Hey guys... Let me bring you up to speed on my truck before I post the question...

I bought a 98 Rodeo with a Supercharger on it and various other performance upgrades (ECU Upgrade, Piggyback ECU, Borla Cat-back, etc). It's got ~50k on it...

Anyway, when I got it about two months ago, I found that laying on the throttle for extended bursts (as just about anyone would do when they first get a Supercharger <img src="/forums/images/graemlins/smile.gif" alt="" />) caused a FLASHING, then steady check engine light. The code I got from this said something about random misfire, and I also got something about the MAF.

Anyway, I replaced the MAF, and did the plugs and PCV...

Still got the same light.

Still haven't replaced the fuel filter, but I have it in the back of the truck and I will one of these days. Anyway, checked for vacuum leaks, found none. Still the same light.

Doing something unrelated (replacing empty slot with 6-disc changer from 98 Amigo) I found that the piggyback ECU was installed very poorly. The engine harness wires were cut and the piggyback ECU was spliced in... 'Cept the wires weren't crimped on or soldered or anything. They were just twisted together with some loose electrical tape on there. What the hell kinda crap is that? Anyway... I didn't have the time or the tools to fix it the right way, but I did a better job of doing it the half-assed way anyway...

Now, this was three weeks ago. Since then, no flashing CEL, no CEL at all...

However, in the meantime, way back when I got the first flashing CEL, I also had some sputtering, wandering idle, and even stalling. Far more noticeable after a period of sitting idle. Now that I seem to have somehow solved my flashing-then-steady CEL, I still have the sputtering and stalling, the wandering idle, etc. It also seems like it lacks a bit of power. Not much, but enough that I feel it, or at least enough that I've convinced myself I feel it anyway. <img src="/forums/images/graemlins/wink.gif" alt="" />

That being said, at this point, I'm thinking the cats (or at least one of them) are on their way out. Dunno if this was caused by the conditions present during the flashing CEL (Flashing CEL means "Catalyst Damaging Misfire") or if it's something that's just occurred over time, but in any event, it looks like that's what I'm looking at...

Side note, dunno if it's related or not, but I swear I caught a puff of black smoke out of the corner of my eye in the rearview tonight when I passed some idiot who didn't know where he was going... Related? Some unrelated gremlin? IIRC, black smoke means running rich... Result of a bad cat??

Anyone feel like backing up my theories? Or am I barking up the wrong tree?

How does one find out if their cats are shot? Is there a test for this? Does anyone do it for free? (AutoZone?)

If I'm looking at replacement cats anyway, what's out there that I can replace them with to at least get an upgrade out of my repair?

Thanks in advance guys,
Chris

http://www.automotiveforums.com/vbulletin/showthread.php?t=380400

Maybe you have a bad TPS

Chris,

Not sure about the idle problem, but if you are going to replcae the cat use a hi-flow cat? I'm not sure of the actual name but I got one installed...nice.

One of these days I would love to make it up your way....I'm not that far from you ...close to New Brunswick these days.....

Mine has the old chevy 3.1 so I'm not sure how much help...But I would love to see it wiht a timing light....

matt

or a short in the wireharness, read towards the bottom of this post:

http://www.automotiveforums.com/vbulletin/showthread.php?t=368175&highlight=harness

Before I replaced anything I would get all the wiring connections straightened out. That could be causing all your problems and you could be chasing nothing. Not saying that there isn't a problem but I would rule out other things first.

Sounds like it could very well be a wiring problem if things are not tight or wrapped properly.I have to take the time to fix my gas gauage harness.The plug at the gast tank won't stay together , I think the clip is broken , so my guage works , then doesn't <img src="/forums/images/graemlins/smile.gif" alt="" /> A short or wierd wiring problem can cause all kinds of gremlins to play around in your truck.

Yeah, this is the first step.
Second step would be to get a wiring diagram and make sure everything else is hooked up correctly. If they did the ECM piggyback that way, who knows what else could be mickey moused....

I don't think this would be your problem as the idle speed is controlled by the ECM, but a lot of times when a blown motor is rev'ing up and down at idle, it's simply the idle speed is to slow. Idling it up a little generally helps.

No one has said it yet but you may have a cracked intake manifold gasket. They cause the symptoms you are speaking of. It seems that some get the CEL with the crakced manifold gaskets and some don't. Mine had to get really bad before it started giving me a light.

By the way I couldn't get mine to show me that I had a bad gasket by using the propane test. Even with a rubber hose extension I couldn't get my idle to smooth out. May have something to do with the fact that mine were cracked on the inside (under the intake).

Joe

My cat's were plugged bad enough that the CEL was flashing at me. In my case, the idle was fine. My top speed dropped to 65 mph, though. That's pretty scary on the interstates around here. <img src="/forums/images/graemlins/scared.gif" alt="" />

I'm with the others. Fix/check your wiring, then see what other problems you may have. I doubt your cat's are bad.

Yeah, I was thinking that but kinda dismissed it because the test for vacuum leaks (spraying carb cleaner all over everything) should have revealed it... But then your next statement...



I don't know what the propane test is, but I'm assuming it's something similar to the carb cleaner thing?

I guess it's possible the IMG is shot...

I've considered the TPS as well, but I'm still not getting any codes, and looking through those other posts, it seems that the TPS problems coincide with CEL's and codes...

So no one thinks it might be the cats?

-Chris