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LMC Truck



Username Post: 02 blazer horrible fuel mileage        (Topic#345510)
Original58 
"4th Year" Silver Supporting Member
Posts: 448
Original58
Loc: Manitoba, Canada
Reg: 10-30-13
06-18-17 07:35 PM - Post#2696451    

My son's 4.3 has excessive fuel consumption. The codes said lean mixture both banks. It has since not produced the codes since clearing them but it literally drinks fuel.
Any ideas where to start?
Thanks
Jeff

1958 Biscayne 283 Turbo-Glide 31,000 mi (now 35,000 and counting) driven daily
1966 Mustang Inline 6- C4 57,000 mi and growing daily
1929 Graham - Paige 612- the eternal headache that I will never sell


 
LMC Trucks
SleeperSS 
Senior Member
Posts: 2438
SleeperSS
Loc: Spanaway, Wa
Reg: 10-17-04
06-18-17 08:41 PM - Post#2696461    
    In response to Original58

A couple of things. I'm going thru this with my SS. No codes, but I put the scanner on it anyway. Turns out my pcm lost its mind and was running 22* retarded. I put a spare pcm in it and like magic advance was 20-30* advanced depending how far my foot was in it. Did a 252 mile road trip yesterday and mpg went from 17-18 to 20.5. How's the exhaust smell? Mine will make your eyes water so it's still way rich. I have a new fpr coming Tuesday and I expect my mpg to go up to where it used to be...23-24 mpg. I'm very anal when it comes to calculating mpg. I use the same pump, fill it to the very top before and after a trip.

U.S.C.G. "So others may live"

'96 S-10 SS
'02 BlaZeR2





 
gchemist 
Senior Chevytalk Moderator
Posts: 23925
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
06-19-17 05:04 AM - Post#2696493    
    In response to SleeperSS

How does power feel? Is the cat still original?
What do spark plugs look like? Dirty air filter? Dirty MAF sensor? Check for loose hoses on vacuum lines and air intake. When filling up, does fuel gallons equal dial readings?



'95 Jimmy SLT (Bought @131,814)
'83 Silverardo XST - ZZ4 powered
'96 GMC Jimmy LS Ret. @236651 miles


 
models916 
Valued Contributor
Posts: 4506

Age: 66
Loc: Addison, IL
Reg: 05-28-10
06-19-17 08:47 AM - Post#2696535    
    In response to gchemist

My 2004 only runs correct on an AC deco MAF. I had a while back replaced it with a Delphi and got bad fuel milage and lean condition at high RPM. MAF should be your first look. It is the first item the PCM looks to for setting ratio.



 
Original58 
"4th Year" Silver Supporting Member
Posts: 448
Original58
Loc: Manitoba, Canada
Reg: 10-30-13
06-19-17 10:06 AM - Post#2696544    
    In response to models916

I cleaned the maf, new air filter. Plugs changed last fall by GM. What a pain to get at the 1 plug. Hardly used since last November.
No other codes show up and I'm trying to not randomly change parts.
Jeff

1958 Biscayne 283 Turbo-Glide 31,000 mi (now 35,000 and counting) driven daily
1966 Mustang Inline 6- C4 57,000 mi and growing daily
1929 Graham - Paige 612- the eternal headache that I will never sell


 
Original58 
"4th Year" Silver Supporting Member
Posts: 448
Original58
Loc: Manitoba, Canada
Reg: 10-30-13
06-19-17 10:09 AM - Post#2696546    
    In response to Original58

How would I go about testing the maf?
Also trying to get the fuel filter off but the threaded end wont budge and there's not a lot of room for my fat fingers .

1958 Biscayne 283 Turbo-Glide 31,000 mi (now 35,000 and counting) driven daily
1966 Mustang Inline 6- C4 57,000 mi and growing daily
1929 Graham - Paige 612- the eternal headache that I will never sell


 
models916 
Valued Contributor
Posts: 4506

Age: 66
Loc: Addison, IL
Reg: 05-28-10
06-20-17 04:39 AM - Post#2696705    
    In response to Original58

Not the perfect test, but if the vehicle starts with the MAF unplugged, it's probably not working and the engine is running on a limp mode.



 
gchemist 
Senior Chevytalk Moderator
Posts: 23925
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
06-20-17 05:18 AM - Post#2696708    
    In response to models916

Cleaning an MAF sensor: http://easyautodiagnostic s.com/gm/4.3L-5.0L-5.7L/h...

MAF testing: http://easyautodiagnostic s.com/gm/4.3L-5.0L-5.7L/h...

'95 Jimmy SLT (Bought @131,814)
'83 Silverardo XST - ZZ4 powered
'96 GMC Jimmy LS Ret. @236651 miles


 
Original58 
"4th Year" Silver Supporting Member
Posts: 448
Original58
Loc: Manitoba, Canada
Reg: 10-30-13
06-20-17 06:17 AM - Post#2696712    
    In response to gchemist

Thanks guys. I'll try this today.
Jeff

1958 Biscayne 283 Turbo-Glide 31,000 mi (now 35,000 and counting) driven daily
1966 Mustang Inline 6- C4 57,000 mi and growing daily
1929 Graham - Paige 612- the eternal headache that I will never sell


 
LMC Trucks
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