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Ok the fucking POS is at it again. 2.5L nissan 4cyl. Same motor as altima, sentra and my pos X-Trail. Throwing a P0300 misfire code. Symptoms are a ruff start followed by running just fine. I have done the below but need help. Coils all tested and spark with new plugs. Resistance all the same. Injectors are all equal resistance and seem to be fine. I put seafoam through just in case. Compression is all at 177. Min is 154, optimum is 181 so with 170k miles 177 is ok since same across all 4. No vaccuum leaks I can find. The only thing I cant test yet is fuel pressure. Need to find a guage to borrow. I am stumped right now. Right after the shitty start it runs strong and doesnt hesitate etc. I will check battery volts and alternator too. So could it be fuel pressure regulator? Please help DTT freinds and family
Meagan's Grand Vitara had some issues recently, turned out it was just a dirty MAF sensor / throttle body housing. I would bet it is just a faulty / dirty sensor somewhere.
Thanks guys, Cleaning the throttle body makes sense, I will try that. I have the factory service manual and have done all the tests in the book except the fuel pressure and they all passed. My O2 sensors are operating correct per the OBD-II scanner live data mode. I have never cleaned the throttle body and I just cleaned the K&N air filter and it was dirty, really dirty. I somehow must have not checked it the last few oil changes LOL. Anybody got a good product suggestion for the cleaning of the MAF and throttle body?
There is specific MAF/MAS cleaner. That will be the problem, they don't like the oil from K&N filters. They are sensitive to chemicals from what I read.
As for the throttle body good ol carby cleaner (which is now called throttle body cleaner by some brands)
Cool, I have lots of carb cleaner LOL, I'll google the MAF cleaning and see what is up. I looked at it last night when I was doing a test for the O2 sensor, spraying a bit of carb cleaner to cause a rich condition and seeing if it made the readings on the OBD sensor change, and it did just like it was supposed too so I will say the O2 Sensor is ok. I was thinking I wonder if it was causing anything to go wonky and was going to Google if there was a test for it. I'll try cleaning it out and see.
Brodie, I can't remember so maybe you can.....is there some kind of oddball warning with TB cleaner? Something like you can use newer TB cleaner on carbs, but can't use older carb cleaner on a TB?
I just woke up, so my head is still fuzzy, and I could be very wrong about all that.
If I remember right there is something about a coating on ford throttle bodys that carb cleaner removes. Also some TBs have the MAF in them and carb cleaner will mess them up.
For the extra few $ may as well get a TB branded cleaner.
So I googled it and found the cleaner, available at local Crappy Tire and it says it fixes all my symptoms. I should have posted this 2 days ago, I'd have it fixed. And yep Rich, can't use old school Carb cleaner on the newer TB's it will mess them up, and the newer TB cleaners probably won't hurt old school carbs but likely won't clean as well. It's $8.95 a can so we will give it a whirl.
LOL. me either but I have tested every other part and they are all good. I am still going to find out if I can test the MAF and see if it is fualty but for $8.95 I will try cleaning it first.
If I remember right there is something about a coating on ford throttle bodys that carb cleaner removes. Also some TBs have the MAF in them and carb cleaner will mess them up.
For the extra few $ may as well get a TB branded cleaner.
You're right about Ford TB coatings. As long as you get a cleaner
thats Ford safe you're ok.that will be listed on the can.
Also check the air gap at the crank position sensor and look for connections/corrosion at the crank and cam sensor wires.
I know you Che ked the coils with an ohm meter, but a coil can test fine but act up under load. Look for carbon or signs of arcing around the coils and boots as well. This is a common concern on the mazdas that I work on, fords that I've seen and Jags/Land Rovers as well. Fairly common across the board
You're right about Ford TB coatings. As long as you get a cleaner
thats Ford safe you're ok.that will be listed on the can.
Also check the air gap at the crank position sensor and look for connections/corrosion at the crank and cam sensor wires.
I know you Che ked the coils with an ohm meter, but a coil can test fine but act up under load. Look for carbon or signs of arcing around the coils and boots as well.
Thanks for the info, I will check cam and crank sensor wires. since it is a Nissan not a ford I am ok on the TB, but I am getting the right cleaner. I also spark tested each coil per my service manual pain in the ass, had to hang the coil with new plug exactly 13-17mm above a metal engine part and have my 10 yr old crank the motor. I got fat spark off each so I am pretty sure the MAF is sending wrong data and causing it to be too rich on start up.
Sounds like an issue I was having with my truck.
Fouled MAF from K&N oiled filter. Cleaner didn't help on mine I had to replace it for some stupid reason. But I found a much better price at napa than through the dealer.
Sounds like an issue I was having with my truck.
Fouled MAF from K&N oiled filter. Cleaner didn't help on mine I had to replace it for some stupid reason. But I found a much better price at napa than through the dealer.
Cool, I just checked rockauto to see and they have one for 85 so if cleaning doesn't work, I'll have to order one. and Joon - Yah I will check the TPS as well, thanks
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