2.7L 3RZ engine health troubleshooting and diagnostics ADVICE NEEDED

Greetings,

EDIT: I changed the thread title and added Table of Contents

Table of Contents:

Initial Compression Tests, etc:
Post 1
Post 6
Post 8

Initial Valve Clearance Check:
Post 13
Post 23

Valve clearance adjustment:
Post 28
Post 31

Post-Adjustment Compression Tests, etc:
Post 33

Intro:
I purchased this 2003 2.7 M/T with 245k miles a few weeks ago. I have no idea what it's maintenance history is. I finally got to do a compression and vacuum test and changed the spark plugs. #1 plug threads gave me a scare but it worked out. Other maintenance items taken care of include oil, oil filter, air filter, pcv valve, transmission and t-case oil changes.

Spark plug scare and fix addressed in this thread: Yellow gunk and cross-threaded spark plug:

My frame rust repair thread:



What I did: Compression test and vacuum test, looked at old plugs for warning signs.

Vacuum test results:
On initial crank, it idled between 15-16 in/Hg. Gave it a few revs and it settled up to 19-20 in/Hg. Video of gauge readings below. Let me know if you see anything I need to address.

https://youtube.com/shorts/KEU5VBOt86M?feature=share

Compression test results:
#1 cylinder dry and wet tests were low with slow pressure buildup; ~106 lb dry and ~111lb wet.
#2 and #3 cylinders were on the low end of the normal spectrum at ~125 lb and ~133 lb respectively with a negligible increase between dry and wet tests.
#4 cylinder was in the normal range at ~150 lb, negligible increase between dry and wet.
#2, #3, & #4 cylinders built-up pressure quickly.
#1 was about 30% lower than #2 and #3; and those two were about 13% lower than #4. Comparison images of the compression gauge readings and a video of each cylinder test are provided below.



https://youtube.com/shorts/JWjdsDTsN0Q?feature=share

Spark plug inspection:
#1, #2, & #3 looked normal to me.
#4 was covered in oil. The #4 boot also had some oil on it. See images.




Other symptoms and notes:
The engine seems to run fine, but it has a slightly rough idle. It has no visible oil leaks on the outside. There is no smoke or steam produced around the engine or exhaust and there are no strange smells. The check engine light is on but my code reader won’t communicate with the vehicle. It’s probably showing bc my downstream O2 sensor is not connected. Some one cut one of the cats out of the exhaust at some point. I am going to fix that.

Help needed:
I bought this to fix up and make it my reliable daily driver indefinitely. I did these tests to get an idea of the engine's condition, but don't know how to interpret the results or know what to do next. I can see there's a compression problem. What is the cause? I have not done a valve clearance check yet, but I plan to. I also intend to try a leak-down test, and can post results later. I would appreciate any of your collective wisdoms.

How bad is my engine?

 

Update: Yesterday, on the drive home from work, the CEL started flashing and the engine vibrated like a misfire. I'm familiar with misfires in my old F150, so I recognized the signs. It lasted about 30 seconds and went back to normal. I was driving at about 45mph in 4th gear. This morning, I got half way to work and it started misfiring and flashing CEL again, but this time it wouldn't stop. I pulled over, shut off, cranked up and it started again once I got moving. I decided to limp it back home and drove my F150 to work instead. Fortunately I just got it back from the shop. Strangely though, the misfire ceased and the CEL stopped flashing a few miles from home. So this tells me its intermittent. Not sure of the implications. I read a few threads this morning and believe it could be anything. I had misfire issues twice in my F150. The first time was a cracked intake manifold leaking coolant into the spark plug wells, the second time was a burnt coil boot. Who knows the cause in the Tacoma? We may find out.

I haven't done the leak-down test or valve clearance checks yet, but i plan to start on those this afternoon and see what I find. Other notes: The CEL is illuminated constantly, but this is likely due to the downstream O2 sensor not being plugged in (crappy cat removal job). I tried pulling codes, but my OBDII+CAN reader will not communicate with it. It powers on, but won't establish a link. I tried other readers from O'Reileys's etc, but none will link in my Tacoma, So I don't know what codes it may be throwing. I fear it may need a new ECU. Any thoughts?

 

That compression seems pretty low on Cyls 1-3, I'd say checking the valves would be the next step as you mentioned.

These days you can't expect hardly anyone to do preventative maintenance so all bets are off when buying a used truck.

 

I’m taking things apart to do the leak-down test and I see #3 and #4 coil packs have what looks like oil in the seam near the boots. Is this normal or an indicator of something? There is no oil on the end of the boots.

 

And the #4 spark plug has oil on the top, doesn’t appear to be on the threads, unless it just burned off. I changed these two weeks ago. The old plug had oil on it. Possibly the tube isn’t seated enough or the valve cover grommet isn’t sealing?

 

Leak down test done this afternoon. Results are worrisome. All cylinders seem to be leaking air through the crank case, which indicates worn rings according to all the YouTube gurus I watched before doing this. Correct me if I’m wrong. I could actually feel the air on my hand coming out of the oil fill hole. I’m sure that’s too much leakage, but I don’t know the percentage of leakage because the quality control of my Chinese gauges from Amazon are a little sus. The second gauge maxed out past the scale and never showed a drop, but they were definitely leaking heavily through the oil port.

Cylinder 4 was also leaking out through the top of cylinder 3. This was odd. Could that be a cracked head between the cylinders? Or worn exhaust valves leaking between the two? Is that even possible? Cylinder 4 had the highest compression during the previous test and was in the normal range. The rest were low.

On the plus side, there were no obvious leaks through exhaust, intake, or coolant, so the valves and head gasket can be assumed to be ok for now I suppose. I’m still going to do the valve clearance check and make any necessary adjustments. Would I see any change in compression or leak down tests after valve adjustment?

Unfortunately I’m no closer to figuring out which cylinder is misfiring, they all leaked air through the crankcase but the compressions were widely varied. If I were a betting man I’d guess it’s cylinder 1 because it had the lowest compression. The problem is I can’t pull any codes. How did mechanics figure this out without OBDII readers? And the misfire is intermittent and only happens while driving. It doesn’t happen at idle. I put everything back together after the tests and the engine ran fine.

My next step is to check valve clearances and report back. But I have a feeling someone is going to say I need to pull the engine and replace the piston rings, and I’m afraid they’ll be right.

I would post more images, but it’s just me pointing my finger at various holes, so here’s a pic of the crappy Chinese leak down tester. I should get a refund for it.

Look at that second gauge, it went all the way around the world.



Ok here I am pointing at leaking holes. The farting buttholes of my engine I guess….

 

Hmm. Leakage between 3 and 4 could be indicative of a head gasket issue.

The leakage out the oil cap is a little more sus though, that does sound like blowby to me. Excessive or not...hard to tell. Its not uncommon to feel wind there with the oil cap and engine running.

You might see a difference after a valve adjustment, particularly if some of them were tight.

 

Ah, you give me hope. Not uncommon you say? I feel like I could deal with replacing a head gasket, more so than a piston ring job. The oddest thing to me is the wide range in compression with the seemingly consistent crankcase leakage. If I’m lucky (which I happen to be sometimes) it will turn out not as bad as I thought. We’ll see what comes of the valve adjustment. I plan to measure tomorrow afternoon, then order any new ones needed after doing the math.

TL;DR recap:
#4 oily with normal compression, possible leak to or from #3.
#3 & #2 low compression.
#1 bad compression.
All leaking by crankcase (volume percentage unknown due to cheap gauges).
Intermittent misfire except at idle, cylinder unknown. Otherwise runs seemingly good.
Can’t read codes.

 

intermittent misfire at idle was a burnt valve on mine. It still doesn't idle great, but I think that might be the nature of it.

Do you know when the last time the valves were adjusted?

 

I’ll count myself lucky if that’s the case for me. I don’t know if the valves have been checked or when. I highly doubt it. It’s history is very shadowy.

 

Checking the valves might be very enlightening then. I had no clearance on one of mine...womp womp.

 

Hopefully we’ll see tomorrow. I appreciate the advice. I’m not a mechanic but like to play one sometimes. So I’m not doing any of this with any real background experience, just the occasional DIY as I’m sure many of us here do.

 

Valve clearance check Part 1:

I don't have complete results yet because I didn't finish measuring all the shims, but I measured all the clearances and #1, #2, and #3 exhaust valves are way out of spec. Real tight. Alternately, the #4 intake valves are a little out of spec. #1 exhaust was the worst and it had the lowest compression. #4 has the highest compression and was in normal range, but is oily. I will post finished measurement sheet when all shims are measured.

Notes:
The crankcase is grimy with black build up on the forward and rear ends. The bottom of the valve cover is almost completely black as well. I thought I took a picture of it, but I guess I didn't. I'll get one later. The plug tubes are grimy, but the #4 tube has the most grime buildup. What is the best way to clean this? I planned to run seafoam in the crankcase a few hundred miles before oil change, and planned to do that several times with very frequent oil changes for a while. Is there another method?

Also, one valve cover bolt snapped off with a stub sticking out of the head. I plan to PBlaster it and try to turn the nub with vice grips or something. Barring that, I would drill and tap it. I plan on replacing all the bolts. Does anyone have better advice?

Finally, the #2 front valve bucket looked like it was crooked, is that even possible? It might have been an illusion. Am I seeing things?

 

A lot of varnish under the valve cover, suggesting the oil change interval has been too long on some occasions. This might suggest sticking piston rings, which if you’re very lucky could resolve with several short oil change intervals using a higher detergent oil.

 

I recently used Valvoline high mileage synthetic. Any other brand recommendations?

 

That’s probably a fine choice…perhaps consider something heavy duty such as shell rotella; has high detergent to deal with soot from diesels. May also consider a larger filter canister (fram3600 fits the 3rz). Try this for some short intervals and look for black oil on the dipstick.

Take it slow and avoid using an engine flush product, as they can cause new problems.

 

Thanks I didn’t know this, Advance Auto only gave me a carquest filter bc their computer said it was the only one that fit that was also in stock. I’ll pick up the Fram.

 

Give me chance to double check the part number before you haul off and buy one.

 

I walk back and forth to advance auto parts all the time, it’s 1/4 mile down the road from me. Dangerously convenient.

 

change your ball joints, notnrelated to the engine but u should chek em out