when cold car making wheird sound?

[Sdavne]

i have a 90 300zx n/a and some times after driving and i let the car sit for alittle like an hr. or so, the car will make a sound like its mis firing. or a bad motor mount. also there is a loss in power when i drive it. it will go away by it self maybe 5 min. after or if i wind down 3 gear to second almost letting it stall but i push the clutch right in after. i changed the plugs. also all motor mounts and trans mounts are new with only 20k on them and they are poliurathane and bushings too. any thoughts??

[thaixcore]

try NGK spark plugs. ive heard they can help hesitation alot. make sure everythings plugged up, lol i was running on 5 injectors for a long time cause i didnt check

[Sdavne]

what do you mean pluged up, thats what it sounds like im runing on 5 cylenders, i did change the plugs with NGK aranimum plugs and still does it, there is still some bolts missin on the top of the coil on plug and one on the ballence tube( vacume tube) u think that could be it to?

[Zwicked]

Pull all the connectors with the spring clip and see if they are corroded. Sounds like and intermittent electrical connection to me. The ones to check are: CAS, PTU, Injectors, Coolant Temp Sensor, AAC, FICD, Air Regulator, TPS, and MAF. Scrape all the corrosion away you can, and then apply some good contact cleaner. Essential that all components have a good connection.While you have them off the injectors, test the injectors with a multimeter to make sure they are all in spec. They should measure 10 to 14 ohms.

Also, the other post is correct. Make sure you are using the NKG Nissan recommended plugs. Unless you are running extreme horsepower no other plug will do as well as the stock ones.

Bolts missing on balance tube? YES any vacuum leak is bad and make sure all your CP's are bolted down. The engine and connections need to be meticulous!

[Sdavne]

I checked the coil on plugs and they all had spark but i do remember i did change the plugs to NGk uranium plugs from platinum plugs and the car was tuned for the platinum but the car starting doing this befor i changed the plugs, it is getting worse and worse and i still can not figure out what it is, it use to only do it once in a while than it started doing it after a turned off the car and then turned it back on ( like if i went into the store and came back) and now that it is warm out it does it the first time i turned it on and now it will not go away? i drove for 30 min today with it like that. i feel a major power loss and also i hear a sound in the exhaust that makes the car sound like a wrx sound. the car is a 1990 300zx n/a 2+0 and as far as the ingectors they are new as well so i do not think it is them.

[es.biggs]

First, bolt your balance tube down. If its not seated right it will leak, and it will leak a lot.

I would also check the ignition timing, when the car is fully warmed up. Grab a timing light, hook it up and point it at your crank pullley. It should light up when the mark on the pulley it at 15 degrees before TDC. If it's not at 15, adjust your Crank Angle Sensor to get it in that 15 mark.