Unresponsive throttle - Slow 197

[Brunoandrade98]

Hi all,

*Apologies for the fairly repetitive posts, but I'd like to make sure I've done everything I could*

My 197 feels sluggish, and has for pretty much since I've owned it. A few months ago, I did a compression test and all cylinders showed 125-ish PSI consistently on all 4 cylinders. I had a garage double check it for me and they got 140PSI - Not sure which will be the more accurate, but my gauge was a brand new Sealey one - Wet test showed figures of 180+PSI across all cylinders on my gauge (can't remember the garage's wet figures), which points to piston ring wear

While this isn't great and I should expect performance loss, I'm not sure if it should be as bad as it is now. I find that the car is very lazy setting off from first but becomes more responsive when higher on the revs. Hard to explain, but I feel that the throttle doesn't do much at low revs when driving off in first and the throttle feels unresponsive.

It's also happened a few times where the car misfires/flatspots at random times, more noticeable when going uphill, where the car stops accelerating and just shudders despite me being on the throttle.

I have a CLIP, so can look at live data, but not sure what I'm looking for, however I did notice that my throttle only goes up to 89.8% when I press it all the way down. I test drove another 197 on similar mileage (unsure on compression figures, but doubt it's been well kept all its life) and despite having a flat spot due to having a de-cat manifold, it felt much more responsive when driving off and more lively higher up the revs as well.

Maybe mine will never be like that until I replace the engine, but I feel it shouldn't be this bad either. So far, I've done:

1. Replaced coils - Have not replaced the plugs, but they're only a year old and it was an issue before and after fitting this set
2. Fitted a MAP sensor holder, which keeps it in place and apparently helps with misfires and performance issues
3. Cleaned throttle body

Any help troubleshooting this would be awesome, as I'm not in a position where I can rebuild the engine just yet and will likely only be a mid-2026 job.

Screenshots attached

Thanks in advance

 

[turkie172]

I had a similar experience so I replaced the plugs, both Lambdas, coils, MAP sensor, manifold temperature sensor, and CAM position sensor, also switched full-time to super unleaded (97), the highest fuel available in Northern Ireland. I got an RS Tuner with a cold start map, which improved things but wasn’t perfect. The RS Tuner log showed the knock sensor registering multiple counts constantly, which reduced after the replacement parts, making the engine feel lighter and more eager. After this while fixing the aux belt and a lower metal water pipe leak, I removed, cleaned, and refitted the knock sensor, then after the second fill-up, the car felt noticeably better.

On top of that, I have another 197, K-Tec Racing at one point fitted a K-Tec manifold, piper one-cat exhaust, new cam belts, knock sensor, along with RSTuning custom map on their dyno, which is great to drive compared to my daily performance wise. A couple of months later I picked up another 197 for my uncle with an upgraded manifold, one CAT, no middle box, and a standard rear box. It has the same cold start RS Tuner map and currently runs slightly better than my daily.

So without exactly experiencing your car I would replace the knock sensor then CAM sensor as the next step with a couple of fuel fills in-between to see any improvements.