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Discussion Starter · #1 ·
Helping dad get his '97 Blazer 4.3L running right. The engine lopes at idle and it can't get out of it's own way when accelerating from a stop.

Got three codes read at AutoZone:

P0102 - MAF - What value am I reading for? Volts or resistance? I get 0.00v on both black/pink & black/yellow. Forgot to write down resistance value.


P0300 - Random cylinder misfire - could be spark plug wires. They weren't replaced with the plugs. Can I test for resistance?? Is there a standard reading to compare to?


P0440 - EVAP - hoping a new gas cap will fix this. Current one's rubber seal is dried and cracked. Also, what does the evap canister look like? Where is it? If gasp cap doesn't fix, what next?





Pulled out the multimeter...

Problem #1 - Reference voltage for MAF 6.00v
I'm thinking there's a short in the circuit. I have continuity in the black & pink wires. But no continuity in the black and yellow wires. I cannot find a wiring diagram that includes the MAF sensor circuit. I'm flying blind on tracking the wiring. Where can I look? My Haynes manual is of no help in regards to a diagram. Is Chilton's better without jumping to big bucks for the GM manual (I'm on the road here without normal internet/comm resources)


For numbers my MAP sensor reference voltage on grey & black is 5.0v so that is good. I tried reading the MAP sensor signal voltage but I need to get alligator clips to use in there instead of the probes. It's a tough angle to see and hold with the engine running.

IAT reference voltage was 5.0v, good. I need to double check the resistance of the sensor, but I believe it dropped from 2.24 to 1.93 between ambient and idling at temp.


Any help with this would be great. Only in town a coupe days and helping dad out as much as I can. Thanks!
 

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MAF - you may want to check on the screen to make sure it's not clogged or dirty and clean it. I'm pretty certain that what you want is volts.

Misfire - could be worn/fouled plugs, bad wires/cap/rotor, low fuel pressure, bad injectors. Could be fuel (low fuel pressure) or ignition related (not enough spark created for complete combustion)

EVAP - the gas cap is the most common. If it doesn't fix it there's a black cyindrical shaped object, which should be near the bulkhead (firewall). Could be in need of replacement hoses or there may be a leak in the system.


I hear that the Haynes manual is much better and more detailed than the Chiltons; in comparison to the FSM which is about $115, it's your next best bet.
 

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Discussion Starter · #3 ·
Thanks for the thoughts. Here what we came up with:

Got the MAP tested and it showed appropriate voltage at idle. But the voltage did not increase as the RPM increased and pressure changed. So we're thinking a vacuum leak?? I might grab a new sensor to replace it 'just so we know for sure' but we don't really feel it'd be necessary.

Rechecked the MAF and the voltage was 10-11v. We pulled it and cleaned it (though wasn't really dirty) and retried. Voltage was off the charts and bouncing all over the place. So uhhmm,we thinking we broke it worse :eek: This will definitely need to be replaced now.

For the EVAP, I replaced the gas cap with a new one. It really didn't change how the truck ran but we should clear the codes and see if that keeps the EVAP code away. I'm not confident it will.

Under the hood is a rich mixture smell when the truck is running. The fuel filter has been changed prior to Dad ran some Lucas fuel system cleaner through. So, least we know that much.

I'm back home now so can't look at the truck. I'll be down there next week to run a team marathon so I might order those sensors and install them if I can (if I'm not wiped out and I get my pizza and beer to recoup me) :D Dad is ready to throw in the towel on the Blazer altogether. I think it can be brought back but it'll need to be torn into a little bit and given some dedicated TLC. He doesn't have much extra time or money to get into it. He's frustrated with it, I don't blame him.
 

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That's to bad. It's easy to get discouraged when you don't know what the problem is, and it keeps costing time and money. It is likely only one or two things that need changing/ adjusting to make it right again. Don't give up on it. your patience will be rewarded. Even if Dad wants to sell it, it will sell better fixed.

also good luck in the marathon! I do not have what it takes to do something like that (willingness to run LOL).
 

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Discussion Starter · #5 · (Edited)
Yeah, it's a brain teaser for sure.

My sister has the '95 Jimmy 2wd 4.3L that needs the tranny I'm looking for in my other post. The '97 Blazer 4wd 4.3Lin this post is Dad's.

There's been talk between dad, my sister and myself wondering if we could swap the good tranny from dad's'97 to my sister's '95. Between the difference of 2wd/4wd and the '95/'97 ecm there'd be soe hurdles to work out. What do you think? Is it worth considering or better off just keeping the two separate? My sister's '95 is in tons better shape than the '97 is (our other sister basically abused the goodness out of it).
 

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Discussion Starter · #6 · (Edited)
hah after I post that ^^ I see one on CL. I'm going to go have a look at it, for $200 and it was rebuilt about a year ago.

And of course it is still in the truck. I've never pulled a transmission before. Much less doing it alone at some dude's place without my own stuff and yard to work in.
 

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ok my blazer had the same random misfire problem was just a vacum leak spray some ether or starting fluid on the lines and where it makes the blazer rev is the leak also it might not be the tranny thats messing up i thought it was mine till i was talking to my buddy and i told him to run the codes with the inspection code reader for the emissions here its the cat that was bad and causeing it to feel like that so try that before you change trannys and that might actually fix the random misfire too
 
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