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Discussion Starter · #1 · (Edited)
I'm so stoked! This post is for you 10-13 MPG folks out there.

I finally found my mileage black hole! After throwing a few hundred bucks in the way of a new VAFM and TPS, water temp sensor, 02 sensor, as well as a thorough off-the-vehicle injector cleaning and all imaginable checks for vacuum leaks etc...

Turns out if your EGR vacuum modulator is bad, it won't necessarily throw a code! I did the FSM "blow test", by pulling the three tubes off Q, P and R, then plugging P and R with my finger while blowing into Q. Air did not flow that freely, even after cleaning the filter under the cap. There are websites out there that say if you can blow air through the big pipe on the bottom, then its bad. Some folks have the diaphram blow out from heat and exhaust pressure, and it gets caked with soot. After I broke mine open, it was dirty but not obviously broken. I tried spraying cleaner through the ports, but I was not satisfied with it.

I ended up getting a new one (Toyota part# 25870-65010) for my 3VZE 3.slow off ebay for $40 shipped, and I topped off and test drove the freeway. I was not light footed, went 70-80 miles per hour and worked the AC part of the time. Even jumped the start a few times. Went about 51 miles. Topped off again exactly the same way.

Long story short, my mileage shot up from 14.71 MPG to 18.76! That's a 27.5% increase. When gas was $4, that's over a buck a gallon sucked out of my pocket!

(If somebody needs a good VAFM, I have a slightly used one for cheap, with only 45K miles on it.)
 
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1998 T100 SR5 2WD
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Um..are you sure it wasn't going from winter blend gas to summer blend gas? ;)

Good on yah!! How many miles did you have on the EGR (best guess)? :D
 

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Discussion Starter · #3 ·
Um..are you sure it wasn't going from winter blend gas to summer blend gas? ;)

Good on yah!! How many miles did you have on the EGR (best guess)? :D
No, I don't think the ethanol blended gas has anything to do with it.

The EGR vacuum modulator was factory fresh at 15.5 years and 46K miles. It little rubber bottom is exposed to nasty exhaust gases after all.
 

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1998 T100 SR5 2WD
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Well...my 1993 T-100 has about 290k on it...the EGR has never been replaced. I still git around 22mpg on the highway though... ;)
 

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Discussion Starter · #5 ·
Everything I've read about our EGR systems (a lot!) says that the EGR valve itself rarely fails, but the vacuum modulator is the culprit 95% of the time. The other 5% is probably the VSV. I think it just wears out or develops pin holes or just plain rips. Intense heat+Rubber+Time = Failure. It is surprising that mine failed with such low mileage. I did open the modulator and it was dirty on the exhaust side, and on the top, vacuum side. :disappoin
 

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gas mileage

to bamzip this a question rather than a comment, is your truck a v6 3.4l or a smaller engine?
mine is is a 96 t100 i used to get 17mpg on average now it is even worst but i amin the process of doing a major tune up.
 

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oooh i missed to mention my toyota had 98k miles on it when i got 9 yrs ago,now about 171k,it has been good to me replaced tires front brakes and shocks
,
i also have haynes book,and really dont know if its a 1/2 ton
or 3/4 ton.
thank you guys.
 

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1998 T100 SR5 2WD
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There were only 3 engine sizes available over the entire line of T-100 from the factory...

1993 - 3.0L V6
1994 - 3.0L V6, 2.7L I4 intro later that year group
1995 - 3.0L V6, 2.7L I4, 3.4L V6 intro later that year group (3.0L V6 dropped at that time)
1996-98 - 3.4L V6, 2.7L I4

I have 2 T-100 trucks...a 1993 SR5 with a 3.0L V6 and a 1998 SR5 Xtra cab with a 3.4L V6.

The T-100 only came in a 1/2 ton and a 1 ton configuration. The 1 ton was only available from 1993-95.
 

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1998 T100 SR5 2WD
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You can also run yer VIN through www.toyoDIY.com and it should bring up what configuration yer vehicle is. ;)
 

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Since you have a 1996...I would recommend that you clean the MAF sensor with some sensor cleaner and pull the fuse on the ECU fer about a minute.

If yer mechanically inclined...pull the throttle body away from the air plenum and give the TB a good cleaning. You might also give the idle air control (IAC) valve a cleaning while yer in there. There's a thread here about that... ;)

If you have the 3.4L...make sure you put in the NGK or Denso dual ground plugs... ;)
 

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average mpg you guys getting on 3.4l 96 ?

thank bam and others, i recently replaced the spark plugs, and cleaned the injectors, but i had to replace the o rings (found a fast and cheap fix) on the end of the injectors, check engine is gone:lol:, once in a while i still get a little hesitation especially when i am on a stop light.
also once a while air bag sign comes on.
any way if someone could tell me roughly the average mpg
on the 3.4l v6 2 wd.
thank you.
 

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1998 T100 SR5 2WD
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When I first got this truck...it got 15mpg going about 65 mph at night fer about 4.5hrs. After I got to my house...the next morning I cleaned the MAF sensor and a quick swab of the TB. Reset the ECU...got 19ish on the way back to San Antonio. Been averaging just around 21 mpg on the highway. I'll see what else I can git after this upcoming road trip... :D

I would really pull that TB off and give it a good scrub...same fer the IAC valve. Mine was crunchy when I was cleaning it up... ;)
 

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When I got my 96 SR5 3.4L auto it had been sitting for 2 years WITH half a tank of fuel. I drove it home(5miles) siphoned all that I could, filled it with premium and did the sea foam routine. Everything was still original on this truck, I changed the plugs(3 densos and 3 NGKs, now all NGK), wires(1995 date on them as others have noted) air, fuel and oil filters. flushed all 12 qts of tranny fluid(didn't drop pan or change that filter though) truck now runs Mobil 1. I get just over 20MPG on highyway at AZ speeds(65-80mph) and for the last few months I have driven exclusively in town only, no highway at all and A/C on 100% of the time(100 degrees here from now till end of summer) I get 20-21 MPG in town with A/C on. my mileage has not changed in the 6k miles I have put on the truck since I got it. BTW I am the 4th(!) owner too. It has never had the timing belt done, and I am sure it is the original water pump,,,that unfortunately has begun to leak. And it only leaks when the truck has been sitting for more than a day...from behind front cover at bottom where the pump is. I just turned over 140k miles so I think I will have to bite the bullet and get the timing belt and water pump done. I love this truck, perfect size and power is good for mid size truck.
 

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Here is something strange i bought two gallons of transmission fluid for my t100, It suppose to use 12 quarts according to chilton book, i drained the transmission and all i got out is about a gallon, although the level was in range,
Any comment will be great, Thanks
 

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tranny capacity..

Hi Samtoyota,

you only drained the small amount in pan, the majority is in the torque converter. The only way to completely change all of the fluid is to have a shop do a power flush, or do the procedure yourself. The info on how to do this is on this board. good luck... BTW I used a full 12 quarts when I flushed mine.
 

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I am afraid i did not find anything on the board as far as t100, I have seen a good description of a camrey but that looks completely different, Unfortunately the chilton book doesn't touch that. THANKS
 

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tranny fluid...

my apologies then, I thought I read a post of Bams that detailed the process. I took the smaller lines off the bottom of the radiator(where the built in tranny cooler resides on my 96) and put the pass side line I believe in a clear gallon jug, started the engine..ran it approx 10 seconds, shut it off, poured a few quarts in the tranny dipstick tube, started engine again, several times repeated this process and the old fluid gets pumped out of the torque converter as you are slowly replacing it via the tranny dipstick tube. took a few times but you will begin to see the clear fluid coming out the hose and then you know you have gotten very close to a full fluid change out. only ran engine for 10 seconds at a time to not let the tranny pan run dry. Of coarse you make sure the level is good when you are all done as well. I put in 12 qts, same as I took out so my level ended right where I started. At the shop I believe this service is approx $100+ or so. do a search for Bams post, I think he probably explained it better. Any more questions, just ask. :thumbsup:
 
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