Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum - View Single Post - Chasing lean/misfire the last 6 Months. Built Longblock

R3b · 03-29-2017, 01:13 PM

Big wall of text but bare with me....

Been fighting this lean idle and misfire the last 6 months. This isnt my first time with ka-t, had a stock motor pushed 10psi on corn till one day it started knocking and bent two rods. Motor had about 160-200k miles. No biggie, go through a tear down, get a bunch of parts. Did a standard motor build with wiseco/manley setup bored out, crank balanced/polish, cometic HG with the head/block decked. Head was cleaned up with new guides/valve stem seals. Running RS rom tune, Martin is a legend! Have z32 maf and 1000cc injectors with precision t3 entry level turbo, tial wastegate, hks bov blah blah blah.

Issue is on start, basically cold the car would run seriously lean and stall out. I got it to idle now messing with the throttle plate and IACV screw but its reading --- on my wideband. Basically 17+ afrs. Now list of things i've tried and swapped out.

-Brand new iacv, had an early ka so had the single jingle connector and wouldnt fit my WS harness.
-Tried two different z32 mafs, good voltage on idle, ground is clean and is in a blow through setup. The housing leaks a little but all of them do on the cold pipe
- New nissan coolant temp sensor
- Tried 3 different tps and two different throttle bodies
- Vaccum tested/smoke tested about a million times. Holds 10-15psi like nothing. Did find a light leak on my ACC, the long skinny under the intake runners. Only see it because of bubbles from soapy water.
- Two new sets of bkr7e gapped at .30
- New cap for dizzy and NGK spark leads.
- Swapped a buddies dizzy and set up timing and no change.
- Brand new bosch o2 sensor s14 style. Its a 3 wire and fits the WS harness.
- five0 1000cc sidefeeds new (yes I know go topfeed) swapped those into my buddies car and loaded a stock rom tune with a regular resize and car idle perfect. I bought a moates chip burner and got a copy of nistune.
-Compression was goodish. I had 150 across besides cylinder 3 which was 120. Had similar compression on my stock motor and turns out my exhaust valve was leaking, was kinda warped along with one in 1st cylinder. No problem, got new BC valves, took off the head and my machinist swapped it in and redid the lash. Thought it was my fix but started the exact same. Check compression and leak down again. All checks out fine.
-Tried 3 different ecus, tried my old 720cc injectors and my buddies stock injectors. Same issue.
Checked brake booster line check valve, not leaking.
-PCV system is VTA to a baffled can, doubt an open fitting on block pcv port will cause it to run lean.
-Did timing a million times, at 20 with light and Nissan datascan and checks out in pictures. Will post later.
- replaced old e85 in the tank with fresh corn. Replaced that with 93 as of last week.
-Fuel pump is a walbro 255, works fine just super loud will replace soon. Swapped in a buddies one and no change.
-New tomei FPR, fuel pressure changes on idle because of how lean it is and terrible vaccum but on key its dead at 3 bar (43psi) was maybe thinking air in the system???? Is it possible to have correct fuel pressure but air in the system?

Here are some videos, one point thought it was the tune and injector latency but nope. Also got it to run rich but still lean on cruise by just doing a resize and maf change on stock tune. Turns out the TTP Min setting is a lot different than Martins tune and the ones I found on here. I doubt tuning can fix this since it runs lean no matter how much I increase the k value. A stock k value on 1000cc which are 3 times the size should not be running lean....

https://www.youtube.com/watch?v=qBbVtNIp5iQ the normal startup, gets worse when bringing the idle screw down and messing with the little nut for the throttle plate.

https://www.youtube.com/watch?v=tvrT4-q70Tg injector latency was pretty low at 650ms on the tune. Bumped it up to 800 and even a 1000 in the video and no change.

https://www.youtube.com/watch?v=YFSLPaKEZvM stock tune with resize/maf change. When I compared the tunes besides tables and k value the only difference was some cold start start up settings and TTPMIN/TTPMax settings. Trail and error I found it was the TTPMIN setting basically forcing the injectors to dump more fuel. It leans out right away with light tap or on cruise.

https://www.youtube.com/watch?v=ehZMTwI_LPQ This is what its like right now with the new valves sealing and 93 in the tank. With 02 on it dies out, without it and opening the throttle a bit and adjusting tps/ idle scew it can idle 1000-1500 easy but still lean and misfires.

03-29-2017, 01:13 PM	#1
R3b Zilvia Junkie Join Date: Mar 2015 Location: South FL Age: 28 Posts: 581 Trader Rating: (0)	Chasing lean/misfire the last 6 Months. Built Longblock Big wall of text but bare with me.... Been fighting this lean idle and misfire the last 6 months. This isnt my first time with ka-t, had a stock motor pushed 10psi on corn till one day it started knocking and bent two rods. Motor had about 160-200k miles. No biggie, go through a tear down, get a bunch of parts. Did a standard motor build with wiseco/manley setup bored out, crank balanced/polish, cometic HG with the head/block decked. Head was cleaned up with new guides/valve stem seals. Running RS rom tune, Martin is a legend! Have z32 maf and 1000cc injectors with precision t3 entry level turbo, tial wastegate, hks bov blah blah blah. Issue is on start, basically cold the car would run seriously lean and stall out. I got it to idle now messing with the throttle plate and IACV screw but its reading --- on my wideband. Basically 17+ afrs. Now list of things i've tried and swapped out. -Brand new iacv, had an early ka so had the single jingle connector and wouldnt fit my WS harness. -Tried two different z32 mafs, good voltage on idle, ground is clean and is in a blow through setup. The housing leaks a little but all of them do on the cold pipe - New nissan coolant temp sensor - Tried 3 different tps and two different throttle bodies - Vaccum tested/smoke tested about a million times. Holds 10-15psi like nothing. Did find a light leak on my ACC, the long skinny under the intake runners. Only see it because of bubbles from soapy water. - Two new sets of bkr7e gapped at .30 - New cap for dizzy and NGK spark leads. - Swapped a buddies dizzy and set up timing and no change. - Brand new bosch o2 sensor s14 style. Its a 3 wire and fits the WS harness. - five0 1000cc sidefeeds new (yes I know go topfeed) swapped those into my buddies car and loaded a stock rom tune with a regular resize and car idle perfect. I bought a moates chip burner and got a copy of nistune. -Compression was goodish. I had 150 across besides cylinder 3 which was 120. Had similar compression on my stock motor and turns out my exhaust valve was leaking, was kinda warped along with one in 1st cylinder. No problem, got new BC valves, took off the head and my machinist swapped it in and redid the lash. Thought it was my fix but started the exact same. Check compression and leak down again. All checks out fine. -Tried 3 different ecus, tried my old 720cc injectors and my buddies stock injectors. Same issue. Checked brake booster line check valve, not leaking. -PCV system is VTA to a baffled can, doubt an open fitting on block pcv port will cause it to run lean. -Did timing a million times, at 20 with light and Nissan datascan and checks out in pictures. Will post later. - replaced old e85 in the tank with fresh corn. Replaced that with 93 as of last week. -Fuel pump is a walbro 255, works fine just super loud will replace soon. Swapped in a buddies one and no change. -New tomei FPR, fuel pressure changes on idle because of how lean it is and terrible vaccum but on key its dead at 3 bar (43psi) was maybe thinking air in the system???? Is it possible to have correct fuel pressure but air in the system? Here are some videos, one point thought it was the tune and injector latency but nope. Also got it to run rich but still lean on cruise by just doing a resize and maf change on stock tune. Turns out the TTP Min setting is a lot different than Martins tune and the ones I found on here. I doubt tuning can fix this since it runs lean no matter how much I increase the k value. A stock k value on 1000cc which are 3 times the size should not be running lean.... https://www.youtube.com/watch?v=qBbVtNIp5iQ the normal startup, gets worse when bringing the idle screw down and messing with the little nut for the throttle plate. https://www.youtube.com/watch?v=tvrT4-q70Tg injector latency was pretty low at 650ms on the tune. Bumped it up to 800 and even a 1000 in the video and no change. https://www.youtube.com/watch?v=YFSLPaKEZvM stock tune with resize/maf change. When I compared the tunes besides tables and k value the only difference was some cold start start up settings and TTPMIN/TTPMax settings. Trail and error I found it was the TTPMIN setting basically forcing the injectors to dump more fuel. It leans out right away with light tap or on cruise. https://www.youtube.com/watch?v=ehZMTwI_LPQ This is what its like right now with the new valves sealing and 93 in the tank. With 02 on it dies out, without it and opening the throttle a bit and adjusting tps/ idle scew it can idle 1000-1500 easy but still lean and misfires.