Exhaust valves just get the 1,000+ deg HEAT running out when they open
The angle/grind of the exhaust valves is very very important, they need a wider surface touching the valve seats evenly to dissipate as much heat as possible to the HEAD when exhaust valve is closed, the head is where the coolant is, the heat needs to be transferred away from the exhaust valve as much as possible, and that can only be done when valve is closed, so the more surface area between valve and seat the better

All valves rotate as they open and close, intake and exhaust, they must or they will get Hot Spots
So the grind angle needs to be exactly uniform on each valve and on its seat

What usually happens to an exhaust valve is that under a higher load(high heat in cylinder) or if engine pings/knocks a bit the valve will get a deformity, and the LEAK starts
Once an exhaust valve starts to leak the HOT gases just eat away at it, and at some point the compression in that cylinder drops low enough so it starts to misfire, it can come and go as the valve rotates, but eventually compression gets low enough for a steady misfire

This is why its good to do all the valves at the same time, because you just never know, lol

Valve seals are in the valve cover area, inside valve springs, they prevent oil from running down the Intake valve's stem and being sucked into the cylinder causing oil burning, blue smoke from tail pipe, and black spark plug tips
Having all 6 changed on each head is a good idea, they are cheap, but you do need a valve spring compressor tool to change them

 

Thanks for the info. I'll see if I can find anyone in the area to do it. In the instance that it's too costly (or there's no one in the area) couldn't I just lap them myself with a suction lapping tool and some compound? I see a lot of YouTube videos explaining how to lap the valves/seats and, while it seems time consuming, it doesn't seem overly complicated.

Do you believe it's too technical to achieve good results by hand?

 

The valve and valve seat will have to be changed in the one cylinder that currently has the low compression

Valve lapping is not the same as valve grinding, lapping is done on valves that have no current issues, its done to confirm a good fit between valve and valve seat
No its not technical at all but you do need a good eye to see if some places on the seat or valve are not being touched from the lapping
Also need a valve spring compressor to remove the valves


Once a head is off put spark plugs back in the head
Flip head upside down and put holders under it so it sits level
Pour water into each valve/head chamber so valves are covered
Leave it alone for 30min-hour
after a bit look inside each port(under the valve), to see if any water leaked out
If there are any leaks then those valves need to be repaired

 

Thanks for the info Ron. I did a complete teardown, replaced the head with the bad valves, and did a valve job on the other head. I reassembled everything and my truck is still failing the exhaust dollar bill test (sucking bill in/out). It's also still idling rough and I still have a severe loss of power. All cylinders are now under great compression (140-150 psi each).

Any ideas as to what it could be? An exhaust system leak maybe?

Thanks again!

 

If compression is OK then no open/leaking exhaust valve so should not suck in the dollar

Is there a noticeable misfire?

 

It feels like it's constantly misfiring but it's not throwing any codes (very rough at idle and low speeds, but feels normal at high speeds). Also, it won't go more than 35-40 mph. It's like it's at half power.

 

Double and triple check firing order on coil pack, follow EACH wire to its cylinder

 

I read thru your post but wanted to answer your original question just for future reference, if you ever decide to rebuild a motor on this or any other vehicle, a true rebuild I allow a month or more for a rebuild. May sound like a long and excessive time but machine work takes time and then the cost especially if you have to bore a motor to a bigger size. Been a long time since I rebuilt a motor but seems like it was $20 per cylinder to have bored .030 over. When you bore over there is new pistons that have to be bought. Seems like I had each risk pin installed by machine shop and it was only $10 per pin. Tanking the motor to clean it was not much at all. All these cost individually are not expensive but to get everything done at the machine shop starts to add up. Then you have to order a rebuild kit according to how much they had to resurface. you may hear 10,30,10 which means your cam bearings size, piston ring size and crank bearing size. There are numerous other procedures that are needed from block, to head, to crankshaft that would take a while to mention.

If you are doing a project a rebuild can be a way to go if not in a hurry but not for a truck you need to get on the road as soon as possible. Going by your experience I would go with a rebuilt motor. At first it may seem like a high price for a rebuilt motor but usually you can get a warranty. You do the work yourself, you are the warranty. I have rebuilt motors and I have bought rebuilt motors. Usually I can buy a motor cheaper then I can rebuild one. As you get experience you may want to rebuild one someday and it is great to hear it fire up for the first time that you did yourself.

From reading your post and RonD has you headed in the right direction you dont need a rebuild. I just wanted to point out some differences of rebuilt motors where you buy it or do it yourself. I have not even scratched the surface of either way but hope to give you some idea about it.

 

Thanks for the advice everyone. I did an upper engine rebuild with a new DS head and new valves on the PS. I ground everything myself, which took hours to do since the seats were in such bad shape. Everything's air tight now with the best compression I've ever had.

I still had lingering issues after the rebuild. It ended up being a bad spark plug wire that I damaged during my teardown.

The truck now runs better than when I first got it 5 years ago. I'm super grateful for all the help, as this has been the biggest project I've ever done on a car.

 

Congratulations on getting it running. Nothing like taking something bad and making it better. What you did is a big accomplishment and has given you something to start building a foundation on. Hearing it fire up for the first time is always a joy. I have been working on motors off and on for over 30 years and if I did not have some kind of issue and all went perfect the first time I would be scared I did something wrong. I just could not be that lucky.

3 tough problems I dealt with.
1 was a new plug wire set out of the box and the coil wire was faulty, I was sure I did something wrong.(Not all new parts are good, always suspect reman parts too)
2 was a head gasket that did not have all the holes punched out and had a water port blocked causing over heating.(I always lay the new gasket on top of old gasket to make sure exact fit0
3 was I ran a resistance check and it passed. Lesson learned, if a 50 strand wire has 49 broken wires and one good wire, the test will pass but not send enough voltage to operate injectors.

You are going to get some problems thrown your way but when you figure them out it is rewarding. ( or maybe I just like learning the hard way, lol)