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2003 silverado z71 soon to be build thread..

Xtremegmc80

Xtremegmc80

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hey! thanks in advance for the help!
;)

problem..

MY silverado z71 has been acting weird lately, it currently has 90,000 miles. i took it to get the computer tested, came out as MAF and small emission leak, got the emission leak fixed by replacing gas cap. no more code for that. now it keeps appearing MAF (MASS AIR FLOW) sensor. i cleaned that out, with the maf spray. it helped for like a day or 2. then i took a 112 mile trip to my finacees parents. it ran horribly! lack of power, hesitation on every hill i went over, had to floor it up hills. when in cruise control, at 65 mph in 55 mph zone, here comes a hill, down shift itself to 3rd. rpm spikes to like 2,500 to 3,000. still losing power, then truck down shift itself again and shuttered and spiked all the way to 5,500 rpms and speedo went back to 65 then it upshift, loses power again. and i had no load, or no weight at all in back! so does maf really causes the engine to lack power if its not funcation good? problem started about 2 weeks ago, it has new plugs, am getting new plugs, fuel filter, clean k&n airfliter, tomorrow, should i get new maf too?? hope u guys can help me out..

this truck is my towrig, dont want to have a hard time towing my 80 gmc!!

truck has 4.8/4speedauto/3.73s. hope u guys can help me out, thanks!!
 
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Is that an oiled K&N? If so, ditch it. Not sure if the MAF gets oil fouled if it can be cleaned enough to work right. Not saying it's your problem, but oil has no place in front of a MAF. If not oiled, disregard.

Double check that your connections are good at the MAF. If you moved it around to clean it, you may very well have made the connection better temporarily. Check the wiring that you can see, make sure there is nothing wrong with it.
 
Sounds to me like your MAF is bad. If you cleaned it and still have problems it is gone.
As Dorian said about the K&N oiled filters they can cause MAF failure unless the MAF is cleaned cleaned regularly. The oil from the filter coats the sensor and gets burnt on after time and takes out the sensor.
MAFs should be cleaned with 99% pure isopropyl alcohol.
I dont know about using sprays you have to be very careful about what you use. Some electrical part cleaner sprays use solvents that can damage MAF sensors.
 
hmm i guess new air filter is coming tomorrow.. just think its weird since i have had k&n in this truck for the last 35 k miles, and the airfilter has never been reoiled... so..
seriously would a maf causes this much lack of power?? thanks
 
Xtremegmc80 said:
hmm i guess new air filter is coming tomorrow.. just think its weird since i have had k&n in this truck for the last 35 k miles, and the airfilter has never been reoiled... so..
seriously would a maf causes this much lack of power?? thanks
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your ECM or PCM which ever you perfer to call it gets a reading from the MAF sensor telling how much air is flowing into the engine. now basically like all engines the more air you flow the better your power and fuel milage is because the engine is running more efficant. by getting a wrong message from the MAF sensor, you could be flowing plenty of air but the sensor could be telling your PCM that your not flowing hardly any air at all, then the PCM leans out the injectors to keep the engine from running rich and so then your really running lean so no power. also it could be really screwed up and saying your flowing more air than possible so than it richens the injectors so then your really running rich. so ya the MAF has a heck of a lot to do with your power. its basically the first thing your engine reads for sensing how much or how little fuel to pulse thru the injectors.
 
If anyone is really familiar with OBD2 perhaps they can comment better than I, but I thought the OBD2 setups have a MAP sensor as a failsafe in case the MAF goes. I would THINK that if the problem were consistent, the MAF was the cause, AND it will run without the MAF connected, with it disconnected the problems should disappear.
 
Yes OBD2 does have a MAP sensor also. I am not sure of all the functions but i know OBD2 uses the MAP Mainly to measure air denseity/pressure for altitude corrections. I know OBD2 with turbos use a 2 bar or larger MAP to measure boost.
And yup if you disconnect the MAF sensor and your vehicle runs better you have found your problem. Your CEL will light with a MAF code also. I am not sure if the ECM enters a limp home mode or defaults to running off of the MAP sensor.
 
the 4.8 does not go into limp home mode when the SES light is lit. Mine went off the other day. the engine through a misfire code. it was raining so hard I couldn't see past the end of the hood, I have a body lift which exposes the plugs and wires with 73K miles on it.

disconnect the MAF and see how it runs. I also have the k&n kit and sure hope that at 90K miles the MAF doesn't go bad. but I have had my k&n on for over 50K now.:dunno: I have cleaned and re-oiled it at least twice that I can remember, the trick is to really lightly oil it and let the oil spread through the filter. if after several minutes there are dry spots, hit it with a light blast. you don't want any extra getting into the engine. them damn sensors are sensitive.:mad:

the filter on my 83 gets drowned in oil and slapped on.:D
 
gmc4cw said:
them damn sensors are sensitive.:mad:

:D
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and damn new tech. has a trillion more wires everywhere. computers, etc.. if something happens to my 80 gmc, i get it fixed in half an hour,. the 03 z71 have to figure out which sensors are bad or etc.. grrrr:rolleyes:
 
well im back. new ac delco spark plugs, fuel filter, maf sensor, and thats not the problem. trucks feel good n has power but still feels lackin of power like u floor it it goes but like easily then finally pulls.. or it would pull then loses power and go easy, i havent gotten her to top rpms on long hill yet, idles feels rough. not too sure, when i first got her it was super smooth and pretty quickly.. but now not really. :( this truck is why i stopped working on my 80 gmc grrr... well lately when i drive normal speed like 50 mph, here comes a stop sign i push the brake to a complete stop, truck stalls. started her up seems fine.. no big deal. im sitting, before it was fine, but now when im sitting in gear it drops to like 300 to 400 rpms.. pretty low(i think) turn the steering wheel truck stalls. if i play with the gas pedal in gear, like driving brake gas brake to test her out i smelled strong odor of gas coming out of exhaust but no black smoke and idles rough for a sec or so then it smoothes out. so i drove her til near bone dry then i put 2 stp fuel injector cleaner in the tank, filled her up with special 89 exxon gas. now its completely full, only 32 miles so far too early to tell if its working better.. hey ya all of u guys with a 4.8 eng and auto whats ur rpm in netural and in gear, i want to know, thanks.

So what else do u guys think it can be? any other places to check?? thanks in advance... im hoping to find the problem before i get fed up and send it to the dealer...:mad: TO LET U KNOW NO MORE ENGINE SERVICE LIGHT IS ON! BUT WHY STILL WEIRD PROBLEMS????
 
gmc4cw said:
new job, tired all the time.
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good to hear.. my job sucks.. i only work like 3 days a week out of 5 days.. i should have kept that gsi job! sucks to be me. but hey my finacee works full time now, so its nice to get things done around here..
 
check your fuel pressure regulator, if you pull the vacum line of and gas comes out of the line it is bad here is a pic of where it is located its the round gold peice on the fuel rail with vacum line
post-56-1125596867_thumb.jpg
 
ive got a 00 gmc z71 with 5.3 and mine started to act weird wouldn't idle very good and hard to start and the fuel pressure regulator was bad
 
my fuel pressure regulator went bad also. it would be hard to start because the bad regulator was letting the engine flood when shut off. it was $25 and no tools to change. there is just a clip that holds it in. if it has not been changed yet you might as well do it. It was a real common problem in our shop.
 
thanks.. never thought of that.. i am gonna check that out monday, if theres no gas coming out of it, i wouldnt care im still replacing it,.. but im defentily am gonna check it out.. thanks again! ill keep u post on monday night to see how it is if napa has the part in stock...:rolleyes:
 
replaced the fuel pressure regulator.. no luck.. well im takin a break from this now, its driveable for now.. well me n my dad went to pick up the saturn today after it sat at the shop for 5 months. no luck. i drove it home, loses power at 3,500 rpms, and wont go over that, nothing works no speedo no rpm tach, no nothing, took it to my other friends shop with a computer test.. well the best thing we found is, maybe 20 different codes appears and i aint replacing everything. the last code say fuel pump disabled, anti theift disabled, everything not working right.. so u know the answer?? A 62000 mile car's brain(computer) is FRIED or shorted out.. so.. tomorrow kevin, the guy that has my saturn, say he'll call saturn dealer and see if theres anything like this before. so i hope something comes up cause this sucks big time! and 1 year left of payment.. grrrr..:mad: this is a 2001 Saturn L200, 2.2 ecotech engine.. any of u guys hear same thing happens to same car in the past??:confused:
 
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