#4 Misfire

[Perscitus]

Sounds good. Re MAF - that's normal, with the engine off it should have some non-zero reading. I think it gets pegged @ some ignition-on voltage, and shows a 'reading'.

[aj_mariner]

Let the car warm up. Disconnected the FPR sensing line and plugged it going back to cyl #4 intake (so it wasn't leaking air past the MAF) thereby sending more fuel pressure to the rail. Here are the new values.

 

 

Equivalence Ratio moved closer to 1 with more fuel, so it is a Fuel-to-Air equivalence ratio (phi). At least with the code scanner I have. Engine idle "seemed" the same as far as vibes go. No major engine jerk or knock, which was easily distinguishable in the past.

[aj_mariner]

Looking at the manual, A/F sensor lambda is supposed to be 1 (stoichiometric). So the EQ Ratio moving closer to 1 is a good thing (no matter if its looking at lambda or phi). With my jerked up logic, it seems like a bad valve in cyl #4 would cause a rich condition (low compression) and a problem with valves would be appear better in winter, and worse in summer?

[aj_mariner]

Found this video on vacuum tester 101 and my gage is doing the exact same swinging as a valve not seating. It is probably a no brainer to most, but utilizing a vacuum tester like this is new to me and thought it might be helpful to others.

 

 

Looks like it might be time to have a shop do my valve lash, but still have one or two more items to rule out. Hopefully it’s not anything worse.

[Infosecdad]

That's pretty cool, thanks for that.

[aj_mariner]

Checked compression on cylinders 1, 2, and 4. #3 was too much of a pain in the ass with my time frame so just did the others.

 

Cold Engine:

#1: 140 psig

#2: 130 psig

#4: 130 psig

 

Also, the plugs on 1 and 2 look great, little white on the ground...but #4 is a little darker with no white.

 

#2 on the left, #4 on the right

 

#1

 

I hate to say it but I was actually hoping for low compression on #4 just to have some kind of clue!!! Still plan on having valve lash looked at...I just fear they will come back with "it was great, didn't have to adjust a thing."

[ehsnils]

So nothing major so far at least. That's good.

 

Just continue the investigation and I think it's good to check the valve clearance so it can be ruled out or corrected at this stage. Catching problems early is usually saving time and cost.

[aj_mariner]

I was really surprised by the compression. Been seeing a lot of lower numbers on even lower mileage vehicles. The lash job should show the smoking gun. With the heavy misfire between 1500-1900 RPM going up decent grades in this cold weather, it makes sense. But time will tell.

[aj_mariner]

Well, got the bad news today. Valve lash check showed no clearance on one of the valves to cylinder #4. F¥KKKK. I guess in a case like this the heads are being pulled an inspected by a machine shop. Made the decision to go ahead with the repairs/investigation. Looking at $2800 before taxes if no other expensive problems arise (new head). I wish I had a garage so I could work on this myself and save some coin. Why is it so hard to just put that towards a new car.

[ehsnils]

Since the compression test checks out I see that you caught the problem before it became a major problem.

 

Make the best out of it. Of course fixing it yourself would save a lot. And it's better to do a thorough job than to cheap out and realizing that a pesky seal sprays oil all over the engine bay.

[aj_mariner]

So I need a vote...the machine shop found a crack in the head along one of the valve guides on the non-problem bank (cyl 1&3). Replace at $685 or....??????

[relative4]

$685 to replace one head and rebuild the other? Sounds like a bargain to me.

[aj_mariner]

The machine shop is $450, which includes reconditioning the drivers side head. The passengers side head new is $685...but the $450 also includes valve guide transfer to the new head. It is a no brainer...I already called the dude back...half bagged...and said go ahead. Also in my stuper...asked why they can't just JB weld that sh!t.

[aj_mariner]

Got the car back today. Runs buttery smooth. Hopefully going to get another 200k out of her after the $5700 bill. That money included:

1. Valve lash check/adjustment

I feel I got dooped on this one. Dealership originally quoted $430 for valve adjustment. I asked 3 times if this was just a lash check or if it included adjustment. In the subie service system the code shows up as an adjustment. Come to find out it is closer to $2100 total if an adjustment has to be made since they have to pull the engine. Others quoted me $1200 check and adjustment and were going to pull the engine regardless. But, they might not have sent the heads out for reconditioning...which found more.

2. Heads got sent off to machine shop for valve grinding and head resurfacing. Dye penetrant test was conducted and a crack was found perpendicular to a valve guide on the head for cyl 1&3. New head installed, old guides and valves transferred. Total shop bill was $340. $685 for brand new head.

3. Dealer tech went through all hoses and found a couple with some cracks so they were replaced.

4. Dealer tech also found that the wastegate on the turbo was cocked, not fully seating. They don't repair turbos, just replace, and couldn't give me a core credit for the old turbo so I asked to keep it so I can send it out for overhaul and recoup a little cash.

 

Lessons learned:

1. I should have purchased several tools before this happened...and did once it happened. But the tools purchased were in haste, and wished I would have had the foreskin to buy earlier. haha. I don't have any android devices and didn't want to spend $250 on a device and Blue Tooth OBD2 adapter along with BtSSM app. Ended up getting a bosch code reader that I can use on my other vehicles. This was key, and saved me a lot of money just replacing sensors since I could see they were acting good.

2. Other tools completely necessary I bought as soon as this started was an OTC vacuum leak tester, deluxe compression tester, and leak down tester. All on Amazon for $170 total. I should have had these a long long time ago. Working on ships, I didn't want to look at anything mechanical when I was on vacation. Lazy me.

3. Trust the work that was previously done, and the parts that were recently replaced.

 

Thank you for all your help and guidance. It has not been a fun experience, but I now know a lot more about my LGTLW than ever before thanks to this forum. Cheers.

 

 

[08XT]

I’m also chasing a misfire demon. 106k on the clock, returned the car to stock at 104k and took a 1000 mile round trip and came home with a stuttering idle. Now the funny thing is that originally I had low power down low and stuttering and tons of power/normal power up high. I replaced all the spark plugs and coils, checked all the vacuum hoses. The misfire was probably cyl 4. Swapped the #2 and #4 Injectors, and no cel ever came back on.... until a couple weeks ago I punched it up high, and now I’m getting a cyl 2 misfire and power is good down low and now it misfires heavily up high. I’m really hoping that it’s an injector issue where before it was stuck open flooding the engine down low, and now it’s crapped out. The car did have a tune on it for about 50k before I returned it to stock. Otherwise it’ll be time to pull the engine and have it built. It’s an 08obxt 5spd so I’m thinking obxt off-road/rally wagon

[aj_mariner]

Refer to lessons learned. Pretty much everybody here will ask for data if you create a thread. Get a good code reader that can read live data and not just trouble codes. My Bosch was $165.

 

If you already have an Android device...go the BtSSM route with Bluetooth OBD2 adapter. It is the best option for these cars

[aj_mariner]

Another thought that I should of had done with the engine apart was to have them install an uncatted up pipe, to protect the money spent. I feel like at 207k, this is on borrowed time.