If you only removed sec.cats maybe the upper cats are a little clogged up, I mean they are the original 30+ year old one s right?
Those compression numbers seem low to me. The cylinder to cylinder difference is also concerning. You shouldn't have over 20% variation.All good points and will try to answer one by one:
No chips in the computer, I have two computers and both run fine
No clogged exhaust
I run FR5 or Autolite 3924 calibrated from 0.054” down to 0.040” in an attempt to fix the poor fuel economy issue and finding that the engine runs the strongest at 0.040”
No apparent extra fuel in the cylinders and all the plugs support that with very little fainted dark coloration.
Zero restrictions in the intake ports.
No known burned valves but I haven’t performed a leak down test and here are the compression test results:
1.- 120
2.- 130
3.- 130
4.- 125
5.- 110
6.- 142
7.- 141
8.- 140
In the past I backed down the timing to the stock 10 deg BTDC but haven’t verify the total advance
To be honest I don’t feel watery eyes or smell too much fumes out of the pipes, what I smell is probable because the secondary cats were removed.
9.5 mpg is so pathetic tha I’m tempted to disassemble all the the way down to the deck and do a valves job and reassemble everything from scratch.
Thank you for all the suggestion.
You’re correct, but I can see thru very good and I can’t see anything unusual just a tan color honeycomb.If you only removed sec.cats maybe the upper cats are a little clogged up, I mean they are the original 30+ year old one s right?
I just ordered a cheap leak down tester to have at least some reference of what’s going on in all cylinders. I’ll get it tomorrow and jump on that task right away.Those compression numbers seem low to me. The cylinder to cylinder difference is also concerning. You shouldn't have over 20% variation.
A leakdown test is strongly advised.
Yeah something weird is going on I will keep and review all the data you’re sharing against what I have.9.5 mpg just doesn't make sense from a fueling perspective. If we figure your combo for a worst-case 16mpg expected, then you're using ~68% more fuel than you should be. So, where you should be seeing close to stoich at ~14.7:1 during light throttle/cruise operations, you'd actually be seing 8.75:1.
On the load-side of the things, needing 68% more throttle means that instead of needing like 20hp at cruise, you need 33.
Or, it could be somewhere in the middle. If for some reason you were only firing on 6 cylinders (I'd hope this would be something you could feel, but don't discount it just because it isn't obvious), while simultaneously using a badly spec'd MAF, you might be running rich, and might be wasting fuel in 2 cylinders simultaneously.
What a quarterhorse would let you do is to monitor the stock narrow-band O2s' AFRs & fuel trim corrections in real time. You'd also see what the MAF is commanding, timing, and all of the other things that can screw up your tune. I'm not a remote tuner, but if you were in my area of NC, I'd hook up to ya to see what's going on. It would provide the type of data that would really allow you to hone in on your issues.
FWIW, I have a way to monitor fuel pressure & AFR in all 3 of my cars, which REALLY helps me get to the root of whether the issue is fuel or timing related.
I’ll see about that possibilityQuarterhorse is like $250 and available through Moates.
I’ll see about that possibility
I just removed the sparkplugs and they don’t look like overly fueled, but who knows… They are side gapped at 0.040” and they run awesome! I tried from 0.054” down to 0.40” and there is were it runs the best.
In regards to compression I will re do the test and one thing for sure there is no Blow-By, I have an oil watch can and there only appear three or four drops of oil once in a while.
Thank you
It is what they call “Side Gap” and the intention is to expose the spark without being hidden under the strap. That is something I followed up to improve the combustion but tuning the plugs with normal ground strap makes no difference on the poor fuel economy, but it kind of make sense to use side gapped plugs so I did that.Why is the strap cut back on all of those spark plugs?
Yeah that’s what I thought. So I will narrow my chances to COMPRESSION AND TIMING.They look slightly darker than I'd prefer, but not 9mpg dark.
It is what they call “Side Gap” and the intention is to expose the spark without being hidden under the strap. That is something I followed up to improve the combustion but tuning the plugs with normal ground strap makes no difference on the poor fuel economy, but it kind of make sense to use side gapped plugs so I did that.
Yep I will do that but first I will run a leak Down test tomorrow as soon as I get the tester I ordered. I’m very suspicious some things are pointing to that or timing.Put a new set of properly gapped, unmodified copper plugs in there and re-evaluate.
One of the things that doesn't need help on a fuel injected Fox is the ignition system. It provides hot and fat spark, all by itself when it's in good condition.
If you really want to play with the plugs, index them.
Actually I tried indexing the plugs but I’ve must done something wrong because my engine ran like crap!!!! I might try that again.
Understood, so tomorrow I will stick with the plan and I’ll put ani update of any findings on the leak down test. I’m worried I will have to take this thin apart but it is what it isI wouldn't sweat that part too much. Gains are questionable at best.
Oil looks normal and may it has a tiny bit of gas smell but almost not noticeableHows your oil viscosity after a lot of miles and does it smell like fuel?
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