Off Idle Hesitation Stumble

[downtoearth1986]

It could be. I would start a process of elimination like your doing. Checking exhaust leaks/clamps, O2 sensors, injector o-rings, manifold leaks, coils, injectors, spark plugs.

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[Torinate]

I hear you. Pulled plug 1 again for another look. It was the highest misfire count. Coil looks brand new.

 

[slime_bullet]

Try this. Start your car and immediately turn your ac on max and drive around and see if you get those misfires

 

[downtoearth1986]

Spark plugs don't look bad. Have you ohm all them to check the internal resistor wasn't broken? All my spark plugs showed 5 ohm on my voltmeter

 

[Torinate]

Try this. Start your car and immediately turn your ac on max and drive around and see if you get those misfires

Yes. I’ve tried a/c both on and off and no changes.

I have not tested voltage on them. Put it back in. Also changed by bypass valve hose again to my usual 34 pill. Tried without the pill again and boost is an on/off switch. Then tried the stock 15 pill and it felt lazy!! So back to what I’ve ran the last 2 years.

Just disconnected my catch can as well to see if there’s any change. Not likely but can eliminate it from the equation.

 

[downtoearth1986]

I know you can ohm the injectors to check if there are in range but it won't display a clog injector. At idle in park do you hear cylinder pings or low misfire noise popping out the exhaust? You can also grab a spray bottle and fill with water. As your engine idles, you can spray a stream along the base of the manifold to hear any sucking noises which can point you in the right direction of a manifold leak. You would definitely hear the engine change idle characteristics by doing that. Then you can eliminate the possibility of a manifold leak. I'm not sure if you had a smoke test done for leaks.

 

[Torinate]

I know you can ohm the injectors to check if there are in range but it won't display a clog injector. At idle in park do you hear cylinder pings or low misfire noise popping out the exhaust? You can also grab a spray bottle and fill with water. As your engine idles, you can spray a stream along the base of the manifold to hear any sucking noises which can point you in the right direction of a manifold leak. You would definitely hear the engine change idle characteristics by doing that. Then you can eliminate the possibility of a manifold leak. I'm not sure if you had a smoke test done for leaks.

Interesting. I do note at idle an occasional small “pop” out the exhaust. What does that mean? I’ve also noticed slowing down as normal, an occasional pop out the exhaust. Almost like a backfire a small mini backfire. Can’t remember when it started, but it’s definitely there.

I’ve done 2 smoke tests myself and nothing. Last one 2 weeks ago I spent an hour and a half going over everything. Nothing.

I have not tried spraying anything on the intake runners / supercharger where the runners where the gaskets are. What would be best to spray and would be the least risk?

 

[downtoearth1986]

Interesting. I do note at idle an occasional small “pop” out the exhaust. What does that mean? I’ve also noticed slowing down as normal, an occasional pop out the exhaust. Almost like a backfire a small mini backfire. Can’t remember when it started, but it’s definitely there.

I’ve done 2 smoke tests myself and nothing. Last one 2 weeks ago I spent an hour and a half going over everything. Nothing.

I have not tried spraying anything on the intake runners / supercharger where the runners where the gaskets are. What would be best to spray and would be the least risk?

Yep. Your car is displaying the same exact symptoms how mine did. Over time the coils will go bad. They may look brand new but over time heat destroys the internals and they stop functioning properly. How many miles are on your plugs? They looked normal just looking at the tips and color. Only other way to rule the plugs out is to ohm them. I believe they all have to fall within the recommended factory range to be normal. A dropped plug could cause a misfire because the electrode could break easily. Checking gap as well. If you haven't tested the cam phasers with the voltmeter then you can do that to. My issue came down to my cylinder #1 coil. My code specified multi cylinder misfire and it provided the specific cylinder code. I had a cylinder #5 but that was were I had a clogged injector from letting e85 sit to long in the rails.

 

[Torinate]

5000 miles on the plugs. Car has not thrown a code. That’s the challenging part. No starting line to figure out what’s wrong. Gaps were exactly what I gapped them at when I put them in - 28. They all looked great.

Any ideas why I’m getting the most misfires at idle versus anywhere else? What does the little pops out the exhaust mean?

 

[slime_bullet]

Yes. I’ve tried a/c both on and off and no changes.

I have not tested voltage on them. Put it back in. Also changed by bypass valve hose again to my usual 34 pill. Tried without the pill again and boost is an on/off switch. Then tried the stock 15 pill and it felt lazy!! So back to what I’ve ran the last 2 years.

Just disconnected my catch can as well to see if there’s any change. Not likely but can eliminate it from the equation.

I did have this issue but turning the ac on slowed the misfires from ramping up.
Im not sure which fixed it, but when I did oil pump gears I changed all the timing components and new vct solenoids, along with a new battery and all new gaskets for the spark plugs, valve cover, and vct solenoids. Now I only get a few misfires, like maybe 5 per long drive cycle.

 

[downtoearth1986]

The misfires (popping)your hearing in the exhaust is either the coils or injectors. If you have some the can loan a good set of coils to check and eliminate that would help greatly. Other than that swapping coils would be a option but your car isn't throwing a specific cylinder code. I saw this video on YouTube were the guy moved a few coils around after some codes was pulled and the misfire went away. And I assume you cleared all KAM codes? I know his mustang is a different year but principles still apply.

 

[downtoearth1986]

I did have this issue but turning the ac on slowed the misfires from ramping up.
Im not sure which fixed it, but when I did oil pump gears I changed all the timing components and new vct solenoids, along with a new battery and all new gaskets for the spark plugs, valve cover, and vct solenoids. Now I only get a few misfires, like maybe 5 per long drive cycle.

Did you check the volts coming off the throttle body sensor while closed and fully open with engine off key-on only?

 

[slime_bullet]

Did you check the volts coming off the throttle body sensor while closed and fully open with engine off key-on only?

I did. I also got a new throttle body because mine was doing that clicking thing at idle. Pcm also took a shit about 5 months ago. Keep frying number 6 coil. New pcm didn't change the misfires but solved my coil from getting fried. I couldn't feel them but could watch them going up on my monitor.

 

[raidernixon]

Yep. Your car is displaying the same exact symptoms how mine did. Over time the coils will go bad. They may look brand new but over time heat destroys the internals and they stop functioning properly. How many miles are on your plugs? They looked normal just looking at the tips and color. Only other way to rule the plugs out is to ohm them. I believe they all have to fall within the recommended factory range to be normal. A dropped plug could cause a misfire because the electrode could break easily. Checking gap as well. If you haven't tested the cam phasers with the voltmeter then you can do that to. My issue came down to my cylinder #1 coil. My code specified multi cylinder misfire and it provided the specific cylinder code. I had a cylinder #5 but that was were I had a clogged injector from letting e85 sit to long in the rails.

This. My 2011 Mustang just had this issue and it was definitely the coils. I almost went insane trying to isolate the issue. No CEL. I can add that the car was misfiring especially at higher rpms and wide open throttle. It would get worse as the engine warmed up. Since they are expensive, see if a buddy with known good coils can let you borrow theirs to see if the car runs any better. It is difficult to test the coils with any certainty if multiple ones are failing/bad as the resistance and other parameters changes with temp and operating demands/stress. Even new ones can be bad out of the box unfortunately...

 

[Torinate]

I’m a little surprised by possibly being the coils. There’s 23k miles on the car. I can understand one going bad or possibly 2 at the same time, but I’ve got misfires all over the place lol. It could be and I certainly appreciate the help! Is there a range the coils should be in if I tested resistance? As you said, could be difficult to test though. Unfortunately don’t think I want to start taking stuff off a buddies car to test and don’t have another set of coils.

I’ve got a few hours tomorrow to try to dig in some more. What else can I try to check for intake gasket leak? Will be difficult to get it right at the blower/head junction. Idled pretty steady as it is now, so what should I notice if indeed there is a leak? I’m a little reluctant to try something really flammable. But I do know they would increase idle speed. By how much though? How noticeable?

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