I am at a loss with the missfires....
07-06-2014, 06:07 AM
#11
Senior Member
Most common causes of misfire on your Ignition System is the Spark Plug Wire Routing. Did you route the wire properly after replacing the wires? Inspect the Crank Sensor if there are any magnetic debris sticking on the magnet.
Your Intake could be flooded with Oil Vapor from the PCV valve.
Your Intake could be flooded with Oil Vapor from the PCV valve.
Last edited by w0lvez; 07-06-2014 at 06:18 AM.
07-06-2014, 02:33 PM
#12
Senior Member
I don't know if this will help but, I've a '97 Scab, 4.6 with 234,000 miles on it. The truck weighs in at about 5300 lbs.
A couple of years ago it started doing what you describe. None of the mechanics I went to could figure it out, it was not consistent, came and went. It never had a code so I lived with it grinding my teeth. Note, I have a California truck since new.
So this year on a Nevada trip, after a hard pull on a hill the check engine light came on. Next was the loss of power. I made it to a big city (yes, there is such a thing in Nevada...depending on what part of the country you live in) and a specialty shop put their analyzer on it, "catalytic converter failure."
My truck has four cats in the system. After $2400 I literally had a new truck I was stunned and learned a lesson.
No way of knowing if this is all or part of your problem but it's worth a shot to have it (them) checked.
Good luck.
A couple of years ago it started doing what you describe. None of the mechanics I went to could figure it out, it was not consistent, came and went. It never had a code so I lived with it grinding my teeth. Note, I have a California truck since new.
So this year on a Nevada trip, after a hard pull on a hill the check engine light came on. Next was the loss of power. I made it to a big city (yes, there is such a thing in Nevada...depending on what part of the country you live in) and a specialty shop put their analyzer on it, "catalytic converter failure."
My truck has four cats in the system. After $2400 I literally had a new truck I was stunned and learned a lesson.
No way of knowing if this is all or part of your problem but it's worth a shot to have it (them) checked.
Good luck.
Good post and very true, - a converter issue could cause the the engine to run in that way. The OP went right for a compression test which was a good idea for overall engine health IMO. The engine is to the point of being wore out in need of a rebuild or replacement. When they are THAT low on compression you'll have intertmitant compresion issues at first, -that's until the cylinders can no longer hold adequate compression no longer. Once they get to that point, -no compresion = no ignition (spark).
BUT, I definitely would confirm compression was tested accurately before writing that one off.
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So yea, check the converters or just disconnect if in question. OR preform a vacuum test (install gauge) and test the converters yourself. You can always take it in for a flow test.
Reason I'm posting about the converters is because I really don't know how much bad converters will influence a compression test ? How bad would they have to be ?? Never experienced that one , but I'd definitely want to cover that question before going further. Hopefully someone here will have a little more on that.
07-06-2014, 04:28 PM
#13
Senior Member
It's more easier to determine Engine's health using a Vacuum Gauge. The Engine is Firing two cylinder at the same time to reach operating temp faster. One cylinder on the Compression Stroke and one in the Exhaust stroke.
The Problem with Compresion Testing is the Engine Needs to be in the Operating Temperature. If you remove the Spark Plug while the Engine is hot it could easily strip the thread because the head is made of aluminum. It's also hard to remove the Spark Plugs while the engine is hot.
The Problem with Compresion Testing is the Engine Needs to be in the Operating Temperature. If you remove the Spark Plug while the Engine is hot it could easily strip the thread because the head is made of aluminum. It's also hard to remove the Spark Plugs while the engine is hot.
07-06-2014, 07:37 PM
#14
Senior Member
Yea, but the OP went right for the heart, so to speak. A compression test won't lie. If you follow with each cylinder in the same way or as close to it as you can be. Usually good enough to call it acurate.
One at time w/a bump starter switch on the relay(solenoid) is quick and honest. Most likely the best way, for the normal Joe. That's IF you choose to test @ operating temp. Testing at relatively the same temp is fine IMO..Uknow, up to two hours after shut down to prepare if need be, then test in succession, - one after another fairly quickly. You can always go back to the first to double check accuracy following your last cylinder. That's if there's and question.
Still skeptical ? Yes there's other ways, -
If your worried about about damaging the plug chamber threads when hot, - remove the plugs cold and anti-sieze them. I've never done that, but yuh could if concerned.
Adding oil or not, -incorporate that one with all , - always compare cylinders with same tests.
Sort of common sense , - or not. Not sure on that one lol.
One at time w/a bump starter switch on the relay(solenoid) is quick and honest. Most likely the best way, for the normal Joe. That's IF you choose to test @ operating temp. Testing at relatively the same temp is fine IMO..Uknow, up to two hours after shut down to prepare if need be, then test in succession, - one after another fairly quickly. You can always go back to the first to double check accuracy following your last cylinder. That's if there's and question.
Still skeptical ? Yes there's other ways, -
If your worried about about damaging the plug chamber threads when hot, - remove the plugs cold and anti-sieze them. I've never done that, but yuh could if concerned.
Adding oil or not, -incorporate that one with all , - always compare cylinders with same tests.
Sort of common sense , - or not. Not sure on that one lol.
Last edited by Jbrew; 07-06-2014 at 07:39 PM.
07-06-2014, 08:24 PM
#15
Senior Member
Aluminum and steel expand and contract at different rates, removing spark plugs from an aluminum cylinder head while hot can actually cause thread and cylinder head damage.
The spark plug has two primary functions:
To ignite the air/fuel mixture
To remove heat from the combustion chamber
A Vacuum Gauge will tell you almost everything.
The spark plug has two primary functions:
To ignite the air/fuel mixture
To remove heat from the combustion chamber
A Vacuum Gauge will tell you almost everything.
Last edited by w0lvez; 07-06-2014 at 08:54 PM.
07-07-2014, 06:19 PM
#16
Okie.
Thread Starter
Would I hook a vacuum gauge to my main vac hose going to the booster? Or somewhere else? If it is indeed a bad engine ive found a temporary engine out of a 98 mustang I planned on swapping intakes on. I know mines a windsor 4.6. But would it matter if the mustange had a Romeo 4.6?