I have a weird one for you guys.
I built my rig about 3 years ago (see build thread linked below if you want an overload of crap info on that). It is a 1995 FZJ80 that I converted to a 1HDT/H151 with GTurbo, intercooler, bigger airbox, rebuilt fuel pump, rebuilt injectors, 3" exhaust, etc etc. I'm only pushing about 19psi because I wanted it to be reliable, not a torque monster. I've driven it about ~35k miles in the last couple of years and it's been amazing. One year ago I ran compression numbers and all 6cyl were very good with very little deviation between them.
Over the last 4-5mo and 8-10k miles it very slowly started running worse. At first I didn't notice. Just a dim sense that it was louder and rougher. Several months ago I noticed that the shift lever would vibrate violently on downshift engine braking, which it hadn't done before, and I chalked that up to it maybe needing engine mounts (even though those were only 3yrs old). Eventually it slowly got to a point last month where I was getting concerned. It was idling rough, almost a miss but not quite. It was smoking more. Idle speed was down about 50rpm. It was louder/rattled more than ever. I could feel the increased engine vibration in my butt and in the steering wheel driving it down the road. I was worried that it was time for a rebuild.
A few notes:
-I travel a LOT so I rarely hit the same gas station twice. So I don't think bad fuel is to blame.
-I keep up on maintenance, replacing the air filter frequently, as I run a lot of dusty roads. Fuel filter replaced yearly (although I only run the stock filter set up).
-I have had a light oil leak at the turbo outflow for a while now that I need to figure out.
-One of the last things I checked was to open the petcock on the fuel filter. No water came out but I did get a puff of air. However I was at 7000ft when I did this.
I was headed back to home base (although over 2000mi to get there) a couple of weeks ago and PLANNED to buy some Diesel 911 and top the oil off with some Lucas additive to see if either of those quieted it down because my inspections found nothing wrong anywhere else under the hood.
The day BEFORE I made it to a town to get these supplies and after a rough 30-40mi washboard run, I fueled up and noticed when I pulled away that the truck seemed to be running smoother. I was flabbergasted. Some more driving and it was obvious that the old 1HDT was running like a freshly oiled sewing machine. Maybe better than ever before. And shockingly, engine braking now barely wiggles the gear lever. 4 tanks of fuel later and my MPGs are up ~15% (3-4mpg).
What the bloody hell happened? God definitely doesn't like me enough to have intervened in this.
All I can think is that I had an injector that was sticking? Or maybe a valve had some schmutz stuck in it that kept it from closing 100% causing a slight compression leak?
But the real head-scratcher for me is the reduced vibration under engine braking. What could cause increased vibration under engine breaking? Or alleviate it? I think the biggest clue is in that. Is that indicative of one cylinder having lower compression? Or a lack/excess of fuel?
Any ideas?
I love that it's running better but I hate that I don't know WHY. Hahaha. Partially because it could turn back in the other direction at any time. And I need reliability!
I built my rig about 3 years ago (see build thread linked below if you want an overload of crap info on that). It is a 1995 FZJ80 that I converted to a 1HDT/H151 with GTurbo, intercooler, bigger airbox, rebuilt fuel pump, rebuilt injectors, 3" exhaust, etc etc. I'm only pushing about 19psi because I wanted it to be reliable, not a torque monster. I've driven it about ~35k miles in the last couple of years and it's been amazing. One year ago I ran compression numbers and all 6cyl were very good with very little deviation between them.
Over the last 4-5mo and 8-10k miles it very slowly started running worse. At first I didn't notice. Just a dim sense that it was louder and rougher. Several months ago I noticed that the shift lever would vibrate violently on downshift engine braking, which it hadn't done before, and I chalked that up to it maybe needing engine mounts (even though those were only 3yrs old). Eventually it slowly got to a point last month where I was getting concerned. It was idling rough, almost a miss but not quite. It was smoking more. Idle speed was down about 50rpm. It was louder/rattled more than ever. I could feel the increased engine vibration in my butt and in the steering wheel driving it down the road. I was worried that it was time for a rebuild.
A few notes:
-I travel a LOT so I rarely hit the same gas station twice. So I don't think bad fuel is to blame.
-I keep up on maintenance, replacing the air filter frequently, as I run a lot of dusty roads. Fuel filter replaced yearly (although I only run the stock filter set up).
-I have had a light oil leak at the turbo outflow for a while now that I need to figure out.
-One of the last things I checked was to open the petcock on the fuel filter. No water came out but I did get a puff of air. However I was at 7000ft when I did this.
I was headed back to home base (although over 2000mi to get there) a couple of weeks ago and PLANNED to buy some Diesel 911 and top the oil off with some Lucas additive to see if either of those quieted it down because my inspections found nothing wrong anywhere else under the hood.
The day BEFORE I made it to a town to get these supplies and after a rough 30-40mi washboard run, I fueled up and noticed when I pulled away that the truck seemed to be running smoother. I was flabbergasted. Some more driving and it was obvious that the old 1HDT was running like a freshly oiled sewing machine. Maybe better than ever before. And shockingly, engine braking now barely wiggles the gear lever. 4 tanks of fuel later and my MPGs are up ~15% (3-4mpg).
What the bloody hell happened? God definitely doesn't like me enough to have intervened in this.
All I can think is that I had an injector that was sticking? Or maybe a valve had some schmutz stuck in it that kept it from closing 100% causing a slight compression leak?
But the real head-scratcher for me is the reduced vibration under engine braking. What could cause increased vibration under engine breaking? Or alleviate it? I think the biggest clue is in that. Is that indicative of one cylinder having lower compression? Or a lack/excess of fuel?
Any ideas?
I love that it's running better but I hate that I don't know WHY. Hahaha. Partially because it could turn back in the other direction at any time. And I need reliability!
