Festiva MPG has dropped to 22 mpg - help!

[Click_It]

Carb'd festiva. Recently had a few dramas with the distributor + fuel pump both failing around the same time and were both replaced. As a result of that the only thing I can think that has really changed is my positioning on the distributor. Obviously too much one way = lean, and too much the other way = rich.

I'd never played with this before, the old distributor was the original. My car has always ran a little thirsty compared to the USA cars (even your carb'd festys) but I put some of that down to our 4 door versions are heavier. Also I know the carbs go bad eventually, I remember when the car was younger it was cheaper to run, I've more or less accepted that short of putting a weber in, that's life with the stock carb.

But out of interest the first tank after changing the above parts I decided to set it up lean, it pinged and was horrible to drive but I was curious what MPG I'd get, so I drove that tank like a pensioner.

Running lean I got 27.7 mpg - that's even worse than before, so I thought "screw that!" I'll go back to running it rich if lean isn't saving me anything.

Running rich I got 22 mpg (!! - the worst by far I've ever gotten out of a Festiva tank, heck my old 3.5L V6 got better mpg than that)

Admittedly it's probably a little tooo-lean right now but really, 22 mpg?

To be fair a few outside factors were working against me. It's winter time here and is colder than the usual winters. I'm currently working 10 minutes from home so the car never reaches optimal temps and I idle the car for a few minutes before setting off for the day. But I'll say it again, 22 mpg really? lol. The fuel light first came on at 152 miles!

I know a weber would probably go a long way to helping both MPG and performance but I've committed myself to the goal (ONE DAY!) of throwing a fuel injected motor in so I don't really want to mess around with expensive bandaid solutions.

Could incorrect distributor positioning be the sole reason for this terrible sudden MPG or could there be another culprit I'm overlooking? Nothing else was changed or tampered with (never touched the carb), unless the new fuel pump is no where near as economical as the old factory pump was. I'm stumped.

EDIT: Oh and one last thing that comes to mind, since replacing the distributor I've never had the car put over a timing light. It is a little rough and can feel it missing from time to time (never happened before all this) so maybe timing is now off and accounting for the poor MPG? Should that be my first thing to get organised? The spark plugs and leads are all good before anyone asks. The ignition coil appears to be good but I'm open to replacing it if anyone believes that could account for much MPG difference. Typically MPG drops in winter but nothing like this extreme.

[ryanprins13]

What else have you checked? Does the thermostat work? Spark plugs have proper gap? How are the wires and so on. Getting what youve already checked out of the way makes diagnosis easier.
Auto or manual?
Brakes dragging? How easy does it roll when you push it?
Checked the trans fluid lately?

Sent from my SM-G920W8 using Tapatalk

[FestYboy]

I think first, we need to establish that the position of the distributor does not affect the air/Fuel ratio in any way whatsoever. Carb cars can handle a wide range of timing, with 0* btdc being stock. That being said, running an entire tank in a pre-ignition state can damage valves and rings and pit the pistons and combustion chamber. It's possible that the new fuel pump's bypass valve is faulty, causing excessive fuel pressure in the bowl which can cause a rich condition, or the return line is clogged or pinched (same result). Fuel pressure at the carb cannot exceed 4psi. 2.5-3.5psi is the range.

I would first verify your mechanical timing between the cam and crank, and then do a compression test. Post the results. Then set the ignition timing to 6* btdc (with the vac tubes in the correct position) as a baseline and use a spark voltage tester to check the coil output at the spark plug boot. The spark should be a vibrant blue/white and snap hard at a 10mm gap. If it doesn't, the coil is weak.

Then if all is good above, check that the secondary in the carb is closed under normal, low load conditions and that the plate is dry.

[Dragonhealer]

What you are describing is ignition timing advanced (and pinking, too advanced!) And ignition timing retarded.
From your description of cascading failure, one possibility is a bad burn in the combustion spaces, caused by exhaust valve clearance too narrow or valve not seating, causing the coil to be damaged.
Set your ignition timing bu the book,
Accelerate the car up a hill from 2000rpm, if it does not missfire, I'm on the wrong track.
If it does missfire, test plug wires, check cap, rotor and sparkplugs. If all that is good, set valve clearances, replace coil.

PS. Festyboy knows way more than I do about the engine management on a carby Festiva.

[Click_It]

A quick reply.

Firstly I dont know why I was saying the disty controls lean/rich. Anyway yeah advance/retarding the timing, I had a quick look at the hoses which all look okay and adjusted the disty by feel (I don't have a timing light but I can take it to someone who does). It now 'feels' close to TDC. I've only driven it 30 miles since and got a very respectable (for my car) 33 MPG, but readings over such short distances are hardly accurate so I'll check again later in the week. It looks like I've certainly improved it though as 22 -> 33 is a massive change. I'll be happy with anything over 28 being winter here.

It's now idling around 900rpm which from memory is a little higher than factory spec (manual) but feels pretty good. There is still some minor misfiring / rough idle experienced so I can probably only go so far until I need a professional to tune the rest out of it. We'll see how it goes, if MPG stays respectable I probably leave well enough alone

[FestYboy]

Invest in a vacuum gauge... And you should look into setting the valve lash as well with a good set of copper plugs. Do not use platinum or iridium, factory coils don't like them.

[Click_It]

I've filled the tank twice since posting this thread. After each time I've been adjusting the dizzy.

After getting 22 MPG I got a 26.5 MPG and am pretty thrilled today I got a whopping 36 MPG! That's better than my average result before all this happened. That tank had some good conditions of open road driving and I've been using a higher octane fuel too though the latter doesn't seem to influence readings much in a 1.3L carb.

It may still not be perfect but if I stay north of 30 MPG I'm happy, and thrilled if I can get more results like this one today.

At the end of the day it's still just guessing though, I should buy some tools and do things more precisely one day.

[FestYboy]

Get a timing light now, do it right, now.

As a precaution, do NOT use lower octane fuel or adjust the dizzy until you've established where things are right now. You can easily burn a valve or break rings with improper timing.

[Click_It]

Okay thanks Festyboy, I'll get onto it this week and report back. Feeling better that I've been using higher octane these last few tanks now. Before all this happened I'd been mostly using lower octane.

[Click_It]

Get a timing light now, do it right, now.

FestYboy, you may have just saved me from blowing up my engine!

I got a timing light onto it. It was advanced by 14 degrees! I'd only driven ~150 miles with it like that and using high octane fuel, never exceeding 4000rpm - hopefully a combination of those things plus a lot of luck prevented me from damaging the valves or rings.

Am a little ashamed at just how wrong I was but am extremely happy for your advice!! Big thank you.

It's on 3 degrees now and feels great. I'll probably avoid the low octane in future and stick with the mid range stuff.

Since my dream of swapping in a B5/B6/BP engine remains out of reach for me I might source a weber carb and ditch the tangled mess that is the stock carb, that should make the car run better in the mean time - I believe I can then increase the timing up to 6 or 7 then also?

[FestYboy]

You should be plenty safe at 6* with the low octane... And that will bump the enjoyment factor as well as mpg.

[Click_It]

Nice, thanks.