my 91 hf will not pass e- check due to high NOx readings, it was flashing the code for EGR, so i replaced that and cleaned out all the build up in the manifold. took it back to check and it failed again , worse this time. The car only gets like 33 MPG and i know it should get more like 40ish, and has very little power. does this sound like a partially clogged or failing converter?? I have checked a few places like autozone and advance for prices and autozone lists it online but it is not available to buy advance has no listing for it and napa lists the same for a hf as they do for the si and i know the hf has the converter mounted on the exhaust manifold, not under the car so its probably not the same part. i some one know any thing about this please let me know.

 

When my cat conv was clogged, the performance and gas mileage were shitty.

 

Had the same problem. You replaced the Egr selenoid. On the block. But you might want to check and make sure the diaphragm is goin up and down. If not, bummer. The cat shouldn't fail on those, but if it did, easily replaced. I would check a couple things....
the o2 sensor on the Manifold.
The egr, "thing"on the block
Make sure all your vaccuums and one way valve **** is working right....
Replace the Pcv valve.
just go over everything....i had a broken diaphragm, the Cleaner ate right through the material...
Good luck fellow HF owner.

 

i replaced the entire egr, including the diaphram, and i have done the pcv valve, before i did this the car ran horrible, it idled at like 1500, now its down to a 900 rpm idle, but it is rough sounding. and the egr ports on the manifold were so plugged that the EGR wasn't even working, now it is but the second time i had it test it put out high NOx reading.
i was told that having a bad cat would cause it to run rich and lead to the EGR ports being clogged more and more so the cat could have been bad for a while and then just lkead to the EGR going bad, or the bad egr could have lead to the cat failing. i have only had the car for 3 weeks so i don' treally know its history. but i have had many crx's one other being an HF and it ran way better than this one.

 

hey dan.. hope u get this stuff fixed. Is this that white crx that you have now?

 

Try and check all the components in your Emission box attached to the firewall. Hook up a vaccuum thing and check all the pressure readings. You said you already got all the carbon build up out of the IM. I went through 5 cans of brake cleaner, and 2 wire brushes... brought all my numbers down. You gotta dedicate a whole day to just checking all vaccuums, clean everything up. And check all the emission components.
At any smog shop they should tell you , "your cat should't fail" but bleh....good luck buddy.

 

sorry if i jacked your tread but are crx and civic cats the same???

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by jdmef9er &raquo;</TD></TR><TR><TD CLASS="quote">sorry if i jacked your tread but are crx and civic cats the same???</TD></TR></TABLE>


The CRX HF and Civic STD cats are the same. All other 1988-1991 Civics and CRXs use an underbody cat.

As for whether the cat is clogged or not, the only way to find out is to remove and visually inspect it. Shine a flashlight in the bottom of it and see that there is light coming through the entire brick. If not, it is clogged. Keep in mind that clogging is common with close-coupled cats. Because they are so close to the engine, they tend to run MUCH hotter than your typical underbody cat. This causes them to burn up. Also, it is not easy to come by a cat for a reasonable price. Your typical weld-in cat generally won't work for applications using a close-coupled cat. You could try to pull a fast one on the emissions tech by hammering out the brick in the close-coupled cat and having a conventional cat welded into the exhaust system in the conventional location. This would be MUCH cheaper than replacing the stock cat.

 

No auto parts store carries the manifold mounted catalytic converter...I tried. Honda dealerships have them, and I've been quoted prices ranging from a little over $400 all the way up to $800. When I was failing emissions, instead of replacing the cat I went and bought a generic cat that mounts under the engine and I also bought a cheap Pace Setter header. This was cheaper than a new OEM cat, and I passed emissions.

 

I have a CRX which I have been working on doing tuneups etc. Got the thing to run pretty good. Passess emissions in ATL. But I think I can get better MPG (I get around 37 around town and 40+ if I do a good bit of interstate).

Started looking at a cat replacement (91 CRX HF) and the dam things are expensive (I guess because they part of the exhaust manifold).

400$ minium I think.. Still mulling over what to do. If I absolutely knew it was a problem I would replace it. BUt don't want to spend that kind of money unless I know I can get positive results...

Also, how hard is it to remove for inspection? In the past I have found exhaust parts to be very hard to remove. Stuck bolts, constricted spaces, rusted bolts that break when you try to remove them etc..

 

The biggest problem you are going to have is rusted bolts. I've removed the CX and VX cat [exact same setup] on my cars but it was a bitch both times.

Read my last post for my solution on my Civic CX that I had.

 

my old hf had a header and under body cat on it, it was like that when i got it though and it passed e check no questions asked so i might just do this again, it sounds much cheaper than getting the honda one.

 

so i found a few places that can get the proper converter, i finally found one on line that can get one for a price i am willing to pay for it. it ended up being like $200. which is more than i origianlly wanted to spend but less than fabing something or buying the oem. its suposed to be in like wednesday or thursday.

and another question - most places only list the HF from 88-90, was 91 just an over run year or something because mine definitly is a 91 hf.

 

what happened is in the later months of 90, the started equipping the Hf's with the mods from the Hfs of the next year.
If you'll notice the PCV valve on the IM on the HF swtiches places from those two years. The guys at the tune up place thought i was lying about the year, and the model. (someone even thought it to be an SI....whoa, shouldn't have taken her there) But overall....your VIN will tell you. but the line it was produced on and the month it was made in will determine where/what kinds of parts are floating around on your block. Good luck.

 

Cleaning out my garrage today, I found my VX header. I still have the VX cat, and last time the engine was run, it passed emissions with flying colors. I'll make no guarantees, but if anyone needs one, make me an offer.