Bag gas milage and some other oddities, 89 240sx KA24E

[outerheaven2k4]

First, here are some symptoms, whenever i press the brake everything dims (headlights, interior lights, etc) along with odd effects to the coolant temp gauge and rpm guage. Along with that, the blinker stopped working, then it did and my brake light doesn't work (both lights are on the driver side). Already replaced the alternator, didn't help much, battery cables are reading good all around, no resistance at all). Checked ground from negative post to chassis, and its good from the looks of it.

I have a small feeling (probally wrong tho) this could be related to the insanely bad gas milage, full tank gives me 112 miles, and the guage IS correct. O2 sensor is new, full tune up already done (plugs twice) and it's burning REALLY rich, the exhaust just smells like being at a gas station. The car idles really well for the most part, sometimes feels like its gonna die at a stop light, but it hasn't yet. Replace thermostat, 02 sensor (like i said before), fuel filter, plugs & wires, cap rotor, and coolant temp sensor, any other ideas? Maybe i'll fix it this weekend, i noticed that my exhaust manifold (the left side) is being held by one bolt, instead of four, i'm hoping it'll fix the gas problems, but i still feel it's gotta be something else. also, no codes from the ecu.

I'm guess a ground problem? I read that there is some sort of braided wire coming from some part of the engine above the o2 sensor to the firewall, i was wondering, is this in my car? if so, i don't have one that i can see. It seems a lot of sensors use this ground (if i so have it) and maybe that's something that could be wrong.

*sigh* Any help would be greatly appreciated? I have searched around..still lost. :confused:

[F3600]

yeah .. you got grounding problem ! Take some big gauge wire install it on your engine to your car body. It Doesnt cost too much.. could be also why you have a bad gas mileage. Do you still have the stock ground on the intake manifold ? if not re-do it and add some more ... good luck

[outerheaven2k4]

the only ground I absolutely know i have is the good ol negative ground, where is the intake ground?

[sykikchimp]

Check you MAF too. I just had to replace mine and my car was running really rich and getting horrible gas mileage. Sometimes it would run smooth, others it would run like crap.

[idlafie]

Two things you want to check:

1). Fuel Regulator could be bad....make sure you are getting proper vacuum to the fuel regulator. I think its 34psi at idle....not quite sure though....anything higher and it's just dumping fuel into your intake.

2). Carbon canister system / Evap system to your gas tank. One of the vacuum / purge lines may have come off / been disconnected or cut. The gas tank system is supposed to be a sealed system with the vent gasses going back to the gas tank thru the carbon canister. If the carbon canister fails, you'll get gas fumes venting thru the canister.

Anyhow, check these two items. If that doesn't work, then use the SEARCH function...there's a ton of postings on Zilvia regarding poor gas mileage.

ID

[idlafie]

D'oh!! :duh: :duh:

About your brake lights/turn signals, check your rear taillights. One of the ground wires inside the brake light/turn signal assembly may have worked itself loose, (don't ask me how... I have NOOO clue...but usually when you start having taillight/turn signal problems it's due to loose wires...I've seen it happen on several cars not just Nissan either!!). If the wires are tight, then check the electrical connections, (including the base unit where the glass bulb itself twist into the electrical socket. The base plate could have melted/fused due to a short...seen that happen too!!

Anyhow, hope this helps..
ID

[outerheaven2k4]

Wooohoo
Fixed one problem. The wire from the block to the firewall! The thing couldn't have been even considered a wire, replaced it with a nice sized wire, the whole thing runs smoother, shifter is perfect, etc. Quite nice actually.

However, the gas milage is still for shit and surging is now more noticeable (mainly in the low rpms, likes high rpms). I get about 40 miles to a half tank now
O_o. No longer get ANY engine codes now :P

I'll check out the fuel regulator, cause i already checked the canister ^_^

[outerheaven2k4]

WOOHOO!
Gas milage fixed?! Maybe, i think it is! :P i'll wait till i kill this tank, but it is insanely better, after 50 or so miles of driving it didn't drop to half a tank like normal :P

In the end i double checked the canister, it seems one of the hoses was loose, put it on, tightened it up, boom all better...but...

New Problem :D
Now its with throttle, when at low rpms and when i let go of the gas, it surges pretty bad, loves high rpm tho. Any ideas?

[idlafie]

WOOHOO!
Gas milage fixed?! Maybe, i think it is! :P .... it seems one of the hoses was loose, put it on, tightened it up, boom all better...but...

New Problem :D
Now its with throttle, when at low rpms and when i let go of the gas, it surges pretty bad, loves high rpm tho. Any ideas?

Click on the attached link...

http://www.240sx.org/faq/index.html

When the page loads, look to the left....scroll down till you find the following two links...
1). Engine Surging
2). Idle is Fast, (Troubleshooting)

The second link also gives you info on how to adjust your idle. Read & take the appropriate actions.

Before you do all this though...make sure your engine is at the right timing. 15 degrees 89-90 & 20 degrees 91-98. While you're doing all this, if you haven't already done so, take the time to do a tune up. Replace your spark plugs, distributor cap & rotor, change both your air filter & gas filter also, clean out the throttle body with a throttle body cleaner & pour a can/bottle of fuel injector cleaner in your gas tank at the next fill-up. Make sure you fill the gas tank completely up when you pour the fuel injector cleaner.

You'll find all the above will help you get your car to idle right, run properly, and improve your gas mileage.

Anyhow, hope this helps..

ID

[outerheaven2k4]

Hrm
Well a tune has been done, all those things said, i've been to that site (infact one of my main references actually). I've looked a bit more, I'm gonna change the spark plugs again (the ones in it are probally bad because i was running super rich before). 02 sensor is infact good, however, the surging may be caused to my wonderful new friend, exhaust manifold leak, it seems i am missing three out of four bolts on the left side of the exhaust manifold. JOY! Gas milage is actually superb now, minus the shuddering :)

[JDMark]

SOHCs are notorious for the busted exhaust manifold bolts, ive heard of it happening alot and when i bought mine it had 3 broken as well (on the left side too, wiiieerrdd). i dont know if it was actually leaking but it definetly didnt make my engine surge.
have you checked out your aiv? clean it or just remove it completly.

[outerheaven2k4]

If you mean the AIV crap in between the exhaust manifold and air filter
yeah it's quite gone
got a question on that though, the little plug that goes in the assembly, connects to this black little round thing, has three vaccum hoses, wth is it for ?

[The Hamsterball]

don't put fuel injector cleaner in your 240. (Nissan does NOT recommend it)..

you're going to notice a big power difference when you bolt up that loose manifold lol...

don't worry, you can probably get those bolts for $6 from the dealership. (i had the same problem).

good luck, and thanks for opening this thread. i have gas mileage problems too, but mine are less horrible. (230 miles to the best tank i drove.. some high way, some city driving)

[JDMark]

Most cases ive seen (including with mine) the bolts have snapped off in the head. i tried but just decided to bring it to a machine shop to get it fixed, wasnt too expensive.

[outerheaven2k4]

actually i'm getting 215-230 mpg, city with minor fun high revs in there, i feel that is good, considering it was 80-90 for a tank :)
gonna check timing, mess with the egr, find any vaccum, and it's about 8 bucks for each bolt from the dealer, unless someone can find cheaper :P

[deviousKA]

check the electrical connection to the cold warm up solenoid, located in rear half of intake manifold. I had similar mileage and rich running issues back in the day, cleaning this connection fixed it (allowed it to shut off). Was on a 1990 sohc 240sx.

[idlafie]

If you mean the AIV crap in between the exhaust manifold and air filter
yeah it's quite gone
got a question on that though, the little plug that goes in the assembly, connects to this black little round thing, has three vaccum hoses, wth is it for ?

Did you disconnect your carbon canister?? Carbon canister is used to keep the gas tank system sealed and to prevent gas fumes from venting into the environment. If you disconnect the carbon canister or remove the vacuum lines that are part of the system, then your gasoline is gonna evaporate...especially during warm weather. That could explain where your gasoline is going...
ID

[outerheaven2k4]

From what it looks like, there are just no bolts in the head (with the exhaust manifold), which makes my life easier, so when i get a chance, i'll go spend 32 bucks and 4 bolts and fix it right, see if it helps any. Timing will be checked on friday. I'll clean off the cold warm up solenoid connections just because i can :P. Seems i did disconnect it when removing the aiv, but its put back in and everything is properly plugged up, so that whole thing is fix :) However, i would like to get rid of the whole rubber tubes that come from the aiv to...well that's my problem, where do they go to? Now the IAC (whatever its called, its in the throttle body) is screwed on, how the hell do you even take it off, i just look at it for minutes on end and still dont know how to even get a screw driver in it :P
I may have a leak somewhere in the intake plastic part, gonna just get a cheap ebay intake and take care of that :)

[w1ngzer0]

Did you disconnect your carbon canister?? Carbon canister is used to keep the gas tank system sealed and to prevent gas fumes from venting into the environment. If you disconnect the carbon canister or remove the vacuum lines that are part of the system, then your gasoline is gonna evaporate...especially during warm weather. That could explain where your gasoline is going...
ID

Carbon canister? Where is that located? I get 200 miles per tank right now. It happened after my engine was fixed. So mabie that wasn't reconnected? or my o2 sensor was fried?

[superman0234]

I would also like to know where it's located, and does anyone know the bolt size and thread pitch, so I can just go pick them up from the hardware store?

Edit: Found the correct bolt guys. Pick up metric size M8 1.25 cap screws, standard pitch and M8 1.25 hex nuts for spacers. :Edit

[outerheaven2k4]

for the exhaust manifold? intresting, guess it's a common bolt because that's the same bolt for the alternator and powersteering belt tensioner thing. how long does it need to be?