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2003 8.1 Hard start and Multiple Misfire help... Crank Sensor?


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Hello just bought a 2003 2500hd Avalanche. Truck runs and drives great, little stumble at idle not sure if that's how they idle or not, picks up and goes great, plenty of power. Some times when I go to start it it starts right Up or sometimes it will crank and crank and crank without starting unless you turn it back to off and then try it again it will start up instantly. Also while I was driving I got a engine light and had the code read and said multiple cylinder misfire. I've read some posts saying fuel regulator and a lot of posts about the crank sensor. Also have an issue with the heat only coming out on the passenger side and cool air from the driver side. I believe it's the blend door. Any tips or tricks or thoughts about what the issues could be would be a awesome thanks guys

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HVAC: Probably a blend door actuator. Their failure is common on these pickups; unfortunately, that doesn't make the repair any easier.

 

Long crank: Check fuel pressure with the key on and engine off. Spec is 55-62 PSI on 4.8/5.3/6.0 pickups. May be different for the 8.1. More specifically, leave the key on and see how long it takes for pressure to bleed down. I'm willing to bet your fuel pressure is bleeding down after the pickup sits for a while.

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Ok so I went out this morning and I cycled the key on and off 3 times without cranking the truck, then on the 4th time the truck started right up perfect. I'm going to check the pressure today, I also am going to check the regulator I've read that they are prone to issues.

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I had a 2500 Avy- check your plugs- use only AC delco or NGK no Bosch or E3. Check your MAF and throttle body- clean them. Are you getting codes- CEL?

 

The CPS usually just dies, rarely does it cause a mis fire. Check your plug wires too. How many miles on the Av?

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Just an update cleaned the throttle body and it runs better actually starts up without having to let off the key and get back into it but still a little stumble at idle I find it's a little worse when in drive like coming to a stop, can feel it in the truck, cleared the p0300 code I was getting and drove it around then the code came back after a drive cycle but now it says misfire on cylinder 1.... I just sprayed some throttle body cleaner in the throttle body, I'm thinking maybe if I take it off and clean it totally and thoroughly it will cure my issue....

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Still has the hard start issue and stumble but only when stopped in drive. Also has no heat on driver side but passenger side works.... Going to check the fuel pressure again tomorrow make sure she's good

Still has the hard start issue and stumble but only when stopped in drive. Also has no heat on driver side but passenger side works.... Going to check the fuel pressure again tomorrow make sure she's good

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