I've got a head scratcher. JDM engine with unknown miles. The engine came CAKED with oil sludge everywhere. Ran it. It's ran good for ~20k miles.

Been having P0300 P0302 P0303 codes for a while now with blinking CEL. Chasing them down. Did the usual plugs, wires, cleaned TB & MAF.

Did a compression test and leak down the other day. Here are the results.



190 186
190 168 (54% leak down)
190 160 (35% leak down)

The X's marked the CEL codes and the ohm readings were for the fuel injectors.

So after much ado, I couldn't help but to think the head gasket was blown, between cylinders 2 and 4 given the low compression and leak down numbers. After pulling the left head the gasket looks good between the cylinders. BUT cylinder #6 looks like the piston is caked with unburnt fuel as it was easily rubbed off with my finger.

The low compression numbers are worrying me. The only other thing I can think of is rings...but only on those two pistons?? It just doesn't make sense as the intake and exhaust valves look okay to me and seem to hold brake fluid for ~30 minutes (sprayed on the inside).

So at this point I am ready to get a new HG and bolt everything back up. Not worrying about the low compression on those two cylinders. Then find the culprit on cylinder #6.

Any advise for me before I bolt everything back up will be appreciated.

Pics below shows head off.

 

I am in a similar boat. Throws a P0302 after heat soak. Cold up to operating temp it runs fine. Shut it off for 10 minutes and come back to a significant miss (heat soak).

Tried plugs and wires. Swapped coil packs. Since it happens after getting up to temperature makes me think an electrical component. I found a set of 6 injectors on eBay that I'm going to try.

 

Seems to be a common theme with these 5VZFE engines. Were you getting a blinking CEL? Also have you tried compression and/or leak down test?

 

Yes on the blinking CEL. No I haven't done a compression test because at only 100k miles and good maintenance I'm reluctant to think its a HG. Plus I'm seeing a rash of injector failures with similar multi-miss symptoms.

Did you have any performance issues prior to your tear down? Besides the CEL, what symptoms did you have? And for how long?

 

I was having the typical misfire symptoms. Runs fine when cold and then after it heats it begins to misfire with blinking CEL at near WOT. Touched cat converter after a little drive and it was noticeably hotter than the downpipe before the cat. Not sure if that's normal but it seems to suggest unburnt fuel from the engine getting burned in the cat. It's been going on for just over a month. But I've been limiting my driving of it since it started.

 

Did you get reassembled yet? Curious if HG solved your problem or if your trouble is still eluding you.

Also did you have any overheating?

Mine has mutated. What was consistently a P0302 misfire is now interspersed with P0300, yesterday also had P0301, today have P0301 and P0305?!?

Now I'm leaning toward a crank sensor or similar pickup. I think the random misses are from the motor shaking during stutter under load but I'm guessing on that.

 

I haven't gotten it put back together yet. I sent the head off to the local machine shop to have pressure tested and resurfaced. Waiting for it to return.

Your mutating codes is weird though. I think you might be on the right track in thinking it's a sensor. Did you do anything in between the new readings, like swapping coil packs or injectors?

 

No. I reset the codes on one evening clearing out the p0300,0301,0302 and drove around the next day getting codes p0300,0301,0302,0305.

The P0302 has been consistent since the miss showed up about 2 weeks ago. I really doubt HG in my case as it wouldn't move from cylinder to cylinder and shouldn't be on both banks. Plus why run like a champ the next day as if nothing was wrong.

With p0302 being a repeated code. I think that injector has taken a dive. Not clogged but the windings are shorting out after getting hot.

 

Months back I also threw a TPS code randomly. I reset it and it didn't come back. I don't remember the number offhand. I may replace that as well just to eliminate it as a cause.

The trouble I have in my research is people are getting to a point where they replace a bunch of stuff at once. So the exact cause/fix could be a bunch of things.

 

The machine shop determined that two of my cylinder head valves were not properly holding vacuum. They reground the seats and fixed it up. Hopefully this solves my problem. It'll be installed this weekend and I'll report back. But I'm also guessing a bad #6 injector as well, so that'll also be replaced.

 

Figure I would update my thread and put it to rest. Unfortunately I don't have a 100% answer to what had solved my misfire issue but as a certified shadetree mechanic I am positive it was the fuel injector. #3 to be precise. I am not 100% sure because after I completed the cylinder head gasket (due to my findings above) the misfire still presisted. After that happened, the CEL code pointed to #3/6 cylinder. Replaced the coil (with an extra I had) and #3/6 fuel injector at the same time...this was after I had moved the coil packs around previously. Anyway. After 100 miles of normal driving and 200 miles of pulling a tent trailer, the truck is still running great.

After all the research I had done, everyone said that the injectors were generally rugged components. Though recently on YT, there has been a rash of fuel injector issues, what gives?

ps. if you're having to undergo a head gasket. Keep in mind that it's no easy task. Getting those crossover to exhaust manifold bolts out are no joke. Be extra care not to strip those f@&kers. But if you're debating on doing the HG vs dropping in a JDM engine...while the JDM is easier, if your engine is low mileage, like mine was, the HG was worth the cursing.

 

Pozi,
Congrats on getting to the bottom of this. Any thoughts on the rust shown in your pics (between both banks)?

I've owned my '01 since new and am now over 360,000 miles. I do all of my own maintenance and continue to wonder how long the original coil packs & injectors will go.....




Andreas

 

That's a good question. I have no idea. This engine was a JDM and it came to me this way.