2G Loss of power

[DSM_15_2G]

I am tired of chasing the issue and I have to try to get some answers here as I am not very inclined,

You can see my build profile but to say in advance, 90% of the stuff is already replaced with new OEM stuff as I was fishing to fix the issue,

The issue: The car has a big ass loss of power and while it does have it, it jerks and engine brakes hard/violently from around 3k rpm all the way to 1500 where it lets off and coasts as it should

Most of the power loss is from 1k rpm and up to like 3k where the power band pulls, but to be honest, 2nd gear feels like 4th and 3rd feels like 5th

To try to describe the issue, when I give it throttle lets say 20% in 2nd gear at 1500 rpm city driving to just speed up a bit, the engine will make the noise and the exhaust but my rpms arent moving that fast and you dont feel any torque or a feeling that its speeding up, it doesent want to rev, feels like IM forcing it, and above 1500 rpm as soon as I let off the gas pedal no matter how easy, it will jerk you and start engine braking till 1500

Now in a few instances it "fixed" itself but only for a minute or two, at light throttle it will respond and as soon as the engine makes that noise the car goes (not talking about pulls but drivability) and you can feel it bringing up the rpms and the harder i press the throttle the stronger it goes.. Whereas normally no matter how much throttle you give it, the engine makes more noise but nothing much happens torque or power wise

Few days ago I burped the coolant and let it idle for 10 minutes to let all the bubbles out, as soon as I took off after that the car was flying and it doesent jerk at all, feels like it should and 5 minutes later, started to jerk and loses all the power

Compression was done, all 4 are good, coilpack is replaced with brand new, new ngk wires, new spark plugs, new oem cam sensor, new coolant temp sensor, replaced maf, replaced and calibrated tps through link, boost leak tested, new oem thermostat, rebuilt throttle body etc,, I did it all and its still f***ing with me like this where it becomes pain in the butt and a chore to drive, i cant relax due to all the jerkings and just no satisfaction as to being sluggish

Forgot to mention, I even replaced my main Engine Harness with a mint one (no fix)

I am very curious why would it drive fine after it idles for some time

I am open to all suggestions and thank you all for helping me

 

[pauleyman]

You have DSMLink, Log it. Make sure ECU is seeing throttle closed. Above 1500 you should have no fuel at no throttle input. You have the best tool to evaluate closed loop/open loop. Closed throttle. Knock. Timing etc. These will tell you what is happening.

Given it ran well recently i would say its unlikely to have mech problems. So check ECU inputs. ECU itself. Grounds, etc and log it

 

[DSM_15_2G]

@pauleyman
I have logged it like a 100 times, no knock, timing is fine, TPS is fine and adjusted. The only thing I can see in that range when the car jerks is that all my fueling goes to 0, and I do have an idea that the jerk I feel is fuel cut when I let go off the throttle but I have no idea how to tackle this.

I even sent my logs to Kevin (rwd dsm) and Kenny Kline and both have said they don't see anything in the logs that could indicate any of the problems. Maybe they rushed it and missed something, maybe I need someone to look it in more detail and maybe figure it out.

But its gotta get fixed cause its really a pain

 

[pauleyman]

Stock car for the most part. Has it ever ran correctly in your posesion? Stock bov? Recirculated? Engine vacuum at idle? Decel? Mechanical timing checked? Logging any and all sensors and seeing ANY abnormal changes during driving or decel. Log it all.
Fuel is supposed to go to zero. It isnt fuel cut. That doesn't really make sense by definition of fuel cut on these cars

 

[WisconsinMonSTAR]

Sorry if I missed it, but did you verify your timing marks all line up correctly? Other than throttle body or ECU/electrical issue, the only other obvious thing i could think of is an issue with your timing.

 

[spyderdrifter]

...To try to describe the issue, when I give it throttle lets say 20% in 2nd gear at 1500 rpm city driving to just speed up a bit, the engine will make the noise and the exhaust but my rpms arent moving that fast and you dont feel any torque or a feeling that its speeding up, it doesent want to rev, feels like IM forcing it, and above 1500 rpm as soon as I let off the gas pedal no matter how easy, it will jerk you and start engine braking till 1500...

To me, this almost sounds like the clutch could be slipping part of the time, then after it heats up it catches, causing the jerking. Maybe not much help, but an idea.

 

[DSM_15_2G]

@pauleyman
The car is stock, for what it is. It was an NA 7bolt 2g from Europe when I got it.. I turboed it with all the stock parts like many here do. Note I had this issue while it was NT.. It would go away and come back all on its own.. Very weird issue.. I am trying to set up link to log sensors but Im not sure how to be honest. I am logging front o2, tps, isc and stuff like that

@WisconsinMonSTAR Yes, the timing is fine + I am on 99 cas so it adjusts itself.. I am also leaning towards an electrical issue as I have replaced everything with brand new oem stuff, even the engine harness
I am replacing another TB again to see if it fixes anything

@spyderdrifter I have thought about it too, but after I turboed the car it drove like crazy the first 5-6 days then later on started going back to sluggish, you could feel power loss every day little by little, and the clutch is replaced with an Exedy clutch

 

[spyderdrifter]

@spyderdrifter I have thought about it too, but after I turboed the car it drove like crazy the first 5-6 days then later on started going back to sluggish, you could feel power loss every day little by little, and the clutch is replaced with an Exedy clutch

What about the flywheel? Resurfaced? Correct step height?

 

[nite owl]

Do you have catalytic converters? if so, possibly plugged?

 

[nmandic]

@DSM_15_2G cao buraz
Ja sam isto iz Srbije . Trenutno zivim i radim u Frankfurtu. Uzeo sam pre par dana eclipsu sa zapoceti turbo buildom koji ja nastavljam. Vidim da si ti vec odavno to odradio, pa se nadam da ces mi pomoci ne mogu da ti posaljem DM jer sam nov ovde, ali ako vidis ovo pusti ti meni neki kontakt, whats up /fb/ insta

 

[97egl]

@WisconsinMonSTAR Yes, the timing is fine + I am on 99 cas so it adjusts itself.. I am also leaning towards an electrical issue as I have replaced everything with brand new oem stuff, even the engine harness
I am replacing another TB again to see if it fixes anything

People are asking if the timing marks on the camshafts and crankshaft line up. Cam timing. NOT ignition timing.

 

[evil_eagletalon]

This smells like a clogged cat.

 

[Blakedwight4]

@spyderdrifter I have thought about it too, but after I turboed the car it drove like crazy the first 5-6 days then later on started going back to sluggish, you could feel power loss every day little by little, and the clutch is replaced with an Exedy clutch

Im having the same issue, what ended up fixing it?