problem with warm engine

[grendel]

ive got a 90 240sx with a stock ka24e, 113k miles. a new problem came up yesterday that makes the car undrivable. when the engine is cold it will drive fine for 5-10 minutes maybe but when it warms up the rpm will start to surge up and down a 1000 or so making the car shake badly. it will start higher in the band and move down till the car will barely run till its cooled off.

new things:plugswiresrotorcapheadgaskettiming chain, tensioner, guidestried different injectorso2 sensor

im waiting on a new fuel pump, thats the only thing i can think is that its dying on me. but im not familiar with nissan engines so if anyone knows something else that would cause this please let me know.

[Hijacker]

is the timing off? was the timing chain installed properly? those are the things i'd be looking at.

[grendel]

the chain is fine and the timing is on. like i said. the car drives perfect while its cold. it ran normal for 2 days after i got done with everything then this new problem popped up.

[gumby]

http://www.nissaninfiniticlub....75639

seems like the mafs is a fragile thing. if you unscrew the 2 bolts and carefully remove it you'll see 2 thin wires. as i understand it. theres a hot wire and a thermistor wire. ecu increases voltage to keep the wire hot as increased air flow cools it. the thermistor reacts to the variations in temperature which alters resistance to the voltage applied to it. the voltage variations are read by the ecu which determines the fuel delivery. if either wire is broken the fuel system will usually run rich. since it has no way to determine exactely how much air is being taken in, it will not vary the amount of fuel delivery to the injectors properly. instead it will just deliver a default amount. this of course will confuse other sensor readings such as the O2 sensor.

i think thats how it goes, dont quote me

[smokin240]

yeah, I took it to the mechanic and they ran some diagnostic tests on it with a computer, and my car is doing the EXACT same thing yours is. He said it was the MAFS so im going to try and see if I can get one cheap and i'll let ya know if it works. By the way, turn your a/c off and your engine will stop trembling when it idles, if that works, its same problem as mine.

[IlIkEmYz]

mine has the same problem and it has 175k on it, can an aftermarket intake cause this too???

Also smokin240 how much did the mafs cost?

[smokin240]

it varies. from dealer i heard it was 600$, I didn't even bother looking at that(mechanic told me, i think he was bs'ing me). I called Napa they said $424. Gumby said you can get it refurbished for 200 or something. Thats still too high for me so im checking out the junkyard tomorrow should get it around 100 or so. Also you can check the Nico classifieds , thats what im doing, there going for about 15-80$. by the way, I have about the same amount of milage (166k) so maybe be a good idea to get a MAFS if you plan to that has low milage because it seems the higher mileage cars are having that same sort of prob.

[xTearsFallForeverx]

I also have a question around this subject. Last week I changed my Intake style to a short ram like seen here http://www.240sx.org/links/ins...x.htmWell when i first started it.. I needed to turn up my idle. no biggie. I did that and adjusted my timing accordingly. Now my car has a hard time staying running at startup. I checked the MAF.. it is working fine.. i suppose.. lol But anyway.. i have to wait for the car to warm up before it will idle. After that it is fine till the engine cools off. Also before i made the change my rpms jumed around by like 500 rmp up down up down.. blah. Do you think i need a new MAF? Could this be the problem?

[smokin240]

Ive heard that same problem (changing intake and having running problems). I never really bothered to check out whats wrong, but if I were you i would check the 240sx forums and do a search for intake problems or something.

[grendel]

well the car wont even idle when its cold now so who knows whats going on. im gonna take it to a mechanic soon as i get time.

[xTearsFallForeverx]

well if ur stuff wont idle cold.. then it may be your MAF. Im pretty sure thats whats wrong with mine. I can get another one for $50. but the new question is.. should i go with a MAF from a ka24de? or is there any difference?

[grendel]

they're different. im selling one of each on ebay. i ended up with extra's trying to make sure that wasnt the problem

[grendel]

i heard back from the mechanic. apparantly the distributer went bad.

[smokin240]

I got the MAFS today and it didn't fix it. Theres a metal piece that looks like is missing in the wire that connects to the MAFS, im going to see if this is the problem.

[xTearsFallForeverx]

is your idle control valve hose hooked up? if not that may be the probblem. try adjusting ur idle control valve? if no try that. about about turning ur idle control sensor? on the right side of ur intake. its a lil black box. try that. if no still is o2 sensor bad? check that again. maybe not plugged correctly. all i can tell you. most likely if it dont run right when it gets warm is the o2 sensor making the env too rich or too lean. o btw i fixed my problem. my idle control hose wasnt hooked up behind the intake which registers as a HUGE vaccume leak. laters.

[smokin240]

really, well it does my problem when it warms up. the "smooth" area is between 2500 and 3500 rpm after that it loses almost alot of power. how do I check my o2 sensor?

[xTearsFallForeverx]

ive always heard that a good o2 sensor is usually white or grey. if its black its usually bad.. but if urs is new then id just check ur connections. make sure you dont have any shorts in the wires. use an electronic multimeter to check if there is current present in the connection coming from the wiring harness.

[xTearsFallForeverx]

o dear. check what grendel said. his distrib was bad? maybe check ur dis cap and rotor button.. i doubt ur distrib can just go bad? correct me if im wrong. check plug wires and such. is ur timing advanced or retarded too far? hell i dunno. I just try to narrow everything down. keep looking and you will find the answer. PS. My car is running great now. I fixed my prob. Also added a new fuel filter and new pcv valve. idle and accel is so much smoother now. next is to replace o2 sensor, dis cap, rotor button, plug wires, and oil change. 201,000 miles on it.. still running like new.

[smokin240]

man, ive been fixing and replacing things for months now and i dont even have a job at the moment to fund my repairs. honestly im sick of guessing and fixing i want to pinpoint the problem and know its the problem and fix it. ive already had 2 mechanics tell me wrong and I dont even know what to do anymore. I gone all the way to hooking it up to a computer and they said it was the MAFS and that wasnt it..... im out of idea's and I seriously need to fix this car to get ready for a cross country trip.. im going to try and eyeball my o2 sensor to see the condition and clean my MAFS with my newbie skills and hopefully fix it which i have a feeling it wont.

[smokin240]

Ive definitly narrowed it down to either a thermostat problem, ECU, or o2 sensor. I think the key to solving the problem is how it does it when it warms up and also how it does it before 2500RPM and after 3500RPM. The more hot the day is, the more narrow that smooth band of acceleration is, and the more it lags and hesitates during the acceleration before and after that RPM band. Does it no matter what when I accelerate hard, past 3/4 of fully flooring it.

[xTearsFallForeverx]

bet its ur sensor going into ur radiator. dont remember what its called.

[smokin240]

yeah i have had the car for 6 months now and havent had to replace radiator fluid, weird... whats the sensor there do?