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I don’t think a vacuum test is going to be the most useful to you given your circumstances.
Compression and a chemical head gasket test would be more useful in narrowing down the possible causes of your symptoms.
Yeah man! You gotta get it! At only about $100 you’ll be so glad you did :cheer:
That’s a good find…a blown head gasket can certainly cause misfires. Have you considered doing the compression test I mentioned? Also you can rent a coolant system pressure tester, or if you want to buy one I can give you a few suggestions.
If coolant smoke is coming out of the tailpipe that’s a very bad sign. You can always confirm that it’s the head gasket with a chemical head gasket test kit.
[quote=”ArmedsouthernEr” post=159565]Don’t forget that if the boots of the spark plugs are deteriorated it can let the spark jump right into the block instead of going through the spark plug. Does the porcelain part of the plug have any carbon tracking on them at all. Like jay said the 3 main things you need to fire those cylinders is spark, fuel, and compression. The vehicle missing under a load is classic sign of an ignition misfire.[/quote]
Right on!
And it could explain a misfire under load. The spark is going to take the path of least resistance. At idle this could mean jumping the plug gap, but under load and higher compression it may actually prefer to jump to the block. Since you have known damaged parts go ahead and replace the plugs and wires with your tune-up. The good thing about you getting a scanner for yourself is that you can clear the codes after the tune-up and see if they come back after a few drive cycles.
Remember to let us know if you fixed it. A lot of people just disappear and we never get the case closed.
Those really don’t look bad at all. You might have heard of the FASTEC diagnostic method. When dealing with a no start it could be…
Fuel
Air
Spark
Timing
Exhaust
CompressionSince your vehicle does run except for a few cylinders misfiring we can assume Timing, Exhaust and Air are good (you could have a carbon deposit on a valve blocking exhaust or air flow but that’s not very common).
So now we’re left with Fuel, Spark, & Compression. If you don’t have any direction you should start with the simplest thing and move on from there. Spark is probably the easiest to verify. Then compression…a compression gauge is pretty cheap and Eric has a video on how to do it. Finally fuel can be verified with an injector balance test and testing to see if you have injector control (scannerdanner has some videos on this). Injector control can be done with a noid light or test light and is easy to do. The balance test requires a tool that provides a controlled pulse width to the injector and a fuel pressure gauge.
Getting engine codes will still be important. Did your scanner come in yet? Also I know the power balance test seemed like a waste but it would good to keep working on that. You don’t want to be doing tests on a cylinder that isn’t misfiring. If you really can’t get any clarity on the power balance test you’ll just have to test all your cylinders (which is what you do anyway when doing a compression check).
Since your visual inspection didn’t reveal much you’ll have to start working “scientifically” through your diagnosis. A tune-up may fix it but I can’t even count the number of times people replace plugs and wires and it doesn’t fix a thing. Hopefully if you do it, it’s because you wanted/needed to do it anyway. But if I had the choice between buying tune up parts or buying diagnostic equipment (like the compression gauge) I would spend money on the diagnostic equipment every time.
With 270,000 miles it’s very possible that you have more than one problem so the heat and no start may not be related as I’m sure you already guessed.
A blown head gasket can sometimes cause a no heat condition because it can force combustion gases into the cooling system creating an air pocket. The water pump will not be able to move coolant if there’s an air pocket around the impeller. A blown head gasket can sometimes cause a no start. So in this case the two would be related. A head gasket test kit isn’t too expensive but it requires the engine to be running. A better option may be to buy or rent a coolant pressure tester to figure out if you have a major leak somewhere, especially around the head gasket area.
With any no start you have to go through every factor systematically, using the FASTEC method is helpful.
Fuel
Air
Spark
Timing
Exhaust
CompressionYou have to verify each one of these. You mentioned a couple of them, but remember you have to increase the quality of your testing until you actually find the problem. For example, you checked the timing belt with a visual inspection and you can tell that the injectors are working because of fuel in the gas. But if you can’t find the problem with a surface level visual inspection you have to dig deeper. This could involve actually verifying the timing and doing an injector balance test etc etc.
You only have one wire because the O2 sensor is getting it’s ground from it’s contact with the metal exhaust pipe. That one wire is the signal wire. A O2 sensor that is fully warmed up will fluctuate between 0.0V and 1.0V with the most common range being like 0.2V-0.8V. The frequency of a normal O2 at idle is around 1Hz meaning it fluctuates about 1 time per second. A good modern multimeter will have a sample rate of 2-3 times per second so you should be able to observe both switching high and low values if you are in Volts DC with the red lead on the signal wire and the black lead touching a body ground. You’ll see the voltage jumping around in the 0.2V to 0.8V range.
You asked about a continuity check…I wouldn’t worry about ohming anything (except if you’re checking for a break in the signal wire). For starters your O2 has no heater (which is obvious because it doesn’t have 4 wires) so no need to ohm that. And in my opinion doing an ohm check on the O2 itself is about the most worthless test you can do on an O2 sensor.
[quote=”Dramegno” post=159384]I will pull them in the morning while I finish a coolant flush. I do know that they are autolite double platinum app 401 gapped at .054 in. When I bought the truck last Wednesday all of the spark plugs were gapped at .045 in. When I had them out they didn’t look to bad but I plan on replacing the spark plugs and wires this weekend. As far as I can tell the misfire is fairly constant if the rough idle/engine shake is any indication, but the power loss is pretty random and a possible sign of other problem(s).
[Edit:] I hope that the scan tool that I am getting in the mail will let me do a pcm based power balance test since it hooks up to a computer via bluetooth. *crosses fingers[/quote]
Unless you paid $1000 or more for that scan tool it’s not going to do a power balance test. To do that you need bi-directional control using factory scan software that is loading into a professional grade scan tool. But keep in mind that there is nothing special about a bi-directional power balance test. The scan tool/pcm is just doing what you can do manually (i.e. disabling an injector).
What you most likely bought is a generic OBDII scanner. Which will still be useful since you can give us the exact codes and also hopefully look at some live data. It’s always difficult to diagnose something like this over the internet, but the next step in this whole process is probably to post a list of all the codes you have.
Ok well try the power balance again, but if the misfire is intermittent like your post seems to indicate it may be difficult. You might have to do the power balance at a higher RPM than idle. Also you could put in a spark tester and see if you have consistent spark. And like southerner said, it may very well be way overdue for a tune-up. Can you take a spark plug out of 3 or 6 and post a picture of it?
Whatever you get make sure it has live data! All plain OBDII code readers are basically the same thing (with some differences in quality). The real difference is whether or not you can read live data and how effectively that data is displayed. If you want to diagnose a problem related to a code you REALLY REALLY want live data.
With a $30 price range you will want to look into the bluetooth type code readers, as mentioned (I’m pretty sure they give at least some live data). They are cheaper because you’re not paying for a display and the other electronic guts, your phone takes care of that.
If a cylinder is contributing power there WILL be a difference if you disable it. It may be very slight (on a V6 and especially on a V8) but it will be there. Also keep in mind that the change may only last for a second because the computer is working really hard to maintain a stable idle and stoich.
I think the engine developing a slight shake is a better thing to take notice of than sound or RPM (unless it’s a four cylinder then it’s always obvious).
You should do the test again, and keep doing it on a know good cylinder until you get keen enough to observe the change. Keep in mind that even if you have a misfire code for 3&6 it may not be 3&6 that is misfiring. It could be a cylinder that is next to it in the firing order. Codes given by PCMs are good guides but they are far from fool proof.
Also your vehicle wouldn’t run if the injectors were stuck open like you mentioned.
Is it waste spark? Are 3&6 on the same coil?
