Finest

This is on my wife's car...96 EX auto, complete stock w/104k miles. She complained about some weird noise that scared her when she was driving. So I took it out for a quick spin and didn't hear anything unusual. Did the basic twist and turns to see if it was maybe a suspension problem, but nothing. Then from a stoplight, I accelerated quickly and right when I let off the throttle, there was a small backfire pop...but I heard it coming from the front of the car, not the rear exhaust. It "felt" like it happened right under the middle console...so that leads me to believe that it might be something to do with the cat.

With 104k miles, do you think that catalytic converter is crapping out? I haven't had time to get under it and unbolt it to check it out....but anyone with similar experiences that can help me diagnose this? Thanx!

97itr86

O2 or spark plugs? When my cat clogged I had no power and it wouldn't rev normal.

2000CX

so a bad(or none in my case) o2 can cause similar problems?

Finest

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 2000CX &raquo;</TD></TR><TR><TD CLASS="quote">so a bad(or none in my case) o2 can cause similar problems?</TD></TR></TABLE>

I believe not having an O2 will cause your car to run in safemode (very rich).

But I drove the car again this morning and it backfired a few times now. Still feels like it's coming from the front since I can "feel" it under the center console/front end. Spark plugs, eh? I'll check those after I put the car on the lift to check the cat.

SOHC_MShue

may be the plugs. When I cleaned my car the other day i got some water in the plug holes and ruined my already bad sparkplugs and wires. They were misfiring all over the place and my car sounded like it was backfiring a lot and stuff. So i'd check your plugs and wires for sure.

Finest

It wasn't backfiring constantly...just a few times on WOT. I'm assuming since the cat is partially clogged, it'll only backfire once the exhaust builds up inside it...usually when I accelerate it quickly. But when driving normally (under 3-4k rpms), it feels fine.

EE_Chris

I would think that if your catalytic converter were even partially clogged, you wouldn't be able to accelerate as fast as normal. Is that the case?

Also, if you thought the converter was clogged, you could do a quick pressure test if you had a gauge. Just remove the O2 sensor and see what kind of pressure you have pre-cat....shouldn't be more than 1-3psi.

What kind of maintenance has been performed on it lately?

Finest

BLEH! Checked the cat and all is well under there. Wasted about 45 mins. So that rules that out...

Now the situation has gotten a tad worse. Now it hesitates when I start off, but once I get above 3k rpms, it's fine. It sputters for a bit, then once above 3k, it revs normally. Still backfires from the front once in awhile when I let off the throttle.

So what I thought was a clogged cat, now turns into a never-ending diagnosis. I guess I'll have to start checking the fuel and ignition now. Argh!

BTW, when I removed the cat, I saw that the secondary O2 sensor had a white coat of color on it. I don't know how a "healthy" O2 is suppose to look like...but any clues?

*cliffnotes: Chasing hesitation/sputtering problem. Checked cat. White O2 sensor. Still no clue?

luti

I had/have the same problem with my car. The first time I got rid of it by readjusting my ignition timing. Recently it has come back and my timing seems good, so I just picked up a new fuel filter, I'll see if that helps.

2000CX

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 98CTRCoupe &raquo;</TD></TR><TR><TD CLASS="quote">

Now the situation has gotten a tad worse. Now it hesitates when I start off, but once I get above 3k rpms, it's fine. It sputters for a bit, then once above 3k, it revs normally. Still backfires from the front once in awhile when I let off the throttle.

</TD></TR></TABLE>

i have this EXACT same problem...pretty sure mine comes from running no secondary o2...might be a clue to whats wrong with yours...you smell fuel at all?

luti

I don't have a second o2 since I have an EX, and I had this problem a little bit before I put my turbo on. Since I installed my turbo the problem has gotten worse and worse.

2000CX

luti...are you still running obdII? what year is the car?

Draco

Try changing the wires. That's what caused hesitation under 3000 rpm for me.

luti

98 and yeah still OBDII

luti

Nope, fuel filter didnt help, and the new plugs didn't do it either. I think it's either a vacuum leak, a problem with my fuel system (faulty injecter), or my iac is fucked.

solo2slocivic

since you mild backfire happens just as you let off the gas i would suspect an exhaust leak.. check for a cracked manifold... pretty common

Finest

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by solo2slocivic &raquo;</TD></TR><TR><TD CLASS="quote">since you mild backfire happens just as you let off the gas i would suspect an exhaust leak.. check for a cracked manifold... pretty common</TD></TR></TABLE>

Cracked exhaust manifold? Hmmm. But would that cause the sputtering below 3k rpms? I do hear some unusual crackling noises when I shut off the car. Like how metal contracts when it's been heated, and cooling down.

staticchmbr

my 87 crx si was doing about the same thing. it was actually backfiring out of the throttlebody. i changed all the plugs, wires, cap, rotor, the o2 sensor, put some injector cleaner in there, and good as new.