MAF questions

[KronicRacer]

friday night i began my project which is an old 5.0 trick gutting the stock maf. i finished the gutting and polishing. also did the two hour battery disconnect.

here where the fun starts. last night
when i went to start it. the car hesitated so i let it cycle in idle for two mins and the idle pulses got lopier and lopier now the car sounds like its cammed and louder. took the car out and then parked it let it idle and again the lopy sound came back i then plugged in the predator and got no codes.

this morning went out and the same thing it hesitated at startup then ran fine. left the park to go to 7/11 turned on again it hesitated. on the road im rowing throught the gears after the light and in 3rd gear at about 3000 rpm it misfired big time 8(all) cylinder misfire until i shifted to 4th. got home shut it down, an hour later i turned on the car again plugged in the predator and nothing, no codes . the idle was rpm was between 749 rpm up to 864rmp like its searching for the right idle. so far its a super crappy idle with no improvements with and exhaust fumes up the yin yang. yea i know loud mouth and o/r prochamber. never had fumes as strong as these before with that setup.

the fumes were so bad it pissed the neighbor across the street. the strange thing here is that there are no codes being pulled on the predator other than the obd test which is normal after a full reset to the computer.

now the question is does this usually happen after the maf is switched? or is there more to it and shouldnt the predator tune be good enough for a bored out maf(i understand there is more of an airflow) ive never heard of the 5.0 having to get retuned on the dyno after gutting the maf. shouldnt the ds predator picked up the misfires? im going to my buddies house later today if the lopiness returns then im throwing back the stock piece.

ive had to reset the computer before with the predator tune and the fumes were never this bad after restarting it.

any insight on whats going on?

 

[KronicRacer]

i also reused the old mass air meter. cleaned the sensors with an ear swab and alchol before transferring to the modded case

 

[Mike97gt]

when you gutted the maf you either messed up the electronics or you changed the flow characteristics so much that the maf is not reading right. either way you need a new maf..

the reason the CEL is not on is because unless it is a electronic fault ( like readings out of range) it probally won't pick up the fault.. the eec stratagy has a very hard time picking up a slightly off maf because the maf is the primary sensor the EEC uses for a/f ratio and really has very little too double check with.. ( problems liek this is why shops charge diag.. codes are not the end all of EEC diag) .. so even if it is off the EEC will correct little with the 02 sensors after warmup and at part throttle but it still will not run right. and unless it is going 25 percent or more rich or lean it will not set a code.

with our cars the way too go is too get a aftermarket maf.. i would not mess around with porting the stock one.

 

[KronicRacer]

im throwing on the stock case back on then. i made a point to be very careful with the electronics when i took them off of the case. im leaning towards the flow characteristics of the meter case thats on there now.

in case i did mess up the electronics will the maf sensor from the 2000 gt work on the 2001 gt? im under the impression at the moment that the injectors were changed from 19# to 24# in 01 or was that only for the bullit?

i would post a picture of the modded case but my digi cam is down and out for the moment. (i put a hammer to it)

 

[Mike97gt]

im throwing on the stock case back on then. i made a point to be very careful with the electronics when i took them off of the case. im leaning towards the flow characteristics of the meter case thats on there now.

in case i did mess up the electronics will the maf sensor from the 2000 gt work on the 2001 gt? im under the impression at the moment that the injectors were changed from 19# to 24# in 01 or was that only for the bullit?

i would post a picture of the modded case but my digi cam is down and out for the moment. (i put a hammer to it)

i am pretty sure but not certian that the 2000 maf will work.. you should be fine by switchign the case.. if you get another case try too port it without going nuts.. the correcty amount of air needs too get to the electronics so the maf can read it.

 

[01TrueBlueCobra]

Only NA Cobra's had 24lb injectors. 99-01 MAM from GT's are the same. In 02 the MAF went to 85mm and the air temp sensor was also intergrated.

 

[Mike97gt]

Only NA Cobra's had 24lb injectors. 99-01 MAM from GT's are the same. In 02 the MAF went to 85mm and the air temp sensor was also intergrated.

ok this answered that for us.

 

[KronicRacer]

i am pretty sure but not certian that the 2000 maf will work.. you should be fine by switchign the case.. if you get another case try too port it without going nuts.. the correcty amount of air needs too get to the electronics so the maf can read it.

well i did not touch the sampling tube at all.

i did leave a 1/4 inch nub on the down flow area of the tube, didnt want to go nuts on it.(smoothed down the edges to attemp to be areo dynamic ) this is where the airflow mustve been screwed up actually



01TrueBlueCobra

thanks for the injector info

 

[KronicRacer]

also if the mam electronics were messed up. wouldnt that throw a code for the ds predator to pick up?

 

[jstreet0204]

I'm not going to preach to you too much on this because I thought at one time ths might be a good idea as well, but it isn't. The stock MAF is a very good component and is larger enough that it doesn't pose a restriction for a n/a application. It can effectively flow enough air to support somewhere around 360hp. Stock MAF's are also very accurate, so changing the characteristics by porting it will, as you already know, lead to problems. You know longer have an accurate mapping of how much air has crossed through it. The eec may now cause it to run rich or lean.
If you really want to port something, port your plenum or even the plastic intake can be opened up some at the ports, but leave the MAF alone until you have maxed the voltage on it.

 

[KronicRacer]

^^^
i think the maf was rated to 400 hp after that is when you need the upgrade.

my reasoning for this what made the other mafs more effective was because of the bigger injectors you would need at 400hp. i figured in theory stock meter gutted would make the flow better like in the old 5.0's i did not however thake into consideration the mapping factor(which im concluding is very very very important). that along with not exceeding my voltage is the reason im switching back to the original case later today. hopefully the other guys in the forum can pick up on this trail and error session

 

[jstreet0204]

^^^
i think the maf was rated to 400 hp after that is when you need the upgrade.

my reasoning for this what made the other mafs more effective was because of the bigger injectors you would need at 400hp. i figured in theory stock meter gutted would make the flow better like in the old 5.0's i did not however thake into consideration the mapping factor(which im concluding is very very very important). that along with not exceeding my voltage is the reason im switching back to the original case later today. hopefully the other guys in the forum can pick up on this trail and error session

Well, those other MAF's aren't always more effective. They all work pretty much the same way. A larger MAF will flow more and the mapping (maf curve) is adjusted accordingly. Basically a MAF will output a maximum of 5 volts. A table of values is input into the eec that tells the eec what voltage is equals how much air has entered the engine. Once the MAF reaches 5 volts, the stock curve says the engine is bringing in 1179 kg/hr of air. The stock maf will actually flow more than that, but since the sensor can only output 5 volts the engine will still think it is flowing 1179 even though it may be flowing something like 1300. This is a very bad situation becuase the amount of fuel added is calculated based on the smaller number causing a lean condition. This is when you need to upgrade. Preferably to another oem ford meter like a LMAF, and remap it in the eec.

 

[Mike97gt]

well i did not touch the sampling tube at all.

i did leave a 1/4 inch nub on the down flow area of the tube, didnt want to go nuts on it.(smoothed down the edges to attemp to be areo dynamic ) this is where the airflow mustve been screwed up actually



01TrueBlueCobra

thanks for the injector info

hey **** happens.. trial and error is the only way too find somthing that works good.

 

[Jones331]

I chopped the post in my 01's maf and the cel came on after 500 miles and 2 track runs. I must say thought that it did feel better and seem a lil bit louder after the chop. I got a C&L after that to correct the cel (thanks Dad) When I traded the car back into Ford for my 04 they said they couldnt get it to pass smog with the stock maf chopped theres my two cents.........jj p.s call C&L and they will explain exactly where you went wrong,heck send in youre stock,chopped maf and they will flow test it for ya

 

[Bulldog Stang]

Just buy the 85 MM C&L MAF and place your stock MAF Sensor back on top of it. I have this set up with the True Flow C&L Intake Pipe, Plenum, and 75 MM BBK Throttle Body. I have no problems or complaints. Car runs great!!!!!