Just installed a 15% reduction pulley (& smaller belt) to my 05 R53, including a set of NGK BKR7EQUP plugs and have noticed a hesitation, feels like a single misfire just before 3000 RPM & about 8 PSI boost, any ideas? Wasn't apparent before the pulley upgrade. No trouble codes according to my UltraGauge.R53 Hesitation after reduction pulley install

 

If you havn't done anything as far as the tune, it's probably the ECU just learning & adapting to your changes, give it some time and see if it changes and goes away. (may take 6 or more start-n-stops, with at least 20 min. of driving between each)

 

Might be stupid question but torque wrench was used on everything correct ?

 

Belt size might be an issue too. With the company I got my 17% from they send the same size belt for all three pulleys they sell and that just doesn't work. Some still don't send e right size with a 15%. I was having belt slippage when I fist installed that was acting like a hesitation in the acceleration.

 

Everything is torqued up ok & the belt is the correct size so I am confident there is no pulley or belt slip.

Others have mentioned it may be a bad plug or the common 'yo-yo' problem, I will change plugs tonight & see if that makes a difference.

 

As long as you have one full hole showing on the tensioner you can rule that out. If not, then I would reconsider swapping the belt. Hope you find the solution soon.

 

absolutely check to make sure the belt is seated properly, that you can see one hole on the tensioner. One very easy way to tell if your belt is slipping,.go for a drive about 20 minutes..then touch the belt a slipping one will be very hot to the touch...very hot.

Also double check the spark plug gap..and that the plug wires are fully and solidly connected.

 

Also think it could be belt slippage....I had this hesitation for months after my install in certain rpms and throttle loads. During my first dyno run ever the tech noticed a power drop off followed by short spikes...installed new (correct 15%) belt and problem went away...I assume based on your post you have a boost gauge so you might check for that drop off...

 

Belt is not slipping & is seated correctly, there is one hole showing on the tensioner strap & plug leads are fully seated.

BTW, you can not gap BKR7EQUP plugs.

 

Problem resolved, Ambroz (KAVS Motorsport) picked it, was the plugs, put the old plugs back in, problem gone, put the BKR7EQUP back in & problem is back.

Cheers & thanks for your suggestions.

 

Correct, when researched the O.E plugs, they were considered an agricultural ( Lawn Mower Grade) Plug!!

But yes, I'm not a fan of the four tipped plug, they were "the thing" In the late 90's, but now a days, there's a reason why Bosch is the biggest backer of it, and why NGK just produces whats O.E.M. In the end, they are garbage, O.E. or not IMHO. I put iridium plugs in the MINI and in my Camaro ( Oddly enough the V6 in 1996 used iridium as O.E, anything else and it will set off a random multiple misfire) and haven't looked back.