Re: Dust damage experience?
Yeah, the no codes thing has been most frustrating. A mechanic friend, separate from the shop I've brought this to, twice, and who I'm going to see next weekend for a compression check, had me pull the TPS plug and see if I got a CEL and, sure enough, did right off the bat.
The shop plugged a scanner or laptop into it both times I brought it, drove it down the highway, and found no issues both times. This was after I got it to run up hills in fifth gear, but when it would only make more noise when you gave it more throttle at 70mph. Unfortunately, I have a habit of re-setting the ECU after changes, so any codes that might have been hidden I sure are long gone.
Oi'! Ok. This has spanned years so I'm going to forget a bit.
To begin with, this truck spent more time in the garage than on the road for a few years because I preferred my older truck. It got used weekends only until I stopped riding dirt bikes for about a year due to a blown out knee. I think, anyway. It took a getting back to regular weekend riding and racing over a year later to realize I had an issue.
What I first noticed was that it was a complete dog on the highway and sucked gas like a climbing cargo jet: I was getting about 18mpg (2wd 2RZ extra cab, all stock) where I used to get 25+.This was where, at about 70, I'd have to downshift it and floor it to hold a reasonable speed up hills; I'd drop to 65 or so, still. Not even really big ones, just rolling highway hills. Then I got pulled from a light by a clapped out Saturn, and had enough.
So I started doing all the maintenance stuff: air filter, plugs, valve lash. Did the valve lash on the loose side, on the tight side, then in the middle. No help.
On another forum, someone suggested a fuel issue, so I finally replaced the OEM filter. This GREATLY improved the highway power. I could hold 70 in fifth gear, but still had to floor it up hills and would struggle to get above that, and I noticed the power would go flat at 2250 RPM. Mileage went up to about 20-21mpg. With fuel system stuck in my mind, I added a set of LC Engineering flow matched injectors and a fuel pressure gauge. Thought I could notice some gain from the injectors if I revved it out, but no gains in drive-ability or mileage. Fuel pressure gauge seemed to indicate a solid 43psi, though I did video it down the highway and it's hard to tell if the pressure is jumping or if it's an undamped gauge flailing around.
Somewhere in there was the first shop visit, where i was told to bring it back if it got worse.
One maintenance Item I realized I hadn't done was the PCV valve. After I did that, the power going flat at 2250rpm went away. Mileage was unchanged.
Here I started to look at other things. I found the throttle body was dirty and not closing all the way. So, I did that and checked the throttle cable play per the FSM, which was wrong. I had also blasted some carb cleaner in the IAC valve, so when I put it all back together, reset the ECU, and the idle was way up, I assumed that was messed up. Replaced it, and turned out that wasn't it. I forget what it ended up being, but I think it was something dumb like the O-ring not sealing right. It idles down fine, now.
So I started mindlessly changing sensors. I changed all except the knock sensor and every once in a while I'd change one and get a tank of gas with it doing 23 mpg and running relatively well, then going back to running like garbage and sucking gas. At one point I changed the coolant temp sensor, and then it started running noticeably worse; power down and lost an mpg around town, and back to 18 on the highway if I tried to go over 75 (and really struggling to get there). So, brought it to the shop, again. Again, they tell me it runs great.
I ended up getting a blue driver OBDII sensor and started really confusing myself. It really didn't point to anything glaring, and showed the coolant sensor to be working. I changed it back, anyway, and the reduced power/mileage persisted. Maybe it was here I started messing with the intake resonators to try and eliminate a vacuum leak. Thought I noticed a difference, but didn't register in the mileage.
On a whim I changed the knock sensor, since I had it and it was the last thing I hadn't changed. Immediately I noticed it liked to rev to red line much easier. Still restrained, but willing. After the ECU reset, it started running in the upper 22mpg range. It seems to like under 55mpg driving better than highway driving, and the power is a little flat, like I have a load in the bed. So, this is where I'm at, today. With the blue driver, I noticed the timing seemed to pick up a bit while driving. I didn't make a note of it before because I was more focused on the O2 and fuel trim readings, but it seemed to want to stay in the teens and low twenties under steady throttle before the knock sensor, and then mid to upper twenties after.
One experiment I did was to reset the ECU, and then drive it around but keep the engine from coming down to idle. If you've reset the ECU, you know the idle jumps up for a bit, then as you drive it, it settles down at stop lights. So, I kept the throttle up at stops to keep this from happening. A bit of a hassle, but in doing this, I got over 23mpg and the engine seemed to run a bit smoother. As soon as you let the idle settle, though; back to coarse running and 22mpg.
I'm sure I'm leaving out a bunch, but no codes throughout this whole thing.
Last edited by YZ250_XC; 03-23-2017 at 10:11 PM.