Help diagnose my ka problem. Stumbling/hesitation under wot - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

naed240sx · 04-18-2008, 01:42 PM

Ok, I have a "diagnose this" question. Any help would be greatly appreciated.

After installing the z32 brake booster this summer, my car started idling weird and dying after letting off the gas to brake for lights. This problem was intermitent, sometimes idling perfect, other times not. Temperature of engine did not matter, and the problem could surface and then go away all during the same period of driving. This problem also came with acceleration issues. If it was idling funny, I would get weak and jerky acceleration with popping sounds from the exhaust.

I reasoned that the Idle air control valve (IACV) had sucked up some dirt or something from the junkyard booster and that this was the source of both issues. I sprayed seafoam into the valve(by removing the idle screw) and this seemed to lessen the problem and make it less frequent. I went ahead and turned the idle up to about 1200 rpms as well, and this made sure the engine would never die even if the idle started fluctuating.

A few months later the problem stopped happening alltogether.

Fast forward to this week:

I went ahead and turned the idle back down to 800. No idle problems, but now when I get on the gas, it does that hesitation thing again, lots of exhaust popping, and really poor acceleration. The problem is most noticeable under wide open throttle, and if I accelerate slowly I don't have much of an issue at all.

I did try turning the idle up sky high again....but it didn't entirely fix the issue...still runs like crap under full throttle.

Any ideas?

bbejj123 · 04-18-2008, 01:50 PM

just a question but what is your timing set at?... it kinda sounds like what happened with my car... i just switched out my ecu to an newer auto ecu and its fine...there may be something wrong with your ecu but there may be mutiple other things wrong as well

flclsteve · 04-18-2008, 01:53 PM

sounds exactly like whats happening to mine as well ill see if i can post a vid the popping sound from my exhaust isnt loud at all

TurboNetic05 · 04-18-2008, 02:00 PM

mine did the popping thing and it was a misfire caused by water that got in with one of my spark plugs. I have no clue how it got there though

naed240sx · 04-18-2008, 02:04 PM

Its not timing. I'm convinced that it is some sort of air metering/vac leak/etc problem because of the effect that the idle screw has on the issue. Can't be timing because it was fine a week ago and had tons of power. It's a really jerky, popping, stumbling sort of problem.

naed240sx · 04-18-2008, 02:27 PM

Video showing how stable and smooth revving is...followed by hard throttle stabs. Listen to the way the throttle hits sound. To quote my friend, "it sounds like it farts"

http://s180.photobucket.com/albums/x...t=MVI_0328.flv

EDIT: video that shows the stumbling better:
http://s180.photobucket.com/albums/x...t=MVI_0326.flv

This was all just done parked, but the sound is similar and the problem persists with the car in gear.

naed240sx · 04-18-2008, 09:24 PM

After driving to the parts store, the car wouldn't start. At this point I realized I was wrong and that it must be electrical related. Replaced the alternator and now it runs like a champ.

04-18-2008, 01:42 PM	#1
naed240sx Zilvia Member Join Date: Jul 2005 Location: Houston, TX Posts: 206 Trader Rating: (0) Feedback Score: 0 reviews	Help diagnose my ka problem. Stumbling/hesitation under wot Ok, I have a "diagnose this" question. Any help would be greatly appreciated. After installing the z32 brake booster this summer, my car started idling weird and dying after letting off the gas to brake for lights. This problem was intermitent, sometimes idling perfect, other times not. Temperature of engine did not matter, and the problem could surface and then go away all during the same period of driving. This problem also came with acceleration issues. If it was idling funny, I would get weak and jerky acceleration with popping sounds from the exhaust. I reasoned that the Idle air control valve (IACV) had sucked up some dirt or something from the junkyard booster and that this was the source of both issues. I sprayed seafoam into the valve(by removing the idle screw) and this seemed to lessen the problem and make it less frequent. I went ahead and turned the idle up to about 1200 rpms as well, and this made sure the engine would never die even if the idle started fluctuating. A few months later the problem stopped happening alltogether. Fast forward to this week: I went ahead and turned the idle back down to 800. No idle problems, but now when I get on the gas, it does that hesitation thing again, lots of exhaust popping, and really poor acceleration. The problem is most noticeable under wide open throttle, and if I accelerate slowly I don't have much of an issue at all. I did try turning the idle up sky high again....but it didn't entirely fix the issue...still runs like crap under full throttle. Any ideas?

04-18-2008, 01:50 PM	#2
bbejj123 Zilvia Junkie Join Date: Nov 2007 Location: La Crescenta Age: 35 Posts: 482 Trader Rating: (0) Feedback Score: 0 reviews	just a question but what is your timing set at?... it kinda sounds like what happened with my car... i just switched out my ecu to an newer auto ecu and its fine...there may be something wrong with your ecu but there may be mutiple other things wrong as well __________________

04-18-2008, 01:53 PM	#3
flclsteve Zilvia Junkie Join Date: Aug 2007 Location: Irvine Age: 35 Posts: 538 Trader Rating: (2) Feedback Score: 2 reviews	sounds exactly like whats happening to mine as well ill see if i can post a vid the popping sound from my exhaust isnt loud at all __________________

04-18-2008, 02:27 PM	#6
naed240sx Zilvia Member Join Date: Jul 2005 Location: Houston, TX Posts: 206 Trader Rating: (0) Feedback Score: 0 reviews	Video showing how stable and smooth revving is...followed by hard throttle stabs. Listen to the way the throttle hits sound. To quote my friend, "it sounds like it farts" http://s180.photobucket.com/albums/x...t=MVI_0328.flv EDIT: video that shows the stumbling better: http://s180.photobucket.com/albums/x...t=MVI_0326.flv This was all just done parked, but the sound is similar and the problem persists with the car in gear. Last edited by naed240sx; 04-18-2008 at 02:53 PM..

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04-18-2008, 02:00 PM	#4
TurboNetic05 Leaky Injector Join Date: Feb 2008 Location: Michigan Age: 36 Posts: 132 Trader Rating: (0) Feedback Score: 0 reviews	mine did the popping thing and it was a misfire caused by water that got in with one of my spark plugs. I have no clue how it got there though

04-18-2008, 02:04 PM	#5
naed240sx Zilvia Member Join Date: Jul 2005 Location: Houston, TX Posts: 206 Trader Rating: (0) Feedback Score: 0 reviews	Its not timing. I'm convinced that it is some sort of air metering/vac leak/etc problem because of the effect that the idle screw has on the issue. Can't be timing because it was fine a week ago and had tons of power. It's a really jerky, popping, stumbling sort of problem.

04-18-2008, 09:24 PM	#7
naed240sx Zilvia Member Join Date: Jul 2005 Location: Houston, TX Posts: 206 Trader Rating: (0) Feedback Score: 0 reviews	After driving to the parts store, the car wouldn't start. At this point I realized I was wrong and that it must be electrical related. Replaced the alternator and now it runs like a champ.