Help! SOHC->DOHC swap, idles weird, 3 codes - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

mike2016 · 12-29-2004, 10:51 PM

Ok i just did the dohc swap and it wont idle good, but it pulls hard and drives good, but it will jerk when i on/off throttle. it won't rev past 6000rpm, it just stop and the intake makes a loud popping noise.

it's a 98 S14 KA running on 92 DOHC Harness + 92 DOHC ECU + 92 DOHC sensors + 92 DOHC distributor...etc

all the junk vacuume lines are removed down to only 1 vacuume line for fpr. checked no vacuume leaks.

It idles perfect for about 5 seconds, then drops so low until it's about to die, then idles good again..then drops.. it just keeps doing this.

** when the idle is dropping , there's smoke come out of the tail pipe, it's unburnt gas for sure, it smells just like gasoline.

timing is checked and but it shouldn't cause the weird idle right ?

ECU pulled 3 codes:

12 - MAFS (I'm using S14 KA MAF, don't have S13 dohc maf)
21 - Primary ignition circuit
32 - EGR system (removed egr, everything)

I thought the S14 KA MAF is the same as S13? the SAFC setting for both MAF are the same at least.

Ritz S14 · 12-29-2004, 11:31 PM

I think it could be your S14 maf. Since the computer is a 92, it expects to see 92 components.

EGR- Did you cover up the egr passages?

Check firing order, and make sure the wires you spliced are soildered.

nightwalker · 12-30-2004, 12:51 AM

fix your maf first. Then see if you still get the same problems.

mike2016 · 12-30-2004, 12:57 PM

yes i blocked off the egr passages. no leaks.

I'll try to find a 92 maf and try that...

firing order.... i wasn't sure if I installed the distributor right,

I cranked it to set No.1 at TDC, then insert the distributor and line up the marks, the rotor line up with No.1 Coil. is this correct? is it possible I had set No.4 at TDC ?

240Driver39 · 12-30-2004, 02:59 PM

s14 maf will not run right on s13....get an s13 maf

mike2016 · 01-22-2005, 03:22 PM

okay i got a s13 dohc maf and changed it, same thing.

i discovered that the IACV wasn't working, due to a mistake in wiring, but i fixed it and it's working now.

if i disconnect the tube going to the IACV from the intake pipe, the car will idle A LOT better, but it still has that stumble every 5 seconds or so.

or if I unplug the MAF (IACV tube still connected) , the car idles normal.

when the idle drops and bog, it just shoot lots of black smoke out the tail pipe... gas mileage sucks too. less than 180 miles on a full tank of 91.

any one ??

vvtisupra · 01-22-2005, 03:26 PM

don't the 92's run air injection ? would that do anything ? also the vaccuum tube right by the coolant upper pipe if its not hooked up to any vaccuum source will idle super bad

mike2016 · 01-22-2005, 03:36 PM

the vacuume tube by the coolant upper pipe? do u mean the fat big tube that feeds the IACV and the IACV air regulator? if i disconnect the tube the car idles better....

12-29-2004, 10:51 PM	#1
mike2016 Zilvia Junkie Join Date: Oct 2001 Location: Los Angeles Age: 44 Posts: 538 Trader Rating: (0) Feedback Score: 0 reviews	Help! SOHC->DOHC swap, idles weird, 3 codes Ok i just did the dohc swap and it wont idle good, but it pulls hard and drives good, but it will jerk when i on/off throttle. it won't rev past 6000rpm, it just stop and the intake makes a loud popping noise. it's a 98 S14 KA running on 92 DOHC Harness + 92 DOHC ECU + 92 DOHC sensors + 92 DOHC distributor...etc all the junk vacuume lines are removed down to only 1 vacuume line for fpr. checked no vacuume leaks. It idles perfect for about 5 seconds, then drops so low until it's about to die, then idles good again..then drops.. it just keeps doing this. ** when the idle is dropping , there's smoke come out of the tail pipe, it's unburnt gas for sure, it smells just like gasoline. timing is checked and but it shouldn't cause the weird idle right ? ECU pulled 3 codes: 12 - MAFS (I'm using S14 KA MAF, don't have S13 dohc maf) 21 - Primary ignition circuit 32 - EGR system (removed egr, everything) I thought the S14 KA MAF is the same as S13? the SAFC setting for both MAF are the same at least.

12-30-2004, 12:51 AM	#3
nightwalker Nissanaholic! Join Date: Mar 2003 Location: Bay area Age: 46 Posts: 2,146 Trader Rating: (0) Feedback Score: 0 reviews	fix your maf first. Then see if you still get the same problems. __________________ In life, we often cast the line of hope fishing for the best possible opportunity. Sometimes with enough effort, the things we catch are nothing short of amazing.

12-30-2004, 02:59 PM	#5
240Driver39 Zilvia FREAK! Join Date: May 2002 Location: Charleston, SC Age: 40 Posts: 1,090 Trader Rating: (1) Rides Gallery: 240Driver39 Feedback Score: 1 reviews	s14 maf will not run right on s13....get an s13 maf __________________ 1990 240sx 5spd fastback

12-29-2004, 11:31 PM	#2
Ritz S14 Post Whore! Join Date: Jul 2004 Location: C A L I F O R N I A Age: 43 Posts: 3,586 Trader Rating: (0) Feedback Score: 0 reviews	I think it could be your S14 maf. Since the computer is a 92, it expects to see 92 components. EGR- Did you cover up the egr passages? Check firing order, and make sure the wires you spliced are soildered.

12-30-2004, 12:57 PM	#4
mike2016 Zilvia Junkie Join Date: Oct 2001 Location: Los Angeles Age: 44 Posts: 538 Trader Rating: (0) Feedback Score: 0 reviews	yes i blocked off the egr passages. no leaks. I'll try to find a 92 maf and try that... firing order.... i wasn't sure if I installed the distributor right, I cranked it to set No.1 at TDC, then insert the distributor and line up the marks, the rotor line up with No.1 Coil. is this correct? is it possible I had set No.4 at TDC ?

01-22-2005, 03:22 PM	#6
mike2016 Zilvia Junkie Join Date: Oct 2001 Location: Los Angeles Age: 44 Posts: 538 Trader Rating: (0) Feedback Score: 0 reviews	okay i got a s13 dohc maf and changed it, same thing. i discovered that the IACV wasn't working, due to a mistake in wiring, but i fixed it and it's working now. if i disconnect the tube going to the IACV from the intake pipe, the car will idle A LOT better, but it still has that stumble every 5 seconds or so. or if I unplug the MAF (IACV tube still connected) , the car idles normal. when the idle drops and bog, it just shoot lots of black smoke out the tail pipe... gas mileage sucks too. less than 180 miles on a full tank of 91. any one ??

01-22-2005, 03:26 PM	#7
vvtisupra Nissanaholic! Join Date: Apr 2004 Location: SB and OC Posts: 2,118 Trader Rating: (16) Feedback Score: 16 reviews	don't the 92's run air injection ? would that do anything ? also the vaccuum tube right by the coolant upper pipe if its not hooked up to any vaccuum source will idle super bad

01-22-2005, 03:36 PM	#8
mike2016 Zilvia Junkie Join Date: Oct 2001 Location: Los Angeles Age: 44 Posts: 538 Trader Rating: (0) Feedback Score: 0 reviews	the vacuume tube by the coolant upper pipe? do u mean the fat big tube that feeds the IACV and the IACV air regulator? if i disconnect the tube the car idles better....