How would you know if you have a bad fuel pump (like not performing well)
 

cuz I always feel that I am running too lean. Sometimes my engine shakes abit when I gas it around 2000-3000rpm and the shakes is gone after 3500rpm. could it also be O2 sensor? or MAF? I did a seafoam treatment today and it seems to improve a little but the problem is still there.

go and buy a 300zx tt fuel filter there like 12 bucks that may be your problem

I did change my fuel filter already.

if you changed the filter, then it probably wouldnt be that. get an OBD port scanner and see if you get any error codes. see what they mean and what they correspond to and see if you can fix any of it (assuming you found a problem while scanning your OBD port)

well I am really a newbie in OBD scanning. the only think I know is that I have OBD 1. can anybody teach me the basic to finish the job? thanks

oh also. would there still be error code even if the engine light is not on? assume the engine light is not burned

and can OBD II scanner scan OBD I?

jackyliem, 2 things: first off, just edit your post, thats what the button's for *hehe*

second, lets get u thru this. the stuff you need to know is OBDII is not reverse compatible. if you have an OBDI/II scanner, you can read both, otherwise you need a version 1 scanner. just to let you know, unless you plan on buying another car thats OBDII, a dual mode scanner is a waste of money. version 2 scanners are usually double the price of a version 1, and i dont know what the price is on the dual modes. if you get one, it will come with a manual that will tell you what you need to know about your port scanner, and what the codes that pop up mean. yes your port scanner may tell you there's a problem even though your check engine light doesnt come on. some problems can be handled internally, so why make you worry, right? (in this case it THINKS it can handle it... i guess not). know also that your port scan may turn up nothing, so before you run out and buy a scanner, check your MAF. sometimes just unplugging it and then plugging it back in will fix the problem. other times it needs to be cleaned. dont ask me if you have to do anything special to clean it, cuz im still waiting on THAT answer in another thread. good luck.

you can spray it w/ electronics cleaner... and be /nice/ to it! don't push on the wires or anything.

yea I know MAF are expensive. my friend just bought on for his celica GTS for 150. thanks guys