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I have a 1994 Chevy C1500, 5.7L engine.
My truck idled high and I finally got around to replacing the idle air control valve. This didn't fix the problem and it continued to idle high. I determined the issue to be a vacuum leak, so I replaced my vacuum hoses and checked connections. I tested by spraying carb cleaner and the engine still bogged down at this so I cleaned the throttle body and made a new gasket for the throttle body because that one was falling apart. After doing this, the truck began idling extremely low. It threw the EGR code, so I have since replaced the EGR valve and EGR solenoid. Neither of these fixed the problem. Next on the list is to replace the throttle body gasket along with the distributor cap and rotor. Additionally, my truck will also struggle to accelerate.
The confusing part is this- there seems to be no rhyme or reason as to the low idle. Sometimes, the truck idles in park at 800-900 RPM and is able to adjust the idle to the load of the AC being turned on. Other times, it idles in park at what is most likely 300-400 RPM because it doesn't even register on the gauge. It does not seem to have any consistency as to if the engine is hot or cold- it just seems to be whenever it feels like it. This evening, while working on it, it started straight up once and idled great at 800 or so RPM and handled AC and headlight load. While the AC was running, we unplugged the wire that makes the AC compressor run- this dropped the RPM down to around 700 and it never recovered from that. The truck was turned off and started again. This time it idled around 700. Truck was turned off and started again- this time it idled around 500-600. The truck was turned off and now it had to be given gas to start and idled low, around 400-500.
Any ideas to explain what is causing this? We are all going mad trying to troubleshoot this and figure it out. We've checked so many things and nothing seems to be causing the problem. Any help would be greatly appreciated.
I have a 2016 Sierra 1500 with the 5.3L engine, 111k miles. About 6 months ago I changed the spark plugs & wires and one of the wires accidently got pulled out by the stupid long bolt in the steering shaft that run way to close to one of the spark plug wires. The truck misfired but I was only a few miles from home. I limped it back, realized the problem, plugged the wire in and all seemed good. Unfortunately, 10 miles later the check engine light came on again, this time just showing P0420 code (catalyst efficiency below threshold, Bank 1). I changed all (4) of the O2 sensors, but the code came back after 10 miles. I then bit the bullet and changed the drivers side cat with a aftermarket weld-on from rockauto, nope. I then paid a muffler shop to replace the passengers side cat (generic) and fix my sad welding on the drivers side. The light stayed off for about 50 miles this time but as always came back on. I then tried to put a spacer between the 2 rear O2 sensors to pull them out of the exhaust stream, light on after 10 miles. I even tried plugging the old 2 rear o2 sensors in the wiring harness and just zip tying them to the frame so they were breathing fresh oxygen, but still the light! My mechanic is out of ideas and suggesting taking it to the stealership and having them replace both cats again with the OEM setup for @$2000. I have almost zero faith that will solve the problem and that it will just be more money that I don't have going into the trash, and the dealer will just shrug their shoulders. Any other suggestions of things to look at/try before jumping off that cliff? I am a backyard mechanic with just a basic OBD2 reader. I do know that all (4) O2 sensors are putting out voltage, but really don't know how to interpret that data.
By scott willman
Okay I have a random misfire code 300 302 304 307 replaced already o2 bank 1 upstream and down stream,new plugs,new wires,new coils, new injectors,maf and map, truck will idle fine then it won’t,check engine light will blink and then stay on,if it’s idling ruff and I take off it stumbles till I hit 25 or 30 mph and then I punch it and it runs fine for an hour down the freeway, then when I stop it may idle ruff or fine what is going on with this truck and it has a lot of power,help......gas engine no flex fuel
I installed a new 6.0 motor with high volume oil pump on my 2008 6.0 LTZ suburban. It has only 500 miles on it at the moment as of 9-5-2019. I installed a new intake, new throttle body, (relearned) new radiator, new plugs, wires, injectors, fuel pump and new heavy duty motor mounts, I have this slight shake at idle and you can feel it in the performance of the truck when driving down the freeway as if something is holding it back, Its not throwing any codes, engine light is not coming on. Had a guy that all he does is reprogram cars and trucks with his computers and when he hooked his high dollar stuff to the truck, the rpm went to zero while it was running and said it was a cam position sensor but when he disconnected it it went back to normal. my regular mechanic hooked up his diagnostic computer (Zuess) right after and it had no codes and we cant find out what is up. Maybe the guys high dollar stuff was messed up. Some guys are saying its the trucks computer but its not showing any codes, it runs fine but it should be absolutely purring like a kitty cat and there should not even be the slightest movement. The guy with the computers said that it has the fuel efficiency program on it that drops to 4 cylinders from 8 to save on fuel, he said the system was on and asked if I wanted it turned off for 250.00. I didn't do it. something is up and its driving me nuts. anybody have an idea at all? the #1 cylinder failed on the original motor and the traction control code came on and said it needed to be serviced. After the motor was replaced it did not come on again and there was no code for it as well. just for some history. Please help
By Chris Lee
Just replaced e driver side engine mount. After the install, my idle/park started rough idling specially it has more vibration and noise during Reverse. Any idea what could cause this?
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I have a 2003 silverado and am having issues. When i first start truck it will miss and sputter and idle will fluctuate for 10 to 15 seconds then will smooth out. when on road at WOT it loses power, feels very restricted, rough runs, misses and the check engine light comes on. Pull code and it is p0151 and p1031. the o2 sensors have been replaced. Any clues as to what i could look for? Could a leak in the intake cause that or a bad fuel pressure regulator? HELP!!!
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