Anyone know how to check if the MAF is functioning properly?

[Jookmasta]

Anyone know how to check to see if my MAF is functioning properly? I ask b/c i think this is what is causing my idle to be erratic after staying steady for five seconds. The car just stalls out after the five seconds of good idle. Any help or opinions would b greatly appreciated.

[WDRacing]

MAF is usually good or bad. When it goes your motor almost always won't rev over 2500 cause your ecu goes into limp mode without any airflow reading.

[Nismo_Freak]

Anyone know how to check to see if my MAF is functioning properly? I ask b/c i think this is what is causing my idle to be erratic after staying steady for five seconds. The car just stalls out after the five seconds of good idle. Any help or opinions would b greatly appreciated.

As Brian stated w/o a proper MAF voltage you will be limited to 2500 RPM.

To check to see if your MAF is causing the issue you should unplug the MAF and start the engine. If it runs and idles smoother then you know your MAF is bad.

[Jookmasta]

the car definitely will go over 2500 when i leave the wastegate open so that the compressor doesnt spool. i did however close the wastegate and got some spool but the car couldnt get past 50 or so cuz it was bogging/shaking so much.............

[WDRacing]

Sounds like somthing else. Check your IC piping connections.

[Jookmasta]

there is a little gap b/w the upper hot pipe and the lower portion of it where it goes thru the hole. The connector is still intact and attaches both pipes but there is a little play with the upper hot pipe and when i put my hand around the silicone coupling, i can kinda squish it in a little to the pipe.........sounds like the cause to bad idle?

[fiznat]

Fuel pressure maybe? I dont think its IC piping if you get a good idle and then it drops. Make sure you're getting a good, consistent supply of fuel.

Also check your plugs and see what they tell ya. Are you smoking at all? If so what color?

[Jookmasta]

well i am running pig rich. so rich that i filled up my tank, drove about fifty miles and the gauge is at a little above half tank. plugs are most likely fouled and i backfire like a mofo. Someone did suggest to use some injector cleaner but i just got the injectors cleaned about three or four weeks ago before i threw them in. I dont have a fuel pressure gauge. and yes black smoke but not like a semi.....................

[fiznat]

Hmm, whats the rest of your setup like. Do you have any way to step that fuel back a little?

Do you have a timing light? Whats your timing look like at idle?

[Jookmasta]

well it is at stock but we did have it retarded at first. i dont think i could tell the timing at the moment cuz the car wont idle. i do have an safc tho and i have it set at 30% and its still running rich. i am running 370cc sr injectors BTW.

as for the rest of the setup:straight T3 internally wastegatedlog manifoldFMIC with 2.5" pipingno cat3" exhaustgreddy type s bov300zx tt fuel pump

[fiznat]

If you really wanna check your timing to make sure its right, pull the plugs and fuel pump fuse, then just check the timing while the starter is cranking the engine. You should be at or close to 0 degrees. Once that is set - assuming your timing is the problem - your car should run longer so you can have more time to mess with the timing at idle.

Not too familiar with how the SAFC works-- does 30% mean it is adding an extra 30% of fuel on top of the regular map? That shouldnt be necessary at idle, especially with the bigger injectors...

Check those plugs!

[Jookmasta]

30% means cutting back thirty percent from the larger injectors

[Jookmasta]

so a quick little update, i tightened up one of the clamps on the hot pipe since there was some serious play on it. It still kinda moves around but isnt completely firm like my cold side. i will check the plugs tomorrow and i think i will try my luck again by starting it up tomorrow. Ill reattach the swingvalve properly so that the turbo spools but i think i will tighten down the type s bov as it is on the loosest setting and there could have been some serious loss of air which could have explained the shuddering.

Im also thinking of resetting the ecu as that probably wouldnt hurt to do. Im still waiting on another MAF to try and i will have to wait till when i roll by my friends place to get the timing checked again since he has the timing gun. um i think thats about it but PLEASE keep posting suggestions....................

[S14tat]

you know what? when my maf died on my completely and didn't get any voltage at all, the car wouldn't stay started. it just starts then dies right away, i would try to rev it, but it would just sputter, and back fire. when i changed the maf, the car was fine.

i know of a person whos maf went back too, and his car wouldn't rev past 2500. but i'm wondering mine wouldn't even idle.

[Jookmasta]

what ill do tomorrow is tighten the bov, hook up the wastegate so that the compressor spools, and see if i can rev the engine higher than 2500..........i will report to yall with the results

[Nismo_Freak]

what ill do tomorrow is tighten the bov, hook up the wastegate so that the compressor spools, and see if i can rev the engine higher than 2500..........i will report to yall with the results

Really sounds like you have a stuck injector.

[Jookmasta]

so even with the stuck injector, i would still be able to run rich? if it is stuck, would fuel injector cleaner work? or how do i fix such a problem besides replacement of the injector............

[Jookmasta]

well i tried it today with the swingvalve shut and i can definitely rev above 2500.............it was idling nicely tho but i think it was b/c the engine was still cold. the idle then went to hell as soon as the engine began to warm up........if it is a stuck injector, what to do???????????

[240SicknessX]

Really sounds like you have a stuck injector.

If it is the case that one of your injectors is stuck shut, it would promote a lean condition in that cylinder, it might even be lean enough to offset the afr of the other 3 cylinders after all the gasses have mixed after the turbo and in the down-pipe. So when the exhaust gasses reach the o2 sensor they have an overall lean condition, because of the lean condition the ecu will probably pull some timing and try to put out more fuel. This would explain the stupid rich condition that you have and the stuttering around 50mph or w\e it is when trying to accel.

The car not idling under 2500, this could be because your plugs are fouled, ecu is pulling timing, and well, it just wont run unless you keep feathering the throttle as you have told me before.

Leave the timing back at stock 20btdc even if the ecu is pulling timing it shouldn’t be enough to retard it so much that it wont run, get new plugs too. (ive pulled the plug wires on my car for the fun of it and mine @ stock timing and fairly new plugs will idel at 650-700 on 2 cylinders. )

Get a stethoscope or some type of listening amplification device and try listening very carefully for the injector pulses. You might be able to hear which injector isn’t firing. OR

Get the car idling\running, and unplug one injector at a time, and see if the characteristics of the idle change, if you find that after you have checked all of them and there is one injector that doesn’t change the idle then try switching injectors on the cylinders and see if you get the same characteristic on that particular cylinder that you switched the supposed bad injector to, if so then new injector.

Aren’t you supposed to have some electrical grease or silicone on the injector plugs or any electrical plug that might see moisture, this will also promote better continuity? Check that and also inspect the injector harness, look around for nicks in the wire or shielding, anything that might look shady.

Im no ASE mechanic, just throwing out a couple ideas.

[240SicknessX]

do you have compression figures before you started this turbo project, if your injector was stuck shut then you might wanna redo the compression test and recheck your figures see if any damage was done, driving it.

(remember to pull the fuel pump fuse while the car is running so that all the fuel pressure is released and no fuel is going to go into the cylunder and alter your results)

[Jookmasta]

well we checked compression before and after the project and even just recently since the problems occurred and its still 180 across the board........

[Jookmasta]

I know for sure that the plugs are fouled but as for checking the injectors like that, i dont see that to be a wise move as the car wont idle in its current state.......wouldnt that be taking a big risk as to the safety of the engine?

[klattr1]

whats your vacuum at idle?

[Jookmasta]

well i have a blitz dtt telling me the boost/vac and it read normally around -.71 or -.73 when i was NA. Since the turbo, it has read around -.35 but no higher than -.40. This is obvioulsy in h kPa i think.

[Jookmasta]

ok so today proved that the car is either possessed or has a mind of its own. I reached home from school and took her out around the neighborhood and just wow. i honestly didnt look at the boost gauge while i was driving but the turbo was spooling like crazy. car felt crazy too. best part is that after about three runs up and down the street in front of my house, i put her back in the driveway and she idled the entire one minute in which my turbo timer does. Could this be b/c the engine wasnt fully warmed up? The temp gauge did warm up after the second run but u know what i mean. I really dont know why the car is acting like this............I didnt hear the BOV go off but i think its due to the droan of my exhaust. I also did add a bit more fuel on the second pass since the car was shuddering when i was slowing down. It was at -29% and i moved it to -25%. I should note that the car feels good at full throttle but when i let up off the gas, the car does want to stall........maybe thats due to the open atmosphere bov????? i havent calibrated the decel air stuff on the safc so that is one culprit to fix.

I think i should ask about this shuddering and bogging. I am by no means any tuning expert and since im still in the learning curve, can someone explain what bogging means and shuddering? (not literally)

From my understanding and from asking my friend Will about it, bogging is the lack of acceleration/power due to rich or super rich conditions. Shuddering is when the gearshift is wobbling like crazy and the car is vibrating/resonating really bad due to lean conditions. Can someone please clarify this or shed some light on this?

The one time that i ran the car on the street with the wastegate attached properly to the swingvalve, the car was shuddering like crazy. Does this mean i need to add more fuel or etc?

BTW, MAF is definitely out of the question as the source of the problem, as is the stuck injector or else the car would miss or detonate..........

[240SicknessX]

BTW, MAF is definitely out of the question as the source of the problem, as is the stuck injector or else the car would miss or detonate..........

umm if the stuck injector wasnt letting any fuel into the cylinder, it wouldnt detonate because it dosent have any fuel in the cylinder to begin with. Now if it partially was injecting fuel then there would be a lack of fuel to detonate with, but if there is no fuel in the cylinder at all, then there is no FUEL to start the combustion process = no detonation.

so the car idels now? have you tried unplugging individual injectors to see if one of them is not working?

you say you are still running rich? (re read my post above about the injector not working and leaning out hte mixture so the ecu will dump more fuel)

whats ur timing set at now?

[240SicknessX]

I know for sure that the plugs are fouled but as for checking the injectors like that, i dont see that to be a wise move as the car wont idle in its current state.......wouldnt that be taking a big risk as to the safety of the engine?

running the engine for less then a minute while having an injector unplugged wouldnt be devistating for trouble shooting purposes, ur not on boost at WOT. plus if there is no fuel in the cylinder, if you dont have fuel air and spark then you dont have the 3 items to have combustion.

[Jookmasta]

first off, timing is at stock aka 20 degrees.

Next thing, with the checking of the injector idea, ur right that there is no combustion without the fuel, air, and spark; but if one of those components is missing, bad things can still occur within the cylinder. I will probably try your idea when i get back over to my friend's place or we could try it if ya drop by. I dont think it makes sense to try that by myself since i cant put my ear to the engine.