2005 jimmy p300 code

[redneck01]

i have an 05 jimmy with 260000 km on it i have owned since new. the sunday just passed i was headding down the hwy at 130 kph and the truck died. i pulled over and looked under the hood to find the air cleaner hose disconected. i tried to restart but nothing it would just turn over, at one point i thought it might start but nothing. towed it home and replaced the coil and distributer cap and rotor and it fired right up. today was the first time i tried to take it to work and as soon as i got on the hwy and it got up to running temp it shut down but not totaly. it wont get up over 80kph and it takes a lonk long time to get there. i got it home and hooked it up to my code reader and mass flow problem came up so i changed the mass air flow censor as well as the ignition modual as well as new set of wires. but it still runns bad and cant revi it up over 3000rpm, even in nuteral. hooked up the code reader again and i get the p300 code for random missfire. also upper and lower rad hose were sucked flat. had to open the rad cap to get them back to a round shape. I have been hard on this truck like everother chev i have and this is the first problem i have had with it. any ideas on what is going on? i am thinking intake gasket but it just stoped running at hwy speeds and i dont think an intake gasket would do that.....

 

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[Jsdirt]

You need a new radiator cap.

 

As for the misfire, I parted out a '00 Jimmy that had the same problem. At that point I'd had enough. Check engine lights every week for 2 years straight will do that to ya ... but that random misfire could be anything from the injector spider leaking, or fuel pressure regulator, to leaky intake gaskets, ignition problems, or in rare instances a partially failed crank position sensor.

 

I took that same engine, removed all electronics, & installed it in a '89 S10 with a carb & HEI ignition - it went from breaking down every week (in the Jimmy) to the most reliable vehicle in my fleet. Better throttle response & performance too. Electronics are wonderful .......... when they're new.

[redneck01]

there are no fuel leaks and i tested the intake gasket and it is has no leaks either. i am thinking fuel pump, crank position censor or fuel reg. Also to elaborate on the back ground of the truck.... I live in northern ontario canada and this past winter if i left the truck for more then two days in the cold with out starting it i would have to turn it over for an hour holding the fuel pedel to the floor to ge ti to start. also latley befor the big break down it would have a misfire when started but would go away once it wormed up. i will run the truck with the rad cap loose but right now it is in my garage as i cant drive it at all.... i have a wife and three sons and we as a family need this truck to run so any help would be awsome guys!

 

I am picking up a 86 k5 blazer as my new dd but untill it is ready this is all i have. i dont have cash for a new truck so i bought an old one, plus i can fix anything on it. but this is still needed so please if you have any idea let me know!