Hi guys! My Z usually idle at 1000rpm after I start it! But recently sometimes after I drive it for a trip (half an hour to 45 mins) I park my car for like an hour.. come back crank it up it will crank up weak and the rpm will stay around 400-500 rpm... I know something's not right so I turn it off and crank again and it will back to normal! Like a month ago I have both valve covers replaced with new valve gaskets and I have upgrade to a set of new UR pulleys! Could you guys tell me what's the problem? If my rpm be that low at startup can I still drive it or it will stall? What needs to be replace or repair? Thanks!

 

Usually when the car cold starts, it runs rich with fuel around 1,000-1,500rpm and will slow down. Warm start-ups will idle at 400-500.

at least that's how it is for me.

I'm confused why 1,000 is normal for you

 

Yes I agree with you I mean when it cold start it is around 1,000 rpm and once it warm up it will idle at around 700rpm! But my car lately when I parked for an hour then go back start it it will start and it will immediately goes to like around 400 rpm I can hear the engine is running very weak! So I dare not to drive it... I switch it off.. wait couple seconds then start it up again... it then will back to normal to around 700-800 rpm!

It is a sympthom of bad fuel pump or MAF sensor??? When it goes to 400 rpm my car will start shudder a bit and it is like going to stall or something...! What's wrong?

 

Can someone help me? What's the problem causing this sympthom? Dirty MAF sensor? Failing fuel pump???

 

Leak maybe?? I'd re-torque all plenum bolts

 

I'm having the same exact issue right now.

Car will idle fine from a cold start. If I drive it around for a bit and come back to it 15 minutes later, the car will drop low in RPM and feel like it's going to die, but won't. Either I turn the car off and try again, or wait a bit and the car will correct itself eventually and the issue will never come up again till I try to start it again. Only happens on warm start up and never have issues while driving once it corrects.

It took awhile, but eventually the car finally through a code for me. I got P0300 (Multiple Cylinder Misfire) and P0103 (Mass Air Flow (MAF) Circuit High Input).

I haven't had a chance to get it fixed yet, only had a chance to clean the MAF, which didn't work. Next i'll check air leaks, spark plugs, coils, and replacing the MAF sensor completely.

Do not drive it while it's idling like that. You'll send unburned fuel to your cats and they'll overheat and be ruined.

 

check air filter as well. who knows

 

I have replaced alot of parts lately!!! Two new Camshafts sensors, crank sensors, Two new valve covers and gaskets, two new fuel return dampers, all 6 new coils, new Throttle Body... and also I have the cranking issue which you can read from my other post! So I dropped my Z off yesterday at the shop and replaced it with a new fuel pump! Just pick it up 3 hours ago... drove back home... will see if that's the problem...!!! Maybe you guys can give me more ideas!!!

I also wonder if my Auto Theft System is causing me problem too??? I have get a new chipped key... but cranking problem exist and now the idle problem!!!

 

I wonder if I should buy a new MAF also??? I am checking on those aftermarket MAF on ebay.. are those good???

 

i'd stick with oem MAF.

 

Yes I know the OEM one is good and I check it is hell of expensive it is like almost five hundred bucks US$!!! Or you guys know where to get a really good deal on MAF and offer shipping to Hong Kong please let me know!!!

 

Change a new Fuel Pump for two days seems like car start up fine!!! Maybe that's the solution for it?

 

$500? Try this:

http://www.courtesyparts.com/22680x-...8-p-18793.html