Hi guys, my car has this poor acceleration issue for 3 years now and none of the mechanics so far could find the problem, but lots of things were done with no luck.
I own a 1.2 mk2 punto 8V which should have a top speed of 155km/h and an acceleration 0-100km/h in 14.5 seconds, am I right? (I googled factory specs)
Well mine has a top speed of 149km/h and astonishing lightning fast acceleration 0-100 in only 36.7 seconds!!! (did multiple tests this was the best)

The following are the things done so far, not fixing the acceleration issue ... yet
- changed complete exaust manifold, also removed catalytic converter (thought it was clogged) gained about 5% power and a hell of noise out of the exaust
- put KN air filter gained maybe 5% power
- engine rebuild because 1 cylinder had bad compression (changed piston rings, valves, flying bearings, valve rubber rings and valve guides) gained about 10% power
- adjusting valve clearence because there was a ticking noise on every rev. Now this is strange because after adjustment I lost around 20-30% of power, despite ticking noise was gone.

Diagnostics show no faults at all, sensors and sensor readings seem fine, O2 sensors working, input manifold vacuum is around 18 idle, 20-22 when driving, new sparkplugs, cleaned fuel injectors a few times had no influence on engine power. Idle is steady but sometimes there is a random "bump" the flow from the exaust is sometimes uneven, fuel economy is awful and there is like unburned fuel smell from the exaust although ECU shows no missfires. I did reset the ECU after valve adjustment but it was the same. Fuel pressure is 3.5 bars and does not drop, very sudden push on the gas pedal makes the engine almost completely stop.

Any ideas on this? Im open for questions and suggestions. I will take the car to check those valve clearences again to a different workshop but before I spend more money on that, maybe there are some good ideas.

Thanks in advance!

buy new engine = problems fixed

My guess, valve adjustment incorrect (the only conceivable way it could have a significant effect on performance), cam timing out a tooth or two.

Compression test (dry and wet) might reveal something.

Thanks man, the sad thing is that the last thing done was the valve timing. Cam timing should be ok cause it was checked by me and multiple mechanics.

Check it. It's easy peasy to do -- all you need is a metric feeler guage, a new cam cover gasket and some gasket goo.

Well guys, I took the car to the official Fiat service, they checked the valve spacings, they are perfect. Thay told me the first O2 sensor was melfunctioning and the mixture was rich, so I replaced the sensor, but everything remained the same. What else has to do with the fuel mixture, could it be the ECU?

kebbz said:

Well guys, I took the car to the official Fiat service, they checked the valve spacings, they are perfect. Thay told me the first O2 sensor was melfunctioning and the mixture was rich, so I replaced the sensor, but everything remained the same. What else has to do with the fuel mixture, could it be the ECU?

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Alot
Map
Engine coolant sensor
Lamba pre and post

Based on other inputs like cam and crank position, with throttle position etc

Lacking power to me sounds like timing is out

Ziggy

I have a diagnostic tool, I can check for vacuum, engine temperature and throttle position, the readings are all fine. But the first O2 sensor readings are uneven. The sensor is brand new and works exactly as the old one, so something else is causing the mixture problem. Cam and crank positions were checked too. Running out of ideas here. Should I try to get another ECU and try that?

Can't see it being the ECU. Generally you'd get a misfire or something pretty drastic.

From memory, narrowband O2 sensors do give uneven readings.

kebbz said:

But the first O2 sensor readings are uneven.

Click to expand...

fingers99 said:

From memory, narrowband O2 sensors do give uneven readings.

Click to expand...

Agreed. After new lambdas (both) and cat, this is what I get (bottom two lines: pre- and post-cat): :idea:



As far as I'm aware: that's how it should be. :chin: