MAF wiring question
Thread Starter
Intermediate
Joined: Apr 2014
Posts: 40
Likes: 0
From: Phoenix AZ
MAF wiring question
I'm chasing a no start issue with my 86 coupe.
On the MAF wire harness should I be seeing the following with key on, not started?
A - ground
B - ground
C - 5 volts
D - 0 volts
E - 0 volts
Thanks
On the MAF wire harness should I be seeing the following with key on, not started?
A - ground
B - ground
C - 5 volts
D - 0 volts
E - 0 volts
Thanks
Melting Slicks
Joined: Aug 1999
Posts: 2,240
Likes: 42
From: Baltimore, MD USA
You can unplug the MAF and the engine should run.
The voltages are correct.
Pin E which powers the MAF will have 12 volts on it when the oil pressure is greater than 4 psi and also when ever the ECM energizes the fuel pump relay.
The ECM will energize the fuel pump relay for two seconds when you turn the ignition key to On. It should also energize the relay when the ECM sees distributor reference pulses which would indicate the engine is rotating.
Thread Starter
Intermediate
Joined: Apr 2014
Posts: 40
Likes: 0
From: Phoenix AZ
Do you have spark? What's the fuel pressure?
You can unplug the MAF and the engine should run.
The voltages are correct.
Pin E which powers the MAF will have 12 volts on it when the oil pressure is greater than 4 psi and also when ever the ECM energizes the fuel pump relay.
The ECM will energize the fuel pump relay for two seconds when you turn the ignition key to On. It should also energize the relay when the ECM sees distributor reference pulses which would indicate the engine is rotating.
You can unplug the MAF and the engine should run.
The voltages are correct.
Pin E which powers the MAF will have 12 volts on it when the oil pressure is greater than 4 psi and also when ever the ECM energizes the fuel pump relay.
The ECM will energize the fuel pump relay for two seconds when you turn the ignition key to On. It should also energize the relay when the ECM sees distributor reference pulses which would indicate the engine is rotating.
I have spark. I just changed the wires, cap, rotor and ignition coil. It's an msd distributor and coil. Fuel pressure is 45 psi with about 5 psi decay over 1 hour in off position.
The engine does start now (I found the tps reference voltage was .77. I adjusted it to .54) but it stumbles badly and will occasionally rev to 2000+ rpm while idling. It also experiences occasional upper exhaust backfires.
When I unplug the maf it idles stable at about 800 rpm but, very rich. I just replaced the maf and the O2 sensor.
The reason I am asking about the maf is that the PO chopped and extended the wire harness for the maf when he installed the SR intake. Could be an issue at this area. That is why I was asking about what the maf reading should be on an OP in the scan and tune forum. I was getting a constant reading on the afr of 5888 through tunerpro rt. Seems waaayyyy too high. Any idea what it should actually be?
Thanks
Last edited by ekistler1971; Jul 3, 2014 at 11:26 AM.
Melting Slicks
Joined: Aug 1999
Posts: 2,240
Likes: 42
From: Baltimore, MD USA
I get the following MAF readings with the car in park using Diacom Software.
355 with Super ram intake and 74219 Camshaft.
10 GPS @ 750 rpm
17 GPS @ 1400 rpm
20 GPS @ 1750 rpm
42 GPS @ 2.5K rpm
57 GPS @ 3K rpm
68 GPS @ 4K rpm
355 with Super ram intake and 74219 Camshaft.
10 GPS @ 750 rpm
17 GPS @ 1400 rpm
20 GPS @ 1750 rpm
42 GPS @ 2.5K rpm
57 GPS @ 3K rpm
68 GPS @ 4K rpm
