Question about 2002 GMC Sonoma Extended Cab
Random misfires. Replaced all wires, cap, button, plugs, spider injector, coil, coil pick up, No manifold or vac leaks. 2 yr old fuel pump, new battery. Has dist. shaft removed and inspected. Told there is no EGR valve on this model to replace. New fuel filter. K&N air filter. New MAF sensor.
I had the same exact problem with my 2000 blazer. I replaced the same things you did. It didn't matter what i did to it i still had the same problem. There was a heavy smell of gas when it was running and a lot of smoke. Here's what i did to fix this. After i replaced the spider injection ($350) i still had the problem so i figured something was telling this thing to stay wide open, which is constantly pouring gas on the spark plugs. Next i unhooked the wiring harness that plugs into the new spider injection (the one on top with about 12 wires). Then i set my multimeter to ohms and grounded the black one and then check each contact inside that harness. I forget now but i'm pretty sure 6 of those should be grounded and the other 6 pulse a signal. Anyway i found that 1 wire that shouldn't be a ground was so i traced that wire back and found a very small crack and instead of being orange about a 1/4 inch of the wire was green. I replaced a section of wire here put on some shrink wrap and it started and ran like new again. I only wish i would have spotted this before i started guessing and spending and listening to know it all's. I don't think i had the key on when i was i checking to see what wires were grounded. Let me know if this helps you.
Posted on Apr 18, 2014
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Posted on Jan 02, 2017
SOURCE: Misfires 96 gmc sierra 5.0
I suggest you have the injectors tested by the dealer, the sludge buildup will not cause a miss fire. to clean the throttle body use carberator spray while holding the engine idle high.
Posted on Aug 05, 2009
2 things come to mind, confirm you have proper fuel pressure, and if you've got a MAF (mass air flow sensor)
in the intake hose to throttle body, remove it, and spray it clean with Tuner spray cleaner, or electrical spray cleaner from radio shack or similar store, and then try it. Not uncommon for the MAF sensor to dirty and cause what your experiencing. If that doesn't cure it, start checking EGR and EVAP system.
Posted on Mar 02, 2010
Unfortunetly....these spider injectors and fuel pumps can have very similar symptoms when failing. What I do know is I work on this motor more than any other motor in my shop. Very common with fuel problems...and I can comfortably tell you that they updated the injector kits on these car for a reason. The original model is junk. I have done these on just about every one of my cutomers vehicles over 150,000 miles. However, I am not going to tell you that is your problem....but it sounds fuel related. Did/does your vehicle skip? Leaking injectors will usually cause a skip due to shortage of fuel to that cylinder. I also have a computer that allows me to monitor the firing of each cylinder, and do an injector kill test. This is what I would do first. Unfortunetly, sounds like you can't so start with this: Clean your throttle body. The pintle that the IAC motor pushes in and out goes into a small port. Spray that port out with carb clean. Get a fine wire brush and get that throttle body clean and shinny. That pintle can easily stick on existing carbon in that port...new part or not. Check for vacuum leaking with carb clean...spray it around the intake and vacuum hoses...see if any particular spot changes how it runs when you spray it. Do you have a vacuum gauge? what is manifold vacuum? Since you are in the intake...make sure your puddled fuel is not due to pulling the main lines off the the injector assembly. After intake is off. hook fuel lines and harnes back up to injector assembly. key up (no start) vehicle...this pressurizes fuel system. look for leaking. The fuel pressure regulator is built on to the side of that assembly....its the round diaphragm with the tube coming out of it. If it leaks fuel out...that may be your problem. And you can replace that without doing the whole injector kit...fairly cheap. If not fixed....what is your fuel pressure. You need to have 60-64 PSI at key up. Try the carbon build up and intake test first...both quick, easy, and cheap. If this is not your issues...its sounds fuel related....just want to confirm that you don have a misfire/skip. That could change diagnosis quite a bit. Keep me posted....more than happy to help. By the way....I own all GM's too...lol...haven't learned my lesson yet
Posted on Nov 14, 2010
SOURCE: 1998 gmc k1500 random misfires
There is more than just ignition that could be the issue, including fuel injectors and EGR. Try this link to see if you get more ideas:
Posted on Nov 26, 2010
SOURCE: My 2001 GMC Safari has
Look and make sure your computer is good! PCM could be failing you! Injectors don't really go bad! Also look at you fuel pressure make sure it's strong!
Posted on Sep 05, 2011
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A code P0300 may mean that one or more of the following has happened:
If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders ( spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.
Random misfires that jump around from one cylinder to another (read: P030x codes) also will set a P0300 code. The underlying cause is often a lean fuel condition, which may be due to a vacuum leak in the intake manifold or unmetered air getting past the airflow sensor, or an EGR valve that is stuck open
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