Bad stutter between 2.5k - 4k

[rbrocky]

Hi all, recently bought a 197 as a track car and am noticing that sometimes (not all of the time), I have a big stutter between 2.5-4k RPM. Pedal goes nowhere, just loads of pops and bangs. Then it will clear itself.

Alternatively, if I nail the throttle, it clears it, or if I drop a gear to take it out of this range, it will clear itself.

This happens randomly, engine hot or cold. Some journeys - not at all. Some journeys, every single time I am in this RPM band.

This is my second 197 (I used to own an R27), and am pretty sure this isn’t “the” 197 flatsport. I’m sure this must have been a pretty common issue in the past, can anyone provide any insight?

Thanks

Ryan.

 

[Usman]

I had a similar problem. After a lot of misdiagnosing, it turned out the be the spark plugs. I would take them all out and check them.

 

[rbrocky]

I had a similar problem. After a lot of misdiagnosing, it turned out the be the spark plugs. I would take them all out and check them.

We thought a similar thing and replaced ours. Sadly still the same issue.

 

[Usman]

Ohh

Any fault codes?

 

[rbrocky]

Sa

Ohh

Any fault codes?

Sadly not. Occasional emissions light (but I think this is a separate issue and due to a faulty lambda).

 

[Usman]

The faulty lambda could be causing the misfires?

 

[Usman]

Plug in an obd reader and look at your lambda sensor readings?

 

[rbrocky]

Plug in an obd reader and look at your lambda sensor readings?

Any idea of expected values?

 

[Usman]

It usually shows up as a graph. The first lambda should move up and down on idle. The second stays relatively flat.

Also, the obd reader will pick up fault codes you wouldnt see on the dash.

 

[Usman]

Also, you are using v power or momentum right?

 

[lewishunter98]

Sounds crazy but when I had my old ktec system my car would do this. As soon as I switched it for another exhaust it went away. Are you running aftermarket exhaust or stock?

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[rbrocky]

Also, you are using v power or momentum right?

I know I should be using 97, but in my old 197, it aided the flat spot. But as mentioned - this is not "the 197 flat spot". Far worse. It's almost like the throttle pedal provides 0 input no matter how hard you press it (apart from full throttle only). It will provide 0 load through the power train. It sounds like we are in an anti-lag mode.

 

[rbrocky]

Sounds crazy but when I had my old ktec system my car would do this. As soon as I switched it for another exhaust it went away. Are you running aftermarket exhaust or stock?

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The car came with an aftermarket one. I think the guy called it a "toyo" god knows, haven't heard of it.

Initially, it was decatted, but he removed this to get through an MOT. I believe it has a cat in it currently, and an aftermarket backbox.

Do the symptoms sound the same?

"It's almost like the throttle pedal provides 0 input no matter how hard you press it (apart from full throttle only). It will provide 0 load through the power train. It sounds like we are in an anti-lag mode."

 

[lewishunter98]

The car came with an aftermarket one. I think the guy called it a "toyo" god knows, haven't heard of it.

Initially, it was decatted, but he removed this to get through an MOT. I believe it has a cat in it currently, and an aftermarket backbox.

Do the symptoms sound the same?

"It's almost like the throttle pedal provides 0 input no matter how hard you press it (apart from full throttle only). It will provide 0 load through the power train. It sounds like we are in an anti-lag mode."

Yep, exact same! It would cough, splutter, sound like it was misfiring like you say anti lag too. If I changed gear when it did it or went through that rev range and it was spluttering it would make a really loud bang sometimes. Mine would still do it if I floored it though

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