csirovy
Newbie
Hello! I have a 1998 Chevrolet K1500 Silverado with a 5.7L 350. It has 282,000 miles on it and I have been chasing a bunch of issues and am finally at a loss and seeking some input and guidance...!
To start let me tell you where this all began... for quite some time I had coolant disappearing, oil was clean and exhaust smoke was white so I narrowed that down to an intake or head gasket issue but kinda pushed it off. (Shame on me) Truck ran and idled normal without issues but I knew in time I needed to get that fixed. What pushed me to finally get this project going was when I noticed my fuel economy worsening. It got to the point where my full tank of fuel only lasted 80 miles so that's when I decided to pull out the wrenches.
I want to make note prior to continuing what had been done to the truck 1 year prior to starting the project. The truck fuel pump went out so i did a full tune up. This is a list of parts put on;
1. Fuel Pump
2. Fuel Filter
3. Distributor Cap and Rotor
4. Spark Plugs and Wires
5. EGR Valve (I don't recall why but I did have a reason)
When I started this project I checked fuel pressure. I unfortunately only have a cheaper Harbor Freight Fuel Pressure Guage so hopefully it's correct, but I observed a fuel pressure of around 40 psi with ignition in the on position but not running. Since the fuel pump was newer I just assumed it was a bad fuel pressure regulator.
So the fun began. Here is a list of all parts replaced during the 1st stage of this project.
1. Serpentine Belt
2. Belt Tensioner
3. Idler pulley
4. Clutch Fan
5. Fuel Pressure Regulator
6. Throttle Body Gasket and O Rings
7. Intake Plenum Gasket
8. Intake Manifold Gaskets
9. Head Gasket
10. Head Bolts
11. Thermostat
12. EGR Line
11. Water Pump
12. Alternator
13. Power Steering Pump and hoses/lines
Upon completion I had a rough idle and cylinder 6 misfire. I contributed this to improper distributor placement since I didn't have a fancy enough can tool to set the CamRetard +/- 2 degrees. I took it to my local mechanic. He plugged in and got the distributor adjusted within tolerance which helped the idle some but the cylindar 6 misfire still existed. I got it back home pulled the plug and wire on 6 to verify spark, which was working as it should. I called up the mechanic and he said that if he had to guess the #6 injector may be faulty since I cleaned everything up during the overhaul. Since this truck has the CFI Spider Injectors he just recommended to replace it with the new MFI Spider Injector Assembly. So I went ahead and ordered that.
I installed the new injector assembly and after putting everything back together i now have a high Idle (Roughly 1600 rpm) but it does sound a lot better. My engine did throw a Mass air flow code. I went ahead and installed a new Mass air Flow sensor and Idle Air Control Valve. The mass air flow code no longer comes on. At idle it still runs around 1600 rpm but does not throw any codes. When I put it into gear it struggles and occasionally acts as if it may die.
I took it on a 30 mile drive, when in gear and off the break the RPMs are high enough to slowly increase speed. I was rolling at 30 mph and let off the gas but yet the speed kept gradually increasing. Also, while driving the Cylindar 6 Misfire code returned.
I put my fuel Guage on it again and still it's showing around 40 psi... could my newer pump be faulty and weak, or is my cheap harbor freight Guage just wrong. I'm gonna go borrow a different guage from my mechanic to compare.
I sprayed break clean all around the intake Manifold, intake, and vacuum hose but did not notice any change in RPM so I don't believe I have a leak. Wish I had a smoke machine...
As a side note I still have a few other parts I need to install. First I need to replace my Fuel tank filler neck because it leaks when I fill my tank. Second, I need to replace my B2S2 (Downstream) O2 sensor as in the past I've had a code but it is not throwing one currently. Lastly I need to replace a downstream Exhaust Flange Gasket as I have an exhaust leak. Just wanted to mention these items in case any of them could be affecting the idle.
All in all, I'm in about $2500 thus far. I don't know what else I can do to figure out this High Idle and Cylinder 6 Misfire issue.
I want to mention that I do not have a compression tester but I don't believe I have an issue with compression since prior to this project I wasn't having any issues other than the loss of coolant and bad fuel economy. Feel free to change my mind!
All input is appreciated!
To start let me tell you where this all began... for quite some time I had coolant disappearing, oil was clean and exhaust smoke was white so I narrowed that down to an intake or head gasket issue but kinda pushed it off. (Shame on me) Truck ran and idled normal without issues but I knew in time I needed to get that fixed. What pushed me to finally get this project going was when I noticed my fuel economy worsening. It got to the point where my full tank of fuel only lasted 80 miles so that's when I decided to pull out the wrenches.
I want to make note prior to continuing what had been done to the truck 1 year prior to starting the project. The truck fuel pump went out so i did a full tune up. This is a list of parts put on;
1. Fuel Pump
2. Fuel Filter
3. Distributor Cap and Rotor
4. Spark Plugs and Wires
5. EGR Valve (I don't recall why but I did have a reason)
When I started this project I checked fuel pressure. I unfortunately only have a cheaper Harbor Freight Fuel Pressure Guage so hopefully it's correct, but I observed a fuel pressure of around 40 psi with ignition in the on position but not running. Since the fuel pump was newer I just assumed it was a bad fuel pressure regulator.
So the fun began. Here is a list of all parts replaced during the 1st stage of this project.
1. Serpentine Belt
2. Belt Tensioner
3. Idler pulley
4. Clutch Fan
5. Fuel Pressure Regulator
6. Throttle Body Gasket and O Rings
7. Intake Plenum Gasket
8. Intake Manifold Gaskets
9. Head Gasket
10. Head Bolts
11. Thermostat
12. EGR Line
11. Water Pump
12. Alternator
13. Power Steering Pump and hoses/lines
Upon completion I had a rough idle and cylinder 6 misfire. I contributed this to improper distributor placement since I didn't have a fancy enough can tool to set the CamRetard +/- 2 degrees. I took it to my local mechanic. He plugged in and got the distributor adjusted within tolerance which helped the idle some but the cylindar 6 misfire still existed. I got it back home pulled the plug and wire on 6 to verify spark, which was working as it should. I called up the mechanic and he said that if he had to guess the #6 injector may be faulty since I cleaned everything up during the overhaul. Since this truck has the CFI Spider Injectors he just recommended to replace it with the new MFI Spider Injector Assembly. So I went ahead and ordered that.
I installed the new injector assembly and after putting everything back together i now have a high Idle (Roughly 1600 rpm) but it does sound a lot better. My engine did throw a Mass air flow code. I went ahead and installed a new Mass air Flow sensor and Idle Air Control Valve. The mass air flow code no longer comes on. At idle it still runs around 1600 rpm but does not throw any codes. When I put it into gear it struggles and occasionally acts as if it may die.
I took it on a 30 mile drive, when in gear and off the break the RPMs are high enough to slowly increase speed. I was rolling at 30 mph and let off the gas but yet the speed kept gradually increasing. Also, while driving the Cylindar 6 Misfire code returned.
I put my fuel Guage on it again and still it's showing around 40 psi... could my newer pump be faulty and weak, or is my cheap harbor freight Guage just wrong. I'm gonna go borrow a different guage from my mechanic to compare.
I sprayed break clean all around the intake Manifold, intake, and vacuum hose but did not notice any change in RPM so I don't believe I have a leak. Wish I had a smoke machine...
As a side note I still have a few other parts I need to install. First I need to replace my Fuel tank filler neck because it leaks when I fill my tank. Second, I need to replace my B2S2 (Downstream) O2 sensor as in the past I've had a code but it is not throwing one currently. Lastly I need to replace a downstream Exhaust Flange Gasket as I have an exhaust leak. Just wanted to mention these items in case any of them could be affecting the idle.
All in all, I'm in about $2500 thus far. I don't know what else I can do to figure out this High Idle and Cylinder 6 Misfire issue.
I want to mention that I do not have a compression tester but I don't believe I have an issue with compression since prior to this project I wasn't having any issues other than the loss of coolant and bad fuel economy. Feel free to change my mind!
All input is appreciated!
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