Every so often during hard accelaration, I've recently noticed a power surge while hard on the gas, the engine bogs down with less than full power, than the rpms and speed pick up like they should at full power, it kinda bogs down again, and surges back to full song again. But the weird part is, it doesn't happen every time. I don't know if this is just a timing problem catching up with me from the break down. : viewtopic.php?f=26&t=2457, or a completely different problem. I dont have a scanguage at my disposable right now, i am getting a really nice one for Christmas. Also i feel a slight miss when the truck drops into overdrive and i cruise at 45 mph, again, is timing ever so slightly off or maybe time for plugs/wires? normal diving the truck drives fine and accelerates smooth. I'm hoping chevy crew has an answer for me.. Now I think it could be plugs/wires because when it's wet out I think the truck runs worse and the surging happens more often, idk if I'm just going crazy or if that's actually the case. What do you think? I doubt it's a transmission problem or anything because i would think it would rev free instead of bog down causing the loss in acceleration and power.
EDIT: 97 Chevy K1500 Z71 w/ 350 Vortec
Power Issues
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Last edited by dvanbramer88 on Fri Dec 09, 2011 5:22 pm, edited 1 time in total.
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dvanbramer88 - Lifer
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What vehicle is this again? Not a TB, right?
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No, sorry. 97 chevy K1500 350 Vortec Z71
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dvanbramer88 - Lifer
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got the codes, i opened my scan gauge early. P0171 and P0174, system too lean banks 1&2. did a little research with the progran that came with the gauge and on my own. THIS IS NOT AN O2 sensor problem according to everywhere i looked.
Issues I've found that cause these codes:
bad or dirty MAF
Vaccum leaks
Bad intake manifold gasket
plugged fuel injectors or weak pump.
fuel filter
EGR valve
I can dismiss the EGR valve, i just checked it and cleaned it.
MAF i also checked and cleaned although it was clean.
Intake manifold and gasket are months old because i did in fact have a leak and a crack in the plastic at them time. I learned enough then to know it is not reoccurring. Also, it would usually only throw one code, not both. You could hear the vacuum leak.
I also checked all other hoses.
All fuel injectors, injection unit and fuel pump are also very new as well.
SOOO that leaves the fuel filter which is probably failing. I researched some and found that a failing filter can cause intermittent power problems, they even used the word "surging" during acceleration as a symptom. I think i found what I'm going to replace first.
Issues I've found that cause these codes:
bad or dirty MAF
Vaccum leaks
Bad intake manifold gasket
plugged fuel injectors or weak pump.
fuel filter
EGR valve
I can dismiss the EGR valve, i just checked it and cleaned it.
MAF i also checked and cleaned although it was clean.
Intake manifold and gasket are months old because i did in fact have a leak and a crack in the plastic at them time. I learned enough then to know it is not reoccurring. Also, it would usually only throw one code, not both. You could hear the vacuum leak.
I also checked all other hoses.
All fuel injectors, injection unit and fuel pump are also very new as well.
SOOO that leaves the fuel filter which is probably failing. I researched some and found that a failing filter can cause intermittent power problems, they even used the word "surging" during acceleration as a symptom. I think i found what I'm going to replace first.
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dvanbramer88 - Lifer
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And if the fuel filter doesn't fix my problem, there is a test i can do with my scan gauge that you can see if the MAF is sending the wrong signals even if it appears clean and functional.
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dvanbramer88 - Lifer
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I replaced the fuel filter and the truck was running better and smoother. A few days later (today) the truck started running like crap.
Codes: P0300- random misfire
P0171 and P0174 Banks 1&2 lean.
Whatever is causing my lean condition has gotten worse i suppose. I'm going to try and get a junk yard mass air flow and EGR valve and see what happens.
My AC compressor was also cycling on and off even though the heat was on. thought this was strange, on board computer failure is listed as a possible cause for the random misfire. Is this another sign? i need to look into this.
Codes: P0300- random misfire
P0171 and P0174 Banks 1&2 lean.
Whatever is causing my lean condition has gotten worse i suppose. I'm going to try and get a junk yard mass air flow and EGR valve and see what happens.
My AC compressor was also cycling on and off even though the heat was on. thought this was strange, on board computer failure is listed as a possible cause for the random misfire. Is this another sign? i need to look into this.
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dvanbramer88 - Lifer
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How old is the fuel pump?
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chevycrew - Veteran
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8-9 months.
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dvanbramer88 - Lifer
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More insight, I have a gut feeling i killed my MAF when i tried to clean it. at idle, the pounds/min intake flow rate is 1. that seems pretty low to me, and if i remember correctly i have seen the truck run at about 4 pounds/min. Also the intake temp reading is way off of the actual outside air temp. It's about 20 degrees higher than the real temperature.
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dvanbramer88 - Lifer
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Since it is showing lean, I would rule out a spark issue. For some reason it isn't getting enough fuel. I would check fuel psi, at idle and WOT, also do a volume test. That is in addition to the maf and iat issues you are looking into.
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chevycrew - Veteran
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im going to play around with diagnosing the MAF tomorrow. There is also a voltage test i found. Then i will look into fuel delivery if i cant find anything conclusive. Like i said, filter, pump, and sending unit are all new. I can check the pressure at the rail but that wont tell me about injectors or injection unit. (which is only 2 years old) And if an injector or two were clogged i would get codes for individual cylinders, not just random misfire and lean banks. So im basically looking at too much air/ not enough fuel across the board. Also i noticed the fuel consumption rate is way up too. Normal idle consumption is about 2/3 gallon/hour. When i was playing with it today, i noticed the fuel consumption rate was about 9/10 gallon/hour. So i think that it has no idea how much air is coming in so it is compensating in a "limp" mode to keep the motor running. It did start to smell rich as i was playing with it tonight. Which again points to bad MAF sensor.
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Duct tape, WD 40, and Seafoam...
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DirtyBacon04 - Moderator
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DirtyBacon04 wrote:Duct tape, WD 40, and Seafoam...
Once upon a time it was that easy. Unfortunately the late 90's SFI fuel injection is a joke. Every time i go to the junk yard the older (95-) TBI models have the entire engines still in the truck. All the 96+ trucks, the same one's i need parts off of are always stripped to bare engine bays. Now such a prevalent pattern says something.
Not to talk badly about my truck, i love the power, it is a great ride, the premium silverado interior is super comfortable. Power everything, great visibility, etc etc. The IFS is very strong too. Rear suspension is a tank. All around a great ride, it's just that the fuel injection related components are crap.
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dvanbramer88 - Lifer
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WELP, i took the $20 gamble and got a junkyard MAF sensor. I used my computer to clear the codes and let it idle in my driveway hooked up to my laptop. Still running like crap. the code for multiple/random misfire came back and a new code for an o2 sensor came up. NONE of the lean bank codes or MAF low imput circuit codes came back after about 30 minutes of running. Looks like i need an O2 sensor. The MAF was indeed failing but wasnt causing the truck to run bad yet.
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dvanbramer88 - Lifer
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I fought a P0300 code forever on my wifes truck. It was the only code tho. Turned out to be the CPS (I had a new one on but the pcm didn't like it, swapped with a dealer part and good to go.)
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chevycrew - Veteran
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dvanbramer88 wrote:DirtyBacon04 wrote:Duct tape, WD 40, and Seafoam...
Once upon a time it was that easy. Unfortunately the late 90's SFI fuel injection is a joke. Every time i go to the junk yard the older (95-) TBI models have the entire engines still in the truck. All the 96+ trucks, the same one's i need parts off of are always stripped to bare engine bays. Now such a prevalent pattern says something.
This is due mostly to people's lack of understanding of how SFI systems work. Their solution is to shotgun parts.
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fishsticks wrote:dvanbramer88 wrote:
Once upon a time it was that easy. Unfortunately the late 90's SFI fuel injection is a joke. Every time i go to the junk yard the older (95-) TBI models have the entire engines still in the truck. All the 96+ trucks, the same one's i need parts off of are always stripped to bare engine bays. Now such a prevalent pattern says something.
This is due mostly to people's lack of understanding of how SFI systems work. Their solution is to shotgun parts.
Ill agree with that. I understand how it works. It just sucks ive been through the entire fuel system over the past two years and everyone i talk to is convinced it is fuel delivery problem causing the random misfire.
I'm going to try seafoam actually. Also im going to add an octane booster on the off chance of bad fuel because the major problem started the day after fueling up. I hope it's just clogged injectors or injection unit. Seafoam, if it does as claimed, will cure that.
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dvanbramer88 - Lifer
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A bad injector would show a misfire for that cylinder.
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chevycrew - Veteran
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chevycrew wrote:A bad injector would show a misfire for that cylinder.
Yea i know, so would a lot of other possible things. That's why this is so difficult. I have a spare dizzy cap im going to switch out in case the one that is on there cracked internally. It happened to me before. But i am really hoping it is just bad gas.
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dvanbramer88 - Lifer
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