Car won't hold idle. Ready to rip hair out. Video included. - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Grocery Cart · 02-24-2015, 06:49 PM

Car is a 1993 240sx with a 1995 ka24de. Has s13 dohc temp sensor, intake, wiring harness, distributor, ecu, and maf.

Starts right up, revs to around 4-5k for a second or two and will stay there if i feather the throttle. Once it starts to go down it will just die. No sputtering, or misfire. Just straight dies.
All vac ports are capped except the necessary ones, fuel filter, new PCV hoses, egr blocked off, IACV cleaned, new plug wires, new plugs (although they may be slightly dirty from running rich a few times prior), timed it, new-to-me known-good IACV and iacv gasket, new-to-me known-good TPS set to .47, I've tried two different mafs. It seems like a vacuum leak but I've gone over it multiple times and didn't see any unattended vac ports.

Video shows me starting it with the maf unplugged, letting it idle, then when I plug the maf in it dies immediately. Didn't even have time to go into the car to show the tach.

Any advice is greatly appreciated.

Kingtal0n · 02-24-2015, 07:15 PM

You have an enormous vacuum leak. Do a boost leak test to isolate it.

Its pretty big so, you might be able to clearly feel it somewhere obvious. intake manifold, brake booster, two places to start. Try clamping/plugging the IACV.

You can be sure that it is between the intake valves and throttle body.

Grocery Cart · 02-24-2015, 07:27 PM

Quote:

Originally Posted by Kingtal0n

You have an enormous vacuum leak. Do a boost leak test to isolate it.

Its pretty big so, you might be able to clearly feel it somewhere obvious. intake manifold, brake booster, two places to start. Try clamping/plugging the IACV.

You can be sure that it is between the intake valves and throttle body.

What makes you so sure it's between the intake and tb? Just curious

Kingtal0n · 02-24-2015, 08:29 PM

the demand for air applies at the intake valve. Imagine running the engine with no intake manifold, it would rev up as high as it could and explode magnificently.

So what stops the air , limiting RPM?

the throttle body.

omgosh · 02-24-2015, 08:32 PM

Mega vacuum leak, or stuck open idle solenoid and warm up valve.

All the air used to idle the engine comes through the big hose off the intake pipe. That hose feeds the idle valve/solenoids. If you crimp the hose, theoretically the engine should have no more air to idle, and will stall. If it continues to run, it is because it is drawing air in from somewhere else, like through a vacuum leak in the manifold, or maybe stuck/broken throttle plate with as much RPM as you are getting.

Grocery Cart · 02-24-2015, 08:38 PM

Quote:

Originally Posted by omgosh

Mega vacuum leak, or stuck open idle solenoid and warm up valve.

All the air used to idle the engine comes through the big hose off the intake pipe. That hose feeds the idle valve/solenoids. If you crimp the hose, theoretically the engine should have no more air to idle, and will stall. If it continues to run, it is because it is drawing air in from somewhere else, like through a vacuum leak in the manifold, or maybe stuck/broken throttle plate with as much RPM as you are getting.

what hose are you talking about?

omgosh · 02-25-2015, 01:01 AM

beatfishe · 02-25-2015, 02:58 AM

good,You can be sure that it is between the intake valves and throttle body.thanks

Grocery Cart · 02-25-2015, 01:53 PM

Quote:

Originally Posted by beatfishe

good,You can be sure that it is between the intake valves and throttle body.thanks

I've got that line connected and it seems like it's good all the way to the iacv with no cracks or leaks.

I just got back from inside and used half a can of brake cleaner trying to listen for a change in idle and nothing. I also tried adjusting the distributor full clockwise and counter clockwise (with the maf unplugged) and no change, plugged in the maf after rotating both times and it did just like it normally does; revs to 4-5k then dies.

Grocery Cart · 02-25-2015, 03:50 PM

Update: I reread omgosh's comment and decided to go outside and plug the iacv hose with my finger. car dropped to 1k and idled smooth. confirmed the vac leak and made it suck harder aka louder. It's between the upper and lower intake mani between the second and third runner.

Bushido · 02-25-2015, 04:11 PM

If i were you, I would have posted thread this in the Tech section...
I would also pull the intake manifold, clean everything, replace the gaskets, and reconnect/replace the vacuum hoses you "capped".
Doesn't look like your motor is turbocharged, so there is no reason to cap those vacuum lines.
Without a tune your car will run rich/worse just capping lines.
Rubber caps will eventually fail and cause problems like you are having now.
If you want to eliminate them in preparation for turbocharging, weld them shut.

Grocery Cart · 02-26-2015, 01:52 PM

All gaskets have been replaced, I removed the egr and carbon canister so all of those lines were useless and didn't go anywhere anyway. From my understanding you only need the for, brake booster, pcv, and iacv hoses. Which are all connected properly (except the pcv apparently if you read my last post) and the remaining lines are caped off. I would prefer to weld them, but I do not have access to a welding machine so rubber caps suffice my needs.
Thanks.

Bushido · 03-04-2015, 07:43 AM

Just know that your car will run rich (worse) without tuning to compensate for the removed EGR system. No point in removing EGR system unless you are turbocharging and tuning.

http://zilvia.net/f/showthread.php?t=192553

xilovelsdx · 03-04-2015, 09:52 AM

Sounds like a tps sensor to me.

02-24-2015, 06:49 PM	#1
Grocery Cart Zilvia Junkie Join Date: Aug 2011 Location: Baton Rouge, Louisiana Posts: 582 Trader Rating: (2) Feedback Score: 2 reviews	Car won't hold idle. Ready to rip hair out. Video included. Car is a 1993 240sx with a 1995 ka24de. Has s13 dohc temp sensor, intake, wiring harness, distributor, ecu, and maf. Starts right up, revs to around 4-5k for a second or two and will stay there if i feather the throttle. Once it starts to go down it will just die. No sputtering, or misfire. Just straight dies. All vac ports are capped except the necessary ones, fuel filter, new PCV hoses, egr blocked off, IACV cleaned, new plug wires, new plugs (although they may be slightly dirty from running rich a few times prior), timed it, new-to-me known-good IACV and iacv gasket, new-to-me known-good TPS set to .47, I've tried two different mafs. It seems like a vacuum leak but I've gone over it multiple times and didn't see any unattended vac ports. Video shows me starting it with the maf unplugged, letting it idle, then when I plug the maf in it dies immediately. Didn't even have time to go into the car to show the tach. Any advice is greatly appreciated.

02-24-2015, 08:29 PM	#4
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 38 Posts: 4,649 Trader Rating: (17) Feedback Score: 17 reviews	the demand for air applies at the intake valve. Imagine running the engine with no intake manifold, it would rev up as high as it could and explode magnificently. So what stops the air , limiting RPM? the throttle body. __________________ 5.3/4l80e/turbo 240sx playthrough: https://tinyurl.com/turbo240

02-24-2015, 08:32 PM	#5
omgosh Zilvia Member Join Date: Mar 2005 Location: Tampa FL Posts: 210 Trader Rating: (0) Feedback Score: 0 reviews	Mega vacuum leak, or stuck open idle solenoid and warm up valve. All the air used to idle the engine comes through the big hose off the intake pipe. That hose feeds the idle valve/solenoids. If you crimp the hose, theoretically the engine should have no more air to idle, and will stall. If it continues to run, it is because it is drawing air in from somewhere else, like through a vacuum leak in the manifold, or maybe stuck/broken throttle plate with as much RPM as you are getting. __________________

02-25-2015, 01:01 AM	#7
omgosh Zilvia Member Join Date: Mar 2005 Location: Tampa FL Posts: 210 Trader Rating: (0) Feedback Score: 0 reviews	__________________

02-25-2015, 04:11 PM	#11
Bushido Post Whore! Join Date: Jun 2003 Location: SFL Posts: 3,562 Trader Rating: (10) Feedback Score: 10 reviews	If i were you, I would have posted thread this in the Tech section... I would also pull the intake manifold, clean everything, replace the gaskets, and reconnect/replace the vacuum hoses you "capped". Doesn't look like your motor is turbocharged, so there is no reason to cap those vacuum lines. Without a tune your car will run rich/worse just capping lines. Rubber caps will eventually fail and cause problems like you are having now. If you want to eliminate them in preparation for turbocharging, weld them shut. __________________

02-24-2015, 07:15 PM	#2
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 38 Posts: 4,649 Trader Rating: (17) Feedback Score: 17 reviews	You have an enormous vacuum leak. Do a boost leak test to isolate it. Its pretty big so, you might be able to clearly feel it somewhere obvious. intake manifold, brake booster, two places to start. Try clamping/plugging the IACV. You can be sure that it is between the intake valves and throttle body.

02-25-2015, 02:58 AM	#8
beatfishe Join Date: Feb 2015 Location: CA Age: 35 Posts: 1 Trader Rating: (0) Feedback Score: 0 reviews	good,You can be sure that it is between the intake valves and throttle body.thanks

02-25-2015, 03:50 PM	#10
Grocery Cart Zilvia Junkie Join Date: Aug 2011 Location: Baton Rouge, Louisiana Posts: 582 Trader Rating: (2) Feedback Score: 2 reviews	Update: I reread omgosh's comment and decided to go outside and plug the iacv hose with my finger. car dropped to 1k and idled smooth. confirmed the vac leak and made it suck harder aka louder. It's between the upper and lower intake mani between the second and third runner.

02-26-2015, 01:52 PM	#12
Grocery Cart Zilvia Junkie Join Date: Aug 2011 Location: Baton Rouge, Louisiana Posts: 582 Trader Rating: (2) Feedback Score: 2 reviews	All gaskets have been replaced, I removed the egr and carbon canister so all of those lines were useless and didn't go anywhere anyway. From my understanding you only need the for, brake booster, pcv, and iacv hoses. Which are all connected properly (except the pcv apparently if you read my last post) and the remaining lines are caped off. I would prefer to weld them, but I do not have access to a welding machine so rubber caps suffice my needs. Thanks.

03-04-2015, 07:43 AM	#13
Bushido Post Whore! Join Date: Jun 2003 Location: SFL Posts: 3,562 Trader Rating: (10) Feedback Score: 10 reviews	Just know that your car will run rich (worse) without tuning to compensate for the removed EGR system. No point in removing EGR system unless you are turbocharging and tuning. http://zilvia.net/f/showthread.php?t=192553 __________________

03-04-2015, 09:52 AM	#14
xilovelsdx Zilvia Junkie Join Date: May 2008 Location: Titusville, FL Age: 33 Posts: 376 Trader Rating: (6) Rides Gallery: xilovelsdx Feedback Score: 6 reviews	Sounds like a tps sensor to me. __________________

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