BrassRing

Recently, both of my pre-cats and main cat failed b/c the pre-cats were running too hot and blew their contents into the main cat, plugging it up. Next, I changed the plugs, wires, oil & filter, O2 sensor, and checked the base timing. Also, no codes.

The pre-cats still glow in the rear section where they reduce to the pipe leading to the main cat. My mechanic wants me to replace the Hypertech chip with OEM. I hear the Hypertech chip doesn't fatten up the fuel mixture and probably isn't the source of my problem.

What do you all think? Could the computer and/or chip be wigging out on me? What should I try next? Thanks in advance for any ideas you have. I've been working slowly on my car since September. My frustration says I need to balance out my wrenching with driving!

BADDUCK

Maybe now you are simply running too lean. Could be the chip.

vinnies87

stock chip for stock car is prob the best position to be in, nothing but poor things about Hype chips... but, wondering if you still may have something plugged up or partial plug...

Kool88vette

I doubt that the chip is the problem. I ran a Hypertech thermomaster for 2 years without any problems. They are basically stock chips with minor changes.

Brimis

Could be something is clogged. I had the same problem and my converter was shot.

BrassRing

I just re-read my initial post and realized I forgot to mention that I replaced all three cats. with MagnaFlows. So I can't imagine there is anything plugged up.

Does anyone have a stock OEM chip they would like to unload?
Or is anyone willing to meet me and swap computers for a few miles to see if that is the problem? I'd hate to spend the bucks on a reman'd computer and chip (I can't find any OEM chips so I think I have to ask a tuner to program me a stock chip - sounds wierd) when I'm not sure they are my problem. Thanks.

rtracy

Hello BrassRing! Did the problem start after you put the aftermarket chip in it? If it did try putting the stock chip back in it. Also did you drop or hit the o2 sensors at any time? It doesn't take much to ruin a o2 sensor. Usually it will make the car run rough if you have a bad o2. That's what was wrong with mine when the cats glowed red.

Kool88vette

I have a 88 chip. I think it will work. Where in the Bay area are you? I could send it priority mail. I'm near Sacramento so you would get it quick.

wayne lowry

When the cats were replaced were the exhaust pipes cleaned out as well ? If they were not you could have very easily clogged up the new units. I have a stock 85 chip you can have if you like.

Kool88vette

That makes sense, I don't think it's the chip.

VtVette

Start at the front of the exhaust and tap the exhaust with a rubber hammer (or even the palm of your hand) working your way back to the rear of the car. If pieces of the old cat are still in the exhaust you may well hear them rattling around.

Cats went bad and blocked exhaust causing cats to get red hot. Cats were replaced. Then chip went bad and caused the exact same symptom in the new cats? I don't buy it. Most likely you still have pieces of the original cats lodged in the pipe. When performing the above test be sure to pay particular attention to the mufflers. Small pieces of the cat can make it's way through the exhaust but they will usually get lodged in the baffles in the mufflers.

edcmat-l1

Something caused the cats to overheat in the first place. I have seen plenty of exhaust systems with hi back pressure that didnt make the cats glow. The one thing that causes this is too much fuel. I have been doing emissions diagnosis and repair for years, and I've never seen a lean condition cause it. Excess Oxygen is not harmful to a cat. Excess fuel is. It can be coming from several sources other than the chip. You need to scan it and see if the computer is trying to pull fuel back out. Negative fuel trims.

VtVette

I gathered from his original post that the cat failed, plugged the pipe and caused the overheating issue. This just happened on my pickup this past weekend. Cat disintegrated internally blocking the exhaust and caused the cat to glow red. Good point on the fuel damaging the cat, rich engine will block a cat in no time. I think the assumption made by others is that a lean condition will cause the engine (and subsequently the exhaust) to superheat and effectively you will get the glowing red condition but it's the headers that glow in that case not the cats.

You figure there is an underlying cause to the failure of the cat, not just age? I thought about a rich condition but I assumed (and that could be the problem here) that very shortly after installing the new cats the new cats were glowing. If it was raw fuel in the form of a rich condition that caused the cat failure it would have taken some time to contaminate the new cats as well?

CorvAdel

Before replacing anything, if it was me, I would be checking fuel pressure at the rail...if the regulator has dumped, it may be contributing to an excess fuel situation...and it won't cost much in time and bux to check.

cv67

Get your A/F ratio checked. Do you know anyone who can scan it?
Chips almost never "go bad."

Casethecorvetteman

Its probably running fatter than the baker's wife mate, that will make them glow after a while.....

Pelleplutt

Have you replaced the ever failing multech/rochester injectors ,if so with what ?

Pelle

-90 vert

BrassRing

Thanks for the chip offers. I called a GM dealer today and they said that the 85 and 88 chips are different than the 90. When I bought the car, the Hypertech Thermomaster chip was already installed. The guy didn't keep the OEM chip.

I hope my guy cleaned out the pipes before welding in the new cats! He's closed on Mondays so I'm calling him tomorrow. This weekend, I'll have to crawl back under there and bang around on the pipes, as was suggested...and maybe take off the mufflers if I get desperate.

I'm pretty sure my original cats failed due to over heating. The tunnel used to get pretty hot against my leg. I found the fuel injector balance test in the GM shop manual just a few minutes ago. Maybe an injector/s are or regulator going foul? Several of you mentioned A/F mixture issues, injectors, pressures etc. Anyone recommend any particular fuel pressure gauge and injector tester (OTC 3398?)?

Thanks for the dialog everyone. This is helping me.

RandyJ75

If you have loose pieces of the old cat in the exhaust system, you will hear them "rattle" when the exhaust gets hot.
Ask me how I know...