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CVO Technical => Twin Cam => Topic started by: KevVallance on January 27, 2022, 08:38:05 AM

Title: Persistent Misfire
Post by: KevVallance on January 27, 2022, 08:38:05 AM

Hola from España.
I have recently taken delivery of a 2009 FLHT CVO.
It has a persistent misfire between 2000 and 2500 rpm.
It doesn't matter what gear you are in or the speed you are travelling at.
Does anyone have any thoughts on the cause and a cure ?
Mucho Gracias Amigo's.

Title: Re: Persistent Misfire
Post by: Joel on January 27, 2022, 09:14:45 AM

Welcome from Spokane Washington.
Spray water on the plug wires when misfiring to see if it gets worse.
The plug wires were ran close to the seam of the fuel tank and they would rub through.
Still I would start with new plugs and wires.

Title: Re: Persistent Misfire
Post by: KevVallance on January 27, 2022, 09:44:58 AM

Hi, didn't think of that.
Already filled with Super Grade Fuel, 3 tanks so far, that hasn't changed anything.
My next port of call was going to be the plugs.
Many thanks.

Title: Re: Persistent Misfire
Post by: kojak on January 28, 2022, 04:44:11 AM

Plugs/wire. Also check your fuel system, starting with filter.

Title: Re: Persistent Misfire
Post by: KevVallance on January 28, 2022, 06:41:36 AM

Many thanks.
I will keep you updated.

Title: Re: Persistent Misfire
Post by: vetteman170 on January 29, 2022, 11:17:06 AM

Check MAP sensor wiring had same problem

Title: Re: Persistent Misfire
Post by: KevVallance on January 29, 2022, 11:28:39 AM

Thank you.
I shall research MAP and look into it.

Title: Re: Persistent Misfire
Post by: Mano on February 03, 2022, 11:03:00 PM

OOOOOOOOOHHH I have the fix for you my friend. It took me almost 2 years to figure this one out and a few $.
I replaced the spark plug wires, spark plugs, coil, twist grip sensor, gas, fuel filter and even repaired the wires and plug at the throttle position sensor and this misfire would just not go away. No check engine light and no codes. One day I was sitting with a old dog and I was telling him my problem and with out hesitation he said..................

Throttle body sensor is covered in oil, remove it, spray and clean with electronic cleaner and you will be ok. I removed it and yes it was covered in oil and dirt. I ended up buying a new one. I have over 200 000KM so I figured it was time. I guess we should listen to the old guys. :D

I tried to download some pictures but cannot resize them. If needed I can do them for you. Let me know.

Title: Re: Persistent Misfire
Post by: busarealfast on February 03, 2022, 11:20:08 PM

check injectors/wiring. Might not be plugged in all the way.

Title: Re: Persistent Misfire
Post by: KevVallance on February 04, 2022, 01:01:25 AM

Many thanks.
I shall let you know.
Gracias Amigo
Ok, I have cleaned MAP Sensor.
Will ride it tomorrow.

Title: Re: Persistent Misfire
Post by: longlast on February 04, 2022, 11:43:14 AM

It's possible there's carbon build up in the cylinders/ heads . Remove air filter start motor up run at 2k rpm hold it there then spray lightly with a pump spray bottle water into the intake body . There will be a lot of smoke (black if carbon build up then will turn white cloudy)  do it three to four times this will clean out the cylinders of carbon build up. Replace plugs n wires.

Title: Re: Persistent Misfire
Post by: KevVallance on February 04, 2022, 01:10:34 PM

Thank you.
Just cleaned MAP Sensor.
Need to road test.

Title: Re: Persistent Misfire
Post by: KevVallance on February 04, 2022, 01:37:51 PM

Cleaned MAP Sensor.

Title: Re: Persistent Misfire
Post by: KevVallance on February 04, 2022, 01:38:46 PM

Dirty MAP Sensor.

Title: Re: Persistent Misfire
Post by: Mano on February 08, 2022, 01:59:42 PM

Yours looks a bit cleaning than mine did. Hope you solved the problem.

Title: Re: Persistent Misfire
Post by: KevVallance on March 10, 2022, 04:49:51 AM

Hi, I'd like to thank you all for the assistance in this post.
As the CVO was still in warranty I took it back.
The fault was an HT lead.
It was a Snug fit and eventually gave up.
Mucho Gracias from the Iberian Peninsula.
Ke.

Title: Re: Persistent Misfire
Post by: longlast on March 10, 2022, 08:13:01 AM

Glade you got it running back to like it should  :2vrolijk_21: .Be safe!!

Title: Re: Persistent Misfire
Post by: KevVallance on March 10, 2022, 08:14:32 AM

And you, take care.

Title: Re: Persistent Misfire
Post by: ultra13 on March 11, 2022, 03:37:36 PM

Can you explain what the HT lead is and the "snug" fit please.

Title: Re: Persistent Misfire
Post by: KevVallance on March 11, 2022, 03:52:12 PM

The lead between the coil and the spark plug. HT.
Snug, as the engine vibrated, it pulled on the cable between 2000 and 2500 revs making it misfire.
Hope this helps.