MAF conversion help

NMBmustang87 · Dec 6, 2011

I have just rebuilt my 302, bored 60 over, flat top pistons, GT40P heads, E303 cam, GT40 intake, 1.6 Scorpion roller rockers, and I just did the MAF conversion. It started out idling badly, so I set the TPS at .99 volts. How long does it take the new A9L computer I also added to adjust to the new setup? It is still erratic with the idling. Sometimes it bogs itself down when I give it throttle, and then other times it levels out, but it is back and forth with that.

Noobz347 · Dec 6, 2011

Heh... I'd meant for one of the Mods to move it for you but I guess this works too.

Start going though your vacuum lines and make sure you didn't miss something. You should also go back through your MAF conversion step by step and make sure you got that correct as well.

What is your base timing set to?

The adaptive control of your EEC is not going to magically fix your idle. You're going to have to diagnose and repair the problem. Have you pulled codes yet?

NMBmustang87 · Dec 6, 2011

Noobz347 said:
Heh... I'd meant for one of the Mods to move it for you but I guess this works too.

Start going though your vacuum lines and make sure you didn't miss something. You should also go back through your MAF conversion step by step and make sure you got that correct as well.

What is your base timing set to?

The adaptive control of your EEC is not going to magically fix your idle. You're going to have to diagnose and repair the problem. Have you pulled codes yet?

I'm not sure what the base timing is set at, the timing light we have quit working, so we set it best we could at this point. I have not got any codes yet. I'm kind of in the tweaking stage right now I guess. We did not splice the pink wire into the fuel pump because my check engine light does not work anyway so we thought there was no need to hook that one up if all that it does overrides the error code. I'm pretty sure the wires are all in the right places. We had to redo all of the vacuum lines whenever we changed the engine. We removed the smog pump, and we closed off that tube, but we have vacuum lines all hooked up from the intake. Thanks for your help by the way.

Noobz347 · Dec 6, 2011

No problem...

Have you tried disconnecting the Mass Air Meter while the car is running? You should get a change in idle (for better or worse) when it's disconnected. If you do NOT get a change then it's not working and you're in LIMP mode (no data being considered from any of your sensors).

NMBmustang87 · Dec 6, 2011

Noobz347 said:
No problem...

Have you tried disconnecting the Mass Air Meter while the car is running? You should get a change in idle (for better or worse) when it's disconnected. If you do NOT get a change then it's not working and you're in LIMP mode (no data being considered from any of your sensors).

AAAHHHAA. I think you got it. I just tried that and that might be it. It did not change at all. At the point I tried it, it was idling under 1000 rpms and a little rough anyway, but it did not change at all when I unplugged it.

Noobz347 · Dec 6, 2011

Yep... so go back through your MAF conversion starting from the MAF connector and ALL THE WAY back your EEC. Something is either incorrect and/or malfunctioning. Don't rule out the meter itself if you're 100% sure that it's a good meter.

Noobz347 · Dec 6, 2011

Afterthought: You did disconnect the vacuum line from the MAP sensor after the conversion, correct? It should be left unplugged to read ambient air.

NMBmustang87 · Dec 6, 2011

Noobz347 said:
Afterthought: You did disconnect the vacuum line from the MAP sensor after the conversion, correct? It should be left unplugged to read ambient air.

Sorry. I had to step away for a little. I do have a vac line going to a vac junction on the fire wall. There is a line off of it that feeds into the brakes, right? Am I looking at the right thing? Do I need to plug up both ends?

Noobz347 · Dec 7, 2011

No... the vacuum tree up against the firewall where the booster plugs in should not be blocked.... to the left of that (toward the center) there's another little black box. It has a wire harness and one vacuum line going to it. That vacuum line should be disconnected and the port left open to ambient air while the line itself should be capped.

NMBmustang87 · Dec 7, 2011

Noobz347 said:
No... the vacuum tree up against the firewall where the booster plugs in should not be blocked.... to the left of that (toward the center) there's another little black box. It has a wire harness and one vacuum line going to it. That vacuum line should be disconnected and the port left open to ambient air while the line itself should be capped.

Ok. That line was disconnected, but during my conversion from the stock intake to the GT 40 intake, those vac lines were all disconnected. I have vacuum lines running out of the upper intake now to the EGR valve and 2 other hoses on the side near the AC cylinder along the firewall. I also have a line running to the vacuum tree. I'm not sure what line even went into the MAP sensor.

Blown88GT · Dec 7, 2011

Here's a link to the Ford Conversion Kit instructions. Shows the MAP sensor.
http://www.foureyedpride.com/vb/album.php?albumid=1526&pictureid=11828

NMBmustang87 · Jan 5, 2012

I have had an ordeal with my MAF conversion and pretty much everything else. Can anyone tell me what lb/hr rate fuel injectors come stock on a 1998 Explorer 5.0 with the GT40 intake? Is it 19# or 24# or what??? That's what I have on my mustang now, and I'm still having idle problems. I just ordered an adjustable fuel pressure regulator because I'm only getting about 28# pressure in the fuel rails so I know there is a problem there. But now I need to know if I need to get a new MAF sensor to match up to the injectors.

95BlueStallion · Jan 5, 2012

Which MAF sensor are you running? Is it calibrated to your current injectors? What color are the injectors you are running? Each size are a different color if they are actual ford brand injectors.

NMBmustang87 · Jan 5, 2012

95BlueStallion said:
Which MAF sensor are you running? Is it calibrated to your current injectors? What color are the injectors you are running? Each size are a different color if they are actual ford brand injectors.

The injectors are orange. They should be stock for the 98 explorer 5.0 with the gt40 intake. I'm trying to figure out if I have the correct MAF sensor. I thought I had 19# injectors, but I heard from someone that 98 explorers had 24# injectors. I have the stock MAF for a 1992 or 93 mustang.

jrichker · Jan 5, 2012

See the "Surging Idle Checklist”for help with all your idle/stall problems. You can guess at the problem and throw parts at it, or you can use the checklist to help you find the problem quickly and inexpensively.
The quick and easy way to dump the codes is in there too, and all you need to do it is a paper clip! The first two posts contain all the fixes & updates. At last count there were 24 possible causes and fixes for surging idle/stall problems. I continue to update it as more people post fixes or ask questions.

95BlueStallion · Jan 7, 2012

Injector Lb/Hr Max V8 HP HP supported by 1 injector Ford Color*
14 Lb/Hr 228 28.56 Gray
19 Lb/Hr 310 38.76 Orange
24 Lb/Hr 391 48.96 Lt Blue
30 Lb/Hr 490 61.19 Red
36 Lb/Hr 587 73.44 Dk Blue
42 Lb/Hr 685 85.68 Lt Green
60 Lb/Hr 800 100

Here is the run down on Ford brand injectors. You have 19 lb injectors, and if your MAF is stock it should be properly calibrated. You could look for a used 1994-1995 MAF, as they are calibrated for 19 lb injectors, and flow a little more than the fox MAF. Sounds like you best bet is going through jrichker's checklist, as much as they may suck.

ID89GT · Jan 8, 2012

Fuel pressure needs to be at around 39.. you are way to low in the twenties. Id check and fix that part

MAF conversion help

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