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Cylinder 3 misfire Tried everything I can think of

-14 psi is impossible.

MAP reads pressure, not air volume.

And nothing reads air volume.

Did you read my post at all or what?
 


matt5112 said:
-14 psi is impossible.

MAP reads pressure, not air volume.

And nothing reads air volume.

Did you read my post at all or what?
Click to expand...

yeah matt
The parameters I'm looking at

Intake Manifold Pressure labeled in PSI
Mass Air Flow Rate in CFM

the MAP is what I assume is giving me the IMP

but I did indeed mean 14 not -14 sorry about that
was thinking I was looking at my boost and had to reverse it to get vacuum...its been a kinda long day thanx for correcting me
 
What scan tool are you using?

MAF does not read volume. It reads air mass, hence name, Mass Air Flow sensor.

14 PSI of boost is a bad sign unless you're running lots of mods and tiny pulley.
 
not 14psi of boost or vac matt

my boost is around -10 at idle and than shoots up as I accelerate I have not gone WoT really so i dont know the total boost but I am getting positive right around the same time the car starts to miss

4 psi intake manifold pressure spiking to 14 under half throttle

been using my torque pro

the MAF reading in cfm I have no idea about matt I just wanted to see if my numbers were where they should be stock and if one was off I was going to research that angle. what the numbers values are were kinda gibberish until your explanation here

I'd link a pic if I could but its just a bar gauge that says MAF(cfm) with value underneath it

at this point the values could lead me elsewhere but my misfire has moved since the new fuel pump it would not let me read the code but im getting a misfire count on cylinder 5

so was going to check the components after engine cools. if all the components look good though I'm going to have to lean towards an air issue I know cylinder 3 and 5 run the leanest which was kinda my reasoning for checking my airflow and pressure numbers. it could be shooting me a misfire count on 5 and than a check engine light on 3 under a load but I wont know till it happens again and lets me read the code
 
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ok well than my only assumption would be that the value goes down as throttle increases and I'm ranging from 4 to -14
scanning while driving is not the easiest for me especially trying to open up throttle in city so if I missed the negative sign while checking gauge it was probably cause I was busy missing the squirrel or child or random bicyclist

not my intention to waste peoples time with impossible values ie mehbad
 


Ha ok so my scanner was recording my highest value and my current values so when I looked at my highest being 14.4 it was as the car shuts down

from idle to about 2.5-3k hard to tell hand throttling motor my values range from 3.7psi to about 8psi max hope thats valid
 
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I've been following this thread and noticed that you have not mentioned trying to run the car in SD.
So, does it miss when you run the car with the MAF unplugged?

Please excuse me if you or the mechanic has already considered this.
 
It was a combination of a faulty coil pack injector and fuel pump BP was nice enough to reimburse me for all the parts and labor
 


if you guys looked though the posts my car had the same problem. i used seafoam and the mystery oil every oil change and so far it has no more misfire which im assuming it was a sticking valve spring..
 
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