My old Astro, driven by son in law, 2000 AWD cargo w/ 152000 miles.
He complains that the truck misses badly. History, coil burnt up at 130,000, replaced coil, cap, plugs...Fuel pump failed at 140000.

Read codes, found multiple cylinder misfire code P0300?. O2 sensor not ready, cat not ready, HO2 not ready. Evap system not ready.

Saw (3) O2 sensors, left, right and rear. Ended up replacing right and rear sensors after nor reading any resistance on sensor during operation.

This reduced the system information to HO2 not ready, evap system not ready.

Couple of questions:
Is the HO2 the left O2 sensor?
Is their a shrader valve to test fuel pressure, I looked but lost the daylight by then? Where is it?(engine idles rough)
Is their a common vacuum leak area?(engine idles rough)

I think that the 'computer' looks for the sensors before going from open loop to closed loop, is that correct.

Thanks for the help.

 

I also had a 2000 with this problem. The P0300 is usually caused by dirty fuel injectors. In my case doing a Seafoam treatment solved the issue, so I'd try that first. If the Seafoam doesn't work GM has some stronger stuff called GM Fuel System Treatment Plus, but it's like $30 a bottle.

The other thing that will cause the P0300 is worn distributor gear/bushing.

I'd focus on the P0300 before touching anything else, as the not ready statuses are usually the computer needing to see GM's drive cycle.

I currently don't think fuel pressure is an issue for you, but the valve is under the engine cover on the left/rear side of the engine.

 

I wonder if the fuel line could be clogged also since the filter was completely blocked?

 

I kinda doubt it. In my 14 years of Astros, across many forums, I've never heard of a fuel line clog.

 

SIL tried to demonstrate the miss to me on recent night. Truck ran fine. He said the the fuel gauge needle moved around and that mechanic told him it was intergral to the fuel pump. That had me thinking about fuel pump.

Seafoam and gas treatment are worth a try and can't hurt.

To evaluate the dist. bush do you look for play shaft twisting or sideways movement or just replace the dist while you have it open. I'll have a few hours on Sunday to make checks.

 

Took another shot at it last Sat. Changed spark plugs, Local auto parts store didn't have ac delco, so no cap and rotor. Did the seafoam from both ends. Still misses on light load.

 

When the cap and rotor were done at 130k, was ACDelco parts used? There is a history of lesser brands failing in the heat of the Astro's engine bay.

 

Will replace the cap and rotor this weekend. Can't find ac delco without 5 day wait. Going with NAPA's best. If it cures the problem for the short term, that's it.

Will post results.

 

Changed the cap and rotor, and the motor has not had a mis-fit all week. I was doubtful, but the proof is in the driving. Thanks for the help.

O2 sensor - not
fuel pressure - not
spark plugs - not

 

Sweet, good to hear.