View Full Version : Issues with the MX3

07-13-2011, 08:24 PM
So, hey guys, I disappeared. :D
I'm busy working 12-15 hour days, and being exhausted.

I bought a Mazda MX3 with a v6 swap, trying to get the rest of the bugs worked out on it.

Yes, I'm aware this is CelicaTech. The MX3 forums suck.

Biggest issue is hydrocarbons. 800+ when it should be under 150.
My CO% and NOx are well below the limit.
I've given the car a full tune-up. Plugs, wires, dizzy cap & rotor, oil change, etc.

Other issue is the temp gauge reading. Turn the ignition on, it goes straight to H.
I'm starting to think this is an actual wiring issue... coolant is clean, full, and circulating. Temp sensor snapped when I went to check it, so that's new.

07-13-2011, 08:50 PM
nothing to do with your issue.. but i kinda missed you around here. the end. back on topic.

07-13-2011, 08:57 PM
I miss being around, but I don't miss being bored as hell and going crazy over a breakup.
I spend most of my day at work, then go home and do more work.

Trying to get this damn restaurant to stand on own.

07-13-2011, 09:25 PM
check your grounds. add more of them.

07-13-2011, 09:34 PM
Did they use the harness from a v6 mx3 or did they make their own? Also, have you ruled out the temp sensor for the gauge? Also, is the gauge cluster in there the original one for the car? Not sure if the i4's and v6's shared the same cluster.

07-13-2011, 10:08 PM
OK, so the car is running rich as hell. Does it use a MAF/AFM or is it pure speed density?

07-13-2011, 10:13 PM
OK, did some research... there are a ton of those K series V6 engines... and it apears they use a MAF. Is it a factory MAF tube that was set for that engine? also, what is the relationship of the intake filter to the MAF?

07-13-2011, 10:34 PM
Catalytic converter manufacturer's efficiency chart says high HC with low NOx and CO indicates a need for a tune-up, an oil change, and running the converter in (getting it up to temperature before testing).

Rich AFR usually also produces high CO in addition to the high HC, but I wonder about oil leakage into the combustion chamber or ignition efficiency.

07-13-2011, 10:46 PM
My first impression was to guess it's running way too rich, also. What kind of diagnostic and/or tuning equipment do you have to work with or is it all just stock stuff?

07-13-2011, 10:58 PM
I'm still putting my money on it being pig rich... As this is a swap, the chances of the MAF being fouled by poor placement (or in a custom tube smaller than stock) could cause serious rich condition leading to high HCs. HCs are unburnt fuel... It could also be that the EFI temp sensor is not wired correct (typically not the guage sensor), causing the engine to be in "warm up" mode giving additional fuel.

07-14-2011, 05:41 AM
Also curious, is this the 1.9l v6 swap, or a jdm swap? Believe there was a 2.5l motor that could be swapped in easily.

07-14-2011, 06:45 AM
If youve tuned up the car and you cant think of anything else, most likely the cause of your emissions issues are a bad cat. How does the car run? Does it run well? Get decent fuel mileage? Burn a lot of oil?

About your temp gauge issue, most of the time temp gauges ground to hot. If you disconnect the lead to the sensor, does the gauge stay on hot, or does it drop to cold where it should be? On a Toyota when diagnosing this, you ground the gauge wire and if it reads full hot, its the sensor itself. If it reads full hot ungrounded, you have a short to ground in the wiring. This is on a toyota tho. Not sure about mazdas.

07-14-2011, 06:55 AM
I doubt it's the cat, because his NOx is low.

07-14-2011, 07:36 AM
True. I guess theres that.

Dunno. Guess we need to see what he says about fuel economy, oil consumption, etc.

07-15-2011, 05:24 AM
Fuel economy blows. Car runs great and has tons of power.

HC ppm: 828 / 141 Fail
CO%: .52 / .79 Pass
RPM: 2678
CO+CO2%: 15.8
NOx ppm: 81 / 1026 Pass

HCs are way above the limit, CO is just barely below it.
I managed to trip a CEL today for the EGR valve, but that might have something to do with residual Seafoam.

07-15-2011, 06:56 AM
EGR is to reduce combustion temperatures, in order to prevent the formation of NOx.

Those are some ridiculously high HC numbers, though. Paired with the barely acceptable CO, looks like you've got extra hydrocarbons in your combustion chamber. This would also lead to lower temperatures, which might explain why your NOx is almost non-existent. So, rich AFR or oil leak would be my best guess, unless you're not going through oil or gas at a high rate. If consumption is good, then I'll agree with spacewedgespacewedgespacewedgespacewedge, catalytic converter. Rare compared to other issues, but it happens.

07-15-2011, 03:39 PM
Fuel economy might have to do with how it's being driven, so I'm not sure if that would even matter here.
but Galcobar is right, something is not burning.... (either excess fuel or oil). Have you tried the rag over the tailpipe test?

07-15-2011, 04:18 PM
Also curious, is this the 1.9l v6 swap, or a jdm swap? Believe there was a 2.5l motor that could be swapped in easily.

I'm going to guess it's the 2.5l V6 motor. I drove one of the 2.5l mx3's before and they are fun as shit. I want one in my wife's Mazda.

07-15-2011, 10:55 PM
...I'll agree with spacewedgespacewedgespacewedgespacewedge

What the hell is that? I typed L uni and got that.

07-15-2011, 11:02 PM
Yoda muther fucker!

07-16-2011, 08:22 PM
If its got a KLDE or ZE in it you might want to checkout probetalk.com, mx6.com, and/or performanceprobe.com.

07-17-2011, 06:24 PM
Replaced the thermostat, and then decided to tear into the throttle body.
One of the vacuum ports in the manifold was completely blocked. It looked odd, so I poked it with a screwdriver and it didn't feel like metal, so I shoved the screwdriver in. Wound up scraping carbon buildup out of it for a good 15-20 minutes.

I definitely have some vacuum leaks. I found two ports that weren't plugged. There's another on the back of the engine somewhere, couldn't find it last night.

07-17-2011, 09:15 PM
hmm, that adds up to some other cans of worms... Make sure the vacuum line to the regulator is good. Otherwise a leak in that line will cause your fuel pressure to be too high. Also the O2 sensor may be overcompensating for the leaks (as the leaks should cause a lean condition as it's unmetered air)