Hello all, I posted a thread not too long ago about a mysterious p0300 code, on my 2003 Mitsubishi montero. Since then I bought a obd2 reader and pulled the freeze frames, which many people had told me to do. I’m not really good with reading results, so I thought I should ask for any advice. And it turns out there are not p0300 codes being thrown at this point. But instead, a p0113, p0303, and p0102. I will post a few pictures below of the codes and data, thank you all for your time!
Montero Misfire Help
- Thread starter Ashton_59
- Start date
nwoods
Expedition Leader
So, from an armchair mechanic position, the P0303 is the same as the P0300 code you had before, but more specific down to a certain cylinder, which is helpful.
The other two codes sound like the Mass Airflow Sensor is dirty or possibly failing. This is the sensor assembly within the air intake that sits just down stream of the air filter. Easy to access, easy to clean with MAF spray, carb cleaner, or even brake cleaner spray. Clear the codes using your ODBII reader, then pull the sensor out, Hit it with the spray, wipe it clean with a clean rag, reinsert, and run the engine a bit (15 minutes) and re-check the codes.
The missfire code troubleshooting still is what we recommend in the previous thread. Run a compression test and maybe a leak down test to see whats up. I highly recommend the videos on these tests from Eric the Car Guy on YouTube. They are Mighty helpful, as is Chris Fix.
The other two codes sound like the Mass Airflow Sensor is dirty or possibly failing. This is the sensor assembly within the air intake that sits just down stream of the air filter. Easy to access, easy to clean with MAF spray, carb cleaner, or even brake cleaner spray. Clear the codes using your ODBII reader, then pull the sensor out, Hit it with the spray, wipe it clean with a clean rag, reinsert, and run the engine a bit (15 minutes) and re-check the codes.
The missfire code troubleshooting still is what we recommend in the previous thread. Run a compression test and maybe a leak down test to see whats up. I highly recommend the videos on these tests from Eric the Car Guy on YouTube. They are Mighty helpful, as is Chris Fix.
Thank you for you helpful insight, once again!
PaydayGabe
Active member
Please use a MAS Cleanser specifically for MAS Applications only.
Carb cleaner or Brake clean can leave a residue upon drying that can effect the function of the sensor and reduce it's lifespan.
MAS Cleanser is more expensive but a new Sensor is definitely more Expensive than the proper cleaning solution.
Good luck with your project. G.
Carb cleaner or Brake clean can leave a residue upon drying that can effect the function of the sensor and reduce it's lifespan.
MAS Cleanser is more expensive but a new Sensor is definitely more Expensive than the proper cleaning solution.
Good luck with your project. G.
I cleaned the maf, with maf specific cleaner. And some good news and bad news occurred. Good news there was no more code for the mass air flow sensor, and no code for the intake air temperature. But bad news the p0300 code popped back up. This seems strange to me, because when the maf was faulty before I cleaned it, it was throwing a cylinder specific code (p0303). But after cleaned it is now throwing a p0300 (random assortment of multiple misfires)
How long have you owned it? I would be doing plugs and wires next if I had no service history to refer to.
Does this code show up immediately after startup idle, or do you need to increase RPM’s to cause it, or are you taking it for a drive when it happens?
I’m not familiar with the 3rd gen Montero engines but I’ll bet the plugs and wires are buried under the intake manifolds.....it’s a big job but may be needed to solve your problem.
Also this is a great write up on diagnosing misfire:
https://www.aa1car.com/library/misfire.htm
Does this code show up immediately after startup idle, or do you need to increase RPM’s to cause it, or are you taking it for a drive when it happens?
I’m not familiar with the 3rd gen Montero engines but I’ll bet the plugs and wires are buried under the intake manifolds.....it’s a big job but may be needed to solve your problem.
Also this is a great write up on diagnosing misfire:
https://www.aa1car.com/library/misfire.htm
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I have owned the car for about a month now, but have not drove it more than 40 miles in total. I test drove it before buying it and inspected it and all seemed good! The previous owner did mention some previous misfire issues and he said they had all gotten taken care of, with receipts for truth. In the last 12,000 miles the water pump and timing belt had been done. And when the misfires started happening he said it would have trouble starting in the morning while it was cold. So he took it to the mechanics and they cleaned the fuel injectors and maf, and he said there was no problems after that. But he said if a code pops up on me to let him know. The day after I bought it I was driving home and a code popped up, p0300. So I called the guy I bought it from and he scheduled an appointment at a shop. I dropped it off the next day, and the shop said they thought it was the intake gasket that was doing us dirty. So the mechanic changed that and replaced all the spark plugs (iridium), as well as checked compression and that tested good. The previous owner spent almost $500 to try and fix it, I’ve never had a buying experience like that, usually sellers will just blow you off. But of course the mechanic just chose to fix some random crap without really digging into it. All that did not change the misfire, the mechanic said the ignition coils “could” be at fault. The spark plug wires had also been changed in the past 12,000 miles, I have receipts. I’m kind of stumped, I don’t want to spend hundreds of dollars on ignition coils and remove the intake manifold and put it back on, just to find out that it is not the problem. Should I get the montero tested for a vacuum leak just to rule that out?
I have no clue how old the the O2 sensors are. I cleaned the MAF and that took away those maf sensor related codes, and after that it went back to a p0300 (random assortment of multiple misfires) code. But I can still hear clinking and hesitation from cylinder 3. I'll check those idling fuel trims. I went back and pulled the freeze frames for the p0300 code and got these, I don’t really know how to read if any of this data is bad, or if it’s all fine, so any input would be great!
DTCFRZF P0300
FUELSYS1 CL
FUELSYS2 CL
LOAD_PCT(%) 53.3
ECT(*C) 50
SHRTFT1(%) -15.6
LONGFT1(%) 3.9
SHRTFT2(%) -12.5
LONGFT2(%) 3.1
RPM(rpm) 2156
VSS(km/h) 27
SPARKADV(*) 18.0
IAT(*C) 16
MAF(g/s) 40.99
TP(%) 15.7
DTCFRZF P0300
FUELSYS1 CL
FUELSYS2 CL
LOAD_PCT(%) 53.3
ECT(*C) 50
SHRTFT1(%) -15.6
LONGFT1(%) 3.9
SHRTFT2(%) -12.5
LONGFT2(%) 3.1
RPM(rpm) 2156
VSS(km/h) 27
SPARKADV(*) 18.0
IAT(*C) 16
MAF(g/s) 40.99
TP(%) 15.7
You can hear engine sounds well enough to ID a specific misfiring cylinder?
Anyway, start the truck up and look at live fuel trim data at idle and post those numbers.
Is your screenshot from idle? If your fuel trims are negative you probably don’t have a vacuum leak. Check out this link:
https://www.aa1car.com/library/what_is_fuel_trim.htm
Anyway, start the truck up and look at live fuel trim data at idle and post those numbers.
Is your screenshot from idle? If your fuel trims are negative you probably don’t have a vacuum leak. Check out this link:
https://www.aa1car.com/library/what_is_fuel_trim.htm