- March 7, 2016 at 9:32 pm #12801AnonymousInactive
I have a 02 GMC 1500 truck with a 5.3 that barely runs until warmed up. Has a 301 code (random misfire). If i park it inside it starts and runs fine, or if i plug it in it runs much better than without. I took it to GM and they threw about 600 bucks at it changing plugs, wires and a censor that i do not have details on. Still the same issue. The catalytic converter is new as well. Maybe the intake manifold gasket is shot? Please help.
REPLY: Yeah, I would bet on the intake gasket leaking (vacuum leak) and causing your misfire. The code P0301 is not a random misfire code, that would be a P0300. The P0301 is telling you there is a misfire on #1 cylinder. The corners are where the intake gaskets usually suck air from so that is the most probable cause of your issue. This also happens mainly when cold, and after it warms up the o-ring material on the gaskets expand and seal up the leak which then makes the truck run fine. Get those gaskets replaced and you’ll be back in great running order.
- March 7, 2016 at 9:32 pm #12941AnonymousInactive
2006 Chevy C1500 4.6L 125K miles. Code p0300 set when vehicle is on along up hill pull, check eng. light flashes then goes off after vehicle is out of the pull and code P0300 is set. Misfire data shows #1 cylinder is the misfiring cylinder. Tune up is new, compression is good and there are no vacuum leaks. Live data shows no problems. #1 plug and wire have been replaced a second time Problem will not show on a power brake test and shows no problem on scope. Has anyone had this problem in the past.
- March 7, 2016 at 9:32 pm #12793AnonymousInactive
I have a 2007 Chevy 1500 ls with a 4.3 motor. The truck won’t fire at all. It was starting but would cut off when it got hot. I have replaced the coil,icm, and cap and rotor. Still won’t start and has no fire. Anyone have any ideas?
- December 19, 2016 at 11:46 am #14407ProtechGuest
REPLY: Have you checked for spark? COMPRESSION? Fuel Pressure? Any trouble codes? Plenty of things can be causing your truck to not start, even a security issue.
- March 13, 2016 at 8:16 pm #12905AnonymousInactive
I have a 1997 Chevy 1500 4×4 with 5.7 vortex. My problem is when you start it up and runs a little #1-4 injectors quit, could it be the wiring harness or fuel injector, or something else?
- November 11, 2017 at 9:41 pm #16329AnonymousInactive
You could have a couple faulty fuel injectors, I’ve replaced quite a few over the years. Also, check the big connector at the top of the plenum for any corrosion, loose terminals or broken/chaffed wires.
If the wiring looks ok, you can try a can of injector cleaner first to see if it will clear up your problem. If not, I’d recommend replacing all eight injectors if you have to take it apart. You will surely need to do others very soon if you don’t.
- March 13, 2016 at 8:16 pm #12903AnonymousInactive
Truck was starting fine. It sat for a few days and now it just cranks like it wants to start but won’t. Tried using starting fluid with no luck. It did this once before but after a few times of cranking it and flooring the gas pedal it started but ran kinda sluggish for a minute or so. To me it sounds like the fuel regulator but i am unable to find it. Anyone know where to find it on 5.7L.
- November 11, 2017 at 9:38 pm #16326AnonymousInactive
On the 5.7 engines, the fuel pressure regulator is inside the upper intake manifold (plenum). You can’t examine it without removing the plenum first. From what you describe, I would recommend doing a fuel pressure check, it really sounds like you have a bad fuel pump.
- March 13, 2016 at 8:29 pm #12912AnonymousInactive
Here we go. Started with a really rough idle checked the code found only a P0306. Changed the spark plugs and wires. Checked the coil pack ends ok. I can hear the fuel injector working (screw driver to the ear trick) did a vacuum check and had a steady reading of 10 off the brake booster. While the car was running idle it stalled and now it wont even crank the motor. Was able to turn the pulley bolt on the motor don’t think it seized. Must be electrical. Any help?
- November 11, 2017 at 10:08 pm #16339AnonymousInactive
If it won’t crank at all, I’d first check the starter. Check for power on the purple wire when the key is in the ‘crank’ position. If you have it, then you have a bad starter…if not, check wiring, computer, fuses, relays, ignition system, etc…
- September 7, 2016 at 6:55 am #16025Lisa R WileyGuest
After replacing front driver side caliper and bleeding breaks, the break petal goes to the floor.
- August 13, 2017 at 11:19 pm #16033AnonymousInactive
I must assume you know the proper way to bleed brakes. May be silly, but you have no idea how many people think they know how to bleed brakes, but do not.
Crack open the bleeder on the caliper, let it gravity bleed for a few minutes. Close the bleeder.
Press the brake pedal several times, hold it down, crack the bleeder.
You should notice the brake pedal drop when the bleeder is opened.
Close bleeder then release pedal.
Do this several times.
If the pedal never drops when opening the bleeder, you are not getting any pressure in that caliper. You may have a bad caliper.
- September 7, 2016 at 6:55 am #14037Brandon millerGuest
So I have a 07 gmc envoy with 4.2 vortex. My wife keeps up with all maintenance at the dealership. Drove it last week to do some running ran just fine. No misses, ac worked, had no loss of power and wasn’t hard to start. The next day she was going down the interstate and it just died. Got it towed back home and pulled the codes. It had mass air flow, and 3 missfires. I put new mass flow seansor on it and all coils and spark plugs plus cleaned throttle body. Reset with battery and jumped it to see if better. Won’t start unless foot is on the pedal and when it starts it really rough and dies when u let off. It threw another code of p0300, checked spark plugs, all good. But notice oil comming up from intake into throttle body. Figured it was from trying to keep starting it. So I changed map sensor, exhaust camshaft sensor, and cleaned crank selenoid. About to change battery and coolant switch hoping that’s it. Please if u can help let me know. Any ideas, but remember I don’t have tech tool to read real time. Thank u.
- September 10, 2016 at 10:42 am #14049Jimmy tGuest
Check that the PCV line )no actual valve) is not plugged or disconnected under the air cleaner box.
Go through the drivers side wheel well and make sure the intake bolts are not loose. The rear ones are most common to come loose.
- October 16, 2017 at 11:00 pm #16196AnonymousInactive
Thanks for the correction on the codes. It is in fact a 300 as opposed to my original claim of a 301. Is there any way to check if the manifold is cracked once i have it off? Maybe it would be visual? I hear people are going ahead and purchasing after market aluminum units instead of using the original plastic ones. What do you suggest? I will let you know how things work out after the repair.
- October 16, 2017 at 11:01 pm #16197AnonymousInactive
I’ve probably done 50 or more intake gasket sets to those engines and have yet to see a cracked intake manifold. I would take a look when you have it off for sure, just to check, but you’ll probably be fine keeping the original unit. I would definitely recommend using GM gaskets, and not any type of aftermarket set. I’ve seen the Fel-Pro gaskets leak almost immediately after replacement on some. Stick with the GM parts and you’ll never go wrong
Viewing 9 reply threads
Viewing 9 reply threads