I have two Blazers, one 1988 and one 1999. The latter has been giving me trouble, as follows: when trying to accelerate or go up a hill, the engine won't go over about 2200 rpm no matter how hard you stand on the gas pedal. In neutral it revs up just fine, though.

History of this problem is a bit complicated. Initially there was a bad misfire, apparently caused by an arcing coil wire, which gave me a flashing CEL. (Which startled me a bit, I've seen my share of CEL's going all the way back to my father's '81 Cutlass, but never saw one flash before.) So my mechanic did a tuneup, replaced the cap/rotor/plugs/wires. The misfire went away, but the problem with the acceleration showed up about then. Then he changed the fuel filter and did a fuel pressure test (checked the output at the injectors), which he said was within normal limits. Fuel pump was replaced a couple years ago anyways. Finally he decided that the catalytic converter was stuffed up; it had been rattling for quite some time, so it probably needed to be replaced anyway, and if raw fuel was dumped into it, it might have melted or something. We ordered a Walker 15827 (from amazon.com of all weird places; I thought they were a bookstore) and he put that in. Still no change. He spent a week testing every bit of the truck he could get his hands on, but couldn't figure it out. (Didn't charge me for those hours either.) So he finally had his friend the diagnostic expert come down and look at the truck with his fancy diagnostic machinery. This guy, after scratching his head for a few hours himself, finally did a back pressure test and found excessive back pressure, even with the new cat. THey looked closer, and found that what he'd thought was a resonator in the Y-pipe was in fact another cat, and that was what was plugged.

OK, fine, whatever, just replace the damn thing and be done with it. Problem is he can't find that part anywhere. The only Y-pipe he can find which claims to be for this car, doesn't have that first cat in it; there's nothing there but pipe.

So the questions are: Can we replace that Y-pipe with the one that doesn't have the cat in it? If so, will that set a code and turn on the CEL? And if not, where in the heck am I supposed to find the correct pipe? Even the dealer didn't find one.

(I called the Walker tech support line, and the guy there said it sounded like I might have a Calif. emissions system, which as far as I know it isn't. Can't check the decal anymore, though, as it disappeared when the fan shroud was replaced a few years ago.)

 

Anything on this page look like what you need?

 

Does this look like it? If so its AP Exhaust #641166.

 

Walker Exhaust carries the California emissions Y pipe for the Blazer. You order a 2001 or newer pipe and it comes with the pre cat. BUT, they also carry the 2000 and older non pre cat pipe which looks like a better deal to me. If you switch to Bosch 02 sensors they list the #13193 for both before and after the cat for Blazers 1998 to 2005 and I think their #13193 would work as well if not better. I'm getting ready to dump the pre cat pipe on my 02 ZR2 in favor of the 2000 model.

 

Well the original had a round converter the size and shape of a grapefruit, but the overall look of it is about like that. Also to rriddle3, there's one by Eastern that also looks like it should fit (#50361).

So now the question is, should I replace the whole thing, or just the cut out the cat and replace that? Eastern also offers just the cat without the pipe, and it's quite a bit cheaper ($96 versus $217). Only thing is, my mechanic doesn't do that kind of welding, I'd have to take it to a muffler shop for that. I wonder which way it would be cheaper, given that the rest of the Y-pipe isn't in such bad shape.

Thanks for the pointers thus far.

ETA: LastC5, are you saying that I can just put the standard Y-pipe with no converter in it? This will save me probably $100 or so... will this cause any codes to pop up? There's no sensor between the first cat and the second, so the second cat can do the work of both of them as far as I can tell.

 

One of the purposes of the pre-cat is to help he main cat do it's emissions cleaning work. Without it there's a possibity of not passing the emissions test standards for your model year.

 

No, I'm saying the standard pipe from Walker has a converter after the convergence of the Y but no pup cat(s). You will need a converter somewhere in the system to meet emissions and keep codes from popping up. Using the 2000 Y pipe with it's converter and wide band 02 sensors like Bosch will keep codes from popping and get you by most emissions unless you're in a state like California where they do a visual inspection.

 

I'm not quite following. Judging by the photo on their catalog, the standard pipe from Walker (#50318) doesn't look like it has any kind of converter in it, unless there's one in the outlet that is no wider than the pipe itself so you can't see it in the photo Is it just me or does that thing look vaguely obscene?. There's already a separate cat in the system downstream of that (actually it's the number 15827 in the above diagram, we just installed it), so it's not like there's nothing there at all; so is this the right one for my truck, which is what all the vendors selling Walker parts claim, or do I need to spend an extra $110 for the Eastern one with the built-in converter. Essentially what I'm asking is, is one cat enough or do I need both. I'm pretty sure the truck was originally sold in NY, which has been tightening emissions lately but I don't think was using CA standards yet in '99.

rriddle3: it would seem from the AP catalog that this cat is only needed for Calif. emissions. Which makes no sense, because there's no CARB approval number, so you can't install it on CA registered vehicles, and the 49-state ones didn't have it to begin with.


Thanks,
Shalom

eta: I'll have to check that intake hose as in thread https://blazerforum.com/forum/2nd-generation-s-series-1995-2005-tech-41/uphill-power-loss-40701/ . It would be a real b!tch if the whole problem was being caused by an $8.49 plastic part, esp. after sinking hundreds of dollars into the vehicle. Thanks to Gimpy for the suggestion. Certainly will do that tomorrow before spending any more money on new parts...

 

Ah, looks like your #50318 pipe will work fine if you already have a down stream cat. The pipe I was talking about is the #50547 which replaces both the Y pipe and the converter in a single piece. I'm liking your way to go better. Now I have to find out whether I can get it to fit my 2002 ZR2.

 

End result was, I went with the plain Y-pipe without the small cat in it. Wound up having to replace the O2 sensors as well, since they'd welded themselves to the old pipe and weren't coming out no how. (OK, we did get one out, but the threaded part sheared off and stayed in the pipe; the other one wouldn't budge even with heat applied.) Truck runs fine, no codes showing up. It's a bit louder than it was, but not significantly so. The truck is due for its next state inspection in about a month and a half; I'll bump this thread then and post whether or not it passes.

Thanks for all the assistance. You guys are great.