SR20DET Loss of power/hesitation/misfire - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

2tone_s13 · 10-18-2014, 03:40 AM

So I'm having an issue with my s14. I'm not at the end of my ideas yet but I am reaching a point where some input might help. If anyone has had a similiar issue and resolved it or any ideas as far as tests, tricks or checks that I can do, id love to hear them. I figured involving the community might help some one at some point too.

Black Top S14 SR20DET

Symptom - Intermittent loss of power, hesitation, misifre, bad idle (rough and pulsates down to 250rpm/comes back up)
This issue will very frequently come and go. It'll come and the engine will "pop" back into the way it should feel. More evident when accelerating. Very easy to feel under light throttle/load/slower speeds.
At higher speeds/loads it is a lot harder to feel.

Actions/diagnoses so far..

First - checked fuel pump. Was missing sock. Replaced with ISIS 255 ltr/hr pump. Came with new sock. All good.

Second - tried another known to be good ignitor chip (friend has an s14)

Third - cleaned MAF. no change

Fourth - i already knew of a vacuum leak in the brake booster. I finally got smart and thought maybe that is causing my performance issue so I pulled the vacuum line and plugged it. Didn't change the issue.

Fifth - checked spark plugs. all looked the same. old and gray. none were wet or dark. i was pretty confident this was normal wear and tear and was a good sign. nonetheless they were old so they were replaced with NGK's gapped to .028" One thing we noticed was #1 and 4 pistons looked abnormally dirty. I only looked at #1 myself and thought it might be significant. It kinda looked wet. Dare i say, oily. It's just kind of weird that the plugs weren't wet at all. For now, I'm just contributing this to the age of the engine.

Sixth - checked TPS signal. seemed good. around .4V closed and 4.5V WOT

Seventh - checked MAF signal. seemed ok. 1.5V at idle.

Eighth - tried to pull codes on ecu. couldn't get the light to blink. Might try more eventually.

My next planned action is to try another known good ecu, checked for clogged fuel filter or leaky injector o-rings, look hard for any vacuum/air leaks, clean iacv (not expecting that to fix it)

10-18-2014, 03:40 AM	#1
2tone_s13 Join Date: Dec 2013 Location: Metro Detroit Age: 33 Posts: 34 Trader Rating: (0) Feedback Score: 0 reviews	SR20DET Loss of power/hesitation/misfire So I'm having an issue with my s14. I'm not at the end of my ideas yet but I am reaching a point where some input might help. If anyone has had a similiar issue and resolved it or any ideas as far as tests, tricks or checks that I can do, id love to hear them. I figured involving the community might help some one at some point too. Black Top S14 SR20DET Symptom - Intermittent loss of power, hesitation, misifre, bad idle (rough and pulsates down to 250rpm/comes back up) This issue will very frequently come and go. It'll come and the engine will "pop" back into the way it should feel. More evident when accelerating. Very easy to feel under light throttle/load/slower speeds. At higher speeds/loads it is a lot harder to feel. Actions/diagnoses so far.. First - checked fuel pump. Was missing sock. Replaced with ISIS 255 ltr/hr pump. Came with new sock. All good. Second - tried another known to be good ignitor chip (friend has an s14) Third - cleaned MAF. no change Fourth - i already knew of a vacuum leak in the brake booster. I finally got smart and thought maybe that is causing my performance issue so I pulled the vacuum line and plugged it. Didn't change the issue. Fifth - checked spark plugs. all looked the same. old and gray. none were wet or dark. i was pretty confident this was normal wear and tear and was a good sign. nonetheless they were old so they were replaced with NGK's gapped to .028" One thing we noticed was #1 and 4 pistons looked abnormally dirty. I only looked at #1 myself and thought it might be significant. It kinda looked wet. Dare i say, oily. It's just kind of weird that the plugs weren't wet at all. For now, I'm just contributing this to the age of the engine. Sixth - checked TPS signal. seemed good. around .4V closed and 4.5V WOT Seventh - checked MAF signal. seemed ok. 1.5V at idle. Eighth - tried to pull codes on ecu. couldn't get the light to blink. Might try more eventually. My next planned action is to try another known good ecu, checked for clogged fuel filter or leaky injector o-rings, look hard for any vacuum/air leaks, clean iacv (not expecting that to fix it)