How does an MAF problem cause a no-start?
10-03-2011, 10:23 AM
#1
Le Mans Master
Thread Starter
How does an MAF problem cause a no-start?
Mods, this is for my son's '94 LT1 Z-28, but I post it here because I think it may be pertinent on this forum as well.
He's having a problem that I can't figure out. Occasionally (it happened once yesterday with the engine stone cold) the engine won't start. Won't pop, stumble, nothing.
Disconnect the MAF (forcing the PCM into speed density mode) and it starts right up. Connect the MAF back up, and everything's fine. Scanmaster shows reasonable response to throttle snaps, etc.
After that the car started up fine every time the rest of the time he was home.
What in the world would cause this? What do I not understand about the PCM/MAF relationship?
TIA, and have a good one,
Mike
He's having a problem that I can't figure out. Occasionally (it happened once yesterday with the engine stone cold) the engine won't start. Won't pop, stumble, nothing.
Disconnect the MAF (forcing the PCM into speed density mode) and it starts right up. Connect the MAF back up, and everything's fine. Scanmaster shows reasonable response to throttle snaps, etc.
After that the car started up fine every time the rest of the time he was home.
What in the world would cause this? What do I not understand about the PCM/MAF relationship?
TIA, and have a good one,
Mike
Last edited by VetteDrmr; 10-03-2011 at 01:50 PM.
10-03-2011, 12:18 PM
#2
Le Mans Master
It is weird - some failing/intermitant MAF equipt cars will start sooner than others. Sometimes you have to "crank" the crap out of the starter (super long crank times) to get the thing to even fire over. Once things are some what "warm" crank time seems reduced.
10-03-2011, 01:52 PM
#3
Le Mans Master
Thread Starter
The strange thing is that, if the engine's going to start, it does so on the 1st revolution, like most modern engines. If the MAF problem rears it's head, it *never* even tries to fire. 
Have a good one,
Mike
Have a good one,
Mike
10-03-2011, 02:19 PM
#4
6th Gear
Member Since: Sep 2011
Posts: 6
Likes: 0
Received 0 Likes
on
0 Posts
Consider this, If the MAF runs on a 5 volt ref signal and that signal goes to ground thru a internal short it can remove the ability to send that same 5 volts to the rest of the sensors such as the crank and cam.
10-03-2011, 02:39 PM
#5
Le Mans Master
Thread Starter
Dutch, that's a very interesting thought. I think I'll spend some quality time with a wiring diagram tonight.
I'll let you know if I find anything. Anyone else have any other thoughts?
Have a good one,
Mike
I'll let you know if I find anything. Anyone else have any other thoughts?
Have a good one,
Mike
Last edited by VetteDrmr; 10-03-2011 at 03:41 PM.
