Car idles low/dies when quickly let off throttle

suprajim54

suprajim54

Member
Sep 2, 2009
119
0
16
Dallas, Texas
I have been having an issue with an intermittent low idle/dying problem. I searched but couldn't find any threads with a similar issue.

Occasionally, if I'm driving and let off the gas real quick the idle drops to about 500 RPM and wants to die. Most of the time it catches itself and idles back to normal (750 when warm). However, if I let off the gas to make a turn, it will actually die. If I feather the pedal a bit, it will stay running. I thought it might be the idle up valve for the power steering, but if I'm sitting still and turn the wheel, I don't experience the same RPM drop and it seems the valve is working like it should. The RPM drop will also happen when I'm going straight, like if I'm at a stop light and push the gas, but have to let off because the car ahead isn't going fast enough.

I recently replaced all of my vacuum hoses, checked my timing, adjusted the TPS, and cleaned the ISCV while trying to track down the problem. The car isn't throwing any codes. The battery was dead and had to be recharged recently, so could it be that the ECU just needs to relearn its values? Any other suggestions of what may be causing this? Thanks for any help.
 
suprajim54

suprajim54

Member
Sep 2, 2009
119
0
16
Dallas, Texas
Well, I have been chasing an oil leak and haven't driven the car much at all in the last couple months (probably less than 30 miles). I can't think of anything that I've changed or installed that would have affected it this way. I've been changing just about every oil seal, though. I just went outside and looked again and found there is a tiny crack on the accordion hose, but it is right where it clamps to the turbo (under the clamp actually) and doesn't look like it goes past the "lip" on the turbo that the hose slips on to. No other cracks on the bottom or on any of the other intake/intercooler piping. Could that small crack be the problem? I don't feel any other loss of power or hear any kind of misfire when I am driving down the road. Any other suggestions?
 
Suprasonic19

Suprasonic19

2JZ no sh*t!
Mar 5, 2007
135
0
0
Stockton, CA
Id take off your accordion hose and check it. Mine looked the exact same, just a little crack under the clamp. But once the clamp was taken off it revealed a very large and long tear.
 
the t3d

the t3d

P B4 A
Sep 30, 2006
839
1
18
Titusville, FL
dude, what you described in the OP....I had the EXACT same problem. I checked and recheck vacuum lines, adjusted the tps, and raised the idle a bit. It was annoying. I also have a recirculated Greddy RS bov. Also I would check the little dashpot on the tb to make sure it's hitting properly. On mine, it was HUGE vacuum leak from the lower intake manifold which was discovered when I smoke tested it(greatest tool ever). Now, she runs great, but on high rev drops it will sometimes stall. Good luck brotha!
 
D.J.T.

D.J.T.

Member
Aug 25, 2010
877
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Arkansas, United States
the t3d;1677136 said:
dude, what you described in the OP....I had the EXACT same problem. I checked and recheck vacuum lines, adjusted the tps, and raised the idle a bit. It was annoying. I also have a recirculated Greddy RS bov. Also I would check the little dashpot on the tb to make sure it's hitting properly. On mine, it was HUGE vacuum leak from the lower intake manifold which was discovered when I smoke tested it(greatest tool ever). Now, she runs great, but on high rev drops it will sometimes stall. Good luck brotha!
Click to expand...

exactly. just because the OP installed new vacuum lines doesn't mean he installed them correctly. One of the new lines might have not been able to hold up. Who knows when i installed a vacuum line i didn't install a clamp because it originally didn't have one & it came off driving hard. clamped it, no problem.

& where did you get your signature pic? i see those everywhere & its been bugging me :icon_bigg
 
suprajim54

suprajim54

Member
Sep 2, 2009
119
0
16
Dallas, Texas
I just rechecked all silicone vacuum lines and all are on good and zip tied. I looked at the dash pot adjustment screw and it is still lined up with the factory yellow paint. I tried to turn it just to see if it would and it appears to be stuck and I didn't want to strip the slot on the end of it without verifying it needs to be adjusted. I double checked the accordion hose and no other rips except the very small one previously mentioned. I will test the dash pot per the TSRM tomorrow when its light, but curious if anyone has any other suggestions or if there are any other things that I should check. Also, how long does it take for the ECU to re-learn? I adjusted the TPS about 2 months ago, but have not driven it much at all (as I said, less than 30 miles). Just wondering if I only really need to drive it to get things back to normal.
 
Suprasonic19

Suprasonic19

2JZ no sh*t!
Mar 5, 2007
135
0
0
Stockton, CA
the t3d;1677136 said:
d On mine, it was HUGE vacuum leak from the lower intake manifold which was discovered when I smoke tested it(greatest tool ever).
Click to expand...

Ive never heard of this, got any more info on this like what you used and how it worked? Id like to try this for my misfire problem.
 
jetjock

jetjock

creepy-ass cracka
Jul 11, 2005
9,439
0
0
Redacted per Title 18 USC Section 798
Smoke machine is used for evap and other tests to find leaks in all kinds of systems. Google it. Not cheap but can be homemade with a little effort. It *is* one of the greatest tool ever made. The only way someone will get mine is when they pry it from my cold dead hands...
 
MKIIISupraGuy

MKIIISupraGuy

New Member
Sep 14, 2009
639
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0
Lousy-ana
Check your alternator and make sure it's pushing positive voltage. If it isn't then your running strictly off the battery's power and can make the car do exactly what you described. This condition is worse/more noticeable if you have high power stereo with amplifier(s), which draw power from the battery as well. Hope this helps man and good luck.
 
suprajim54

suprajim54

Member
Sep 2, 2009
119
0
16
Dallas, Texas
MKIIISupraGuy;1677673 said:
Check your alternator and make sure it's pushing positive voltage. If it isn't then your running strictly off the battery's power and can make the car do exactly what you described. This condition is worse/more noticeable if you have high power stereo with amplifier(s), which draw power from the battery as well. Hope this helps man and good luck.
Click to expand...

Hmm, that's an interesting thought. Although when the car dies, it fires right back up. If I don't drive the car for awhile (maybe 3 weeks), the battery will go dead. I figured I just have a drain somewhere. Now that I think about it, the windows do sometimes seem to roll down slow and other electrical issues. The previous owner had all kinds of vacuum lines rerouted and timing set too high so I was chasing those avenues and ignoring the obvious. I'm going to check that now. Thanks for the suggestion.
 
S

Supra0089

New Member
Jan 13, 2009
367
0
0
New Hampshire
Yup...I have an auto, with an HKS recirc valve...give it any gas and let off fast it stalls. Give it wot, let off and if the car shifts after you let off it dies. On idle, floor it, let off, it dies? If this sounds familiar, it's your BOV. It won't go away until you get a piggyback/standalone, or put the stock bov back on. Its especially annoying with an auto. Just get used to throwing it into neutral when it stalls on the road and give it a quick start while rolling haha. Or, you can also manual shift the tranny so it always has a little bit of load and that keeps it from stalling. Goodluck.
 
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