Gas Mileage issues

[boostmaster]

As some of you may know I purchased an 88 LX a few months ago.

Car had many issues but just about everything has been fixed. For some reason my mileage went down drastically and I'm confused so I figured I' run it past you guys.

Here's what I've done so far:

1. New O2 sensor
2. New PCV
3. New OEM T-STAT (finally got heat- but temp gauge still doesn't work)
4. Exhaust (Pipe was missing from downpipe all the way to the muffler so I added the pipe in between)- no cat.
5. New Iridium Plugs
6. New Valve cover gasket
7. Seafoam treatment
8. Radiator flush and refill
9. New Rad cap
10. New Gas cap (it was missing)
11. New Synthetic oil/filter

When I bought car, I drove it around 70 MPH for about 6 hours- got 46.7 mpg w/o exhaust and crappy plugs. After all of this new stuff and just local driving in town we're getting 27.7 mpg. WTF?!?!

I understand that stop and go will decrease the mileage some but THAT much? I was thinking if the car got such good gas mileage with nothing done to it that it would surely go up with some of the basics taken care of.

I didn't change plug wires or distributor as it starts right up with zero issues and runs great.

Can anyone think of anything that might be causing the drop in MPG??

[FestYboy]

the plugs? never been a fan of iridium or platinum plugs, always saw improvements when i switched back to the standard copper core plugs. also, the O2 may not be right for your car. if you have the bosch replacement, i know several people on here who had to trade the bosch for the denso just to get the car running right again. never been impressed with bosch products.

[freshtiva]

That kind of drop is not normal. My festys ( 5 speeds )get 40 +/mpg mixed driving. Is it an automatic ? If so, thats about right. Not a big auto fan. Ruins a good car IMO.

[mechanicaldj]

I second the plugs

If the car didn't come with them from the factory, DO NOT USE THEM!!!!

i use NGK V-power myself, never a problem

[boostmaster]

Really? I thought for sure that these would work much better! I just bought that freakin' O2 for $35 bux! It was running fine with the old crappy O2. (I mean, it runs fine now but the MPG is horrible).
Ugh. They were pretty expensive. I guess I'll swap them out and see what happens.

BTW, I also have new fuel filter, air filter.


Car is 5 speed...

ANy other possibilities?

[MJD]

Really? I thought for sure that these would work much better! I just bought that freakin' O2 for $35 bux! It was running fine with the old crappy O2. (I mean, it runs fine now but the MPG is horrible).
Ugh. They were pretty expensive. I guess I'll swap them out and see what happens.

BTW, I also have new fuel filter, air filter.


Car is 5 speed...

ANy other possibilities?

Didn't the early ones take an Autolite 64 ? I have a '88 L with carb. engine, and the Ford dealer parts guy, friend, told me of the Autolite 64 plugs a few weeks ago when I rescued this junky '88 from a re-cycler. After I talked to the former owner who said it was running when they took it (smokes a bit sometimes), I got all enthused about getting it to run, and it actually did. I did change the oil and put some # 64 PP ? ....I think, from NAPA. Primed it a bit, and got it to running. So ......my little parts car has been saved, and I may even get it more road worthy as time goes. Now my parts car needs a parts car -- ha ha
Mine is only a 4-speed, Festiva L.
I would at least try something original from factory specs in the spark plugs. Can you see what number ones you had from your old plugs you replaced ? I have some old farm tractors too I use, and in the spring, the first thing I do is put in new plugs...what a difference ! The IH tractors I have are 4 cylinder engines too from the 1950's era.
What if you put your old plugs in, cleaned, and drive a while to see if that may make any difference ? Also, keeping it under 60 mph maybe ?
Is air OK getting to carb ?
Just a thought ..........


MJD

[boostmaster]

Aircleaner is new and looks perfect so I assume air is ok.

I pulled the old plugs (Motorcraft- I think) but they were really fouled and if I recall correctly on of the contact ends was worn to nothing. O2 was fouled as well. Car still ran fine. I run Iridium and platinums in my other cars and get decent mileage (for what they are)- BUT, I really expected to see a major improvement in the MPG when changing these.

I have done everything I can think of.

BTW, I have new tires that I got at a JY and they apparently have flat spots so the give me a shimmy around 45mph. I know I need to change these too- I suppose this might affect mpg a bit. Any thoughts?

I don't want to keep throwing money at the car. I really like it but I need it to perform better than what I'm getting now. (Only good part is that I filled it up with $16 the othr day Haven't seen $16 in a LONG time.

[FestYboy]

have the J/Y wheels ballanced, and get those plugs swapped!

[boostmaster]

The wheels were balanced. It's the tires that have flat spots. I had them rotated around and the car only shakes at 45mph. Before or after 45 it's fine.

I've been working alot so I'll probably be getting new plugs today or tomorrw.