SR20DET . ECU dropping timing to zero on throttle.. MIND BLOWN any ideas?

[GhostlyCoupe]

The car:
PLMS daughtercard
Freshly rebuilt SR20DET
100% stock including SMIC

Symptoms:
Lack of power
Backfiring under boost
Bogging when applying throttle
Code 55 (no codes, knock sensor bypassed with 1m Ohm resistor)

Diagnosis:
Using NDS I was able to log what the car is doing. When throttle position is greater than about 1/4 ( >1.0v ) the ECU is retarding timing to 0 and upping injector duty to almost 40%.

I used the map trace and it's going into the +20-30 timing range on the map but for some reason the ECU is just dropping the timing to 0.

I'm kind of stumped on why the ECU is retarding timing and upping injector cycle so bad. Any ideas?

[KiLLeR2001]

Knock sensor perhaps... Check the connections

edit: I'm assuming you are using the 1m resistor temporarily, I surely hope you don't plan the run without a knock sensor for the remainder of the engine's life. It's a nice safety feature to have.

Try resetting the ECU by removing the negative cable on the battery for 15 mins or so.

[GhostlyCoupe]

The knock sensor circuit will actually be turned off when I take it in for a tune. Was just hoping to get some decent use out of it until I get it there next week.

I can reset the ECU instantly with NDS so I can tell you that doesn't help.. done it a thousand times lol.

[Prozac]

Had a turbo inlet gasket blow on inside wasnt visible , loss of power , lack of boost , backfiring.

[rcdad123]

put a knock sensor back on and see what happens. i`m betting that is the problem. just remove it when you get to the dyno tuner.

[GhostlyCoupe]

put a knock sensor back on and see what happens. i`m betting that is the problem. just remove it when you get to the dyno tuner.

Problem is I just can't get the sensor to not throw a code.

I've been over the sub-harness front to back and it has no breaks and perfect continuity with no shorts.

The sensor itself ohms out at about 640 so that checks out.

The main issue is that even when I depin pin 27 at the ECU which drives the circuit, the voltage remains at 3.3v. My research has shown that pin 27 should show a reference 5v with the knock sensor harness wire at 27 depinned.

[GhostlyCoupe]

Fixed knock sensor. Problem still persists...

Timing is dropping to 0 at anytime throttle is applied.

[KiLLeR2001]

Possible bad ECU? Do you have someone you know with a known working ECU you can test? Shouldn't be too hard since you are 100% stock. Stock spark plug gap is 0.036" for SR20DET.

[AwesomeO]

Sorry to bring this old thread up but this is the same problem I have!!!

So far Iv replaced the maf, harness, fuel rail with good working injectors and fuel regulator, tried a different ecu as well.

Just adding to the log hopefully we get this fixed

[beems240sx]

check basics first. boost leak test. just curious if the spark plugs are correct heat range and gap. what are you running? and it almost sounds like the ecu is attempting to go into limp mode by pulling timing to save from detanation essentially freaking out because it cant tell knock

[AwesomeO]

yesterday i changed the wiring harness for a new one and the spark plugs as well with no luck.

just acquired another CAS and an ignitor. will check tomorrow and come back with answers.

[beems240sx]

slow down. dont just start swapping things around like crazy. what spark plugs did you put in? i always run NGK BKR7E if memory serves right. do you have a wideband? did you boost leak test it?

[wangan_cruiser]

how many miles on these "freshly rebuilts"?

possibly the rings havent seated yet.

[AwesomeO]

slow down. dont just start swapping things around like crazy. what spark plugs did you put in? i always run NGK BKR7E if memory serves right. do you have a wideband? did you boost leak test it?

spark plugs were purchased from FRsports on a special. exactly the ones you mentioned :)

no wideband. will borrow from a friend.
boost leak wasnt performed yet.

how many miles on these "freshly rebuilts"?

possibly the rings havent seated yet.


i forgot to mention that this engine isnt rebuild and the car was driven flawlessly when first purchased, the problem occurred the next day.

[beems240sx]

i bet you have a boost leak. go to home depo and make a quick tested and pressure the system to 15psi and see where its leaking

[AwesomeO]

i bet you have a boost leak. go to home depo and make a quick tested and pressure the system to 15psi and see where its leaking

will do sir! thank you for the support. i'll be back with more logging tonight as i'm going to change the CAS and ignitor. boost leak will have to wait till tomorrow.

[AwesomeO]

*****UPDATE***

changed the CAS, re did some vacuum lines, car runs WAAAAAAAAY better now.

came to find out that the alternator is bad.

looks like problem is solved.... will be back with more news stay tuned..

[AwesomeO]

CAR RUNS AWESOME!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

the cas, and a charging terminal were the problem!!

my problem is solved!

hope this will help other people in the future.