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03-02-2012, 09:43 PM #1
Please Help with 1995 Driveability
I searched the forums and other forums with no luck on this one; I found similar threads, but none that match my symptoms exactly.
I have a '95 Silverado 4.3L TBI 5-Speed with 177k miles. It is getting increasingly more difficult to start. Hot, cold... It makes no difference. It is beginning to get to the point where once it does start, it stalls back out once or twice before starting and running unless you feather the accelerator pedal while it is sputtering. When driving under load or accelerating, I can feel a jerking that is similar to the jerking you get with bad plug wires, only it is not as bad as what you normally feel with a bad plug/wire. When you turn the key off, the engine shuts off with a rattle that shakes the truck.
To date, the only code it sets is an EGR code, but that is after driving at highway speed for 45 minutes or so. If you shut it off and restart it, the Service Engine light goes out. On my 1200 mile trip recently the symptoms seemed to come and go, and I had NO service Engine light in my entire 9 hour 600 mile return trip, although I DID feel it bucking from time to time - Primarily through the mountains.
I have replaced the fuel filter (The old one was not plugged up), plugs, wires, cap and button. All replaced with AC/Delco parts. I also replaced the Ignition Control Module on the distributor. I did notice that the right side of the distributor cap was not tight due to a stripped hole on the deck of the distributor, but I remedied this by using a nut and a bolt to secure the cap. It is tight. Initially, I thought it was burning rich, but now I think it is a gasoline smell from under the hood.
My next thought is Fuel Pressure Regulator. I bought one tonight but have not installed it yet. Please help me to not spend a fortune on this! I need ideas!"It went together didn't it? Well then there has to be a way to take it apart!" - Me.
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03-03-2012, 07:33 AM #2
Tom, a couple of questions.
What condition were the old plugs when you pulled them.
Have you used any injector cleaner lately.
Have you actually measured the fuel pressure with a guage.
My gut is thinking your running rich, or leaking excess fuel, hence the overrun when you shut down. Then when u say that you have to gently throttle the pedal, basically you are allowing extra air to mix with the extra fuel to allow it to run smoother.
Get yourself some Techron F.I. cleaner (or something similar) and run a couple of treatments and see how it performs.
Do you always get your gas at the same place, maybe try a different brand.
Don't do it all at the same time or you won't really know what the fix was.
The EGR code is a little concerning, not sure how to determine if the egr is "not working, sticking closed" or "stuck open", or "partially open and leaking". An EGR leak can cause you some engine performance issues. Here just a couple of months ago my wife had an EGR error code with her saturn, so I removed it and cleaned the plunger area real good so it moved freely again and all has been well since.
As far as your bucking in the mountains, do you normally travel to the upper altitudes, being in N.C. you are closer than I am, I have been out east thru the mountains with my Mcycle and have noticed perfomance changes with the altitude changes.2010 Silverado LT 1500 5.3L 4X4
'95 BMW K1100LT
'97 BMW K1100LT
03-03-2012, 10:13 AM #3
I have the same engine and I had a similar problem with mine and it turned out to be a bad injector. One of them was leaking a little was dumping more fuel i than it should be. Take your air filter assembly off so you can see the two injectors. Have someone turn the key on so it turns your fuel pump on but dont start it. See if one of your injectors drips a little bit under the pressure. If it does its junk. Also, start it and watch the injectors with the assembly off and see if one is kind of runy or not spraying like it should be. Make sure the vac line to your MAP sensor is good too, along with all your vac lines. Even a slight pin hole in it can cause it to run a little off or start hard. In rare cases I have seen the small rubber line between the fuel pump and the sending unit in your tank go bad and get a small hole in it so you start to lose fuel pressure. It happened to my brthers truck and showed similar problems like yours. Do this...Fuel Sytem----> Ignition System----> Compression Troubleshoot in that order. That means check everything in your fuel system first to make sure its working then move to the igntion system and so on. Start with fuel pressureHope this helps a little good luck!1995 C1500 4.3L 2WD. JET TBI Spacer, JET stage 1 chip, 10mm Taylor custom wires, Pulstar Iridium Pulse Plugs.
260k miles and still going strong...
03-03-2012, 09:00 PM #4
The old plugs looked okay on the tips, although several of them had cracked insulators. they were AC Delco plugs. The wires were non OEM wires. I have no idea what brand they were. I get gas at many different places, particularly when traveling. I have run seafoam through the fuel twice to clean the injectors. The EGR moves freely and functions fine. I am going to replace the solenoid tomorrow when I do the fuel pressure regulator. I travel through the mountains at least once a year. I have never had any problems out of any other vehicle, including an identically equipped 95 Chevy 1500 long bed 2 wheel drive while towing a camper.
The issue is really random. The hard start seems to remain constant with some occurences of turning the key and it hits fast but the motor has to sputter itself up to speed. In these instances, the computer runs the engine at fast idle for 2 to 3 seconds and then brings the engine speed down. Once running it does not stall out. randomly, upon acceleration, the engine will feel like it is skipping or misfiring. Again, this is random. I have not checked fuel pressure. I don't have a tool to check it on this model without the valve on the injection.
When the engine is running at idle, the injectors make really nice fan spray pulses.
I will try turning the key on and looking for leakage on the injectors. I will also make sure the vacuum lines are clear, although if they were stopped up or leaking, I would think that it would run like this all the time instead of at random intervals.
I will look more at this tomorrow. Thanks for the replies. I will check all of those out.
03-03-2012, 10:43 PM #5
- Join Date
- Jan 2012
Check your spark advance mine had similar symptoms and that was the cause
03-09-2012, 10:38 PM #6
So it looks as if the problem only surfaces after the truck has warmed up a bit. First thing on a cold morning, it starts and runs great. Once it starts acting up, I can smell gas. I am thinking maybe coolant temp sensor. I will try that and the fuel pressure regulator tomorrow.
In spite of all of this, I LOVE my truck!
03-10-2012, 04:01 PM #7
So today, I pulled the TBI off, cleaned it (again) and replaced the fuel pressure regulator. It didn't entirely fix my hard start issue OR my misfire. I also replaced the coolant temp sensor. No love. I didn't find any fuel in the vacuum line for the FPR, but I DID smell a strong gasoline odor in the line. Maybe the vacuum module?
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