Engine randomly shakes at idle?

[DorianrZX]

Hey. It was out of the blue when i stopped at a light and my car started to shake quite vilontly. My idle is somewhat steady ( 700-900). When i rev the engine the shaking goes away until it drops to idle again. The shaking comes and goes but it gets quite annoying . all my power is there when im driving. I dont know if its my mounts my car has 106.xXX miles so they shouldnt be too worn. I havnt tampered with the engine in a while either.

any ideas?

[evildky]

I'd suspect some sort of misfire, could be anyting form a fouled plug to a cracked valve seat

[DorianrZX]

if it was a cracked vavle seat, wouldnt I loose power? also i have new Platinum +4 plugs

[Doomday300]

if it was a cracked vavle seat, wouldnt I loose power? also i have new Platinum +4 plugs

eww, get ngk weather thats the problem or not

[evildky]

no a caracked valve seat wouldn't reduce power, at high rpms it might seal well enough, at idle it might not, an it also might not show up in a comrpession test, a leakdowntest and stethescope with the plenum off wil help find an intake valve leak, the exhaust side is a bit tougher to pin down

and yeah put some normal plugs in, ngk or denso platinums

[Zwicked]

A few things can cause that

- vacuum leak ... do a boost leak test- bad injector ... test with multimeter- dead o2 sensor ... run o2 diagnositcs- dead AAC valve ... test with 12 volt power from battery to solenoid

[xbillisedgex]

bad injector(s) just had mine done and the same thign happened to me

[blackz32]

most def an injector..almost 100 percent positive. had the same problem ..6th injector was bad which caused a miss and it shook violently. costed me 1400 for all new injector harnesses and 1 injector now it runs like a champ

[Cyman]

I currently have a bad injector, and my Z does the same thing, but I agree with zwicked, not 100% positive it's the injectors in your case.Pull out a multimeter and check, if they're all good, move on to other solutions.

[300freekzx]

How to check with the mulit meter. Is there a write up?

[P3ngy]

[Cyman]

just pull the injector connector and check the resistance. should be around 12 ohms. anything above 14 ohms I'd recommend replacing asap.

[300freekzx]

It is question that deserves an answer. Is measured in OHMs WATTs what?

[Cyman]

Ohms?while you're in there I'd recommend cleaning any corroded injector connecters.

[xbillisedgex]

also if it is a injector just some ideas from experience if you decide to take the intake off to change the injector do all of them because i took it off did #6 then put the intake back on the found out 5 and 3 were bad also right after i did it. they werer fine when i checked but its alot of money but it saves your sanity in the end

[300freekzx]

Awesome and Thanks

[SlickDrift93]

Okay so im a little upset at the moment my girlfriend currently has a 91' JDM 300ZX. With 115K miles.

The car when we got it was pretty much been babied after thoroughly inspecting the car, only issues were the rear main seal was slowly leaking nothing major and the diff seal as well. Other than sometimes typically on a cold start, there was a very obious rough shaking idle, and if you drive off while it shakes it seems to lag as if i hit the gas pedal and the engine lags to catch up to hitting the gas pedal. and the rpm is round 1K to 1.2K, after car warms up it goes away.

So I figured I'd go ahead and service those issues but first I did the 120K service. Which basically I did a lot; New Crankshaft sprocket front & rear washers, heavy duty idler studs, new spark plugs, new timing belt, Upper & Lower idler pulleys, drive belts, Also I changed the fuel injectors to new style 370cc. That way she can pump 93 with ethanol blend due to shortage or lackof 91+ no ethanol gas in my neck of the woods. With that we had to change the connectors on the fuel rail and adapter kit for it to work with old fuel rail style. We used the viton plenum seals as well to go with.

After all that the damn car still shakes on a cold start. When I replaced the fuel injectors; fuel injector number 1 was loose so I assumed that was the issue but it clearly is not.

Any help is appreciated. Sorry for digging this thread up, been lurking forums for a while but this is my first post. Thanks in advance!

[z.Leinbach]

try fuel dampener and regulator, as well as new pcvs. also make sure the air flow meter is clean and the tps, and crank sensor is calibrated properly, also test your coils. and maybe replace the boots if the coils are good

[SlickDrift93]

Okay, ill have to ask my mechanic about that, other issue i forgot to mention is when it does shake and afyer even it warms up a little, when you press doen on the gas it moves nowhere. Basically you rev it up to 1500rpms and it creeps only and its acting like a manual in first gear taking off. Car is auto.

[DCaff300ZX]

If what was mentioned above has no help, look at the IACV and connectors, CTS and connectors, and also PTU harness connectors. I finally after many many months looking for a problem I could never fix replaced my PTU subharness, and wow- FINALLY lost my idle issues and some other minor stuff it was doing randomly.