Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - Noob starting at 19.6MPG in '00 Ford Explorer

cajunfj40 · 09-06-2017, 05:59 PM

Slowly developing a baseline, and getting stuff fixed.

I seem to be settling in at about 18.Xmpg average when mostly commuting.

Got fed up not knowing whether the check engine light was the known rear O2 sensor, or something else, without having to stop at the parts store to check it all the time. Bought a Bosch OBD1100 scanner. This truck has very few PID's.

Hello pending misfire on Cylinder 3! Had a misfire code there earlier but it was cleared the last time I had it checked, so it is only back as a pending now and then.

Trouble is, when I put that pending code together with the following tidbits:
Happens only on 1st cold startup in the morning.
Occasional coolant smell.
Slowly dropping coolant level in reservoir (pint/month?).
When I changed the spark plugs, all were nasty/old, but Cylinder 3 was brand new and different from all the others.

That points very dismayingly towards a likely flaw in the head gasket or cylinder head, causing coolant to leak into Cylinder 3 overnight, and cause the misfire in the morning until it gets blown out.

So, I need to pull the #3 sparkplug this weekend before starting the truck up and see if there's coolant in there. Might as well do a compression test, too, to check whether the cylinder bore is chewed up by coolant washing off the oil. If the compression is low in that cylinder, that means this engine isn't worth expensive repair.

If the bores are fine, it's still $1000+ to fix, as when you do head gaskets on this engine you are likely to find cracked heads, and while you have it apart why put back in the likely worn-out pushrods and rocker arms (poor top-end oiling on this design + non-hardened pushrods = wear and valve clatter over time), plus all the bolts likely to break, etc.

Finding a used 4.0 OHV of the right configuration ('97-'00 only) that's any good would be difficult, as the problems are common. I could put an SOHC in it - much wider year range - but I'd need to swap the PCM and engine wiring harness in, as well as either get the PATS redone by a tuner or swap the dash, too. Plus the SOHC only came with a manual behind it after 2001, so there's that complication.

So I may be doing one of those "head gasket in a can" fixes, and just driving it.

Wonder how it would hold up to lean burn mods? If the engine is toast, might as well get it toasty...

09-06-2017, 05:59 PM	#18 (permalink)
cajunfj40 Lurking Eco-wall-o-texter Join Date: Dec 2015 Location: MPLS, MN area Posts: 128 Thanks: 0 Thanked 65 Times in 45 Posts	Well hello there, potential cracked head/head gasket... Slowly developing a baseline, and getting stuff fixed. I seem to be settling in at about 18.Xmpg average when mostly commuting. Got fed up not knowing whether the check engine light was the known rear O2 sensor, or something else, without having to stop at the parts store to check it all the time. Bought a Bosch OBD1100 scanner. This truck has very few PID's. Hello pending misfire on Cylinder 3! Had a misfire code there earlier but it was cleared the last time I had it checked, so it is only back as a pending now and then. Trouble is, when I put that pending code together with the following tidbits: Happens only on 1st cold startup in the morning. Occasional coolant smell. Slowly dropping coolant level in reservoir (pint/month?). When I changed the spark plugs, all were nasty/old, but Cylinder 3 was brand new and different from all the others. That points very dismayingly towards a likely flaw in the head gasket or cylinder head, causing coolant to leak into Cylinder 3 overnight, and cause the misfire in the morning until it gets blown out. So, I need to pull the #3 sparkplug this weekend before starting the truck up and see if there's coolant in there. Might as well do a compression test, too, to check whether the cylinder bore is chewed up by coolant washing off the oil. If the compression is low in that cylinder, that means this engine isn't worth expensive repair. If the bores are fine, it's still $1000+ to fix, as when you do head gaskets on this engine you are likely to find cracked heads, and while you have it apart why put back in the likely worn-out pushrods and rocker arms (poor top-end oiling on this design + non-hardened pushrods = wear and valve clatter over time), plus all the bolts likely to break, etc. Finding a used 4.0 OHV of the right configuration ('97-'00 only) that's any good would be difficult, as the problems are common. I could put an SOHC in it - much wider year range - but I'd need to swap the PCM and engine wiring harness in, as well as either get the PATS redone by a tuner or swap the dash, too. Plus the SOHC only came with a manual behind it after 2001, so there's that complication. So I may be doing one of those "head gasket in a can" fixes, and just driving it. Wonder how it would hold up to lean burn mods? If the engine is toast, might as well get it toasty...