No power past 4000rpm!?!

[Steveman09]

Well I've just had a problem pop up out of nowhere, what happens is, if I got WOT as soon as I reach the 4000rpm mark and above I have little to no more power, I tried a different coil thinking this was the case but it didn't change anything. I've also noticed bad COLD Drivability, this problem popped up out of nowhere and as you all may know I have the E-Manage setup on it, everything was fine up until one day it just went wack, I've tripple checked my maps and settings, everything is fine, I haven't modifyed any settings to make this happen. I put a Fuel Pressure Gadge on the car and drove it around and watched the readings as follows :

 

 

IDLE 32PSI SOLID

WOT 65PSI SOLID

 

When I hit the loss of power area the Fuel Pressure did not change at all.

 

I still thought it was fuel related so I went ahead and did some Datalogging with the E-Manage to see how things were going, and I was shocked as to my findings.

 

here's a pic of a run :

 

 

As you can see right when my loss of power happens between 4000-5000rpm the Injectors go from 65% duty cycle to 5%?!?! This confirms my suspecions about Fuel Starvation. Now I need your guys help, I'm not sure whats causing this, possibly bad injector, injector resistor pack, STOCK ECU Injector Driver bad? I have elliminated fuel cut completly by claming the MAF to 5.00volts (FC happens at 5.2v) The other thing that gets me is the COLD Drivability, it surges and bucks like crazy and doesn't want to go. The way I have the E-Manage setup is for Normal Crusing (no boost) The Factory Hotwire MAF still controls things to maintaine stock mixtures for the best milage and drivability, but when I hit boost the 3bar Greddy Map Sensor takes over and I tune from there for the midrange and topend. This is why I think there is somthing wrong with the Fuel Injection system on the car.

 

I've allways had light surging during cruising even before I put the E-Manage on, so I'm woundering if somthing finally broke.

 

Any help would be appreciated, because I'm stumped.

[rallyruss]

I will give it a try. or at least throw some ideas at you.

 

the timing AND fuel have both been pulled back hard. like as if ther is a knock or false knock detected.

cold drivability hmm dont know. can you get any more peramiters when the event occurs? like o2, maf, or ect?

I really dont know how your set up works so forgive me if I am off base. I have only done a small bit of work with a SDS efi system and it never paned out for me the way I wanted.

[robm]

That is one strange graph. Have you really plotted RPM vs time? If so, how do you read it?

 

Have you actually plotted % vs RPM? That would make more sense, I think.

[Steveman09]

That is one strange graph. Have you really plotted RPM vs time? If so, how do you read it?

 

Have you actually plotted % vs RPM? That would make more sense, I think.

 

Yes I have in that pic I selected a spot where the injectors are falling off, shows rpm it happened and everything.

[Steveman09]

I will give it a try. or at least throw some ideas at you.

 

the timing AND fuel have both been pulled back hard. like as if ther is a knock or false knock detected.

cold drivability hmm dont know. can you get any more peramiters when the event occurs? like o2, maf, or ect?

I really dont know how your set up works so forgive me if I am off base. I have only done a small bit of work with a SDS efi system and it never paned out for me the way I wanted.

 

The timing is being pulled back because I'm telling it to.

 

As boost and rpm go up timing must come down on a turbo car to maintaine no detonation. I have it set to pull back from 8deg to 11deg at redline.

[idosubaru]

throttle plate sticking or not going any further?

probably not, that shouldn't affect fueling like that and you'd likely see other issues, but easy enough to check.

[Mark Humble]

Strange curve indeed. Looks like the injectors start to kick back in as soon as you started to lift off the throttle. Makes me think TPS or the ECU just decides to drop the injector pulse for no reason. Can't think of any other sensor in puts that could cause the ECU to do this.

[nipper]

do you still have a cat on this thing? Could be the cat is partially clogged

 

 

nipper

[Steveman09]

Strange curve indeed. Looks like the injectors start to kick back in as soon as you started to lift off the throttle. Makes me think TPS or the ECU just decides to drop the injector pulse for no reason. Can't think of any other sensor in puts that could cause the ECU to do this.

 

I'm starting to wounder the same, the TPS was replaced when I did the engine with an OEM one and I have since then calibrated and rechecked it a few times, even recently.

 

 

I did however had issues with the TPS Valve not being very consistant in the emanage program. At idle after a few runs it would show 2-3% bouncing back and forth, then I would have to recalibrate it in the emanage program for it to return to normal, then it would do the same again.

 

I'm also going to try regrounding the ECU and see if that helps.

 

Another thing I have been thinking about is the Coolant Temp Sensor, even tho it too has been replaced when I built the engine, I wounder if the terminals on the harness are corroded and causing a false reading.

 

If its not reading 140F or higher I wounder if the top end Fueling is effected?

[Steveman09]

ok after banging my head against a wall for the past few days trying to figure this out I finally figured it out today

 

 

Just for kicks I went ahead and disconnected the Coolant Temp Sensor (ECU one) And went for a drive, datalogged the run, and guess what :

 

 

 

It pulled like there was no tomarrow, it was such a good feeling to finally figure it out.

 

I then ran some test on the sensor, I was shocked since I just replaced it when I rebuilt the engine and its OEM.

 

Here's the results :

 

When fully warmed up its reading 230ohms on the sensor itself.

 

Then with the harness connected and engine idling backprobing the sensor produces .545volts.

 

This doesnt seem right to me, does anyone have the specs on the sensor? I read a post where Garner said with engine cold backprobing should product around 4volts or so, then when warm should be around 1volt.

 

The only Specs I could find were :

 

68F = 2-3kohms

122F = 700-1000ohms

 

but I'm not sure if those are correct since I pulled them off of ALLDATA which somtimes mixes up Turbo/SPFI cars info.