vadim

As of late I noticed a strange power surge at 3500-4000 RPM. Never had it before. It feels like an extra push, the car almost lurches forward when it happens. It seems to only occur at WOT.

It does not seem to be the clutch, as it happens in every gear around the same RPM.

Has anyone experienced this with a pulleyed M111?

I wonder what it is. Will reset the ECU tomorrow to see if that cures it.

BabyBenz6spd

I'm sorry, but I don't see having that "extra push" being a problem~ :p I love to get that extra push from my car.......like a Turbo or VTEC type of push

vadim

It feels like a "push". This means that the torque build-up curve is non-linear with a dip right before this push - something that did not exist before. In case of a turbo it would be expected and natural, but it sure is odd in this engine.

nukblazi

I mean, that's klinda the sweet spot with the pulley.

A. How long has the car been pulley'd?
B. What temps? All temps? At night when cold, in the day?
C. Have you changed your driving style? Remember the ECU is adaptive.

vadim

Not a sweet spot - it feels like a rapid series of jerks that culminate in one final lurch. As I said - it developed only recently, probably a couple of months ago.

A. Over 2 years
B. All the time
C. No. Driving as hard as I ever did.

nukblazi

I don't know of a dyno in the area, but you need to hit up a dyno jet and/or scan your codes.

If you want to make it up to the schnell meet we could take the car for a ride. This is a strange problem, could be fuel delivery, timing retard....

How long as it been happening? "As of late..." This tank of gas? This winter? Since my last oil change? Lastly, are you under warranty?

Amit1

Don't buy into the ricer philosophy that VTEC is actually worth a crap. We already have variable valve timing (better than the Honda/Acura VTEC system) in our cars. The ricers don't even know what VTEC is so they compare it to a turbo or a supercharger. Thats like comparing rims to exhausts. Forced induction compared to an engine manangement system? What a load of bull.

Ricers

vadim

I guess I have to dyno it, after all. There is a tuner shop in Fairfax called Autothority - they have a decent setup.

Timing - unlikely, unless the ECU went bananas. I use only 93 gas from Shell, Exxon and Mobil, so there should not be any reason for the ECU to retard the timing. Don't want to think that this may be a sign of the S/C going bad. Or maybe this is something related to the throttle actuator or throttle position sensor?

As for how long this has been going on - as I said, a couple of months. Not sure if there is any correlation with the winter gas formula(s), though.

nukblazi

There is def a loss with winter gas. They (gas companies) have also switched to a new preservative that rots the blatters of fuel cells, could be that is causing a problem with street cars. A simple possibility I thought of last night is the FPR. Not sure if that could be it. Also could be the fuel filter. Replace the little things. Reset ECU, change fuel filter and FPR, use a pressure gauge on the fuel rail...

If you can't figure it out I have a good MB shop up my way.

The ECU could have went bananas. Disconnect the battery for 1 hour, reconnect and see if it's fixed. Doubt it is the SC.


FYI- Shell Mobile and Exxon gas sucks. Sunoco, Amaco, BP, Hess- Sunoco is prefered and is what I run and ONLY what I run in my car unless I have NO choice.

vadim

I will certainly try to troubleshoot as much as I can before taking it in. Fuel filter - doubt it, car too new (32kmi). FPR - but why only in this RPM range?

I am narrowing it down to ECU-gone-bananas or S/C. Will see after I power-cycle the ECU.

As for gas, do you have any performance data showing that some brands are better than others? I am really curious. There are no Hess here, but one Sunoco. Shall try it tomorrow, weather permitting

nukblazi

I had found some older data on the web that some here had disputed. Beyond that, I am going by personal experience rebuilding motors and how my current cars had performed on different gases, knowledge of what companies have tended to be the source of "Bad gas" diagnosis and tips from other drivers/racers people in the industries who have something to say. When a Exxon engineer advises people to say away from Exxon/Mobile gasolines...

Auto-X and track days Sunoco 94 if you can get it. The MD stations only have 93 for the past year though. Most race cars run sunoco fuels and tracks with stations sell sunoco... hmmmm!

vadim

Thanks! I'll give it a try and listen to my butt-dyno Sunoco not too far from my house used to have 94 - have to check if they still do.

Deutscher_Wagen

I hate you all!

Most gas stations only sell up to 91 up here at this altitude.

BTW: when SC's go out, isn't that usualy a one shot deal, not a gradual outage? Also, when SC's go out wouldn't it behave the other way around... IE: floor it, gradual rise and then inversed boost spike?

I would definaltly reset ECU.

Also, how old are the spark plugs?

vadim

The spark plugs are original, and should be good for many more miles (now at 32 Kmi), but I already have a new set that will also be tried after the ECU reset.

Deutscher_Wagen

I change mine every 2 years

vadim

These spark plugs should be good for at least 70-80Kmi, 30K for them is nothing.

Deutscher_Wagen

^ figured that might be the case... may be worth the try though.


I'm still having a hard time not changing the oil more often.... It's driving me nuts.

vadim

As I wrote earlier - I will try a new set if the ECU reset does not change anything. Where there are parts, there are failures - got to try what I can by elimination

vadim

Update: just got my car back from the 2nd service B. No more power dip and surge around 4K RPM.

Replaced were Purge Valve and Air Mass Sensor. Still don't know which of them contributed to the problem, but now the power curve feels very linear and the response is quicker.