Rebuilt KA24DE surging, giving code 34 - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

GoodFellaDavey · 05-13-2011, 09:10 AM

Hi guys, having a surging idle problem with a freshly rebuilt KA24DE and I'm also getting a code 34 off the ECU, which I believe is knock sensor. Here are the details:

-93 KA24DE swapped into 89 chassis
-Motor was from an automatic car, I'm using the 89 tranny and 93 automatic ECU, with a tranny harness from a 91-93 manual.
-Freshly rebuilt
-On start up, engine surges between 1800-2300 RPM
-When I clamp off the hose to the IACV, the engine stops surging and holds a steady idle at 1800RPM
-I removed the IACV and cleaned it, but it hasn't changed anything
-Carbon canister and PAIR valve have both been removed as I didn't have them with the swap. The four vacuum lines for them have been capped off near the throttle body
-I have been starting the car with a booster pack and don't have a battery installed, just running right off the booster pack. Picking up a battery today.
-Ignition timing was properly set. (At TDC, slid in the CAS so that the rotor lined up with #1 and was facing towards the front of the car)
-ECU is giving me Code 34 Detonation sensor circuit
-Car has been sitting for a year at least before the engine was swapped in, so the gas is at least a year old.

Does anyone have any idea of what might be causing these issues?

theboy · 05-13-2011, 09:25 AM

code 34 is an open or short in the knock sensor harness. Basically jiggle the harness and connector and itll go away. If not then replace the sensor. That will not make it idle funny. You probably need to time it. Just because the timing chain was put on correct doesnt mean you dont have to fine tune at the dizzy. Get yourself a timing light and set base timing to 20 deg. (+/-2deg.). If it hasnt gone away, then start looking for a vaccuum leak.

GoodFellaDavey · 05-16-2011, 09:08 AM

Just as an update in case anybody finds this thread on a search. The problem was the throttle body and iacv. The throttle body was slightly bent (engine came from a donor car that was in a front end collision) causing the throttle plat to not quite close properly. Swapped on a new throttle body and the idle smoothed right out. However the the throttle was still sticky... when you blipped the throttle at idle, it held for quite a while then finally dropped. Although I had already cleaned the IACV I decided to replaced it with one from a different motor and it solved that issue as well!

I also tested continuity of the knock sensor harness (as per FSM) to determine it was the knock sensor that was failing. Then I bypassed the knock sensor using the 1 megaohm resistor trick and I didn't get the code again. Going to replace the sensor today. Also I swapped in the 5spd ECU and retimed the car. When you use the auto ECU it throws your timing out 5ish degrees.

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05-13-2011, 09:10 AM	#1
GoodFellaDavey Join Date: Mar 2002 Posts: 25 Trader Rating: (0) Feedback Score: 0 reviews	Rebuilt KA24DE surging, giving code 34 Hi guys, having a surging idle problem with a freshly rebuilt KA24DE and I'm also getting a code 34 off the ECU, which I believe is knock sensor. Here are the details: -93 KA24DE swapped into 89 chassis -Motor was from an automatic car, I'm using the 89 tranny and 93 automatic ECU, with a tranny harness from a 91-93 manual. -Freshly rebuilt -On start up, engine surges between 1800-2300 RPM -When I clamp off the hose to the IACV, the engine stops surging and holds a steady idle at 1800RPM -I removed the IACV and cleaned it, but it hasn't changed anything -Carbon canister and PAIR valve have both been removed as I didn't have them with the swap. The four vacuum lines for them have been capped off near the throttle body -I have been starting the car with a booster pack and don't have a battery installed, just running right off the booster pack. Picking up a battery today. -Ignition timing was properly set. (At TDC, slid in the CAS so that the rotor lined up with #1 and was facing towards the front of the car) -ECU is giving me Code 34 Detonation sensor circuit -Car has been sitting for a year at least before the engine was swapped in, so the gas is at least a year old. Does anyone have any idea of what might be causing these issues?

05-13-2011, 09:25 AM	#2
theboy Zilvia Addict Join Date: Apr 2010 Location: Chicago Age: 32 Posts: 618 Trader Rating: (10) Feedback Score: 10 reviews	code 34 is an open or short in the knock sensor harness. Basically jiggle the harness and connector and itll go away. If not then replace the sensor. That will not make it idle funny. You probably need to time it. Just because the timing chain was put on correct doesnt mean you dont have to fine tune at the dizzy. Get yourself a timing light and set base timing to 20 deg. (+/-2deg.). If it hasnt gone away, then start looking for a vaccuum leak.

05-16-2011, 09:08 AM	#3
GoodFellaDavey Join Date: Mar 2002 Posts: 25 Trader Rating: (0) Feedback Score: 0 reviews	Just as an update in case anybody finds this thread on a search. The problem was the throttle body and iacv. The throttle body was slightly bent (engine came from a donor car that was in a front end collision) causing the throttle plat to not quite close properly. Swapped on a new throttle body and the idle smoothed right out. However the the throttle was still sticky... when you blipped the throttle at idle, it held for quite a while then finally dropped. Although I had already cleaned the IACV I decided to replaced it with one from a different motor and it solved that issue as well! I also tested continuity of the knock sensor harness (as per FSM) to determine it was the knock sensor that was failing. Then I bypassed the knock sensor using the 1 megaohm resistor trick and I didn't get the code again. Going to replace the sensor today. Also I swapped in the 5spd ECU and retimed the car. When you use the auto ECU it throws your timing out 5ish degrees.