All,
I wanted to share this with everybody as I have been through the process, it has been a hoot to say the least. If you are having these issues please continue...if this has already been hashed out here then accept my apologies.
This is a bit of a read so I apologize for the length, however if the title of this post caught your eye, grab a cup of Java and spend a few minutes reading. This was one of the most confusing issues to properly diagnose as there are literally hundreds of articles written on the internet voicing the same issues with dozens of purported fixes.
I own a 96 Tahoe with 183K on it. At about the 150K mark I started noticing very hard starts when it was either raining or humid out. I got the dreaded and oh so helpful code of "random multiple misfire" which could be any one of about 25 things (roll's eye's). Being as I was trained WAY BACK in the 70's on how to work on cars, tuning up the Hoe isn't too much of a hassle for me, so that's where my journey began.
Replaced everything available to replace on the ignition system, Plugs, wires, coil, cap, rotor. I noticed absolutely no improvement.
I then went through and waterproofed every electrical connection under the hood. Still after all of this, I was getting the multiple random misfire code. The fuel pump crapped out on me around 160K, I blame myself for not doing the preventative maintenance on that one as I know better. Still after the new pump getting the same code, except now I was getting what I call a fishing pole tug type of misfire when on the highway with my cruise control activated.
I then started digging a bit deeper and learned that Chevy had recalled this vehicle because the gasket at the Fuel Regulator would fail, when this occurs it allows the seal to break and fuel to drain back into the tank. On a lark I changed the start up procedure wherein I would turn the key to power the fuel pump, leave it running for 20 seconds before I started the car, although this seemed to work a bit better I still had the same issues when it would rain. So I now know I do have fuel draining back into the tank when the car is sitting....but why won't it start in the rain?
"Scratches head in confusion.....drinks another Makers and water...thinks for a while".
Popit valves...did I say popit valves? I meant to say "POP-ITVALVES".
I don't know where I stumbled onto the issue of popit valves but I did, and when I did everything started to come together for me a bit. First of all, shame on GM for ever putting this piece of crap in their cars. They are quite literally repairs waiting to happen, and GM took the cheap route when designing this FI system. A trap door hooked to a spring, in the worst part of the combustion chamber, waiting for 40psi to push it open. Can we say "carbon deposits".
Ok, so I knew my fuel regulator was bad, or at least the gasket was bad. Then I had an instance wherein fuel from a stuck open popit valve filled my exhaust manifold and it BACKFIRED IN THE MANIFOLD...I thought someone had shot at me.
So I took the plunge to not only replace the fuel regulator, but to install the Borg Warner MPFI conversion kit. There would be no reason that I can see to replace the Fuel Regulator without doing this conversion if you have a higher mileage Vortec. The intake cover has to come off, everything is right there...shell out the buck to do it. Being that this requires a bit more time than I had on my hands I took it to the mechanic that serviced all of my fleet vehicles. He checked with the local Chevy Dealer, and low and behold the dealer rep. advised him NOT to buy the Delco kit, but to buy the Borg Warner kit as they had much better luck with this unit.
DONE!
It is like I have a new truck.
GONE IS THE TERRIBLE SMELL AT IDLE
gone are the dirty looks from everyone sitting in traffic around me,
gone are the idle stumbles,
gone are the fishing pole tug misses at cruise,
gone are the hard starts and BACKFIRES IN THE MANIFOLDS,
gone are the no starts in wet weather,
gone are the no starts in the cold,
gone are the random misfire codes,
gone is the atrocious gas mileage.
Gone is the no start anxiety...
It now idles properly at 800rpm, smooth as butter. Runs great and throttle response is so much better.
I only wish to convey this to anybody out there who is struggling with this very difficult situation to diagnose. I methodically went through everything I knew to do, and the fix was the conversion to MPFI. For those possibly looking to poke holes, I did the crank position indicator and a lot of other things I may have forgotten in the body of this post.
Not sure if you will have the luck I did, but the popit valves wil always be a problem with these vortec 5.7 engines(4.3 and 7.4 as well). No matter how many times you seafoam them, there is really no way for them to work well in the environment they find themselves.
if you haven't read about the MPFI conversion simply google it as they are everywhere. The technology used in the conversion kit to MPFI is light years ahead of the popit valve technology.
So, if this helps anybody that would be great. If this has already been covered here in detail somewhere I apologize as I could not find it.
My email is public and I will gladly answer any questions that I can.
Cheers to you, and thank the jesus it's almost boating season
eace:
I wanted to share this with everybody as I have been through the process, it has been a hoot to say the least. If you are having these issues please continue...if this has already been hashed out here then accept my apologies.
This is a bit of a read so I apologize for the length, however if the title of this post caught your eye, grab a cup of Java and spend a few minutes reading. This was one of the most confusing issues to properly diagnose as there are literally hundreds of articles written on the internet voicing the same issues with dozens of purported fixes.
I own a 96 Tahoe with 183K on it. At about the 150K mark I started noticing very hard starts when it was either raining or humid out. I got the dreaded and oh so helpful code of "random multiple misfire" which could be any one of about 25 things (roll's eye's). Being as I was trained WAY BACK in the 70's on how to work on cars, tuning up the Hoe isn't too much of a hassle for me, so that's where my journey began.
Replaced everything available to replace on the ignition system, Plugs, wires, coil, cap, rotor. I noticed absolutely no improvement.
I then went through and waterproofed every electrical connection under the hood. Still after all of this, I was getting the multiple random misfire code. The fuel pump crapped out on me around 160K, I blame myself for not doing the preventative maintenance on that one as I know better. Still after the new pump getting the same code, except now I was getting what I call a fishing pole tug type of misfire when on the highway with my cruise control activated.
I then started digging a bit deeper and learned that Chevy had recalled this vehicle because the gasket at the Fuel Regulator would fail, when this occurs it allows the seal to break and fuel to drain back into the tank. On a lark I changed the start up procedure wherein I would turn the key to power the fuel pump, leave it running for 20 seconds before I started the car, although this seemed to work a bit better I still had the same issues when it would rain. So I now know I do have fuel draining back into the tank when the car is sitting....but why won't it start in the rain?
"Scratches head in confusion.....drinks another Makers and water...thinks for a while".
Popit valves...did I say popit valves? I meant to say "POP-ITVALVES".
I don't know where I stumbled onto the issue of popit valves but I did, and when I did everything started to come together for me a bit. First of all, shame on GM for ever putting this piece of crap in their cars. They are quite literally repairs waiting to happen, and GM took the cheap route when designing this FI system. A trap door hooked to a spring, in the worst part of the combustion chamber, waiting for 40psi to push it open. Can we say "carbon deposits".
Ok, so I knew my fuel regulator was bad, or at least the gasket was bad. Then I had an instance wherein fuel from a stuck open popit valve filled my exhaust manifold and it BACKFIRED IN THE MANIFOLD...I thought someone had shot at me.
So I took the plunge to not only replace the fuel regulator, but to install the Borg Warner MPFI conversion kit. There would be no reason that I can see to replace the Fuel Regulator without doing this conversion if you have a higher mileage Vortec. The intake cover has to come off, everything is right there...shell out the buck to do it. Being that this requires a bit more time than I had on my hands I took it to the mechanic that serviced all of my fleet vehicles. He checked with the local Chevy Dealer, and low and behold the dealer rep. advised him NOT to buy the Delco kit, but to buy the Borg Warner kit as they had much better luck with this unit.
DONE!
It is like I have a new truck.
GONE IS THE TERRIBLE SMELL AT IDLE
gone are the dirty looks from everyone sitting in traffic around me,
gone are the idle stumbles,
gone are the fishing pole tug misses at cruise,
gone are the hard starts and BACKFIRES IN THE MANIFOLDS,
gone are the no starts in wet weather,
gone are the no starts in the cold,
gone are the random misfire codes,
gone is the atrocious gas mileage.
Gone is the no start anxiety...
It now idles properly at 800rpm, smooth as butter. Runs great and throttle response is so much better.
I only wish to convey this to anybody out there who is struggling with this very difficult situation to diagnose. I methodically went through everything I knew to do, and the fix was the conversion to MPFI. For those possibly looking to poke holes, I did the crank position indicator and a lot of other things I may have forgotten in the body of this post.
Not sure if you will have the luck I did, but the popit valves wil always be a problem with these vortec 5.7 engines(4.3 and 7.4 as well). No matter how many times you seafoam them, there is really no way for them to work well in the environment they find themselves.
if you haven't read about the MPFI conversion simply google it as they are everywhere. The technology used in the conversion kit to MPFI is light years ahead of the popit valve technology.
So, if this helps anybody that would be great. If this has already been covered here in detail somewhere I apologize as I could not find it.
My email is public and I will gladly answer any questions that I can.
Cheers to you, and thank the jesus it's almost boating season
eace:
Last edited:
