backfires like crazy with other problems.

[808faded]

whats up everyone i got a 1990 coupe sohc motor, with intake headers exhaust and coilovers. i have a lot of problems that i cant figure out. i searched but each thread with the same problems as me theres always different solutions so i thought i'd post one up.

For one my car eats gas like nothing i get 140-160mpg on full tank and that was with normal driving(shifting around 2-2.5k rpm) just to see how much i'd get on a tank. My car also eats oil every once in a while. my car will have a good amount of oil for a while then one day its almost dry, and thats with checking it almost every other day.

another thing is my car backfires a lot. i mean a lot. when my car warms up and im driving i get that random 2k rpm backfire when shifting. but when i let my foot off the gas all i hear is my car backfing really bad. and also when i let off the gas my car comes to a stop a lot faster then it should, it feels like im on the brake but im not.

i also have loss of power 1st and 2nd gear it dosent accel. as fast as it should. and when im driving on the freeway and im in 4th gear my car wont go past 4k rpm like my foot will be on the gas and once the rpm hits 4k my car will just stop accelerating.

i also have ****ty idle, my idle is around 500-800 and when im reversing or going forward sometimes my car jus dies, but it starts up again right away. and when i go into neutral my idle fluctuates up and down 300-900 rpm and then holds idle again. today my car died on me coming to a stop when i put it in neutral good thing to that my car starts up again with no problems.

I know this was a lot to read and i have a lot of problems but i really need the help. this my only car and i gotta get to work and take my daughter to school so i really need this car to be running. So i thought i'd ask the nissan proffesionals on here instead of going to a shop and paying $$ out the *** to hear them tell me that it might be this or it might be that.

Thank you in advanced and if you have questions just let me know and i'll post em up as soon as i can. I come on here a lot but i dont normally post, but im on here a lot.

[aceof07]

the first thing i would recommend is to make sure all your maintenance is done(spark plugs, wires, rotor and cap, Coolant Temp. Sensor, clean your MAF with MAF cleaner, oxygen sensor, and also clean out you Idle Air Control Valve aka IACV., Check for vacuum leaks.) also make sure that your timing is spot on, use a timing gun and set to 20* after TDC. if you do all that and its still acting up, perhaps one of your sensors is dead, ECU is not working right, or an electrical problem.

[808faded]

oh yea sorry i forgot to say i changed spark plugs/wires cap n rotor. is there any type of maf cleaner you would recommened? probably gonna do that next

oh and how would i check for vacume leaks, i read on here i should use seafoam but how do i use it. i dont wanna mess anything up

[aceof07]

i highly recommend this one. http://www.autobarn.net/maairflsecl1.html just go to your closest autoparts store and get one. other cleaner can actually damage the MAF. One way of checking for leaks i've heard of is spraying carb cleaner around the vacuum lines and see if your idle changes. just look for any signs of damage and replace them, you should just go ahead and re-do all of them. its a pain but its worth it and its not too expensive.

[808faded]

shootz i'll head down to the store tomorrow morning. thx for your help, i'll post up tomorrow night and let you know how it goes

i'll try get the carb cleaner while im down there man i hope i dont got a vacume leak. would suck to have to replace the hoses

thx again
Modified by 808faded at 12:28 AM 9/25/2008

[89twoforty]

SOHC is 15*, DOHC is 20*.

IIRC

Everything else I agree with. Clean the MAF and the IACV, should make a huge difference with that alone.

It might not hurt to replace hoses soon anyways, chances are they've never been replaced. 18 year old rubber will only hold for so much longer.

[808faded]

yea thats true maybe i'll change the hose's this weekend. how would i go about cleaning the IACV?

[89twoforty]

Try reading through this, should help you out quite a bit. If not, at least they're interesting pictures.

zerothread?id=251133

If you're not comfortable removing the unit there is another way mentioned in the thread.

I've never personally done it this way, but I've heard a few mention it.

Ghetto way to clean iavc is.

step 1. start carstep 2. while having a friend rev engine, partially remove the 2ND (bigger of the 2 hoses) right beside eachother on your intake(stock - going from engine to airbox)step 3. if you have managed to keep car running while pulling it PARTIALLY OFF then continue if not restartstep 4. spray a **** load of throttle body cleaner in there and reatach hose while keeping engine running.repeat as needed

Modified by 89twoforty at 1:08 AM 9/25/2008

[808faded]

thx man im reading through it right now

[89twoforty]

No problem. Good luck with it.

[aceof07]

hey there 89twoforty, thanks for taking over where i kinda left off, i'm more of the DOHC kinda guy. i love it when we come together and actually help out. OP let us now how your cars doing.