I've been noticing this since some time after installing a high flow catalytic converter, I don't know if it's related or coincidental.

2002 Acura RSX, K20A3 (has dual runner intake manifold), 84K miles.

Under ~ 2K RPM, in gear and with load, there is a slight hesitation and lack of smoothness. I thought maybe it was my spark plugs again, so I replaced them with OEM spec NGKs, same part no. as per the shop manual. It seemed a little smoother for about a day, but now it seems the same as before the new plugs.

The engine smooths about above 2K RPM, and there is no other driveability issue.

Could this be a valve adjustment issue? I don't think it's a PCV problem. Maybe a vacuum leak?

These cars are notorious for dirty IACV problems (the IACV sits at the bottom of the throttle body and stuff just naturally falls into it), I clean mine out annually with TB cleaner. But a dirty IACV usually results in crazy idle fluctuation, not hesitation and roughness.

One other thing - I broke the IM bypass control solenoid nipple a long time ago when replacing a tiny inline filter and used superglue to patch it back together. It hasn't come apart, but it feels a little weak when I put mild pressure on it.

Anyone care to chime in on what the issue may be here? Thanks in advance!

Only engine code is intermittent P0420, which is caused by the high-flow converter. I've replaced both O2 sensors - I just need to add a defouler on the secondary sensor.

Thoughts:

. Clean IACV, IACV hoses, ports, throttle plate, and throttle body.

. Replace PCV Valve and clean hose with brake cleaner.

. Replace fuel filter.

. Check vacuum hoses and intake manifold for leaks.

. Ensure coils are fine. Did you coat porcelein and main electrode with dielectric grease? Attenuated spark on a 4-cylinder engine is noticeable.

You're a smart guy and I doubt, from afar, that I can "nail" the solution for you. Just go over everything.

Thanks for the suggestions.

I plan on doing all of #1.

#2 I have been postponing because I think I will have to at least partially remove the IM to get a wrench on the PCV. Grr!

Fuel filter! Really? It consists of a screen on the fuel pump, inside the gas tank. There is an access hole under the back seat, but I've heard they rarely need replacing. Of course, anything can happen.

When I pulled the IM to replace my starter a couple years ago, I reused the original rubber seals for the ports to each cylinder, even though the shop manual said to replace them.

Coils are almost new, I bought them from a salvager with ~ 11K miles on them after my originals were soaked in oil. Only thing I see with them is some rust on the outside, from being in contact with lightly rusted spark plug tubes.

Two of the plugs (and their corresponding coils) had white chalky stuff (almost like a salty substance) on them when I replaced the plugs last weekend. The other two did not. I don't know what the cause of that stuff developing is/was.

No, I didn't use dielectric this time - I did on the last set of plugs and they were the ones in use when the issue developed.

I just checked - the filter is part of the fuel pump assembly, can't be purchased separately!

New from dealer, pump costs ~ $250!

Interestingly, although Honda/Acura parts sites don't list this part, I found this on eBay. Wonder if it's any good:

2002 - 2004 ACURA RSX FUEL FILTER NEW OEM:eBay Motors (item 130303113202 end time May-27-09 21:20:24 PDT) (http://cgi.ebay.com/ebaymotors/2002-2004-ACURA-RSX-FUEL-FILTER-NEW-OEM_W0QQcmdZViewItemQQ_trkparmsZ72Q3a1205Q7c66Q3a2 Q7c65Q3a12Q7c39Q3a1Q7c240Q3a1318Q7c301Q3a1Q7c293Q3 a1Q7c294Q3a50QQ_trksidZp3286Q2ec0Q2em14QQhashZitem 1e56abb7f2QQitemZ130303113202QQptZMotorsQ5fCarQ5fT ruckQ5fPartsQ5fAccessories)

It's likely the real deal, if the part no. checks out.


I changed the fuel filter, after 25,000 miles, on my Taurus this morning.

It's likely the real deal, if the part no. checks out.

I punched the part no. into an online Honda parts catalog - nothing came up.

I asked the seller about it, I haven't heard back yet.


I changed the fuel filter, after 25,000 miles, on my Taurus this morning.

25,000 - or 250,000?

I change it every 25,000 miles. Ford recommends replacement every 30,000 miles.

Well, then, it's really odd that Honda/Acura has no replacement interval for the fuel filter - or the PCV valve - on this car/engine...

I always thought that was odd.

Guys on the RSX forums say the fuel filter should be good for the life of the car!

Many makers say replace platinum plugs every 100,000 miles. In most cases, they NEED to be replaced at 50,000 miles or less.

Leaving a PCV Valve in too long is a good way to prematurely wear out an engine. On my Civic, Honda recommends replacing it every 24 months or 60,000 miles, whichever comes first. For the fuel filter, Honda recommends replacing it every 48 months or 60,000 miles, whichever comes first. Lack of regular preventive maintenance is often a marketing ploy, since most people don't want to be bothered.

Well, it seems like there are plenty of recommended service intervals for this car, just a few odd omissions.

Like the PCV and fuel filter.

As I just finished asking on another forum - why is there no ordinary in-line fuel filter for this car, like there is on most cars? Are we supposed to buy ultra-clean, pre-filtered fuel from the stealerships?

Furthermore, the fuel filter I posted the link to is usually described as a strainer, as if it only prevents large particles from entering the fuel supply.

Have you ever worked on a K20A3? (Base model RSX and '02-'05 Civic Si, though I'm sure other Honda engines are similar.)

The PCV valve is nearly impossible to get a wrench on. And the only fuel filter is located in the fuel tank!

Have you ever replaced an in-tank fuel filter that is the only fuel filter for the vehicle?

Oh, BTW, my iridium plugs (supposedly good for 100K) looked horrible at 50K or 60K, when curiosity finally (and luckily) finally got the best of me!

The most difficult PCV Valve to replace is on my 24 valve Duratec engine. I had to design and fabricate a tool, in order to replace it. The local dealer wanted $350 for the job, because they would have to remove the UIM and LIM. With my tool, I replaced it in 45 minutes. Not one of Ford's better ideas.

There's always a cost to pay, when working on performance engines.

:eek: $350 to replace a PCV valve?

Well, I'm not sure I have your talent, but where there's a will, there's a way...

A lot of these RSX guys have made custom oil catch-cans for their PCV systems.

Is this really as helpful as they claim? If oil getting into the intake system is such a problem, why don't manufacturers put a filter on the PCV system?

Dayuuuummmmmmm!!

PCV was almost a piece of cake after all!

Had to go to two stores to find one in stock. But removing it was not as bad as it looked like it would be.

Used a long, straight, slender screwdriver to remove the tube from the PCV, then I unclipped one electrical connector that was in the way. After that, I was able to slide my 17mm deep socket right on that sucker, and broke it loose!

Great. Did it help the situation? Be sure to remove the hose and clean it thoroughly. Also, clean the port going to the plenum.

At first it felt like it resolved the problem completely, but after driving around a bit, I'd say it resolved about 90% of the problem, LOL.

I ordered a PCV, washer, two clamps and the entire hose (it's only about 18" long) from a Honda dealer in AZ yesterday. So I think I'll replace it all again when those parts arrive.

Who knows - the OEM PCV may be better than the off-brand part I bought. And the hose will be new and clean.

BTW, the PCV itself had some gunk on it, on the outside. It looked pretty clean inside, as did the threads in the crankcase. The little ball still rattled around like it should, but the spring was probably ready for retirement and I'm sure there was crud build-up inside that I couldn't see.

That sounds quite successful.

That sounds quite successful.

:p

Yes - thanks for your advice and encouragement!

Well, I decided to clean the TB and IAC tonight. Took it out for a spin, and the idle now fluctuates MORE than it did prior to the cleaning, and the low RPM hesitation is as bad as ever. Especially in first gear, of course.

Why would this issue worsen with TB/IAC cleaning!

Also - there is a slight and momentary hissing noise when releasing the throttle plate, as the intake reverts to IAC intake. Is this normal?

Did you use a new O-ring, when you reinstalled the IACV?

I didn't remove the IAC or TB - I removed the intake tube and sprayed them down while manually manipulating the throttle.

I would remove the IACV from the plenum and clean it with brake cleaner. Ditto for the IACV hoses. Ensure upper and lower ports are clean.

I realize that would allow for a more thorough cleaning, but why would my quick and dirty cleaning make matters worse?

And, is it normal to hear a hissing sound when the throttle plate closes?

BTW - the TB looked pretty clean, the IAC was likely pretty clean as well.

Not sure. I've never experienced what you are describing.

Sounds like some sort of vacuum. How does the IAC/throttle transition occur? Via vacuum? Does the IAC close completely when the engine is using the throttle, then reopen when the throttle plate closes completely?

The throttle plate is not suppose to close completely (but almost). There should be a slight gap--about the thickness of a sheet of carbon paper. Under guidance by the ECM, the IAC motor opens and closes the valve, which regulates idle rpm by controlling air flow through the hoses by-passing the throttle plate. There's an IACV inlet screen that often gets clogged with dirt. Nothing improves idle more than thoroughly cleaning the IACV, hoses, and ports.

OK, OK, you've talked me into this heinous job!

I hate dealing with coolant more than anything. I'll soak in carcinogenic used motor oil all day long, but coolant gives me the willies. Call me weird.

And, I have to find replacement gaskets for both the TB and the IAC. IDK if I can find non-OEM gaskets. Probably, after driving around to 3 or 4 stores!

I also need a five-point bit set to remove the IAC from the TB. Maybe the TB/IAC were designed by GM!

Reason I want to do it now is of course the "holiday" weekend. On a "holiday" weekend, I can accomplish all the usual domestic chores and sometimes fit in an extra one like IAC cleaning.

Thanks for the explanation.

One other thought - when I pulled the IM to replace my starter a couple years ago, I did not replace the rubber O-rings/gaskets.

Should I do so now? I'm thinking not, those rubber O-rings don't deteriorate like other gaskets, especially in a relatively low heat zone like the IM.

This is a super simple job, in which there's no need to deal with coolant. You likely won't even need to replace the O-ring. If needed, just lightly coat the O-ring with silicone grease to improve seal.

This is a super simple job, in which there's no need to deal with coolant. You likely won't even need to replace the O-ring. If needed, just lightly coat the O-ring with silicone grease to improve seal.

Ha!

The IAC is UNDERNEATH the TB, there is no access to remove the IAC without first removing the TB, which of course has coolant lines attached to it.

Why do you think I first chose to just spray TB cleaner without removing the IAC!

IM gaskets should always be replaced and torqued evenly (and in proper sequence) with a torque wrench. They get compressed and don't seal properly. All it takes is a "little" leak. I would replace them.

IACVs are always on the rear of the plenum or on top. I've never seen one on the bottom.

Here's a Honda parts catalog, it shows the IAC (#1) on the forward bottom. And, believe me, there's no way to get tools in and beneath the IAC to remove it from the TB.

http://www.hondapartsunlimited.com/scacura/jsp/prddisplay.jsp?inputstate=5&catcgry1=RSX&catcgry2=2002&catcgry3=3DR+BASE+LEATHER&catcgry4=KA5MT&catcgry5=THROTTLE+BODY&ListAll=All&vinsrch=no&systemcomp=Engine

Sounds like I will be on a gasket hunt this weekend. Hopefully I can find one store that has all the gaskets I need.

Is this what your's looks like?

http://www.superhonda.com/photopost/data/501/kommon_sale_001.jpg

Remove both of those bolts and off it comes. The "figure 8" O-ring is inside.

Mine sort of looks like that.

You know, the idle is pretty normal - it's settled down since last night, maybe I dislodged some dirt and/or otherwise disrupted things enough that the ECU had to relearn.

The RPMs don't act up when I put the car in 1st and let go of the clutch, but the car just doesn't want to get up and go, unless I release the clutch and depress the gas JUST SO. Makes me wonder if the IAC has anything to do with this annoyance.

That's not an IACV issue. Have you ever replaced the Ignition Control Module and coil?

No, don't have those - but I have replaced the ignition coils and was thinking about getting the ECU reflash by Hondata.

Guys that have had their ECU reflashed claim it eliminates hesitation - just don't know if my hesitation is normal or not for this car. I'm thinking not; I don't recall it being this bad until recently.

The other thing these cars are notorious for are faulty TPS'. But I'm not sure what the symptoms are.

Yeah, I was thinking you had an older Acura.

Hesitation is not normal in any car. I would work tirelessly to eliminate it, especially in an Acura.

Hesitation is not normal in any car. I would work tirelessly to eliminate it, especially in an Acura.

Tirelessly, and at great cost :(

I've already replaced one vacuum line, I just ordered the forward main vacuum line.

New PCV and PCV hose are on their way, I also just ordered TB, IAC and IM gaskets.

Maybe the cure is in one of those...

Possibly, but you bought an Acura for performance, right?

LOL - sort of - why do you ask?

I'm TRYING to find the solution, jeez!

I bought it primarily because it's a Honda - reliability and longevity and economical operation. LOL @ the last one - I got bitten by the modding bug and I've spent too much money on this car.

One of the main reasons I bought the RSX instead of a Civic was styling. I just didn't like the looks of the Civic coupe. It's grown on me since then, but I still prefer the RSX' appearance.

If I'd wanted performance (of course I'd like to have my cake and eat it too, but that's not possible) I'd have at least bought the Type-S.

As far as I can tell though, the only Acura that performs is the NSX.

HONDA = Hold On, Not Done Accelerating

Wow. This is a tough one.

Assuming all other things equal and there are no other causal factors (like an intake manifold/vaccuum leak, etc) you likely have induced this performance degradation in changing the catalytic converter (CC). Interestingly, by changing out the CC, you have negatively impacted at least two variables that could affect smooth operation of this engine:

#1-The exhaust system gas flow (meaning air/fuel/exhaust) is carefully orchestrated and engineered during system design. In some places within the path, gas flow is meant to slow down, in others, it is meant to speed up. Exhaust pipe diameters, radius and number of bends, even the exhaust pipe "tip" are all engineered so as to optimize gas flow at different points for different reasons. Reducing resistance to gas flow generally has a positive effect on most engines (namely older engines), but can cause problems in other (newer, emissions-equipped) engines.

#2-When the catalytic converter was changed out, not only was gas flow changed, but the temperatures as sensed by the O2 sensors changed. The O2 sensor signals the computer as to actual temperature measured. The computer (not knowing anything about a CC change) continues to do its job by attempting to change the fuel mixture (thru enrichening or leaning) based upon optimum temp/actual temp deviation so as to effect optimal baseline temps and thus acceptable emissions. The result of your scenario has manifested itself in the ways you describe.

FIX: I know this is probably a real pain, but I would reinstall the original CC and re-check performance. You just may fix your car---and for no money---wouldn't that be great! Good luck with it, whatever you decide!

NOTE: Be sure to check local laws in "modifying emissions systems." Finally, if you determine the new CC did in fact introduce the problem, check with the performance CC company via wesite, etc for their recommended solutions---sometimes they have "fixes" to overcome these type performance degradations.

DrRotor - thanks, you may be spot on.

Hence the desire for Hondata reflash - it's supposed to be mapped for freer flowing intakes + exhausts.

I've never heard of anyone complain about performance issues after installing intakes, race headers, etc. - without reflash.

But most of the people that add those items to their cars have the programmable ECUs and they make their own adjustments.

And, of course, I sold the OEM CC for scrap months ago.

I just re-read your post and had a thought -

I doubt the A/F sensor is impacted much by installing a shorty header (the only new exhaust part before the sensor), and the secondary O2 sensor surely is affected by the aftermarket cat, but it plays no role (on my car) in air/fuel metering. It only tells the user if the cat is "malfunctioning". That can be resolved with a "defouler", which I just haven't gotten around to doing.

However, the change in backpressure is likely an issue with the now less restrictive exhaust. But most of the "experts" for this car have told me the stock ECU can compensate for such a minor change as a less restrictive bolt-on exhaust.

I received and installed an OEM PCV and tubing today. Seems to run even smoother, but not 100%.

These cars are renowned for their jerkiness getting off the clutch in first gear, so it's a little difficult to know if I still have a problem, LOL.

I think I still have a vacuum leak - I was listening to the car in the garage tonight after pulling in and hearing a sound. I notice when I turn the steering wheel that there is a brief "pfffff" sound that appears before the RPMs bump up from turning the wheel. Is that normal?

Update - I replaced the forward vacuum hose that runs from the IM to the metal portion of the vacuum "hose" (I replaced the aft rubber portion that runs to the MC a while ago) and I replaced the IM O-rings and re-glued the tiny vacuum line to the IM runner while I await the arrival of the replacement solenoid.

My brake pedal is firmer and sits higher up. I am afraid to say that the engine feels smoother too, with less of the hesitation I described at the beginning of this thread. Afraid because there is always the psychological effect of replacing something and thinking the problem is gone... I'll reserve final judgement until I've driven the car for a few days.

Next up, apart from the cracked IM solenoid is the TB O-ring. I was able to replace the primary IM O-rings without completely removing the IM, maybe I'll be lucky that way with the TB O-ring.

I was surprised to see clean, fresh-looking oil on the old IM O-rings. I guess (and hope) that is normal PCV blow-by.