Poor Mileage

corbanbrook · Post by **corbanbrook** » March 7th, 2006, 10:38 am

Well.. I think a CV joint or Wheelbearing went the other day.. this thing is falling appart faster then i can fix it.

Checked the MPG yesterday. 18 MPG. down 1 from last time.

Taking it to the mechanic at noon to have it checked out. Seems like i Keep sinking more and more money into it and no improvements. Starting to think I may have to replace the clutch before I see the MPG go up.. slippage is probably killing the mileage.

corbanbrook · Post by **corbanbrook** » March 7th, 2006, 10:41 am

Well.. I think a CV joint or Wheelbearing went the other day.. this thing is falling appart faster then i can fix it.

Checked the MPG yesterday. 18 MPG. down 1 from last time.

Taking it to the mechanic at noon to have it checked out. Seems like i Keep sinking more and more money into it and no improvements. Starting to think I may have to replace the clutch before I see the MPG go up.. slippage is probably killing the mileage.

Tunes67 · Post by **Tunes67** » March 7th, 2006, 12:56 pm

Have you done a compression check on your engine yet? If not.. that should have been one of your first steps.

Tunes67

corbanbrook · Post by **corbanbrook** » March 7th, 2006, 1:35 pm

No i have not yet..

car is at the mechanic right now. I will call him up and ask him to do it.

What should the compression rating be at for a SOHC?

Tunes67 · Post by **Tunes67** » March 7th, 2006, 1:47 pm

Depends on overall mileage.. its not so much what the numbers are as too how even the numbers are.. anything above 150 is good.. 130-150 is fair.. below that is pretty much gonna be a noticable loss of power. But the main thing to watch for is numbers that vary greatly.. if you have 150, 145, 155, 40. Well you got a big problem in #4 cylinder.

Tunes67

corbanbrook · Post by **corbanbrook** » March 7th, 2006, 2:00 pm

Thanks Tunes67,

makes sense.

I just phoned him up and asked him to throw in a compression test.

in 3 hours i should have the car back.

corbanbrook · Post by **corbanbrook** » March 7th, 2006, 6:04 pm

Well, the front rubbing turned out to be part of the wheel well sheild bend in and rubbing against the wheel. So that was an easy fix.

Had him install the coolant sensor because i couldnt get it in.. and the new spark plugs.

First of all the engine engine light doesnt come on anymore, the idle doesnt bounce around and seek, its steady at 750 RPM. And it just feels more powerful.

I dont know if its the combination of coolant sensor and spark plugs, but the accelleration is like im driving a completely different car. Starts up the second i turn the key.

I think the Splitfire Tripple Platinums were a great buy at $8 CAD ea. I can feel it.

Had the engine compression checked. 140-115-95-140 so the 2nd and 3rd cyls are under compression.. said it would be $600-$1000 to fix that. So im just going to live with it and do an engine swap at some later point.

I have a good feeling about this and cant wait until my next fill up. At this point if i get it to 23 MPG i will be happy.

Tunes67 · Post by **Tunes67** » March 7th, 2006, 6:26 pm

Rap the piss outta the engine and do another compression test.. you may have carbon buildup on the valve faces. A dozen good hard rev ups may break it up and allow the valves to seat better giving you better compression. Its a long shot.. but wont hurt anything.

Tunes67

corbanbrook · Post by **corbanbrook** » March 8th, 2006, 10:25 am

When you say 'Rap' are we talking about my knuckles, a ballpean hammer or something more heavy duty...

You are scaring me man.

Car is doing fine. I had to take it out last night just to drive it around.

I figure I will see a lot of fuel savings just due to the idle sticking at 750RPM instead of 2000RPM... waiting around in drive through for Tim Hortons Coffee in the morning, and fast food for lunch.. 10 mins or so of 2000RPM idle aday .. a week of that adds up.

One thing i noticed which was a little strange was the power draw. When it was idling around 2000RPM i never noticed it much.. sure it would drop when i turned on the heater full blast and defrost. But it would be bouncing around so much i didnt think much of it.

Now idling at the proper speed.. I turn on the heater fullblast and it drops to about 500RPM.. and when i turn on defrost.... well then It drops to 100RPM range and then bounces between 1000RPM and 100RPM.

Time for a ground wire kit, me thinks.. Hopefully the spring is fast approaching.

Tunes67 · Post by **Tunes67** » March 8th, 2006, 11:02 am

When I say Rap, I mean rev the engine to wide open throttle for 10 seconds.. repeat a dozen times or so. Makes the valves work harder... opening and closing RAPidly

This will break up carbon build up on the valve faces.. which in turn will help them seat better which in turn will raise up the compression in those low number cylinders

Well it could help raise it up.. depends on how much carbon is there really. It wont hurt anything and it might help.

As for your power issue.. Ground wire kit is a good idea.. check the 4cyl faq section.. I did a write up on how to make your own.. or you can buy a kit for a little more cash. Also a good idea would be a alternator upgrade or replacement. Not sure if a GS alternator will bolt up to a SOHC engine.. but I know it will for the DOHC engine.. just need a longer mount bolt. Instant upgrade from 65-70 amps to 90 amps.

Tunes67

corbanbrook · Post by **corbanbrook** » March 8th, 2006, 5:19 pm

In Neutral? or while driving? wont this redline my engine? or is there some REV limiter that will keep it from exploding?

Tunes67 · Post by **Tunes67** » March 8th, 2006, 5:51 pm

LOL It wont explode.. not unless there is some serious damage inside it.. do it in neutral in your driveway. If it makes you feel better.. do it for shorter sessions like 5 seconds but do it twice as often.. the idea is to just work the valves harder than normal driving so that it might break off the carbon build up on them. 95 PSI is likely showing a valve that has started to burn.. likely this cylinder wont get much better no matter what without a valve job. But hey.. its worth a try.. and its free

Tunes67

corbanbrook · Post by **corbanbrook** » March 8th, 2006, 10:31 pm

You are right Tunes! if that Valve is going down .. its going down in a 9000 RPM firery ball of glory!! viva la resistance!

highlife · Post by **highlife** » March 9th, 2006, 8:29 am

I cant wait to read the next entry.......

corbanbrook · Post by **corbanbrook** » March 10th, 2006, 11:58 am

Filled up today to calculate the new MPG.

21.5 MPG an increase of 3.5 MPG on average.

Pretty happy with that increase. At least im out of RX-7 fuel consumption territory. Since the car has been operating like a dream since the water thermo sensor and new plugs I have been driving more aggressively, this next tank of gas I will try to take it a little easier just to see.

I talked to my mechanic yesterday and he said he would go over the entire car and let me know what needed fixing. He mentioned that the back struts needed replacement so i figure its a good time to just upgrade to some good performance struts. That will probably help a little too.

He said he was getting in some new decarbonizing cleaning solution in a couple of weeks and wanted to try it out on my engine to see if it would increase the compression.

Just wanted to say thanks to everyone who offered advice and helped me raise this $500 MX-3 from the dead.