Misfire Problem - Could use some help

[LittleCaesar]

Get to the local hardware store for one of these:
https://www.bernzomatic.com/Products/Hand-Torches/Instant-On-Off/TS8000BZKC

Or with the little butane torch heat the nut up, then take a candle and drip the wax so that
it gets between the threads. Give it a minute, then try and remove. But the first method works better IMHO.

 

[mtbtim]

Ok Dudes, Greg and I have eliminated some more things trying to figure out the misfire cause.

The other day, we were finally able to replace the rear O2 sensor by cutting off that heat shield and getting on the rusted stripped nuts with a channel locks to spin them off. This time, the pending code came up at the usual 5-8 mile range but the actual P0301 misfire code took around 50 miles to show up as opposed to the normal 20 miles it usually pops up at.

Yesterday, we swapped out all the coil packs, took a drive the pending code popped up. We swapped the MAF sensor, took a drive and the pending code popped up. Then we swapped the ECU. I found a guy parting out a Tacoma on Tacoma World and picked up the ECU for Greg for $150. We swapped out the ECU and the F*cking pending code popped again.

So, there's still some other things we haven't eliminated yet like checking the fuel pressure, performing a leak down test on the #1 cylinder and swapping out the knock sensors.

Now, here's something we forgot to share. Greg's engine has a very noticeable engine knock under load. When the engine is idling or in neutral, the engine sounds normal. When he puts it in gear, there's a fairly loud knock. I got under the rig with my mechanic stethoscope and listened near the bell housing and I could hear the knock. But, when I put the stethoscope right under the oil pan, the knock gets much louder letting me know it's not transmission related but something in the lower end of the engine.

So, here's a question for you guys. Could a bad knock sensor be causing this? Or, is a properly working knock sensor picking up the engine knock, reporting that to the ECU and causing the P0301 CEL code? According to Greg, the engine has not suffered a change in performance. The fact that he says his engine is running strong leads me to believe there isn't a true misfire going on.

Anyway, we are going to do a leak down test next and most likely check the fuel pressure. I would think either a bad cylinder or poor fuel pressure would cause a significant drop in engine performance but we've gone this far and we may as well keep eliminating possibilities. Greg's registration has been expired for almost 1 year so we're hoping to find a solution short of an engine swap.

 

[rideexileex]

Ok Dudes, Greg and I have eliminated some more things trying to figure out the misfire cause.

The other day, we were finally able to replace the rear O2 sensor by cutting off that heat shield and getting on the rusted stripped nuts with a channel locks to spin them off. This time, the pending code came up at the usual 5-8 mile range but the actual P0301 misfire code took around 50 miles to show up as opposed to the normal 20 miles it usually pops up at.

Yesterday, we swapped out all the coil packs, took a drive the pending code popped up. We swapped the MAF sensor, took a drive and the pending code popped up. Then we swapped the ECU. I found a guy parting out a Tacoma on Tacoma World and picked up the ECU for Greg for $150. We swapped out the ECU and the F*cking pending code popped again.

So, there's still some other things we haven't eliminated yet like checking the fuel pressure, performing a leak down test on the #1 cylinder and swapping out the knock sensors.

Now, here's something we forgot to share. Greg's engine has a very noticeable engine knock under load. When the engine is idling or in neutral, the engine sounds normal. When he puts it in gear, there's a fairly loud knock. I got under the rig with my mechanic stethoscope and listened near the bell housing and I could hear the knock. But, when I put the stethoscope right under the oil pan, the knock gets much louder letting me know it's not transmission related but something in the lower end of the engine.

So, here's a question for you guys. Could a bad knock sensor be causing this? Or, is a properly working knock sensor picking up the engine knock, reporting that to the ECU and causing the P0301 CEL code? According to Greg, the engine has not suffered a change in performance. The fact that he says his engine is running strong leads me to believe there isn't a true misfire going on.

Anyway, we are going to do a leak down test next and most likely check the fuel pressure. I would think either a bad cylinder or poor fuel pressure would cause a significant drop in engine performance but we've gone this far and we may as well keep eliminating possibilities. Greg's registration has been expired for almost 1 year so we're hoping to find a solution short of an engine swap.

Knock only under load? What about timing - Belt jump a tooth? When was the timing belt last done? Are the cam and crank position sensors clean? Mounted properly / damaged?

I have had a misfire code, but it ended up being a sticky injector.

I don’t think fuel pressure would be it - that would affect everything. And Cyl 1 is roughly in the “middle” of the fuel rail.

Knock sensors only retard the engine above 3k RPM if that helps, but they are just glorified microphones. ECU should throw a code if there is an issue.

 

[JRZEE2000TR4LTD]

Crank sprocket and CS sensor encoder OK? Seem to remember several threads about problems there (especially after a TB change) from not torquing the CS bolt properly or damaging the encoder somehow and it can mess up the timing. Have an old timing light?

 

[LittleCaesar]

Doesn’t sound like fuel.

It almost sounds like a timing issue, have y’all checked the timing? Doesn’t Techstream give you the timing advance in degrees?

When you clear the code and put the engine under load before the code pops back up does the engine knock under load?

 

[mtbtim]

Knock only under load? What about timing - Belt jump a tooth? When was the timing belt last done? Are the cam and crank position sensors clean? Mounted properly / damaged?

I have had a misfire code, but it ended up being a sticky injector.

I don’t think fuel pressure would be it - that would affect everything. And Cyl 1 is roughly in the “middle” of the fuel rail.

Knock sensors only retard the engine above 3k RPM if that helps, but they are just glorified microphones. ECU should throw a code if there is an issue.

Yes, only knocks under a load. While sitting there idling in Park or Neutral, no knock. As soon as he puts it in gear, there's is a very notable knock coming from the lower end of the engine.

Don't know when the last time the timing belt was done. He has 150k on it so I'm guessing the timing belt was changed already but I'll have to ask him to be sure. I also don't know anything about the condition of his crank and cam position sensors. I haven't torn down the front of his motor yet, but who knows, maybe we will investigate.

Thanks for the info on the knock sensors.

 

[mtbtim]

Knock only under load? What about timing - Belt jump a tooth? When was the timing belt last done? Are the cam and crank position sensors clean? Mounted properly / damaged?

I have had a misfire code, but it ended up being a sticky injector.

I don’t think fuel pressure would be it - that would affect everything. And Cyl 1 is roughly in the “middle” of the fuel rail.

Knock sensors only retard the engine above 3k RPM if that helps, but they are just glorified microphones. ECU should throw a code if there is an issue.

Crank sprocket and CS sensor encoder OK? Seem to remember several threads about problems there (especially after a TB change) from not torquing the CS bolt properly or damaging the encoder somehow and it can mess up the timing. Have an old timing light?

Don't know this either since I haven't torn apart the front end of his engine and neither has Greg I'm guessing. I don't have an old timing light but I could probably pick one up on Ebay or Craigslist. Checking the timing is a good idea. What confuses me is he says his engine is running fine to him and he hasn't noticed any change in performance unless it's very very slight. I would think if the timing was off it would be running rough.

 

[mtbtim]

Doesn’t sound like fuel.

It almost sounds like a timing issue, have y’all checked the timing? Doesn’t Techstream give you the timing advance in degrees?

When you clear the code and put the engine under load before the code pops back up does the engine knock under load?

We have not checked the timing but we will for sure. I don't know if Techstream gives the timing advance but I'm going to find out.

Yes, the engine knocks under load even before the code pops up.

 

[DaMonkey]

clues that seem to be sticking out:

- knock
- isolated to 1 cyl

lifters? that would be the mechanical place i'd look. still suspect electrical too, look at actual current going into injector. techstream only shows you what the ECU knows which is the current it's trying to send.

don't give up on this! you're getting close, you'll find it.

 

[LittleCaesar]

Any other anomalies with Greg’s ride that maybe are there but not apparent, such as a hard start? Bad exhaust smell?

I would also look closely at Cylinder #4, as it is #1’s correspondence on the left bank.

Do you get a strong blue spark from cylinder #1 or a weak yellow spark? I know 4Reak Show mentioned the ignighter could be funky, I have never seen one on Toyota go bad but have replaced many on Chevys and Fords due to heat. They can cause some funky things to occur.

I would start with the leak down test to solidify your hypothesis that the engine is solid though the knock is a little concerning. Is the crank bolt torqued down to 217 ft/lbs?

 

[mtbtim]

Update

Hey Dudes,

So here's an update to our quest to find the cause of Greg's #1 cylinder misfire problem. We checked his timing and checked to see all his timing marks lined up today. His timing was within spec. It was fluctuating between 12-15 degrees BTDC and the spec is between 3-19 degrees. We took the upper timing cover off, got the crank pulley lined up with it's timing mark (0), and verified both cam sprockets were lined up with their respective timing marks and they were.

We also did a leak down test for the #1 cylinder. We found he only had a 7% compression loss which is considered good. A 5-10% loss is considered to be acceptable.

So, here's what has been done so far:

1) Replaced spark plugs
2) Replaced spark plug wires
3) Swapped coil pack positions- misfire didn't follow the coil pack
4) Swapped in coil packs from another engine
5) Swapped out MAF sensor from another engine
6) Replaced all the fuel injectors with refurbished ones
7) Replaced the upstream air/fuel sensor and downstream O2 sensor
8) Replaced the ECU with a used one from another Tacoma, same year and model
9) Did a compression test of all cylinders. Compression was good in all 6 cylinders
10) Checked the timing and verified the timing belt was on correctly
11) Did a leak down test of cylinder #1

I've used the program Toyota Tech Stream and either I don't know how to use it correctly or it's just not that helpful to diagnose this problem. I see that it picks up the misfire but doesn't give me any clue what triggered the misfire. Is the knock sensor picking something up? Who knows.

One very notable thing is Greg's engine has a very audible lower end engine knock when it's under load - in gear. In park or at idle, the engine is quiet. I listened with my mechanic's stethoscope and it's definitely coming from the lower end of the engine. However, Greg's engine doesn't have any detectable loss of power or performance. The idle is steady and smooth.

So Dudes, where should we look next? Do we drive it off a cliff or keep looking. If you have ideas, we're all ears.

 

[Spktyr]

Hey Dudes,



So here's an update to our quest to find the cause of Greg's #1 cylinder misfire problem. We checked his timing and checked to see all his timing marks lined up today. His timing was within spec. It was fluctuating between 12-15 degrees BTDC and the spec is between 3-19 degrees. We took the upper timing cover off, got the crank pulley lined up with it's timing mark (0), and verified both cam sprockets were lined up with their respective timing marks and they were.



We also did a leak down test for the #1 cylinder. We found he only had a 7% compression loss which is considered good. A 5-10% loss is considered to be acceptable.



So, here's what has been done so far:



1) Replaced spark plugs

2) Replaced spark plug wires

3) Swapped coil pack positions- misfire didn't follow the coil pack

4) Swapped in coil packs from another engine

5) Swapped out MAF sensor from another engine

6) Replaced all the fuel injectors with refurbished ones

7) Replaced the upstream air/fuel sensor and downstream O2 sensor

8) Replaced the ECU with a used one from another Tacoma, same year and model

9) Did a compression test of all cylinders. Compression was good in all 6 cylinders

10) Checked the timing and verified the timing belt was on correctly

11) Did a leak down test of cylinder #1



I've used the program Toyota Tech Stream and either I don't know how to use it correctly or it's just not that helpful to diagnose this problem. I see that it picks up the misfire but doesn't give me any clue what triggered the misfire. Is the knock sensor picking something up? Who knows.



One very notable thing is Greg's engine has a very audible lower end engine knock when it's under load - in gear. In park or at idle, the engine is quiet. I listened with my mechanic's stethoscope and it's definitely coming from the lower end of the engine. However, Greg's engine doesn't have any detectable loss of power or performance. The idle is steady and smooth.



So Dudes, where should we look next? Do we drive it off a cliff or keep looking. If you have ideas, we're all ears.

Pull an oil sample out and send it in for analysis. That can tell you how bad/what is causing the lower engine knock.

Also, does he not have forward and rear O2 sensors, being an OBD2 V6 truck?

Further on the misfire, has a visual inspection of the wiring harness taken place and have you checked for shorts with a multimeter between the computer and ignition connector? (I haven’t quite read the whole thread) Have you checked PID data for cylinder 1 while running? That was useful in diagnosing a recent misfire issue I had.

 

[LittleCaesar]

I know the 5vz in the past has from time to time thrown rods through the block. Maybe a rod, bearing cap is on its last leg. How does the engine sound and feel when turned over by hand?

Does Greg change his own oil? I would be curious if he has ever seen any metal flaking in the oil? An oil analysis is a good idea.

 

[96RedRunner]

Ha, don't drive off cliff just yet.
Drain the oil through a paper paint strainer type funnel or whatever to check for metal.
Though a pain in the arse pull the pan and check lower end.
On a engine I was dianosing idled fine lower end knock under load, the wrist pins were worn is what it ended up being.
One of the pins had reached the point of causing the knock others not far behind going by micrometer measurements.
Wrist pins can be rough checked with pan off plugs out push up and down on pistons from top and bottom.
To get precise measurements you'll need a depth micrometer for plug hole push from bottom.
Most would just change engine.

 

[mtbtim]

Pull an oil sample out and send it in for analysis. That can tell you how bad/what is causing the lower engine knock.

Also, does he not have forward and rear O2 sensors, being an OBD2 V6 truck?

Further on the misfire, has a visual inspection of the wiring harness taken place and have you checked for shorts with a multimeter between the computer and ignition connector? (I haven’t quite read the whole thread) Have you checked PID data for cylinder 1 while running? That was useful in diagnosing a recent misfire issue I had.

We haven't done any of this. We had the opportunity to get a good look at the wiring harness when we did his injector replacements but haven't torn down the motor since. I did have his rig connected to tech stream and saw that it picked up the misfire but other than that I didn't know what telltale things to look for.

Greg's rig has an upstream air/fuel sensor from what I remember and not an O2 sensor. We did replace both though with Denso replacements.

An oil analysis is a good idea and I do have a Blackstone Labs kit at my house we can use. I think we will do this soon.

 

[mtbtim]

I know the 5vz in the past has from time to time thrown rods through the block. Maybe a rod, bearing cap is on its last leg. How does the engine sound and feel when turned over by hand?

Does Greg change his own oil? I would be curious if he has ever seen any metal flaking in the oil? An oil analysis is a good idea.

The engine felt fine while I was turning it over by hand. I didn't notice anything odd.

I don't know if he does change his own oil but I'll ask him. I think I need to get him back over for an oil change and send off an oil sample to Blackstone Labs.

 

[mtbtim]

Ha, don't drive off cliff just yet.
Drain the oil through a paper paint strainer type funnel or whatever to check for metal.
Though a pain in the arse pull the pan and check lower end.
On a engine I was dianosing idled fine lower end knock under load, the wrist pins were worn is what it ended up being.
One of the pins had reached the point of causing the knock others not far behind going by micrometer measurements.
Wrist pins can be rough checked with pan off plugs out push up and down on pistons from top and bottom.
To get precise measurements you'll need a depth micrometer for plug hole push from bottom.
Most would just change engine.

I considered this because I know how to get the front differential out of the way because I've done it many times now but I was hoping to not have to get this involved with fixing the issue. If it was a worn wrist pin, would just replacing the pin fix the issue or would the worn wrist pin have resulted in further wear to the engine and a full rebuild be recommended. This is above my pay grade because I've never torn into an engine quite that far yet.

 

[96RedRunner]

If knock is coming from lower end be it wrist pins or rod bearings is usually indicator for rebuild or replace engine. Some people might pull head replace what's worn close it up n go, lack of funds can make you do a lot.
Hard to tell until you check bottom end see where problem is.

 

[4Reak Show]

I would try and see if the knock coincides with the misfire counter.

Using the scan tool you should be able to select which pids to display. The fewer the pids, the faster the program will respond. So I would just put misfire counter #1 on only and see if it counts it WHILE the knocking noise occurs.

I'm guessing the knock is unrelated. It could be a symptom of the lasting misfire, but I doubt it's the root cause. Cylinder 1 is closest to oil pump, so in theory it would get the greatest shot of lubrication from a pressure/flow standpoint. Also, you need 4 things for an internal combustion engine: air, fuel, spark, and compression. (And 5 if you count it all occuring at the right time.) that being said, compression and leakdown should have ruled out compression/sealing/breathing issues and therefore show a mechanically intact combustion cylinder operation. (Bearings may be wearing out, but the sealing is done with the rings and valves). So I'd be aiming at the other three things.

Air you checked off with the MAF/02 change. Those are the main factors in proper breathing information to ECM.

Fuel you checked off wth new injectors and a fuel pressure test.

Spark is still in the air for me as well as it occurring at the right time. That being said there is the igniter (ignition module) to try as well. That is what actually feeds and fires the coils based on main ECM inputs.

And the ECM bases its judgment on the crank and cam sensors. Those would be worth replacing since getting to them requires timing cover removal. And you gotta check the tone rings for those sensors as well. Any chip or Nick on a tooth will throw the whole system off.

Good luck.

 

[SilverRidgeRunner1]

Have u hooked up the 1 Cylinder to a scope to measure the wave forms on cylinder 1. Sense it is a constant misfire I think u would be able to see something in the waves to indicate a direction of travel.