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MAF sensor, O2 sensor, Evap Control, & Service Engine Soon light ... [Archive] - S10PLANET.COM

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BaLLZaCH1
10-03-06, 02:56 PM
Hello again,
I am back - it has been quite a while :-)


Anyways,
I have a 98 S10 4.3, recently I have (Recently meaning the last year or two) have had this on-again-off-again problem that comes up sometimes ...

My engine will sputter, then MIL come on. The 3 codes read either "MAF HIGH INPUT VOLTAGE" (OR) *LOW INPUT VOLTAGE* (Which is weird because I dont understand how it could be either of them ...) For the first 2, and the last code is, EVAP System fault.


The exhaust is very very rich and milelage is horrible. - If I reset the computer, OBD2, depending on its mood it will might give me an 'Evap' code again, but after reset it will eventually stay off.

But the engine still runs RICH for a week or so until it finally calms down, and goes back to normal.



I have checked and cleaned the Mass Air, and have read that evap faults are kind of pointless, but what I dont understand is WHY THEY HAPPEN AT THE SAME TIME, every time ?


Now for the technical junk:
My 4.3 has 160thousand miles on it. I have recently replaced my Crank trigger, TPS sensor, distributor, coil, ecm, computer, and others (Due to another weird unexplained issue that I will not go into right now) - The o2 sensor was changed YEARS a go to a Simulator, because I damaged my exhaust and had to re-rout it. I DID HOWEVER, keep my Cat, and actually replaced it with a new one not very long a go. (These problems were not originally because the simulator (Have had it many years)... I should also note that this is a new gas cap (for evap fault) and there is no manifold leaks that i know of....


So, my question is, does anyone know why all 3 codes are spit out at the same time ? And what the problem 'could' be ? I was going to re-weld a new bung into my rigged exhaust and get a new o2 sensor, (And I know will would help overall efficiency but dont think it could cause a MAF fault, and especially not an EVAP, - possibility of TPS but it has already been repalced) - but anyways, I dont wanna throw more money at it buying a new MAF and O2 sensor when the faults dont make sense in the first place.



Well I was just hoping somebody might know what I am talking about...

Thanks !!!!

rat
10-03-06, 05:54 PM
You might check the ecm B fuse in the underhood fuse box, but the camshaft position sensor is also on that circuit, so that would be out of wack also.

Poncho Driver
10-04-06, 04:38 AM
What about your EGR? Do you have a catalytic converter? Have you had it checked?

Sparky2263
10-04-06, 12:58 PM
You've described a basic MAF error problem. Question is, is it the MAF itself, the 12V supply to the MAF or a ground problem? Disconnect the MAF, re-set the ecm and drive. Full throttle won't be very good, but it should drive fine if the MAF is the problem. With the MAF disconnected the VCM will calculate fuel based on other sensors.

The evap code won't cause any driveability problems so you can ignore it for now.