OK so I have 7% loss of compression on CYl 2 and 8% loss of compression on Cyl 8. There is a misfire. Pulled the valve cover and everything looks fine. Injectors aren't leaking, plugs look good, COP are working fine. ANyone have any ideas what can cause this. The car shakes at idle and falls on it's face as soon as you go to pull out.
expert advice needed on a mis
- Thread starter 01BlueCobraVert
- Start date
Dangit I wish I could help ya with that but I don't have a clue. Is the car throwing a code?
Jamie R.
'01 Silver Cobra
Jamie R.
'01 Silver Cobra
have you done anything to it engine wise? bent valves can cause this. I actually ran into pretty close to same prob. the car wasn't throwing any codes, and had power losses and missing a lot. i had two bent intake valves.
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I got no codes. It shakes at idle but nothing crazy sounds wise. Ford has no idea. They said that they need to remove the head to see and if they do that and find nothing, then I am out 1200 bucks and an engine in pieces. :shrug:
yea get yourself some compression gauges. take all the plugs out. then one by one check comp and do like 3/5 cranks and then check pressure. all should be close to each other. in my case i think i did 5 cranks and was getting 135psi for all but #6 cyl got 5psi. but this is a cheap way to make sure, w/ out spending that much money yet.
You guys see all these TSB's...
TSB for 2001 Ford Mustang Cobra V8-4.6L DOHC VIN V Technical Service Bulletins
Maybe these two deal w/ my issue
AUGUST 2004 Ignition System - Engine Misfire Diagnostics Tips
NOVEMBER 2005 Ignition System - Coil-On-Plug Misfire Diagnostic Tips
TSB for 2001 Ford Mustang Cobra V8-4.6L DOHC VIN V Technical Service Bulletins
Maybe these two deal w/ my issue
AUGUST 2004 Ignition System - Engine Misfire Diagnostics Tips
NOVEMBER 2005 Ignition System - Coil-On-Plug Misfire Diagnostic Tips
honestly i doubt that would be your prob. your car should have been to a garage by this time. but you can always check it out. you might be able to call ford or if it tells on that tsb site, what they dealer had to do and how they marked the car if it was seen by a tech. they usually do colored paint spots, stickers and such...
The car is already sitting at Ford and they told me, they have no idea why it is missing. The car has 33K on it and I had white smoke pouring out my exhaust. No coolant in the oil or the other way around. They said they need to pull the head. The oil was changed every 2K-2500 miles. They asked me about how often I changed the oil because when he pulled the valve cover, he said everything looked brand new.... I was told the next step is to pull the head. The problem is if they do and they don't find anything, I am out 1200 bucks. If they do find something then depending on what went wrong my warranty will cover it. I just ahte to be out 1200 w/ a motor i pieces if they find no issue. :shrug:
My car is already at Ford or I would have. I honestly went in thinking "White Smoke" blown head gasket. I would have looked into it more myself had I known all this was going to happen....
It sounds like you need to just let them tear it apart since it's in their hands and you can't check anything yourself. Another option would be to tow it home to check these things out yourself or find somewhere else cheaper to work on it.
Ask Ford to do it for you. At worst they don't find anything but the cost is cheaper than them ripping the head off.
one of the worst threads I've ever seen with regard to the responses. Seems like no one even read the first post.
now.
1. How do you know the cops are fine? How did you test them?
2. Same for the injectors?
3. 7-8% leakdown is not stellar, but the cylinder should still fire well. Where did the air leak from? out the intake, the exhaust, or the crankcase?
4. What plugs are you running?
Now, I would say you may not have a misfire, as that would be shown by a check engine light.
Whats your fuel pressure at idle and when you go to accelerate?
now.
1. How do you know the cops are fine? How did you test them?
2. Same for the injectors?
3. 7-8% leakdown is not stellar, but the cylinder should still fire well. Where did the air leak from? out the intake, the exhaust, or the crankcase?
4. What plugs are you running?
Now, I would say you may not have a misfire, as that would be shown by a check engine light.
Whats your fuel pressure at idle and when you go to accelerate?
I went around this block last year and thought it was the COPS. I reinstalled the originals and the car ran fine. Keep in mind, this happened right after I filled up my gas tank over at a local Cheveron. Ironically, I went back to that same Cheveron and the same problem came back. I finally did some diagnostics and watched the pressure to the left and right bank of injectors. The pressure seemed fine until WOT. The pressure would increase and then start to stumble when i reached over 3500RPMs. It looked like steps on the graph through 1st and 2nd gear. I would smooth out in 3rd gear but could still see the steps in the fuel pressure.
This, however, has been going on for at least 10 tank fills. If it was water, I would think that it would have gone away by now. I'm now thinking fuel filter, fuel pump, or maybe the fuel pressure regulator?
ok.. I found out the information and steps to test the COPs on our cars. There are two tests that you have to perform. One is for primary resistance while the second test is for secondary resistance. Tools needed would be a voltage meter that can test ohms.
For Reference:
- Stock coil resistance as per Autozones product
- Primary Resistance: 1.2 - 1.9
- Secondary Resistance: 3.5K - 7.5K
- Accel Super Coil - Part #: 140034
- Primary Resistance: 0.660 ohms
- Secondary Resistance: 6.1K ohms
- Accel's recommended percentage tolerance: 10%
- The higher the resistance = less energy to the spark plug = misfire or poor ignition.
To test for Primary Resistance:
To test for primary resistance, you will want to set the dial on the multimeter to 200 ohm. You take the positive and negative lead and hold them against the pins where the harness connects to the coil and see what the resistance level might be. If it falls within the recommended parameters, then so far so good. For example, I tested my Accel coil packs and they all read at 0.8 ohms. Since my multimeter is cheap, it rounds up instead of giving the correct resistance. I'm assuming that this part is good as it was the same across the board but will verify at work with a better meter.
To test for Secondary Resistance:
To test for secondary resistance, you will set the dial on the multimeter to 20k ohms. You will then take one of the test leads and press it against the connector that connects to the spark plug. The other lead then needs to be pressed against one of the pins at the top of the coil. Check to see what the resistance is and verify that they are within the recommended parameters. My Accel coil packes ranged from 5.24k to 5.32k. This verifies that my coil packs are all good. Since the amount of resistance is lower than the specifications, this means that more energy from the coil can be transferred to the spark plug to produce a hotter spark.
I hope this information will help you and others that might think you are having coil pack issues. If any experts could chime in and verify that what I have posted is accurate, please do. I personally feel that this is correct but will admit that I am not an expert and do not work on cars for a living. I just hate paying someone thousands to incorrectly diagnose my car only to have myself look at it and fix their screwups.
For Reference:
- Stock coil resistance as per Autozones product
- Primary Resistance: 1.2 - 1.9
- Secondary Resistance: 3.5K - 7.5K
- Accel Super Coil - Part #: 140034
- Primary Resistance: 0.660 ohms
- Secondary Resistance: 6.1K ohms
- Accel's recommended percentage tolerance: 10%
- The higher the resistance = less energy to the spark plug = misfire or poor ignition.
To test for Primary Resistance:
To test for primary resistance, you will want to set the dial on the multimeter to 200 ohm. You take the positive and negative lead and hold them against the pins where the harness connects to the coil and see what the resistance level might be. If it falls within the recommended parameters, then so far so good. For example, I tested my Accel coil packs and they all read at 0.8 ohms. Since my multimeter is cheap, it rounds up instead of giving the correct resistance. I'm assuming that this part is good as it was the same across the board but will verify at work with a better meter.
To test for Secondary Resistance:
To test for secondary resistance, you will set the dial on the multimeter to 20k ohms. You will then take one of the test leads and press it against the connector that connects to the spark plug. The other lead then needs to be pressed against one of the pins at the top of the coil. Check to see what the resistance is and verify that they are within the recommended parameters. My Accel coil packes ranged from 5.24k to 5.32k. This verifies that my coil packs are all good. Since the amount of resistance is lower than the specifications, this means that more energy from the coil can be transferred to the spark plug to produce a hotter spark.
I hope this information will help you and others that might think you are having coil pack issues. If any experts could chime in and verify that what I have posted is accurate, please do. I personally feel that this is correct but will admit that I am not an expert and do not work on cars for a living. I just hate paying someone thousands to incorrectly diagnose my car only to have myself look at it and fix their screwups.
^ good info
cobraracer46
Banned
^Bad info.:bored: It's a waste of time to ohm test coils because a coil is not being tested while it's under stress. In other words, the proper way to test an ignition coil is while it is in the car and the engine is running.:burnout:
The instructions I got for testing them were from Accel's website. I just expanded on what what said there by explaining the steps i took to test my coils.
The other way requires an oscilloscope or a scanning tool with an oscilloscope built in so that you can measure the ignition pulses when the coil is sent a signal. If you can find a shop to test them that way then by all means go to them and have it done.
The other way requires an oscilloscope or a scanning tool with an oscilloscope built in so that you can measure the ignition pulses when the coil is sent a signal. If you can find a shop to test them that way then by all means go to them and have it done.
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didnt read everyones post but. 7 and 8 % isnt really bad.
I would start with a new set of plugs and see how it responds.
from the little i read, it sounds like a plug/coil or maybe even a maf problem.
normally if you are missing on one cyl, then you really notice it the most at idle. and it will be down on power higher in the rpms but the shaking will normally go away in the higher rpms
I would start with a new set of plugs and see how it responds.
from the little i read, it sounds like a plug/coil or maybe even a maf problem.
normally if you are missing on one cyl, then you really notice it the most at idle. and it will be down on power higher in the rpms but the shaking will normally go away in the higher rpms
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