Random misfires.......
Thread Starter
|
Posting Guru
Joined: Nov 2003
Posts: 1,858
Likes: 1
From: Dark side of the sun.
Random misfires.......
Truck has a random misfire. Sometimes it will haul *** and other times it just moves. Like early in the morning when I'm driving to PT,get on it to go it will drop dead on its face then haul *** shortly after,thus spinning the back tires which MP's hate...
I've got 8 brand new champion plugs gapped at .060 and new wires on it,new fuel filter,ran lucas oil and sea foam through the fuel tank and intake. I run 88 octane fuel in it because since I got back from Korea,apparently texas doesnt have 87,89,and 91 octane. Its now 86,88,90. It's Chevron brand. I quit using the fuel on base. This is a calafornia truck and is complaining about an O2 sensor. I'm just sick of vehicles malfunctioning out here. I miss my '89....20 years no problems......new chevy and this.....go figure for a chevy but I need something at least somewhat reliable. The fuel gauge is already bouncing around........What could it be?
Its embarrasing being the only mechanic in your company out of all the infantry and snippers,tankers,etc...and cant even fix my own crap. I need help guys.
Thanks.
I've got 8 brand new champion plugs gapped at .060 and new wires on it,new fuel filter,ran lucas oil and sea foam through the fuel tank and intake. I run 88 octane fuel in it because since I got back from Korea,apparently texas doesnt have 87,89,and 91 octane. Its now 86,88,90. It's Chevron brand. I quit using the fuel on base. This is a calafornia truck and is complaining about an O2 sensor. I'm just sick of vehicles malfunctioning out here. I miss my '89....20 years no problems......new chevy and this.....go figure for a chevy but I need something at least somewhat reliable. The fuel gauge is already bouncing around........What could it be?
Its embarrasing being the only mechanic in your company out of all the infantry and snippers,tankers,etc...and cant even fix my own crap. I need help guys.
Thanks.
Posting Guru
Joined: Feb 2004
Posts: 1,388
Likes: 0
From: Saratoga, NY
Bad idea to put champions in a GM vehicle. You should stick with ACDelco. I'ts had to diagnose your problem with what little info you have given. I suspect you have a fuel or ignition problem and it's tough to no where to start without a scan tool. I have replaced several fuel pumps in these trucks for similar problems, but then again with out doing a fuel pressure test your guessing.
Butt-Head
Joined: Apr 2004
Posts: 9,405
Likes: 2,894
From: Reed Point, MT
The fuel gauge jumping all over is due to the sending unit in the tank. You'll have a P0463 stored in the PCM for that.
As far as the driveability issue, I would instantly suspect a fuel pump. Have the fuel pressure checked and use an ammeter to check the amp draw of the pump. These trucks require 50 PSI minimum to run correctly and anything less will cause lack of power or O2 sensor low voltage codes. The amp draw should be between 8.5-10 amps on a healthy pump. I usually use my FLUKE 97 scopemeter to check the waveform (instantly lets me know if a pump is shot), and can tell if it's got a bad commutator.
I would start there....let us know how it goes.
As far as the driveability issue, I would instantly suspect a fuel pump. Have the fuel pressure checked and use an ammeter to check the amp draw of the pump. These trucks require 50 PSI minimum to run correctly and anything less will cause lack of power or O2 sensor low voltage codes. The amp draw should be between 8.5-10 amps on a healthy pump. I usually use my FLUKE 97 scopemeter to check the waveform (instantly lets me know if a pump is shot), and can tell if it's got a bad commutator.
I would start there....let us know how it goes.
Trending Topics
Thread Starter
|
Posting Guru
Joined: Nov 2003
Posts: 1,858
Likes: 1
From: Dark side of the sun.
bad fuel pump,$400 I dont have. Whats a procedure to test the pump? When the dumbarse at autozone scans the computer it just gives a P0300 (Random misfire) and no voltage change on O2 sensor in bank 2.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Top 10 Ford Trucks Coming to Mecum Indy 2026
Brett Foote
5 Best / 5 Worst Ford Truck Wheels of All Time
Joe Kucinski
Ford Super Duty: 5 Things Owners LOVE, 5 Things They LOATHE!
Joe Kucinski
Every 2026 Ford Truck Engine RANKED from WORST to FIRST!
Michael S. Palmer
The Best F-150 Deal of Every Trim Level (XL through Raptor)
Joe Kucinski
Butt-Head
Joined: Apr 2004
Posts: 9,405
Likes: 2,894
From: Reed Point, MT
Well, then that ixnays the sending unit...that's part of the pump, but it can be replaced separately.
Does it misfire when cold? Does it run ok when hot? You said when you drive to PT...so I assume around 0530. Here's a quick test to see if you're leaking vacuum around the intake ports.....spray brake cleaner around the cylinder head mating surface of both sides of the intake. Listen/feel for a change in idle speed/roughness. The gaskets on those are plastic with rubber o-rings. They lose tension (especially when cold) and will cause a misfire. I've seen them so bad that the thing will miss and set lean codes when hot. If you can get a scan tool that shows data, check the MAF reading at idle....it should be 5.2-6 grams/second....if it's less than 5, then you've got an intake leak.
If you had issues with BOTH O2 sensors, I'd say check the MAF sensor....especially if you've got one of those EVIL K&N filters on it...but since it's only Bank 2 (passenger) it's probably not that.
Anyway, I'm not condoning just throwing parts at the truck...a proper diagnosis is a must. I'm just throwing ideas out there.
Does it misfire when cold? Does it run ok when hot? You said when you drive to PT...so I assume around 0530. Here's a quick test to see if you're leaking vacuum around the intake ports.....spray brake cleaner around the cylinder head mating surface of both sides of the intake. Listen/feel for a change in idle speed/roughness. The gaskets on those are plastic with rubber o-rings. They lose tension (especially when cold) and will cause a misfire. I've seen them so bad that the thing will miss and set lean codes when hot. If you can get a scan tool that shows data, check the MAF reading at idle....it should be 5.2-6 grams/second....if it's less than 5, then you've got an intake leak.
If you had issues with BOTH O2 sensors, I'd say check the MAF sensor....especially if you've got one of those EVIL K&N filters on it...but since it's only Bank 2 (passenger) it's probably not that.
Anyway, I'm not condoning just throwing parts at the truck...a proper diagnosis is a must. I'm just throwing ideas out there.
Thread Starter
|
Posting Guru
Joined: Nov 2003
Posts: 1,858
Likes: 1
From: Dark side of the sun.
Its always misfiring. In the morning like you said,around 0530 it will stumble dead on its face then kick up. And tonight I was driving to the PX,it had power like a sumbitch,but coming back,it had almost none. Its random. I have no idea. I'll try the brake cleaner trick next pay day.
Posting Guru
Joined: Feb 2004
Posts: 1,388
Likes: 0
From: Saratoga, NY
Nothing wrong with champion plugs when used in a lawnmower or a Chrysler product. But for GM engines stick whith what came with the engine and you'll never have a spark plug compatibility issue. Don't believe the BS the other plug companies give you about more HP and gas milage, a load of crap.
Thread Starter
|
Posting Guru
Joined: Nov 2003
Posts: 1,858
Likes: 1
From: Dark side of the sun.
This next pay check i'll replace them with ACdelco plugs.....I still don't see whats wrong with champion but I'll take your word on it. It ran fine with the last plugs it had but they were old and wore out. I do have a set of Bosch wires on it though. And at a tune of over $50 a set,they're staying,lol.