4.2L Sensor Locations Comments Page 2

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Question: Alternating idle RPM (Varies from 650 to 900). I have check, clean and replace throttle body, spark plugs, ignition coils, o2 sensors (both), air and fuel filters, fuel pump pressure, IAT and MAP sensors, and the truck idle RPM some days is fine some others is not, I am getting crazy about it, please help (calling from South America).
 Answer: It would help to know what year engine model vehicle you have. Is it car or truck. If the idle seems to be surging more when the engine is cold, you need to check for vacuum leak.

I swapped out a 4.3 v6 for a 4.3 later model Vortec v6. The truck was a 93 GMC Sonoma. I got the engine to run but the transmission won't shift. What makes the transmission shift on a 4l60e.
 If all you did was about the engine then that should not affect the transmission in any way. The sure to check your electrical connector and all fuses.

I'm looking for the mass air flow sensor on a 2003 GMC Envoy xl with 4.2 v6 I did a v8 but this is different, is it called by a different name. Love your site.
 The 4.2L straight six cylinder engine does not have a MAF sensor.

2002 Oldsmobile Bravada, i also have rough idle,and its shaking bad,.i have this after cleaning throttle body,changing spark plugs with ac Delco. Then i realize my camshaft actuator solenoid leaking,.At first i clean it and remove the oil from electrical connection, then it runs like new. But after 80kms it goes back shaking bad. So i did clean it again because i have to wait for my new parts,.So i put the new solenoid but after 70-80kms it happens again,.What should i do? Oh and i forgot to tell that every time i have rough and shaking idle i have blinking (CES) and then will stay.
 A blinking engine light means the engine misfire is bad enough to cause possible catalytic converter damage. The solenoid would not be causing your misfire. If it is only at a hit idle and goes away with a little throttle input, you may have leaking valves in a cylinder. This is a common problem on certain years.

This is a great website filled with lots of good info. Good job guys. I have a 2002 Chevrolet Trailblaer just got the a/c running again and it is working ok. The passenger side is cold. The driver side is not as cold but not warm. The original problem ended up being the button on control panel. I bypassed that with a toggle switch. Is there a reason the driver side is warmer. Also the rear vent with the power button and control nob does not work I don't think it ever has. Where do I start at to see whats going on with that?
 Sounds like the drivers side temperature door actuator is bad. It is located under the drivers side of the dash on the side of the center HVAC case. There are a few there, so look at the picture of the location when you are at the dealer buying the part.

Where is the location of mass air flow sensor for a 2005 GMC Envoy?
 There is no MAF on the 4200 engine. On the 5.3L v8 it is on the intake air duct.

Where is the schrader valve located on a 2004 GMC Envoy 4.2L to connect a fuel pressure test gauge?
 If it is not on the fuel line on the drivers side front of the valve cover, then it is located of on the fuel filter under the truck. It is a plastic valve tap.

I replaced a 4.2 in a 2004 trailblazer. This is one of the worst engines I've replaced. This is a salvage yard motor (known good). I have everything hooked up except for adding coolant (had to order an upper hose). I tried starting it and it won't start. I sprayed carb cleaner in the intake and it ran on that and died. When I crank, I don't get any oil pressure and the tach doesn't move. Not sure if I should get a tach reading without running or not.Do I have two problems going on? Maybe an oil pressure switch and a cam sensor? The came with the motor, could possibly been tipped over because I did have to replace the upper coolant hose tube on engine. I have checked atleast 10 times to be sure evrything is connected. Thanks for your time,I'm LOST!!!
 You probably wont see the tach or oil gauge move while cranking. You need a scanner for that. You have spark because it runs, to crank sensor and ignition or good. Sounds like no fuel pressure or injector pulse. Is the theft or security light on? Get a fuel pressure gauge on it. If you have pressure, then you do not have injector pulse signal.

2003 Chevy Trailblazer with the check engine light on. I had the codes ran at a local shop, and was told that the crank shaft sensor needs to be replaced. Where is it located????? I was also told there is a leak in the cooling system, but I dont know what that means. Please help!!!
 The crank position sensor on the 4.2L is located on the drivers side of the engine block. Can get to it through the wheel well or from under the truck. A leak in the cooling system means you have a antifreeze leak.

2002 OldsvBravada 4.2 inline 6. Service Engine Soon (SES) and Reduced Engine Power (REP). Restart clears REP. Multiple codes, but P1271 is always included. Dealer initially said they found rodent chewed wires and charged $500 to splice. Problem returned. Dealer then recommended replacement of the throttle body. After reading forums, I cleaned the throttle body assy (TBA). Problem returned. I replaced the throttle body with new. Problem returned. I replaced the Accelerator pedal assy (including the Accelerator Pedal Position Sensor module) with new. Problem returned. I pulled a wire out of the connector attached to the TBA. Replaced the 8 pin connector with new (with pigtail). This also replaced the splices the dealer had done to repair reported rodent chewed wires. Problem still exists. I'm looking for next steps. I strongly suspect a broken or shorted wire, but would like to know if there are logical places this is known to occur.
 If wires were chewed up and repaired, there may be more in other places than were first found. You are going to have to check all the harnesses. No common areas of broken wires.

Camshaft actuator & the camshaft position sensor was replaced and the oil pressure gauge still didnt work and the computer throws the same codes still .... why??
 OK, so what is the code? What makes you think that a cam actuator solenoid was going to fix an oil pressure problem on your truck?

2004 GMC Envoy xl with a 4.2l v6 my service engine soon light is on I replaced the map sensor and the light is still on i disconnected the battery for more than a half hour then reconnected it started it up the light was off turned the truck off and back on the light came on again its still reading the code for the map sensor need to get inspected but cant because of this.
 If replacing the sensor did not fix it, then you either have a wiring problem at the connector or toward the PCM, or something else causing that code. A vacuum leak or carbon in the throttle can also cause this.