Car shakes under 1200rpm - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

cmat1120 · 04-10-2014, 06:16 PM

So i have an sr20det and when the rpm's drop below 1200 the whole car shakes. I also can't get the car to idle under 1000. I think vacuum could be the culprit for the high idle(boost guage is showing less than 10 psi of vaccum at idle), but I can't figure out why it shakes so much. It doesn't feel like it's going to stall, but rather just makes the whole chassis vibrate. It immediately goes away once i rev it up past 1200 rpm though. One thing is that the car does have an aem fic and I believe it to be improperly tuned for the current setup and idk if that could cause anything(maybe improperly setup ignition timing?). If anyone knows of any solutions or anything to test I would appreciate it. Thanks.

kruked · 04-10-2014, 10:37 PM

IACV, vacuum leak(s), solid motor mounts...

cmat1120 · 04-10-2014, 10:51 PM

Damn, just realized motor mounts are what I forgot to look at while I was under the car today. I'm gonna take it to a shop to test for vacuum(smoke machine) and I sprayed the IACV, but if the shop can't find any vacuum leaks I'll take it off to clean it fully. Is there a way to look at the motor mounts from above? Also my transmission bobs when going over bumps and stuff. While under the car today I noticed there were two bolts on one side and zero on the other... thats not right is it? lol. Where can I get those other two bolts from?

Also I understand that the IACV and/or vacuum can cause the high idle, but they wouldn't cause the shaking would they?

kruked · 04-10-2014, 11:59 PM

Easiest way to see if your motor mount(s) is/are shot for me would to be to put a jack w/ a 2x4 in between the oil pan and to slightly jack up on the engine. Look for noticeable separation in the engine mounts. Be sure to have a flash light handy, a good, bright flash light.

Another way is to start the car and rev the engine a coupe of times while you have the hood open. Rev the throttle body w/ your hand, not w/ your foot on the peddle. If the engine jumps around dramatically, possibility that the engine mounts are shot.

2 bolts in the transmission cross member?... yea, that's not good. Best bet would to be to take one of them out and go to your local hardware store and ask them to match it up. Length won't matter if it's too long, you could always cut it to length if you have the right tool.

Vacuum can cause idle fluctuation. If idle dips below roughly 5-600 rpm the car will shake more violently because it's stumbling for air and it's about to stall in some cases.

If your car is shaking bad at 1200 rpm, I would lean more toward motor mounts.

cmat1120 · 04-11-2014, 12:10 AM

What are good motor mounts for daily driving that don't lift the engine up at all? I've tried looking, but all I can find is people saying nismo for DD and really stiff ones/hockeypucks for not lifting the engine up. I would like something in between and preferably somewhat cheap. Or if someone can tell me just how bad it is(and if its not horrible) then I might just go with hockey pucks as I know I have those so it would be almost free. Also the install for motor mounts is jack up the engine, take out one mount, put new mount in, then repeat for other side then let engine down right?

04-10-2014, 06:16 PM	#1
cmat1120 Join Date: Apr 2014 Location: Arizona Age: 25 Posts: 27 Trader Rating: (0) Feedback Score: 0 reviews	Car shakes under 1200rpm So i have an sr20det and when the rpm's drop below 1200 the whole car shakes. I also can't get the car to idle under 1000. I think vacuum could be the culprit for the high idle(boost guage is showing less than 10 psi of vaccum at idle), but I can't figure out why it shakes so much. It doesn't feel like it's going to stall, but rather just makes the whole chassis vibrate. It immediately goes away once i rev it up past 1200 rpm though. One thing is that the car does have an aem fic and I believe it to be improperly tuned for the current setup and idk if that could cause anything(maybe improperly setup ignition timing?). If anyone knows of any solutions or anything to test I would appreciate it. Thanks.

04-10-2014, 10:37 PM	#2
kruked Nissanaholic! Join Date: Feb 2012 Location: someone's sisters' pants Posts: 2,288 Trader Rating: (37) Feedback Score: 37 reviews	IACV, vacuum leak(s), solid motor mounts... __________________ I like my bikes how I like my b¡tches...naked! 2014 Triumph Street Triple

04-10-2014, 11:59 PM	#4
kruked Nissanaholic! Join Date: Feb 2012 Location: someone's sisters' pants Posts: 2,288 Trader Rating: (37) Feedback Score: 37 reviews	Easiest way to see if your motor mount(s) is/are shot for me would to be to put a jack w/ a 2x4 in between the oil pan and to slightly jack up on the engine. Look for noticeable separation in the engine mounts. Be sure to have a flash light handy, a good, bright flash light. Another way is to start the car and rev the engine a coupe of times while you have the hood open. Rev the throttle body w/ your hand, not w/ your foot on the peddle. If the engine jumps around dramatically, possibility that the engine mounts are shot. 2 bolts in the transmission cross member?... yea, that's not good. Best bet would to be to take one of them out and go to your local hardware store and ask them to match it up. Length won't matter if it's too long, you could always cut it to length if you have the right tool. Vacuum can cause idle fluctuation. If idle dips below roughly 5-600 rpm the car will shake more violently because it's stumbling for air and it's about to stall in some cases. If your car is shaking bad at 1200 rpm, I would lean more toward motor mounts. __________________ I like my bikes how I like my b¡tches...naked! 2014 Triumph Street Triple

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

04-10-2014, 10:51 PM	#3
cmat1120 Join Date: Apr 2014 Location: Arizona Age: 25 Posts: 27 Trader Rating: (0) Feedback Score: 0 reviews	Damn, just realized motor mounts are what I forgot to look at while I was under the car today. I'm gonna take it to a shop to test for vacuum(smoke machine) and I sprayed the IACV, but if the shop can't find any vacuum leaks I'll take it off to clean it fully. Is there a way to look at the motor mounts from above? Also my transmission bobs when going over bumps and stuff. While under the car today I noticed there were two bolts on one side and zero on the other... thats not right is it? lol. Where can I get those other two bolts from? Also I understand that the IACV and/or vacuum can cause the high idle, but they wouldn't cause the shaking would they?

04-11-2014, 12:10 AM	#5
cmat1120 Join Date: Apr 2014 Location: Arizona Age: 25 Posts: 27 Trader Rating: (0) Feedback Score: 0 reviews	What are good motor mounts for daily driving that don't lift the engine up at all? I've tried looking, but all I can find is people saying nismo for DD and really stiff ones/hockeypucks for not lifting the engine up. I would like something in between and preferably somewhat cheap. Or if someone can tell me just how bad it is(and if its not horrible) then I might just go with hockey pucks as I know I have those so it would be almost free. Also the install for motor mounts is jack up the engine, take out one mount, put new mount in, then repeat for other side then let engine down right?