C230K hesitant at 4000rpm till about 4700 rpm

[Abbaso]

Hi guys as per title my car has a picked up a problem. When I drive below 4000rpm its perfect pulls like a train once the rev counter reaches 4000 rpm you really feel the drop in power then after about 4700 its normal again. It's more pronounced on an incline. Also if I hold it flat out the problem isn't too bad or you really can't feel it.
Any ideas on what it could be?? I was thinking along the lines of fuel pressure. The other thing that comes to mind is the vvt anybody can enlighten me on when its activated and deactivated. I've got a fuel pressure gauge but it doesn't have the right fitting for the MB rail and don't wana cut the fuel line to stick it in between with a T piece. I've done that to other cars but don't wana do that here.

Thanks

[RemoLexi]

I'd say your on the correct path with the fuel pressure to start.

Also check your supercharger clutch- possibly worn and slipping up in the higher RPM range. Dumb - but check that all the boost hoses aren't damaged, and also see if you can get your hands on a cheap o2 sensor air/fuel meter, that way you can tell what's happening- if it's too rich then possibly have a boost leak, of its too lean then hook up a fuel pressure gauge.

[Abbaso]

Thanks for the reply. I will hook up the boost gauge to see if I'm losing boost at that rpm. I've ordered the Walbro gsl392 pump in the meantime. Hopefully that sorts it out if not would be preventative measures as the car is at 246000 km. I'm also getting a P0803 code.

[John Jones Jr.]

Abbas, worth while making sure your fuel tank has no crap in it before fitting the new pump. I found crap in mine but only noticed it when the jacked up at an angle and the was filter off.

[Abbaso]

Abbas, worth while making sure your fuel tank has no crap in it before fitting the new pump. I found crap in mine but only noticed it when the jacked up at an angle and the was filter off.

Yes John I will see how much of a mission it is to take off and will clean it. I don't think it will be that dirty as its a plastic tank. I know the metal types are known for rust inside. I should have the pump by Thursday latest I think. Will pm you if I need info on the fitting.

[Abbaso]

Just a quick update. I hooked up the boost gauge yesterday to see if she was losing boost at the said rpm. The car behaved no hesitation in the problem area. Reading on gauge was just over 0.6 bar at WOT. Changed over fpr for the 4 bar and noticed the vacuum line of the super charger going to the breather was off. So reconnected but didn't have time to drive it.

[John Jones Jr.]

Yes John I will see how much of a mission it is to take off and will clean it. I don't think it will be that dirty as its a plastic tank. I know the metal types are known for rust inside. I should have the pump by Thursday latest I think. Will pm you if I need info on the fitting.

I should have been more specific when I said 'crap'. What I actually found was maybe some dirt, water and god knows what else but for sure it wasn't even 90% petrol (car was driving perfect) - I wonder is the crap etc accumulating on just that side of the tank due to it's design.

Oh, sure PM me if wish, doubt very much you'll need by assistance, just make sure if you haven't got the 90 degree banjo fitting, have a some 8mm fuel hose so you can make a nice smooth turn and the extra length of hose will fit very neatly under the pump/filter plastic cover. One other thing, the f/pump & filter carrier are made of rubbish metal so might be worth your while cleaning painting it first before fitting the pump and smearing grease or the likes between the carrier and the floor before bolting it back up. Mind too that you don't break the little rubber carrier hangers, replace if in doubt as these insulate the pump from shock & vibrations (cable/zip ties are not the way to go), thus you won't be using the new pump's insulation sleeve that's supplied.

[Abbaso]

I should have been more specific when I said 'crap'. What I actually found was maybe some dirt, water and god knows what else but for sure it wasn't even 90% petrol (car was driving perfect) - I wonder is the crap etc accumulating on just that side of the tank due to it's design.
7
Oh, sure PM me if wish, doubt very much you'll need by assistance, just make sure if you haven't got the 90 degree banjo fitting, have a some 8mm fuel hose so you can make a nice smooth turn and the extra length of hose will fit very neatly under the pump/filter plastic cover. One other thing, the f/pump & filter carrier are made of rubbish metal so might be worth your while cleaning painting it first before fitting the pump and smearing grease or the likes between the carrier and the floor before bolting it back up. Mind too that you don't break the little rubber carrier hangers, replace if in doubt as these insulate the pump from shock & vibrations (cable/zip ties are not the way to go), thus you won't be using the new pump's insulation sleeve that's supplied.

Thanks John. I'm still waiting on it hopefully get it by the week end though vi have fitted the 4 bar fpr. Once pump is installed will put it back on the same dyno to measure still contemplating the performance filter.

[Abbaso]

A quick question to all the guys on this thread. What fuel are you guys using. Here in SA we've got 95.

[RemoLexi]

I think all of California the highest octane we can get is 91.

There are a couple 76 stations that will sell 100 & 110 octane for 'race' purposes. But at $9/ gallon, ill stick with 91.

[Abbaso]

We used to get 97 until a couple years back. Even the race fuel has dropped from 102.6 to 98 octane now. Not sure what's the current price of race fuel here now.

[John Jones Jr.]

95 here.

[stefcep]

we got 95 and 98 RON in Australia. But I think in the US the equivalent fuel is about 4 ratings lower. So an Aus 95 is a US 91.