Emission test fail, high CO

[Miki Kanerva]

Hello ! I drive ’98 Honda Prelude which i bought for 800€ (cheap eh?).

SKIP A ROW IF YOU WANT TO GET TO THE PROBLEM

The car was bruised and scarred with bearings nearing end of their life cycle and CV joints popping, which i replaced from my old prelude which ended up in ditch during winter.

PROBLEM:
I had to go get the car inspected, it nailed the test except for rear brake (which is just rusted and will be replaced) and emission test, now i did not read the emission test paper any more but the inspector said that it had almost 5x the CO gasses than it should + a small oxygen leak which can be because the pipe leaks right before muffler.
The inspector also said that the catalytic converter shouldnt be the problem and that it looks like the car is getting too much gasoline.
The car also likes to stutter and twitch on steady gas soon after starting to drive the car (nailing the pedal with clutch pedal on floor lets the engine rev freely) and it feels like it having hard time if i increase pedal pressure like it doesnt want to go and the stuttering soon also disappears, only to appear next time the car is being driven (this happens after few minutes of driving, no matter if the engine is warm or cold)
It does every now and then lower the idle for whatever reason, other than that it idles pretty normally for what i can see.
The car also does seem to want to turn off after revving the engine while standing still (the rpm go very low but quickly recover)
It also puffs blueish smoke when being rev’d around 3-4k, atleast it did during the emission test. Havent paid attention while driving. Not ALOT smoke but enough to be seen and it isnt that thick of a smoke either.

Now what i have done: Checked O2 sensor (the 2 black wires and there was resistance) I will change it from my old one just to be safe since the other car had working sensor, replaced PCV valve, replaced MAP, Air filter is clean, Changed spark plugs, replaced intake tube since it was slit open (dirt in intake?)

I want to know if you guys have any ideas what i should be looking for or what i should replace, since i have the other car with the same engine in it, so i can just salvage parts from that. All ideas are welcome at this moment.

Hope you can understand my confusing text 🙂

Topic

[Ty]

You might swap the fuel pressure regulator with the one from your parts vehicle and then check the fuel pressure to make sure it within spec.

[Miki Kanerva]

Okay i will replace that aswell then, it never occurred to me since the car starts like almost instantly when i crank the engine and i have a volvo which had bad regulator and i needed to crank good amount of time until it started.

Thanks for this advice aswell !

[Ty]

Your welcome glad to help!

When it comes to fuel pressure all vehicles are different some need more starting pressure some less and the same goes for running pressure.

[Miki Kanerva]

Okay i have switched the o2 sensor and FPR and the car continues to puff grayish smoke out of exhaust, more when being rev’d obviously.
Im starting to worry if this is indication of blown head gasket ?
First i just thought that it might be all the WD-40 that i sprayed all over the exhaust manifold to get the nuts out (had to change whole exhaust manifold because the damned o2 sensor was tightly rusted shut) but i did run the engine for like 10 min which in my mind would have evaporated all the WD off and gave it good 2,5k rev for like 20 seconds but the damn thing just puffs that smoke out at steady rate.
Condensation would be other good option, but doesnt condensation smoking stop pretty fast after being started?
The car didnt seem to misfire while giving that 2,5k rev, but i did hear the valves klacking, not that i would worry about it, sounded normal klacking to my ear while giving rev.

EDIT: The smoke doesnt smell funky, and its very faint smoke so it isnt thick cloud
Also no milky goo on oil cap, but a faint smell of gas was present, but very faint smell.

[Ty]

Starting to sound like a valve issue.

Valves out of adjustment or bad seals.

[Ole Eggers]

If the CO is high, your car is running rich / the catalyst is bad. Do you have any codes on it ? Did you get a paper from the test with the numbers for HC, CO2 and O2 ?

I wonder if it has an EGR valve that may be clogged up. IIRC, there is a video where Eric shows how to clean the EGR system on a Honda. The old ones didn´t check for flow in the EGR system, only if the Valve was present and responding or not.

[Jake F]

The split intake hose won’t throw dirt into your engine system. Bet you got a nice increase in power after that replacement.

I thought during emissions that CO was taken from the end of muffler. Have you checked welds underneath your vehicle lately. Even if the manifold’s gasket is on the way out, you should still be able to figure out why you can’t pass. You might be due for some spark plugs and wires, dis cap rotor, and a clay bar for detailing the exterior.

[Miki Kanerva]

So the emission test numbers
Idle: CO 1,20, CO2 6,50, HC 145, O2 10,30 (leak in exhaust most likely, atleast i fixed some leaking near end of the pipe with puddy, i know it isnt reliable but should work for the next test)
2,5-3k rev: CO 5,80, CO2 9,00 HC 245 O2 2,00
and Lambda 0,950

Now i did clean some gunk out of the EGR valve (300k km engine, there was some but the valve did move) and i will need to go and find my diagnostic tool to see if there are any error codes, but here are some results if you can figure anything from them

EDIT: Diagnostic completed, Check engine light 3 fast blinks…now if i read the instructions correctly, it means MAP is bad ? which if weird seeing how i changed it, faulty connections maybe (?) But then again the check engine light doesnt come on when the car is running, and it did come on when i had the whole connector separated from the sensor. Just so we are on the same page here NO OBD ports only that lousy 3 pin and 2 pin, i used the 2 pin short circuit to read the codes

EDIT 2: Or was the code left on the memory ? i havent removed the fuse after replacing TONS of parts

EDIT 3: Latest update, white smoke possibly condensation, puddles at exhaust tips, smoke pretty odorless

[Ole Eggers]

Just for the fun of it and to exclude, do you have an infrared thermometer ? Run the car to make it nice and hot and then have someone hold it at 2500 RPM for a couple minutes. Then measure the temp on the catalytic converter at both ends. The exiting end of it should be a good 100 degree celsius warmer than the intake end. If that is indeed the case, the converrter should be good.

When you cleaned the EGR, did you also make sure that the flow channels are clean ? Some of the Hondas has a plate under the fuel rail you can take off and clean the EGR channels underneath. Those old Hondas can´t check for EGR flow…. only activate the valve, which won´t do much if the channels are clogged.

[Author]

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