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Tracking down cause of poor MPG.

Old March 13th, 2019, 12:11 PM
  #11  
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Originally Posted by Roger1 View Post
If I rev the motor it does make a crackling noise.
Clogged cat?
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Old March 13th, 2019, 12:32 PM
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Originally Posted by mountainmanjoe View Post
Clogged cat?
That's what I was thinking it could be.

We don't have emissions here, so it's not on the top of my list.
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Old March 13th, 2019, 12:57 PM
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OK... I was under the impression that you wanted to fix your mileage.
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Old March 13th, 2019, 1:55 PM
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Originally Posted by mountainmanjoe View Post
OK... I was under the impression that you wanted to fix your mileage.
Yes, I do. Am I to assume the fact that I wasn't concerned about the cat, that it could be part of the problem?

I'm not a mechanic and don't know a lot of this stuff. I'm not good at diagnosing things. If I know what the problem is, then I can figure out how to fix.
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Old March 13th, 2019, 2:09 PM
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An engine has pistons, right. It's a glorified pump. Air and fuel goes in one end, exhaust comes out the other, and you make power in the process. What do you think will happen to your power when you block a pump? Why do people upgrade their exhaust to make more power?
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Old March 13th, 2019, 2:22 PM
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Originally Posted by mountainmanjoe View Post
An engine has pistons, right. It's a glorified pump. Air and fuel goes in one end, exhaust comes out the other, and you make power in the process. What do you think will happen to your power when you block a pump? Why do people upgrade their exhaust to make more power?
Should it be at the top of my list to change?

Can I just throw on the cheapest cat available for it?

What if I straight piped it?

Last edited by Roger1; March 13th, 2019 at 2:25 PM.
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Old March 13th, 2019, 2:38 PM
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Anything would be better than a blocked cat but the top of your list should be to diagnose your problem, not throwing money at parts until it goes away. At least give the cat a bump to see if that's where the rattle comes from.

If you're unwilling to investigate yourself, then have a mechanic look at your van. He might find the problem right away and be able to give you an estimate to repair it. He might say it will take longer, so just set yourself a limit on how much you're willing to sink into tracking the problem down.
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Old March 13th, 2019, 2:43 PM
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Originally Posted by Roger1 View Post
Answers to everyone's questions.

It has 157K on it.

I've only owned it for about 7 months and have put less than 1K on it. I had been looking for some time for a van, but here in the Tamps Bay area vans are overpriced and I will only buy something that is a good deal. My plan was to buy something newer with less miles, but I snagged this one super cheap and figured it would be OK for the time being.

Air filter is only a few months old.
Tires 225 75 16 have less than 500 miles on them. Upon purchasing the tires I didn't check to see what air pressure was put into them.
Brakes have less than 750 miles and bearing where repacked at the same time.
Have not done a tune up.
No idea how old exhaust is. If I rev the motor it does make a crackling noise. We don't have any emissions laws here in FL
Have not checked for any codes / haven't had check engine light ever come on.
The overwhelming majority of my trips are 2-6 miles round trip.

At what speeds should the tranny shift at when driving normally up to 45 mph.

I will be driving to GA next month and can see what it gets HWY.
Your trips might be to short it probably doesn't have enough time for the engine to warm up.
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Old March 13th, 2019, 10:39 PM
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Ditto on Silents comment. The cat takes a while to heat up, and they only work when hot. Short trips are killer.
The cat and its performance affect fuel mixture etc. It could also be an internally messed up muffler. Try banging on the muffler with your hand or a rubber hammer. Does it sound loose inside?
Def check for codes, and have your exhaust looked at. Not having emissions laws is beside the point. Your van needs to run smoothly to get the best mpg.
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Old March 14th, 2019, 12:14 AM
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Yes the engine is less efficient when cold, but I've never gotten 9mpg even on short trips.
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