Fuel Pump/P420 Question

[MSM2000]

My 2000 Safari has a Code P420. It lacks power when accelerating and stumbles, but cruises at 60mph on flat roads o.k. It just takes some time getting to that speed. I was convinced I was running rich because gas mileage has been falling or timing was out of whack somehow. I checked fuel pressure today and managed only 45 psi. I changed the fuel filter, but no change in pressure. I was under the impression these fuel pumps just quit working and did not necessarily start losing pressure. And would this cause my code? I wouldn't think a lean condition would cause this code. I expected a rich condition to cause it. Can anyone educate me please? Of course, I filled the tank yesterday before checking the pressure and now have to drive it until the gas is gone to change the pump. Any help would be greatly appreciated. Thank you.

[colinemckay]

P0420 is one of those funny, not-officially-supported codes that doesn't point to a specific problem.

My van (98 Safari) has been running with it for a while. I'll take care of the problem in the spring, when the weather gets better. It hasn't affected my gas mileage, at least not to any significant degree.

My research into the code for my van came up with the following possible causes:

1. EGR Valve
2. O2 Sensor
3. Catalytic

So I don't think your performance problems are related to the code. They sound like a fuel pump problem. 45 PSI is a little low.

However, I'm not a mechanic, nor do I play one on TV. So keep your fingers crossed, and hope that someone else replies!

[maxwedge]

60-65 is the normal fuel pressure .

[MSM2000]

I appreciate the inputs. I am going to recheck the fuel pressure with another gauge. Someone told me the thing shouldn't even run with less than 55 psi of pressure. I will probably change it out anyway since I already ordered one and this one has 137K+ on it. Thanks.

[thepolishmafia1337]

well sir it seems to me that you have a problem with an input to the cpu. code p420 means that the cpu thinks the engine is running lean and it has reached its enrichment limit so it throws a code. i would start with the basics, un metered air. or a failed within range mass air flow sensor or manifold absolute preassure sensor witch ever one you vehicle has. not too sure what the 4200 inline six has.if you have access to a scan tool check the PIDs air intake should be around 17-22kg with the ac on at idle.

[maxwedge]

Originally Posted by thepolishmafia1337

well sir it seems to me that you have a problem with an input to the cpu. code p420 means that the cpu thinks the engine is running lean and it has reached its enrichment limit so it throws a code. i would start with the basics, un metered air. or a failed within range mass air flow sensor or manifold absolute preassure sensor witch ever one you vehicle has. not too sure what the 4200 inline six has.if you have access to a scan tool check the PIDs air intake should be around 17-22kg with the ac on at idle.

P0420 is a cat efficiency code, does not mean the pcm percieves a lean mixture those are different codes, if they were set that would preclude the cat code, different issue. The Astro does not have a 4200 inline 6, it has 4.3 Vortech engine, different animal.

[maxwedge]

To add, the Astro has a 4.3 Vortec, not an inline 4200 .

[MSM2000]

I bought a new pressure gauge and come to find out, my fuel pressure is fine. She holds steady at 60 psi going down the road. But I still have the same problems, though it doesn't seem as bad. Because I'm used to it maybe? I took a 45 mile trip yesterday and she ran fine on level roads at 70 mph. But she would lose power on grades and getting to 70 mph took some time. I changed the coil tonight because I had a brand new one laying around. No change. The plug wires are brand new and the AC Delco cap/rotor are 8 months old. I keep thinking it's a timing issue. I'm officially stumped and am open to suggestions. Thanks in adavance.

[maxwedge]

Next I would make sure you fuel filter is clear or just replace it, then do a back pressure test on the cat convertor.