I have 97 Chevy silverado 350 5.7. When I start it up the truck runs good for about a minute or so. When the idle comes down to normal it starts to stumble and the rpms go up and down. Has new plugs, wires, cap and rotor. Just changed the map sensor today and it still does it. I decided to see what would happen if I just unplugged the map sensor to see what it would do and when I did it the motor ran ran good . It stopped stumbling and all. Not sure what the problem is. Should I leave it unplugged. Is it another sensor. I have heard it might be the coolant temp sensor. Need yall help.

 

Throwing any codes?

 

No codes are coming on. I don't understand when I unplug the map sensor it runs right.

 

Check the intake system to make sure it's not cracked or hose is ripped. Sounds like a leak behind the maf. When did this start happening?

 

If he needed a new sensor, it would have thrown a code, right?

 

Not sure how long. But I just changed the spider injection not to long ago and had to take all that off. Iwill have to go over it tomorrow when I get a chance. Could it might also be a upper manifold leak. Like I said I had to take all that off to change the spider.

 

Sensors give false readings sometimes that cause the ECM/PCM to adjust in improper ways. So basically you got troubleshoot the problem. Even if it does thrown a code, you still have to determine if it's the sensor or something else causing the problem.

 

LAOutlaw. I have a '72 Cutlass being built for me with the 350/carb'd, and this would make a great write up with picks if your going to tear anything apart.

 

Have you tried cleaning the MAF sensor?

 

Squirt the oval area where the electrical connector for injectors is located if the idle changes the oring is not sealing correctly. One other thing to note and I have seen DIY's do it on these older trucks is they do not get the correct injector installed into the correct cylinder. It will run with this very same problem if the injectors are not installed in the correct cylinders. You gotta look real close at the injector body to verify the number on it before installing. They do not install front to back in order like you think they would.