P0304, P0175, P0172

(Sorry if this has already appeared. I originally sent it 8/31/05, but it has not appeared on my news server yet.)

A friend's 1997 Astro with a 4.3 liter engine has 245,000 miles on it. Recently, it started to miss. When I ran the scanner for codes, I got P0305 (misfire cylinder 5), P0175 (System too rich, bank 2), and P0172 (System too rich, bank 1).

With my limited knowledge, I suggested he do a complete tune-up: replace spark plugs (platinum), spark plug wires, rotor, distributor cap, fuel filter, air filter, pcv valve and run some Chevron Techron Fuel System Cleaner through it.

My friend said the cab company we drive for had done a complete tune-up some 25-30,000 miles ago so would replace the #5 spark plug and wire and use the Chevron Techron. We changed the spark plug, but could not find the correct single spark plug wire, so re-used the original one. The number five cylinder started to fire, but the number four cylinder stopped firing (P0304) The Chevron Techron did not correct the other problem. I suggested that he at least replace the distributor cap and the number 4 plug. He has done so, along with the 2 & 6 plugs and wires. He will replace the plugs and wires on the other side this week end.

When he replaced the distributor cap, he said a piece of metal fell out of one of the holes the wires go in, and when he replaced the #4 plug, the insulator was cracked. But against all my expectations, #4 cylinder is still missing. I ran the P0304 code, erased it, and it came right back.

I wanted to exhaust the cheaper things that I know how to do before suggesting anything expensive. My next thought is that the fuel injector for #4 cylinder is malfunctioning.

I suggested that he go to a garage that I have tried just for them to diagnose the problem and we could do the work if it was within our knowledge and abilities.

I personally have not ridden in it, but my buddy says it only misses at idle and smooths out as soon as he gives it any gas. I think it still misses at fast idle, but smooths out when he drives it.

Thanks in advance to anyone who has any suggestions.

Reply to
wkbrown
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Tell him to not be so cheap and replace ALL the wires and spark plugs, cap and rotor at the same time...regardless of the last tume up. 25,000 is a long time on that tired motor.

Eightupman

Reply to
Eightupman

You need to look at this from a wholistic standpoint. The engine is running rich on both banks, which pretty much rules out plugs, wires, cap/rotor and individual injectors. The missing is likely due to this rich condition, as you saw the miss jumping from bank 1 (plug 5) to bank 2 (plug 4), which again suggests a bigger problem than individial cylinder components.

The fuel pressure regulator or "spider assembley" inside the intake manifold is a likely cuprit and has known issues with blowing out and causing rich running conditions. If you pop the upper intake manifold plenum you'll be staring the spider assembley right in the face. Any presence of liquid gasoline in there suggests a failure.

Doc

Reply to
"Doc"

don't forget that the vacuum take-off point for the HVAC system is in the #

5 intake runner...................

Reply to
TranSurgeon

Exactly right. And I don't know the details of what the cab company replaced and what quality replacement parts they used.

The other driver seems rather careless about maintenance probably because he won't take off long enough to do what it takes to keep a cab running 80 or 90,000 miles a year.

Thank you for your input.

Reply to
Ken Brown

Thanks Doc, I am going to print out both replies I have gotten and pass them along to the other driver.

After I sent the first message, the other driver told me that the cab company is going to attempt to repair it because he can't get it through emissions inspection and therefore can't get new license plates until it passes. Your information still might help, because the mechanics at the cab company aren't very experienced and seem, like me, to be mostly parts changers rather than mechanics.

I have been reading and researching this group ever since I bought my Astro three years ago and a lot of smart people are good enough to take the time to answer questions for those of us not as mechanically gifted as they are. Thanks again.

Reply to
Ken Brown

I don't want to embarrass myself by speculating on what this means, but I will research it and find out.

Thank you for your reply.

Reply to
Ken Brown

VACUUM LEAK = LEAN MIXTURE IN # 5 = MISFIRE

Reply to
TranSurgeon

The g-man is back! How ya doin' bud?

Doc

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Reply to
"Doc"

Thanks for the clarification.

Reply to
Ken Brown

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