2003 f-250 v-10. It’s had a miss for a little over a year, annoying but not the end of the world. Ive taken it in to 3 different shops trying to get them to figure it out. Only one shop had any options to try. They replaced all the plugs except for one, that cylinder had a heli coil put in a few years back, they said they could t get the plug out without the heli coil coming out too. Now the miss has turned into stuttering from the engine while driving. 2000 rpms is pretty good, under that and it’s almost undriveable. Feels like it’s going to break the flex plate. It’s also not constant, definitely worse lower rpm and lighter throttle. Anyone have any ideas or thoughts?

 

If this miss is related to anything the OBD-II protocol monitors there should be a DTC or "code" triggered with the CEL lamp illuminated---do you have that condition?

The Heli-coil'd cylinder could be properly repaired with one of the Time-Sert kits--many good independent shops are experienced with that operation.

Unfortunately I don't quite understand what this miss is or where it originates---your description isn't that clear.

 

When was the last time your cops were changed?

 

Just thinking out loud here. You mentioned that the miss is worse at lower RPM's? Generally with coil/plug/ignition related misfires, they tend to get worse in higher RPM's and they will generally throw a misfire code on that cylinder. (I'm using the word "generally" because it is not always the case, especially with these V10's it seems...). Since you're feeling the miss at lower RPM's and no misfire, it generally points to a vacuum leak or faulty MAF, even a TPS or IACV.

Do you have a code reader? Did you verify there are no codes? How about fuel pressure?

You might need to get a OBD2 bluetooth adapter and download ForScan. Start reading live data and see if you can pinpoint what is happening.

 

For me 5.4 V8's I've found the misfire vibration to be more noticeable at lower RPM's and seemingly smooths out as those rise.

I was initially thinking if this was an F-350 it might not have the full OBD-II system but even at that a confirmed ignition problem would indeed be shown in a scan and the CEL also illuminated.

Things might be different for the V10's but I've never seen anything to say DTC's for misfires are not part of the OBD-I system though. At this point changing ALL COP's is NOT necessarily the definite "fix" for these reported issues.

 

How many miles on the vehicle?
You can get a lot of misfires before a code is set, particularly if they are random, not just one cylinder.
First, I would get the heli coil out of there and repaired with a Timesert or other good repair technique.
Timesert carries a repair insert for prior heli coil repairs, don't know about any others.
What plugs were installed? If not Motorcraft SP479s, then replace all the plugs and torque them to 25 ft/lbs.
How long have the spark plug boots been in there? If over 50k get a new set of boots and put those in, too.
This might clear up the misfire and at least get you to a point where you know more about the overall condition of the ignition.
The misfires should be visible in the live data from the computer even though a code is not set and would tell you if one cylinder or multiple cylinders have issues.
Interesting the 3 shops couldn't see that.
Check all the vacuum lines/fittings for cracks/leaks, particularly the PCV hose near the throttle body plate.
Check the air intake tubing between the MAF and throttle body for any cracks/leaks and clean the MAF.
Check the fuel pressure at the fuel rail test port.
If the misfiring gets bad enough it can ruin a catalytic converter.

 

To my knowledge only 1 of the cop has been replaced. Only about 100,000 on the engine. I do have a code reader, it’s not a super expensive one but has seemed to always do the job. There’s also one one the tuner I have that I leave plugged in constantly as I use it to view engine temp, load, throttle position. I’m not sure what I’m looking at or would be looking for when viewing the engines live data

 

I'd verify that the O2 sensors are switching, check long term and short term fuel trims as well, ensure they are within +/- 15%. There is generally a misfire counter you can verify if you are actually getting a misfire (I've yet to know if that actually works).

 

Ok, dug a little more and found code P1000. Which looks like it could point towards a number of things. Any of the problem areas related to this more likely to be the issue, more common of a problem?

 

Looks like second O2 sensor is done (bottom left)? Stayed at that number the whole drive

 

Well, fortunately/unfortunately that reading for O2 B1 S2T is normal. It is confusing to say the least.

Your short term fuel trims look good.

I would pull up the PID's for the MAF, checking voltages at hot idle (0.7V to 1V) and Key On, Engine Off (0V), however seeing those fuel trims make it look like it will be OK, but it is worth trying.

Other than that, I would be interested if there are methods for using a scan tool to determine if there is a way to validate a particular cylinder is not firing correctly (i.e. Power Balance test, which I have still yet to find out how to do)... Can you say that this is a dead miss or just a slight miss?

 

is it normal for the o2 b1s2t reading to not change at all, regardless of throttle position or load? What do you mean by dead miss or slight miss?