Poor Mileage

Tunes67 · Post by **Tunes67** » February 27th, 2006, 3:45 pm

50 mpg in a protege? Not gonna happen. Your dad is pulling the wool over your eyes LOL

Tunes67

Bochek · Post by **Bochek** » February 27th, 2006, 5:29 pm

Tunes67 wrote:50 mpg in a protege? Not gonna happen. Your dad is pulling the wool over your eyes LOL

Tunes67

Nope, i seen it myself. 840km / tank i believe it was

He drives ALL highway, grimsby to toronto and back every day. Not in rush hour.

I will get the numbers to conferm it.

Bochek

highlife · Post by **highlife** » February 28th, 2006, 1:26 pm

Just read the bonfire analogy and I can accept that. Are there any symptoms which can be attributed to a weak spark other than poor mileage ? My car starts fine cold or hot, and runs smoothly and consistantly at all RPM's hot or cold.
One other thing you were talking about the sohc compared to the dohc, the 94 dohc is rated 29/37 while the 93 sohc is rated 28/35 - this is from the http://www.fueleconomy.gov site I posted earlier.

Tunes67 wrote:You have to understand that the hotter the spark, the more complete the combustion.. and a weak coil output can cause an engine to seem like its running rich. The engine isnt running rich because of the ECU.. its just not burning all of the fuel in the mixture. This goes down to a molecular level... and I am not a scientist LOL so I am not sure how to really explain this. But maybe this analogy will do.. If you have a cigarette lighter lit... and you dump a bucket of gas on top of it.. what do you think will happen? Likely it will extinguish the flame. But.. if you dump that same size bucket of gas onto a bonfire.. BOOM. Same sort of thing happens inside our cylinders.. if the fuel isnt atomized properly or there is more fuel than what the spark can fully ignite.. your engine just isnt going to operate at its peak efficiency. Again.. I am speculating a bit.. its even possible that the power draw is effecting the performance of the ECU or other components.. not just the ignition system. There are two reasons I speculate its the ignition system though.. One.. poor placement of the distibutor & coil. In my DOHC B6 engine.. the distributor is mounted on the end of the exaust cam... to an aluminum head and the distributor body is aluminum as well. So the distributor is getting more heat than some engine designs I have seen. No big deal except in our cars.. the coil is also inside the distributor. Heat has a way of distrupting magnetic fields.. well magnetic fields are what the coil uses to produce spark. Granted.. the effect would be minimal... but consider this as well.. Most of our distributors are now 12+ years old. My second point: Look at how often our coils and distributors in the MX-3 fail. Its so bad that folks here on this site have even found a way to modify their distributors to run external coils and ignitor modules. I would also love to hear from those folks as to how their winter mileage works since their modification.

I admit that I am speculating... But I think my theory is strong enough to validate future experimentation. But since I just bought a GS car.. my RS isnt likely to see much work for a while. But I would love to see winter gas mileage from a RS that is running a GS alternator and has converted their distributor to an external coil & ignitor module. I'd be willing to bet that their mileage would be closer to or the same as their summer mileage. Just a few more random thoughts.. Cheers

Tunes67

Tunes67 · Post by **Tunes67** » February 28th, 2006, 2:00 pm

I havent seen that site before.. but I know I have seen somwhere that the SOHC was rated higher than that site rates it. I will have to do a bit of searching to find it again. But if I recall correctly.. I thought the SOHC was rated 30/39 city/hiway respectively. The numbers they show for the DOHC also seem slightly inflated from what I have read elsewhere. I remember the DOHC as being 27/36 respectively. I think the numbers I got were the ones Mazda advertised rather than an independant site. But I will look around and see what I can find. That site is fairly accurate for my DOHC ATX though.. I average right around 30-31 MPG with my car between freeway & city driving.

Now as for the weak spark. You might notice a difference in the coloration of the spark plugs when you remove them. (Note: There are many other things that can cause spark plugs to have different coloration not just weak spark) Let your car get fully warmed up.. Sit at idle and one at a time.. turn on each of your electrical options. Rear Window defroster, heater blower (1-4 in steps), Wipers, headlights, and stereo (increasing the volumn will increase the stereos electrical load).

Watch your tach and kind of feel for additional vibrations. If you see your tach dip or if you feel your idle become rougher.. this is what I am talking about. This happens in my car.. and in some MX's its so much more drastic that when you step on your brakes.. your headlights will dimm significantly for almost a full second before coming back bright. Your dash lights may also dimm momentarily when you hit your brakes. Now this is mainly the electrical system through out the entire car.. not just the ignition system. Everything has a draw.. but when there isnt enough power to go around.. it makes an ignition system that is already rather anemic a lot weaker. There are lots of folks that upgrade their alternators & ignition systems just to get around this problem with our cars. If your car doesnt exhibt these symptoms.. you are one of the very lucky few.

Tunes67

corbanbrook · Post by **corbanbrook** » February 28th, 2006, 2:54 pm

Well. My buddy went to toronto today, and is going to pick up a set of Spitfire Triple Platinum spark plugs with the V shape electrode. (Suppose to create a superior spark) Burns the fuel more efficiently less emissions, better MPG by about 1.

I was also looking at the Sonic Spark Plugs, same sort of design except they claim their plugs create a wave of ultra sound to disburst and break up the fuel mist as it ignites it.

Tunes67: I know exactly what you are talking about. Every morning when i start my car i see the idle drop as i turn on my head lights, or heater or defroster, drops by 100 RPM each time i turn something on.

Well.. im getting a little fed up. If after these plugs i dont see any improvement, Im going to take this thing to a mechanic and have a real man fix it

Even after the o2 sensor replacement the idle is still really rough. Ive become accustomed to noticing the symptoms when it wants to stall out on me. Idle is always bouncing up and down.. and check engine light flashing on and off... I dont really pay attention after im warmed up.. it drives fine.. Its just that half way point where ive been driving it for 5 mins. and its reaching normal operating tempurature.. the idle will bounce from 1500-2000 RPM.. as soon as I engage the clutch it just sputters... miss fires and stalls flooding the engine. Usually I notice it before it does that... I just rev it to 4000 RPMs in neutral for a few seconds and the crazy fluctuating idle drops back to around 750-1000RPM and its golden from that point on until the next time i drive my car. In any case i think this has something to do with the poor mileage im getting.

Tunes67 · Post by **Tunes67** » February 28th, 2006, 2:58 pm

and check engine light flashing on and off

Have you tried pulling CEL codes to see what is indicated? Easy to do and will help prevent you from running off on wild goose chases when trying to figure out what is malfunctioning.

Tunes67

Bochek · Post by **Bochek** » February 28th, 2006, 3:22 pm

Well a fluctuating idle CAN be caused by a bad ground on the "ignitor module" i believe there called. i dont know where their located but there about the size of a quarter. only square.

Il see if i can find it in the online shop manual.

I believe these to be a large transistor that controlls the coil...

My dad had problems with his car and fluctuating idle exct. and this solved the problem. just sand the dirt off under it. or run a small wire from the - of the battery to it.

Il get back to you on this.

Bochek

Tunes67 · Post by **Tunes67** » February 28th, 2006, 3:26 pm

There are tons of things that can cause a fluctuating idle in our MX-3's. Vacuum leaks, IAC Valve failure, Dirty Throttle Body, Plugged Air Filter, Coolant Temp Sensor failure, O2 Sensor Failure.. the list goes on and on.. best thing to do is pull error codes and see what is indicated.

Tunes67

Bochek · Post by **Bochek** » February 28th, 2006, 3:45 pm

i agree, but this wont bring up a error code, If you look @ page G-020 in the online shop manual, there are 3 transistors

the igniton controll module.
1 for the SGT signal.
and 1 for the SGC signal.

the for the sgt signal is grounded

represented by a :

|
|
-----
---
-

Try cleaning the ground here. I helped on both my car and my dads.

Bochek

corbanbrook · Post by **corbanbrook** » February 28th, 2006, 7:37 pm

Tunes67: Pulled the codes. and found two: codes 9 and 17.

9: water thermosensor
17: O2 Sensor (inversion)

not sure why its still showing O2 sensor because i replaced it.. could i have hooked it up incorrectly? or perhaps the ECU is storing the OLD code?

corbanbrook · Post by **corbanbrook** » February 28th, 2006, 7:43 pm

Ahh nm, i see there is a section in the manual for clearing codes on the ECU in the After Repair Procedure section.

Tunes67 · Post by **Tunes67** » February 28th, 2006, 8:08 pm

Water thermosensor.. there is your fluctuating idle man.. $30 part at most parts stores. 10 minute job.

Tunes67

Bochek · Post by **Bochek** » February 28th, 2006, 8:09 pm

Tunes67 wrote:Water thermosensor.. there is your fluctuating idle man.. $30 part at most parts stores. 10 minute job.

Tunes67

agreed.

only mine was 50 bucks, not 30.

Bochek

Tunes67 · Post by **Tunes67** » February 28th, 2006, 8:11 pm

Thats cause you live in the great white everything is more expensive north

LOL Just yankin your chain man

Tunes67

corbanbrook · Post by **corbanbrook** » March 1st, 2006, 9:58 am

Well i phoned up part source this morning and they have never heard of a water thermo sensor.

Do they perhaps go by a different, more reconizable name?

I cant find it in the shop manual either? where is it located under the hood?