Flat Spot & Sluggish (solved!)


New Member
I travelled to Bath last weekend and collected my 3rd R :oops: . Its a nice standard white uk car :wink: , but it has a minor problem.

Its got a flat-spot under part throttle which is through all the rev range, and under full throttle it splutters through the flat spot and is quite sluggish at pulling away, then after a gear change and full throttle again it pulls like it should do :? .

During the flat-spot i can hear boost building but no go lol, it feels like a really laggy T28 :? :lol: .

Its definately not the 'interwarmer' effect, as im aware of this and have experienced the heatsoak feeling in my first R :roll: :lol: .

I've changed the fuel filter & leads, and its had a recent service replacing the dizzy cap, arm & HKS plugs etc. I've also done a fault code check and it reads 55 - all clear, so i presume its not the afm, det sensor or such like.

It's a very high mileage engine (over 150k :shock: ), but apart from the above problem it runs and idles mint and reads 155 across all four cylinders.

Has anyone got any ideas on what to try/check next?

Get injectors cleaned maybe?




Maybe the Spark Plugs? the gaps might have been change for higher boost before put back to std before selling? or just old/dirty plugs.

Mines hesitating & spluttering but i/m putting it down to spark plugs at the mo..


New Member
When you do the fault code check if you start the engine while it is still flashing the code, there is another sensor that it confirms is working. Can't remember which sensor it is though :roll: .

You could always check that one aswell. :)


check the catalytic converter, mine was blocked or near blocked. Also try out some injector cleaner stuff, it might help.

hope you get it fixed.


New Member
Cheers, I'll try all that suggested, i havn't got a cat tho mate, its got a decat pipe on there :wink: .

Anyone else?? :?

Fire & skill

Vintage member
make sure the maf sensor connection is good, give it a clean and make sure its clipped in properly - just an idea :?

gtir bean

New Member
my det sensor was playing up recently but it never showed up on a faultcode check.its like a different car now its fixed.


New Member
gtir bean said:
my det sensor was playing up recently but it never showed up on a faultcode check
:? maybe worth checking, i might swap it with the other engine i have :wink:

ive also just changed the afm and filter so we'll see if that works



It was the afm that was dodgy. Swapped it for a different one and it runs perfect now. Pulls quite well on standard boost :lol: .

So much for the fault code check :roll: