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First off thanks for being awesome Astro crew. I’m a Chef and not the best at wrenching’ I have a ‘03 Astro AWD lifted with 97,000, 34” super camper, and completely customed interior with security gate, insulation, compost toilet, sink, 1000watts lithium batteries, 210watts solar, 2 person extra long twin bed. For the life of me, I can’t find a mechanic that can fix my P0302 “service engine” warnings when I am climbing up hills and putting the throttle to the floor at around 60mph in 4th gear. If you or someone you know within 100miles of the Bay Area can fix the problem, I will Venmo you $100 bucks after the service engine light stops coming on, no BS. I’ve been to 5 mechanics, zero have been able to diagnose the problem, and these mechanics are highly rated/recommended from others. Hope to get some good insights and get on with some other work I know how to do. Thanks for reading!
 

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First off thanks for being awesome Astro crew. I’m a Chef and not the best at wrenching’ I have a ‘03 Astro AWD lifted with 97,000, 34” super camper, and completely customed interior with security gate, insulation, compost toilet, sink, 1000watts lithium batteries, 210watts solar, 2 person extra long twin bed. For the life of me, I can’t find a mechanic that can fix my P0302 “service engine” warnings when I am climbing up hills and putting the throttle to the floor at around 60mph in 4th gear. If you or someone you know within 100miles of the Bay Area can fix the problem, I will Venmo you $100 bucks after the service engine light stops coming on, no BS. I’ve been to 5 mechanics, zero have been able to diagnose the problem, and these mechanics are highly rated/recommended from others. Hope to get some good insights and get on with some other work I know how to do. Thanks for reading!
Remove your engine cover and start your car.

Since this is cylinder 2 misfire code. Pull cyl 2 spark plug wire. If the engine was rough and there was no change. Than cyl 2 spark plug, wire and coil are suspect.

If the car runs smooth at idle and pulling plug 2 cause the engine to run rough. Then let’s look at another simple issue.

Does the engine run rough when loaded going up a hill or in hot weather?

If it misfires when hot, then the simple fix is to flush your radiator, get new thermostat and radiator cap. When radiator caps get old they blow out the antifreeze into the overflow tank at below 16 psi. Sometimes as low as 4 psi. This gives the false impression you have enough antifreeze, but in reality, it’s created a steam pocket in your heads. The localized hot spot can cause misfire under load or hot weather.

Also try these tests

1). Start your engine and open the gas cap. If the engine gets rough and replacing the gas cap still have the engine running rough, change your gas cap. A leaky gas cap can vent Evap can vapors into the intake with uneven gas distribution and misfire. $20

2). When was the last time you changed your oil filler cap. Start your engine and remove the oil filler cap. If the engine was running rough before removal and no change after removal. Change your oil filler cap to prevent vacuum leak. Check your dip-stick, or better replace the dip-stick O-rings to prevent vacuum leak. $20

3). When was the last time you clean or changed your PCV. Stuck PCV can cause too much oil vapor from entering into the intake manifold. This can cause misfire. $10

4). California cars have EGR. These valves are known to clog, corrode and cause misfire by sending too much exhaust gas into the intake manifold. This vapor can be concentrated towards one cyl, #2 misfire. Clean cost $15 in cleaning fluids or. $150 for new EGR with gasket.

Otherwise, perform a tune-up. Replace plug wires. Get new iridium spark plug and gap them. Change your air filter, oil/filter, and fuel filter. Perform a fuel system cleaning, get full tank of pure premium petroleum gas and 10 oz chevron Techron.

DIY service should cost less than $250 for everything.

Best Wishes

The last item to check are your O2 Sensors. But this would be global issue with an entire bank of cyl. Misfiring. The O2 Sensors start going bonkers around 150K-200K miles. The harder you drive your van with a load the quicker the O2 sensors go out. This manifest itself as rough idle and rough acceleration getting away from stop light. The idle mixture, acceleration from stop and cold engine operation need the most careful calibration. When the o2 sensor starts to go these are the points that starts to get rough and wobbly running.

Best Wishes.
 

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Common Sense + Critical Thinking
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He did state that it only happens under two conditions. Should get an evap code if the cap/etc is leaking. His van will not have an EGR either.
 

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I know I sound like a broken record, but I too have a '03 that had a P0302 misfire for over 9 months. No one could figure it out. I almost drove it off a cliff, just for fun, b/c I was so frustrated. ALL of my issues were fixed when I found a TSB on codes P0300 and/or P0335. It has to do with the CKP sensor. I had replaced it early on along with a multitude of other parts at the same time. the TSB states that if you change the CKP, you need to 1.) check the Depth for proper clearance and it may require 1 or 2 shims and 2.) check the timing cover for damage, if cracked, replace. my NEW CKP didn't come with shims so I had no idea about SHIMS. 1 shim, no codes, no misfire. Do yourself a HUGE favor, check it... mine had hairline scratches on it, that you could barely see, so it was making contact with the reluctor ring. FYI, I know you have a specific P0302 code, but I did too. I think it was b/c that cylinder had the most, but if you hooked up to a scan tool that can monitor, most, if not all of the cylinders would misfire.
 

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I had replaced it early on along with a multitude of other parts at the same time. the TSB states that if you change the CKP, you need to 1.) check the Depth for proper clearance and it make require 1 or 2 shims and 2.) check the timing cover for damage, if cracked, replace. my NEW CKP didn't come with shims so I had no idea about SHIMS. 1 shim, no codes, no misfire. Do yourself a HUGE favor, check it... mine had hairline scratches on it, that you could barely see, so it was making contact with the reluctor ring. FYI, I know you have a specific P0302 code, but I did too. I think it was b/c that cylinder had the most, but if you hooked up to a scan tool that can monitor, most if not all cylinders, would misfire.
I was thinking along these lines as well, wondering if the CKP had been changed without checking/shimming.
 
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