Another Misfire Thread

[Gray035]

I figured I would start a thread for my misfire problem. I've seen a bunch of others, but almost never see the solution (if any is ever reached). So I'll use this one to chronicle my issue.

My X5 started to stumble at idle a few weeks ago, and threw a code for the #2 cylinder (I can't remember the code number). Turned out that one was easily resolved with a new coil.

A few weeks passed and then a similar stumble started with the infamous P1351 code, which is misfire cylinder #5 with fuel cutoff. I switched the coil to a different cylinder and the code did not follow, so not the coil.

The code and stumble seem to pop up together only at idle. If the x5 is turned off for a decent amount of time or the code is cleared the engine smooths out. But they keep coming back.

I did a smoke test (the cigar and Harbor Freight pump method) and discovered a fair amount of smoke coming out around the DISA. New O-ring will be going in there.

I suspect that things might improve a little after that, but that the problem will not go away completely.

Other things I'm thinking about:
(1) CCV - previous owner said entire system replaced, but who knows for sure. Will check it out.

(2) Fuel Pump or Filter - I have read in other threads that fuel pumps are a common culprit for this type of issue.

(3) MAF ?

(4) There is a terrible oil leak somewhere on the bottom end (maybe CCV, maybe oil pan, I don't see any oil around the oil filter housing from the top, but still need to check from the bottom. This is not new so I don't think it is related to misfires/P1351 code, but will need to be addressed.

I will update this thread as I work through this code issue. Hopefully I will be able to post a solution for everyone to see.

Lastly, I've had an OBDII app on my iPhone for years, but am only now trying to figure out how to analyze the data it can produce. Right now I'm using DashCommand, which works fine to read and clear codes. I want to be able to run reports and all that. If DashCommand cannot accomplish that I will upgrade to OBDFusion. I will post the reports here (hopefully some of you who are knowledgeable can help me out there).

Please let me know if any of you have any insight.

[upallnight]

Could be a bad injector. If the injector is not providing as much fuel to that cylinder the computer see the cylinder when it fire as not providing the same amount of power as the other cylinders, it counts that as a misfire. OInce the computer count x numbers of misfires from that cylinder it shut off the fuel supply to that cylinder and now the cylinder is dead. Resetting the code or shutting off engine just reset misfire counter. You replaced the coil or swap out the coil, but did you swap out or replace the spark plug?

[StephenVA]

When you pulled the plugs, was there any oil in the plug tube shafts (plug holes in cam cover)?

One of the first approaches to miss fire/stumbling, is to do a quick process of elimination. Hand on tail pipe- is there a DEAD miss or random cyl drop off?
Ignition side- all OK plugs coils, etc
Fuel side - what is the pressure in the fuel rails? Do the injectors misfire, drip, spray patterns equal cyl to cyl?
Air intake - filter to cyl head. Clean, sealed, and not deteriorated?
Oil Separator - leaking, split, puking oil everywhere? (Mayo under oil filler cap?

Misfire can be read with a scanner. Move around cyl to cyl or stays in one cyl?
Stays- look into THAT cyl - Ign & Fuel delivery systems
Moves- look up stream - Ign & Fuel delivery systems and look for AIR LEAKS. Your smoke detection method shows a leak in the intake area at the DISA valve. Pull and inspect.

This list of test and measure has been around since the '60's..... The only changes is what happens upstream to the fuel (injected vs Carb) and Ign (coil on plug vs cap/rotor/wire) systems.

Helpful?

[Gray035]

One of the first approaches to miss fire/stumbling, is to do a quick process of elimination. Hand on tail pipe- is there a DEAD miss or random cyl drop off?
Ignition side- all OK plugs coils, etc
Fuel side - what is the pressure in the fuel rails? Do the injectors misfire, drip, spray patterns equal cyl to cyl?
Air intake - filter to cyl head. Clean, sealed, and not deteriorated?
Oil Separator - leaking, split, puking oil everywhere? (Mayo under oil filler cap?

Misfire can be read with a scanner. Move around cyl to cyl or stays in one cyl?
Stays- look into THAT cyl - Ign & Fuel delivery systems
Moves- look up stream - Ign & Fuel delivery systems and look for AIR LEAKS. Your smoke detection method shows a leak in the intake area at the DISA valve. Pull and inspect.

Yes. This is helpful. I've already completed most of this list:

(1) 1K on new spark plugs
(2) haven't checked fuel pressure yet
(3) the air intake has been smoke tested...will replace DISA O-ring. The DISA itself appears to be in good working order.
(4) Need to look into oil separator (aka CCV right?), but PO said it was replaced. No mayo under oil cap.
(5) the misfire is stays on cyl 5 even though coil has been moved (need to inspect spark plug and switch that to another cyl to see if any effect).

I think there's not much more I can do while I'm waiting for DISA O-ring. Once that leak is plugged I can continue trouble shooting.

[Gray035]

Well my misfire seems to be getting worse. I installed a new DISA O-ring and cleaned the MAF. I also put some injector cleaner into the fuel tank. None of these things has made any difference. A week ago a code would come up like every couple days after a reset. Now the code comes back within minutes of reset. It has gradually gotten this way.

I used DashCommand to log some data, but I admit that I don't know the first thing about interpreting what I saw. Here is a link to an .lgf file. This data was at idle just after codes were reset. Near the end of log the code comes back. At that point the fuel trims go to zero and there are no more readings from the oxygen sensors. Anybody know how to interpret this data to help me get to a diagnosis?

https://www.dropbox.com/s/v77rtnlppf...%20PM.lgf?dl=0

[StephenVA]

Originally Posted by Gray035

Yes. This is helpful. I've already completed most of this list:

(1) 1K on new spark plugs
(2) haven't checked fuel pressure yet
(3) the air intake has been smoke tested...will replace DISA O-ring. The DISA itself appears to be in good working order.
(4) Need to look into oil separator (aka CCV right?), but PO said it was replaced. No mayo under oil cap.
(5) the misfire is stays on cyl 5 even though coil has been moved (need to inspect spark plug and switch that to another cyl to see if any effect).

I think there's not much more I can do while I'm waiting for DISA O-ring. Once that leak is plugged I can continue trouble shooting.

Thanks for the insight.
You only need three things to make a internal combustion engine to run> Fuel, spark and compression. That is it.
If the issue is Cyl five, then I would recommend a few simple tests, Pull plug> Fuel fouled - oil fouled? Dry as toast?

Quick tests: Replace plug (it only 5 bucks) Run better or same? NO?
With the plug installed, start the engine run at idle. Does each injector click with the same pacing, especially #5? Just place your finger on it you will feel it. There are lots of tools out there to read the signal it self if the answer is NO.
Quick Fuel pressure test. The rail has a Schrader type valve on it. Connect a fuel pressure gauge. (you can buy or rent one). Replace fuel filter if not done on your watch. While you are there grab a fuel sample and look up Fuel testing for water) The water in fuel test> Here is what is done on aircraft...
Find the low point on the fuel system and drain out a fair amount into a clear glass container and let it sit for a minute. IF there is water in the fuel it will appear on the bottom of the container in "drops." It is easy to spot and proves the point water is heavier than fuel and for sure doesn't mix with it.

Quick cylinder compression test, using a compression test gauge (Sears sells 'em). All within 10% of each other and over 135? Note Must be done with all the plugs removed. Lots of info this procedure all over the internet.

This will get you started.

[StephenVA]

When you have a sec, update your forum signature to have the year and model of your application as it helps a whole lot when responding. My guess is you have a 3.0, based on your questions and postings.?!

[Gray035]

I understand the fuel, spark, compression concept, but you have to admit that it's a lot easier to sort out with a 60s carbureted motor.

Anyway, I switched the plugs between cylinders 4 and 5 and there was no change. They both looked fine (not fouled).

I guess the next step is to start looking at the fuel supply.

Thanks for the help!!

[Gray035]

Updated. Thanks!

[StephenVA]

We are getting closer. Finger on Injector, feel the pulse (clicking signal?) The injector magnetic end gets energized and pull up allowing fuel to flow. Think of the hose end sprayer type with the finger trigger. Same concept.
The question here are: Is there a injector pulse signal, Did the injector respond electrically, and last did fuel flow?

With real shop level test equipment, all it takes is a exhaust gas meter and a method to "kill" cylinders one at a time for 15 secs at idle, then read the HC increase at the tailpipe (make sure air pump is off). The cyl which has NO changes is the one not getting fuel supply. Then the questions are Valves working? see compression tests and visual inspection of valve train. (No weird ticking or tapping sounds RIGHT?)
Most techs at this point just slap in an injector and see if the problem goes away. AFTER checking the fuel rail. pressure.https://www.youtube.com/watch?v=FBBJhrJMyYM
https://www.youtube.com/watch?v=axxl98lToN8

Potential failed part: The offending injector (if pulsing) has a clogged inlet screen or blocked pintal. Usually the latter one shows up as a blackened plug and a "hard restart after 15 mins when hot as fuel just drips down on the intake valve.