Low Power Bad MPG - Need more ideas
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azcat90
New member
Be careful
Be careful not to spray it on the exhaust manifold. Thank the good Lord I was able to blow out that fire...
Be careful not to spray it on the exhaust manifold. Thank the good Lord I was able to blow out that fire...
JRZEE2000TR4LTD
Senior Member
None of the hoses going to the airbox are vacuum lines including the fuel pressure regulator. If you have a lot of "stuff" in that hose clean it out but I doubt that's the problem unless you find gas or it smells like gas which means your regulator is leaking by.
JRZEE2000TR4LTD
Senior Member
Sure, as I said check that FPR hose for gas. To check the FPR, get a MightVac and connect it to the hose and put some vacuum on it. It should hold indefinitely. If it doesn't or if you pull some gas through, you FPR is bad. Secondly, put a vacuum gauge on the manifold and check for any low or fluctuating readings (with the engine running of course). I don't have all the tables in front of me but you can tell a hell of a lot from engine vacuum at different rpms and loads.
A couple questions. How many miles on your rig? Is it Cali emissions (2 cats) or Federal emissions (1 cat) Reason I ask is if you have Cali emissions, your rig has 2 O2 sensors (the front is actually an A/F sensor) which could affect performance. Also, when in Park, and you rev the motor, does it have any problem getting to higher RPMs? Any backfiring?
JRZEE2000TR4LTD
Senior Member
Not a vac Pump a hand held MightVac about 20 bucks
JRZEE2000TR4LTD
Senior Member
Oh OK Sorry bout that. I don't think that something they rent out though.
No and I'm not spending $40 on that or the vacuum gauge they had. Dad's got a mighty vac I'll borrow when I see him next week and I'll buy a vacuum gauge online somewhere.
Oh well. At least now it's got entirely fresh coolant, new t-stat with the jiggle thing pointed at 6 instead of 11 like it was, synthetic fluids in both axles and transfer case, and fresh mobil 1 in the engine. Only thing that didn't get changed was transmission fluid and that's only because ny drain pan was full from everything else so it'll have to wait until I get back from Florida.
On another note, any good way to check and see what gears are in it? Short of jacking it up and spinning the tires and counting driveshaft rotations? Is there a sticker somewhere? Didn't see anything on the rear diff when I was under there.
Oh well. At least now it's got entirely fresh coolant, new t-stat with the jiggle thing pointed at 6 instead of 11 like it was, synthetic fluids in both axles and transfer case, and fresh mobil 1 in the engine. Only thing that didn't get changed was transmission fluid and that's only because ny drain pan was full from everything else so it'll have to wait until I get back from Florida.
On another note, any good way to check and see what gears are in it? Short of jacking it up and spinning the tires and counting driveshaft rotations? Is there a sticker somewhere? Didn't see anything on the rear diff when I was under there.
gamefreakgc
Elite Member
Your doorjamp sticker on the driver's side will have the gear code, but they are hard to decipher. If you have an automatic Limited, 99% sure you have the 4.10 gears. If it's a manual transmission, you'll have a higher gear ratio like the 4.56 since it's a 5-speed. If you have the e-locker and an auto you've got the 4.30 gears. Most 4Runners have the 4.10's though.
JRZEE2000TR4LTD
Senior Member
You can use the vacuum gauge on the MightyVac and skip buying the separate vacuum gauge.
I'd think 4.10s would be plenty to motivate this rig with 32's down the highway.
Replaced the TPS last night on a whim. Definitely made the engine more responsive but still gutless between 2000-2500 and won't hold even 70mph on flat ground. Must be doing something right as the last tank showed 14.4mpg. I'm beginning to think that gear hunting is just something I'll have to live with until I get a set of 4.88's in. Seems weird to me that 4.10's wouldn't be enough gear to hold speed even with 32's. Guess I'm just used to the power curve of bigger V6's or V8's.
Still going to do the FRP test and vacuum test but beyond that I have decided though that I'm tired of chasing things down so I'm looking for a shop in Austin that I can take it to and let them go over everything with a fine tooth comb just to put my mind at ease. I can do all of the repair work but I'm limited in time and proper tools for serious diagnostic work. Let the shop diagnose it and then I'll take care of fixing it.
Still going to do the FRP test and vacuum test but beyond that I have decided though that I'm tired of chasing things down so I'm looking for a shop in Austin that I can take it to and let them go over everything with a fine tooth comb just to put my mind at ease. I can do all of the repair work but I'm limited in time and proper tools for serious diagnostic work. Let the shop diagnose it and then I'll take care of fixing it.
So I did a test on this last tank to confirm a thought I had about gearing. Last tank I ran with OD on and I got 14.4mpg. This tank I ran with OD off (yes even at 80mph) and got 15.8. So even though the engine was turning 3500rpm there was less of a load on it and it was working easier to move the rig down the road. So it's not that there's necessarily something wrong with my engine (although I'm still going to check the FRP and fuel pressure), it's just horribly under geared for as tall of an OD as it has. That's an easy fix.
BamaDrewski
New member
Have you taken off the throttle body, cleaned it and also the IACV (Idle Air Control Valve)?
The IACV is on the bottom of the throttle body and have four (4) soft metal phillips head screws so be careful taking them out or they will strip. I usually clean my once every 12-18 months and just did it again. Makes a huge difference in performance and mileage when it is squeaky clean. (I use spray carb cleaner, a brass brush, a dremel with a polishing pad and LOTS of Q-tips to get in the nooks and crannies. If you have not done this, I would recommend you do it regardless. I think you will see a difference. Also, take your rig to a muffler shop and have them pressure check the Catalytic Converter. (Costs about $20) They drill a hole before the CAT, insert a pressure gauge and check the pressure. If your CAT is clogged, that could also be the low power culprit.
gamefreakgc
Elite Member
I'm not convinced it's the gears, unless something in your 4Runner specifically. Toyota didn't make a mistake when designing the ratio for the O/D gear, there must be something that's causing the issue.
I second checking for exhaust blockage in the cat or muffler.
All of that was done a couple of weeks ago. Except the cat testing. I'm not spending the money to test one when I'm going to do an entire exhaust anyways. I'll just cut it off and use some flex pipe in it's place for the time being. Hell I may do that tonight.
Only reason I'm hesitant to think it's a clogged cat is you can feel the acceleration and power pick up as it climbs it's way through the 2500rpm range. If the cat was clogged I'd tend to think it would choke out more at high RPM and not less. At 3500rpm at 80mph in 3rd gear the engine, exhaust, and intake go completely silent like the whole thing is floating on air.
