Advice on codes: HELP A NOOB!!

[Electricat]

I recently purchased a Royal Blue '95 ATX SHO, 113K miles. It was non-running when I got it, replaced the CID and it ran great. The only code it was showing was a 326. The previous owner did a lot of work to the car, but the plug wires appear to be original, so replacement is obviously in order. No oil seen in the plugs wells.

The cats had been cut out by another previous owner, so I replaced the Y-pipe with a used one. It ran decent at first, but quickly (within 10mi.)got worse, now it idles and runs rough at all RPM's, and at one point had the cats glowing red. Checked codes, and here is what I got:

172 - Oxygen sensor not switching - system is or was lean - Single Right or Rear HO2S

173 - Oxygen sensor not switching - system is or was rich - Single Right or Rear HO2S

176 - Oxygen sensor not switching - system is or was lean Left or Front HO2S

326 - Pressure Feedback EGR shows low pressure EGR not seating or not seating intermittantly

332 - EGR did not open/respond during test or if memory code did not open intermittantly

335 - EGR feedback signal is/was out of range

542 - Fuel pump open bad ground or always on


I'm thinking to replace the plugs and wires, both O2 sensors, and the EGR valve.

I'm also concerned about the cats, and whether they were/now are damaged. No noticable rattles, but they got awful hot. Could they be a part of my problems? Any other suggestions on this?

I appreciate any help on this! I have a good automotive background, although the SHO is the most complex vehicle I have ever owned. I'm looking forward to learning and driving this thing!! It is discouraging to have problems with it right away like this though! THANKS in advance!

 

[rangerj]

Electricat,

Your O-2 sensors are failing. The connection and wiring is OK because the computer is still getting the signal. The sensors have stopped switching, or are taking a long time between switching from rich to lean, and back.

The O-2 sensor switch between rich and lean continuously, with every exaust pulse, and very rapidly when they are working correctly.

When the computer is not getting the information it expects (what it is programed to expect)from the O-2 sensors it runs the engine "rich" because this is safer for the engine. A lean engine can burn valves, and/or burn a hole in a piston.

The down side of this is the effect on the catylitic converters. A rich mixture will get the cats very hot, as evidensed by them glowing, or getting red hot. This can cause them to "melt down" if the condition is allowed to continue for too long.

Change your O-2 sensors, clean your EGR system (tubes - aka nostrils), and you most likely will have to replace the EGR valve. Check your EGR connections, but if the valve is the original change it.

When you are done with all this, and you experience a lack of power, check for a plugged up exhaust from the cats being melted and blocking the exhaust flow. If it has not gone on for too long the cats may still be servicable.rangerj

 

[Electricat]

rangerj, thanks for the help! What you said is generally what I was thinking, and I appreciate someone with SHO experience confirming it!

I have a bad feeling about the cats...I was following my wife in my truck when the car was having trouble, and it blow a piece of something glowing red out the tailpipe....I'm thinking it was a piece of cat!

As far as power levels, I haven't really got the car running out on the road yet, so I"m not sure how it should feel when it is running strong...If a cat is plugged, will it be fairly obvious?

<small>[ November 22, 2003, 01:41 AM: Message edited by: Electricat ]</small>

 

[projectSHO89]

rangerj covered it pretty well.

Just wanted to add that if the thermostat or the ECT were malfunctioning, it can also cause a rich mixture to dump into the cats.

If you pull that y-pipe again, it can be tested with an electric leaf blower for flow capacity. If it is restricted, you will hear a definite change of pitch of the blower motor.

While it may become obvious later whether the EGR valve itself needs replacement, it wouldn't spend those dolars just yet. There are several other things that should be checked first to see if it is good or bad.

Since you have the emmissions test to worry about most likely, putting the gutted y-pipe back on won't be an option.

I'd go with the plugs, wires, and the EGR nostril test and cleaning (if needed) as a start. That red chunk that was expelle was obviously something that was in your exhaust system. My guess was a bunch of crud that had been trapped in there during previous over-rich operation. For a chuck of cat to go through the resonator and a muffler doesn't seem very likely.

Steve in Florissant with ugly-red SHO.

 

[Electricat]

Thanks Steve! I've seen a lot of your posts on here, it seems like you know your stuff.

I actually live in Florissant also, near New Florissant and Lindbergh. Well...I only live here for a couple more hours tho....I am moving to Granite City today, bought a house!

<small>[ November 22, 2003, 09:51 AM: Message edited by: Electricat ]</small>

 

[projectSHO89]

Heh!

Wife and I just bought 5 acres out south of Pacific we intend to build a house on next year.

Back to the boonies for this old farm boy.

Steve

 

[rangerj]

Steve,

I've been trying to get my wife to do that for years. I want 5 acres in the "country", a 1700 to 2000 sq.ft. house, and a 3000 sq ft. pole barn with heat, water, electricity, and a hydrolic lift. She wants to be no more than 15 minutes from a Mall. Go figure! rangerj

 

[Electricat]

projectSHO89:
Heh!

Wife and I just bought 5 acres out south of Pacific we intend to build a house on next year.

Back to the boonies for this old farm boy.

Steve

NICE!! Good luck with the house! We were also looking to move out Pacific way, but couldn't find anything in our price range other than mobiles. Hoping the next place I buy will be in the country, but at least getting into a small town for now is an improvement. I'm just not cut out to be a city slicker!

I was thinking....I may have seen your car a while back at the Auto Zone on Lindbergh! It was a red first gen. SHO, kinda rough looking paint.

Thanks again guys for the help!