 2tom2
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Posted: 6/10/2012 9:35:24 AM
THE IMAGE ABOVE IS A PAID ADVERTISEMENT When it starts the only way to keep it running is to feather the throttle on/off. I replaced the TPS and Checked the EGR for vacuum leak but its still a no go for running at idle or at constant throttle. It has fuel and fire. I drove it home,a distance of about 10 miles pushing/ letting off the pedal. I can hear the fuel pump run for 60 seconds of so when switch is turned on so I feel confident that the fuel pump is working. The only other thing I know for sure is I have cramps in my right leg now from pushing the pedal on and off 20K times 
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Posted: 6/10/2012 9:53:50 AM
Get a can of carb cleaner and spray around vac hoses while running. If the rpm changes you have a leak.
It almost sounds like a bad idle air control motor or an airflow sensor! |
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2tom2
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Posted: 6/10/2012 11:22:30 AM
I changed the IAC with no difference
I need to search for a vacuum leak but i am gonna have to draft an extra foot. I would like to see the injector stream while I'm at it just to see what it looks like as well ( I don't think that has to anything to do with current problem) |
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foreman2000
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Posted: 6/10/2012 1:58:55 PM
I could come by and give you a hand. Been working on chevy/gmc trucks for 12 years.
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ExKalifornian
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Posted: 6/10/2012 3:22:25 PM
2tom2, while the truck is running, tap the the mass airflow sensor with the handle of a screwdriver. If the engine rpm changes at all, your MAF sensor is bad.
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foreman2000
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Posted: 6/10/2012 3:28:54 PM
I would say maf or a bad tps even know you replaced it I have seen many bad "new" sensors.
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2tom2
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Posted: 6/10/2012 9:17:02 PM
Originally Posted By foreman2000:
I could come by and give you a hand. Been working on chevy/gmc trucks for 12 years. I appreciate the offer. With the rain I gave up fooling with it for today. |
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Posted: 6/10/2012 9:57:10 PM
Really sounds like a stuck open egr valve to me. I'd suggest pulling it and cleaning thoroughly also inside where it bolts on.
If you need help tomorrow Tom I can swing by. |
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2tom2
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Posted: 6/11/2012 11:27:48 PM
Originally Posted By GeorgiaBII:
Really sounds like a stuck open egr valve to me. I'd suggest pulling it and cleaning thoroughly also inside where it bolts on. If you need help tomorrow Tom I can swing by. I just got in and saw this. It will be Thursday evening or Friday afternoon before I get a chance to get back on it If you have nothing important going on give me a holler. I will IM my number |
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foreman2000
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Posted: 6/12/2012 12:32:39 AM
I should be free...
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Posted: 6/12/2012 12:23:41 PM
When was the fuel filter last changed? I never had an issue like this with my 94'.
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Emu
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Posted: 6/12/2012 3:47:15 PM
I'm anxious to hear how this turns out. My '89 baby Blazer with a 4.3 in it, and all but 300k miles on it, just came down with nearly identical symptoms. When it went bad I was able to limp it home the last 6 miles or so by pumping the throttle. As I neared the house I realized that it would run when the pedal was pushed just 1/8-1/3 of the way down, but it spits and sputters and tries to die when I push down further, it's under a load, I try to make it rev up, or if take my foot off the pedal completely.
I KNOW it's got 3/4 tank of gas in it. I filled it up just 2 days before it crapped out, and have put less than 60 miles on it since. The gauge has always worked ~ok~ though it does stay full for a long time, and the bottom half tank doesn't last long at all...  BUT, the funny thing is, right before it crapped out, I noticed it was registering FULL on the gauge, and still is. Fifteen minutes earlier I remember looking at the guage, and it definately said 3/4 tank. Not sure if this is a coincidence, or a clue??? 
I've got a buddy who is a pretty durn good shadetree mechanic, and he is leaning towards the fuel filter and/or the fuel pump, 'cuz it's acting like it's starved for petrol. Of course when he asked me when I last changed the fuel filter I was like: "ummmmmm, it has a fuel filter that needs changing....?"   
I replaced the fuel pump <100k miles ago, and yes I do hear the pump running, but according to him he has seen other instances where the pump runs, but is worn, and is not putting out the full volume. I have always been of the notion that fuel pumps either work or they don't, with NO exceptions....  
I'll let you know what fixes mine, once I get around to fixing it. It doesn't have to be my daily driver since, just last week, (after 6+ months of it being stranded at my shop) I finally got my '00 Astro van back on the road after replacing, wait for it....., THE FUEL PUMP!!!! 
So there isn't a huge hurry to get my Blazer back on the road, and with me being broke, lazy, HATING to work on a car, and currently having a way to work and back, wellllll.... 
Good luck getting yours squared away!!! I'll be watching here for updates! |
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2tom2
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Posted: 6/12/2012 8:52:35 PM
[Last Edit: 6/12/2012 8:54:38 PM by 2tom2]
Originally Posted By jmarkma:
When was the fuel filter last changed? I never had an issue like this with my 94'. I had a NIB box one that I installed just is case the 3 month old was stopped up. I knew it wasn't the problem as soon as I removed it though. No crud came out and it weighted just about the same as the NIB one. My brother was over last night to borrow my trailer so he ran the pedal for a few minutes while I shot it with carb cleaner looking for vacuum leaks. That theory is shot down down 
I am running out of options. I am goning to swap out the EGR with another, if that does not solve it that leaves the fuel pump or computer. Neither of which i have a spare one laying around
runaway sentence fixed |
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Posted: 6/12/2012 9:14:57 PM
[Last Edit: 6/12/2012 9:17:13 PM by Stasher1]
When was the last time you put in new plugs, wire, rotor, and cap?
I had similar issues with my 95 Suburban (5.7 TBI, non-Vortec) a few years ago and wound up taking it to a local mechanic who diagnosed it as bad intake valves and quoted my ~$2400 to remove/rebuild/replace my heads. I told him to stick it in his ass, drove it home and replaced the heads with a reman set from Dover...still had the problem. Started replacing everything on the top of the, coil, EGR, TPS, etc....still had the problem. One day I was messing with something under the hood while it was running, set my hand on top of the distributor and it shocked the piss out of me. Apparently the wires were bad and were arcing across the top of the distributor cap, causing a misfire...or multiple misfires.
I had spent two weeks and $1500 on parts, just to find out that I needed $25 worth of plug wires. Moral - Start with the simple stuff first. |
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Posted: 6/12/2012 10:08:53 PM
Originally Posted By 2tom2:
Originally Posted By jmarkma:
When was the fuel filter last changed? I never had an issue like this with my 94'. I had a NIB box one that I installed just is case the 3 month old was stopped up. I knew it wasn't the problem as soon as I removed it though. No crud came out and it weighted just about the same as the NIB one. My brother was over last night to borrow my trailer so he ran the pedal for a few minutes while I shot it with carb cleaner looking for vacuum leaks. That theory is shot down down
I am running out of options. I am goning to swap out the EGR with another, if that does not solve it that leaves the fuel pump or computer. Neither of which i have a spare one laying around
runaway sentence fixed I'll call you tomorrow, Been talking with another buddy that is very good on this stuff and he's thinking fuel pressure is a suspect, if it's below 10psi these tbi motors go nuts. |
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foreman2000
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Posted: 6/12/2012 10:48:37 PM
You may have fuel but it may not be enough. You need 35+ psi to run like it should.
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Posted: 6/13/2012 6:53:53 AM
Originally Posted By Stasher1:
When was the last time you put in new plugs, wire, rotor, and cap? I had similar issues with my 95 Suburban (5.7 TBI, non-Vortec) a few years ago and wound up taking it to a local mechanic who diagnosed it as bad intake valves and quoted my ~$2400 to remove/rebuild/replace my heads. I told him to stick it in his ass, drove it home and replaced the heads with a reman set from Dover...still had the problem. Started replacing everything on the top of the, coil, EGR, TPS, etc....still had the problem. One day I was messing with something under the hood while it was running, set my hand on top of the distributor and it shocked the piss out of me. Apparently the wires were bad and were arcing across the top of the distributor cap, causing a misfire...or multiple misfires.
I had spent two weeks and $1500 on parts, just to find out that I needed $25 worth of plug wires. Moral - Start with the simple stuff first. Good point, I had some missfires and random bouts of not wanting to start which was caused by needing a new cap and rotor. It did cause some hesitation at low RPM's I'd at least pull it and take a look. |
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votefromrooftops
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Posted: 6/13/2012 7:38:10 AM
[Last Edit: 6/13/2012 7:38:37 AM by votefromrooftops]
i'm not a chevy tech but i, have someone knowledgable perform a diag. test and see if there are any DTC's, would verify proper fuel pressure, you can have pressure and not volume, Fuel filter, how does it flow? if you have a scanner that can read values, on a Ford the MAF voltage will be slightly higher than TP voltage, so when you throttle the vehicle the MAF voltage will continue to stay high than TPS, i would think that GM and Ford would work the same.
the problem with hestiation on Accel is there are so many thing that can cause this, our CVT system will cause this, fuel, exhaust, vacuum leaks, timing, EGR, EEC parts, aftermarket add ons, etc....i hope the guys local to you can get you squared away |
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