Mx3 with KLZE swap running rich, afterburn

[cout]

(if you don't like reading, the short of this is that the car is running rich, we don't know why, we haven't checked much, but we're interested if there's anything obvious we should check. but if you do like reading repair stories, then by all means, read on...)

Just bought a 1993 Mx3 with a 1994 KLZE from an Mx6. Got a good price since it wasn't running, but after a little determination and a weekend of work we got it started and even replaced the water pump (wish we'd found this forum sooner, though -- there's quite a lot we had to learn the hard way!).

Anyway, the car runs a more than a little rich, and has lots of afterburn. I contacted the original owner and he says it's always done that and will even shoot flames out the tailpipe! While that's normal for my rx7, it doesn't inspire confidence in me for the mx3.

I asked about the MAF/ECU and he said he used the ECU that came with the motor and the MAF that came with the car. From a few hours perusing the forum archives, I've gathered that the Mx3 comes stock with a JE50 VAF (not MAF -- btw, what's the difference?) and that is indeed what is installed.

The ECU is a K801 but we haven't opened it up to see if it's chipped. Is this the right combination for the straight-neck KLZE intake?

Also I keep reading about fans and a mismatch in the number of sensors between the '93 and '94 model years; it looks like there's a manual switch for one of the fans. But shouldn't there be an extra sensor connection somewhere? Does the chipped K801 take this into account?

What other possibilities should we consider for the car running so rich? The intake is fairly free-flowing, so it seems like it would be running too lean if anything (yes, I read the back pressure faq -- but a low-velocity exhaust wouldn't cause the engine to run rich, would it?)

We haven't done much testing for this yet; we were hoping to check the most likely culprits first, but we're not sure what those culprits might be.

Things we've considered but haven't checked:
* spark plugs
* bad VAF or O2 sensor
* poor vacuum
* wrong timing

Anything else?

[wytbishop]

The K801 is probably your car's orignal ECU. The ZE will run on it even if the number of temp sensors is not correct. The deal with the temp sensors is more of an annoyance than anything. It may be affecting fuel consumption (though I don't think so) but it will cause the fan to run constantly which is I suspect why there is a manual switch operating your cooling fan. If you pop the cover off the ECU and remove the top circuit board you should be able to tell just by looking if the EPROM has been changed. If not you can contact the Probinator and he'll sell you one for your application.

The VAF is a Vane Airflow Sensor...as opposed to a Mass Airflow Sensor. Just a different way of accomplishing the same thing. The JE50 is the one you want. It will say JE50 right on it clear as a bell.

The most correct solution for the temp sensor problem IMO, is to remove the intake and swap the coolant filler neck from a K8 onto your ZE and remove the manual switch. Then the number of sensors will match your wire harness and ECU...problem solved. If your ECU is not chipped get one. It won't solve the richness problem but it will help. Test your O2 sensors and make sure they're working. That will be big. Make sure you have no intake leaks.

There has been a long discussion on here about fuel consuption that has never been settled. Some guys get great mileage with their ZE's. I get about 22mpg with a probinator chip and JE50 VAF on a straight neck ZE. My O2 sensors are new and the car is in pretty good tune...so I don't know what else to tell you.

[cout]

Thanks for the MAF/VAF explanation. I think there should be a glossary somewhere in one of the FAQs (or maybe a wiki?).

However, I'm still confused. According to this post:

http://wwww.mx-3.com/phpBB3/viewtopic.p ... 89#p515689" onclick="window.open(this.href);return false;

The Probinator came out to replace the KL31/36 ECU's for these reasons:
- A $40 substitute to a $250 ECU
- Probe/Mx-6 owner can use their stock ECU rather than sourcing a JE50 from an Mx-3
- Those running Curved-Neck intake manifolds, specifically those with ZE Mx-3's, can get the proper VRIS configuration

But since I have the JE50 and afaict I have the straight neck manifold:

http://rubystuff.org/mx3/MX-3%20009.jpg" onclick="window.open(this.href);return false;

doesn't this mean I don't need the probinator chip? Will it even work with my application?

BTW I'm not nearly as concerned about total fuel consumption as I am about the fuel mixture and the resulting afterburn; I'd like to avoid uncontrolled flames as much as possible.

OTOH if I could shoot flames on demand, it would be great for creme brulee.

[wytbishop]

In the post you quote Mike mis-typed one thing...” Probe/Mx-6 owner can use their stock VAF rather than sourcing a JE50 from an Mx-3” This is one of the issues the Probinator chip solves for Probe and MX6 owners.

The ZE has basically exactly the same sensors as the K8 and that’s why it plugs and plays so well in the Mx3 and that’s why it will run right off the stock MX3 ECU. Likewise, the KL31 or KL36 ECU will plug right into the MX3 harness. Before the Probinator came along everyone was always trying to find KL36 ECU’s because they usually don’t come with the engine when you buy from an importer. The Probinator provides an EPROM chip that mimics the KL36 fuel map, eliminates the EGR codes and sets the correct VRIS open and close rpm for the type of manifold you’re using...solving the problem of locating a jspec ECU which is expensive and difficult. It basically turns your stock MX3 ECU into a very good approximation of a KL36.

From your picture you do have a straight neck so if you need a chip you would call him and he will ask you what IM you have and he’ll set you up. Since you don’t have the KL31 or 36 ECU you do want to be chipped if you aren’t already.

As far as the fuel consumption issue. In general what I hear tells me that the majority of ZE swaps suffer slightly poorer fuel mileage but nothing like what you’re describing. Something else is wrong with your engine. You might have a bad injector which is sticking open or a fault in your ECU or a bad IAT sensor...I can’t say. Mike, the guy you quoted, and Fowljesse are the only guys that come to mind who brag about the mileage they get. Everyone else I’ve heard says they get somewhere from 20-25ish mpg.

[reaper_cory]

hello everyone, this is my first post in this forum, I am from portugal and my MX3 is a 1.6 DOHC 1998 black, is slightly mod, and in the midst of the changes that i made, I had 1 problem with the maf, and it happened to me exactly the same problem that you have, to much fuel , but everything wytbishop said "including the maf"also has logic. is a complicated case, good luck , and great engine you got there:)

[cout]

Thanks, that clear's up a lot!

I'll check tonight whether the ECU is chipped then go from there.

One quick question (just for curiosity sake): what's the difference between the KL31 and KL36? Which cars do they come from?

[cout]

One more question, how adept do I need to be at using a soldering iron to install a chip, or is there a socket for the IC?

Also I respect the work that probinator has done so I don't want to rip him off by buying a clone, but are the chips on ebay any good?

I'm thinking of buying both just to see.

[wytbishop]

One is from an MS8 (J-spec MX6) and the other is from a Eunos 800 (J-Spec Millenia)...not sure which is which off the top of my head. I believe the KL36 is the MS8 ECU.

The main difference would be the VRIS points. The MS8 had straight necks and the Eunos 800 had curved necks.

The EBAY chip is not the same thing. I installed my own chip. You need a desoldering pump and a good quality pencil style iron. His chip is a moer modern architecture than the old chip, so he supplies it with a socket to adapt it to the board. Yo udesolder the old chip, solder in the new socket and snap the new chip in...took me about 30 mins.

[cout]

But if they're the same pinout, either one should drop into the provided socket, right?

Is there a difference in the programming of the EPROM?

If not then that's evidence someone copied the probinator maps. But the money should go to whomever did the work.

[wytbishop]

The only chip that I'm aware of on ebay is the crap that's supposed to increase HP and fuel mileage. It's a lie. That chip is actually a resistor that alters the signal from the VAF and IAT to get the ECU to alter fuel delivery. Unless you have a link to something that I'm not aware of.

[cout]

Hmm, no, these look more like ICs that are soldered onto the ECU:

http://cgi.ebay.com/ebaymotors/ws/eBayI ... gory=33597" onclick="window.open(this.href);return false;
http://cgi.ebay.com/ebaymotors/ws/eBayI ... gory=33597" onclick="window.open(this.href);return false;

I did consider going the resistor route myself as a cheap hack to get the engine to not run rich, but I don't know what the pinout or expected voltages are of the VAF.

[wytbishop]

I had not seen those. Hard to say what the fuel map would look like. "Aggressive fuel and timing curves"...could mean anything at all. Bumping the rev limiter is something i've heard of other guys doing but would only be useful or adviseable for drag racing on a built motor.

I guess if you have the time and money there'd be no harm in trying them both. See if there's a noticeable difference.

But as I said before, I think you have another problem. Even on the stock ECU the engine should run better than you're describing.

[Mnemonic]

I'm not saying this is whats wrong but I would say it has a higher % chance of being the problem. The K series engines already run richer than they need to so when you take an engine like the klze and use a k8 ecu you're making it run richer than it normally does on its own. Now this shouldn't cause you to shoot flames out of the rear, but you will run rich and your gas mileage will suffer greatly. Now what this combination does do is over time is it will fowl down the spark plugs making the gas mileage even worse and this could be the cause of the magical flames shooting out the back as more fuel is being dumped into the exhaust since you don't have adequate spark to burn the fuel off. Being this is also your cheapest solution and good maintenance I recommend replacing the spark plugs and see if that makes any difference in fuel consumption/flame shooting.

Timing could have some play in it, but considering the computer can advance or retard the timing to make sure its running properly I would say this isn't the 1st thing you should check, but then again checking and adjust the timing is free if you do it yourself so then why not check to see if its the case, but I doubt its the single cause to the your problem.

[Daninski]

As far as the second coolant sensor simply stuff a rag into the pipe to catch the metal and drill out a hole then thread it to accept the second sensor. Swapping out the neck is like 10X the work. I just drilled and tapped my friends car and it was childs play.

[wytbishop]

well sure...you can do that...if you don't mind cutting corners.

Corner cutter.