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1994 5.7L Tuning, MPG

tanman_2006 said:
Check for vacuum leaks also when there is high idle.
Click to expand...

I did. This truck does not seem to have much of a vacuum system. Everything is electric or hydraulic. Really the only vacuum lines I could find were associated with the EGR valve, all the lines and connections looked okay.

Any opinions here on going to an MSD coil and maybe a .045 plug gap (stock .035) ?
 
Alright, think I have the truck running better now. Rebuilding the throttle body with new injectors really helped out. 15mpg on my last trip. Can't expect too much more than that.

It does smell rich after driving sometimes. I'm going to attribute this to having a 1 wire O2 sensor. That sensor is probably not up to temp as I cruise around the parking lot and shut down.

Been reading a lot about the TBI and ways to improve. Tbichips.com has some good info. I think i'm going to replace the massive stock catalytic converter with a high-flow unit, replace the Y pipe and add a 3 wire O2 sensor. Not sure if the y pipe on my 2500 is the same as the 1500 series trucks though. This might add 10hp and improve the in-town gas mileage. The recommended Y pipe is this one.. http://www.jegs.com/i/Flowmaster/389/Y250300/10002/-1

I was considering adding headers but from what I see, not really worth it on a stock truck. Apparently the big gain to be had with the exhaust is the cat and Y pipe.

Does anyone have experience with the TBI chips from this vendor? He claims a 10%hp increase on the stock truck with no MPG loss. You can run 87 octane if you switch to a 170 degree t-stat.
 
rlb said:
3 Wire O2 mod done. Rich exhaust smell gone.
Click to expand...

This also helps with the dribeability in parking lots and at slow speeds. I've had the early TBI's surge at slow speeds, and doing the 3 wire O2 mod takes care of it.
 
THEFERMANATOR said:
This also helps with the dribeability in parking lots and at slow speeds. I've had the early TBI's surge at slow speeds, and doing the 3 wire O2 mod takes care of it.
Click to expand...

It worked as advertised. Rebuilt injectors and the O2 sensor change have made a huge difference in how the truck runs.

I bought this 250,000 mile truck and put new tires on it, shocks, steering (pitman arm, idler arm and bracket, tie rod ends) and it basically runs like new. The body and interior were in good shape but I had to fix little things here and there (door hinges etc...).

Only thing I need to do now is look after the brakes. I have a handheld vacuum bleeder so i'll suck out all the old fluid and replace. The front brakes are okay, plenty of pad left and no shimmy. The back brakes, I haven't had a chance to get the drums off and have a look at them yet. I bet they haven't been worked on in years and need to be cleaned and lubricated. Do the drums adjust themselves when braking in reverse? Might get a local shop to do it, I generally avoid working on drum brakes whenever possible.
 
Oh yeah, I need to look into fixing the temp reading on the dashboard. Moves up as the truck warms, but will only read 150F when the truck is fully warmed up. T stat is new. IR temp gun reads 200F at the t-stat housing and along the heads. Both temp sensors (the two wire and the one wire) are new from the dealer. I also cleaned the grounds at the thermostat and a few others in the engine compartment.

I want to replace the connector and last 6" of wire for the one wire thermostat. It fits okay and isn't loose, but looks beat. Is there a source for these connectors, possibly with a pigtail? Sure I could find one at a bone yard but a new one might be only a few bucks more. I'm thinking I could just snip the wire a few inches up and put a new connector on it.

I'm also going to look into the instrument panel grounding. I know on the 1500's, this grounded to the back of one of the cylinder heads? At work now but i'm going to start here when I get home this evening. The volt meter gauge drops a couple volts when the headlights are turned on or the a/c blowers are cranked up, so I think there is a bad ground somewhere...
 
The temp gauge sounds typical of that dash style. The needles just don't point to the right area typically.

The Y pipe and 3" high flow cat are a good addition as said earlier. Should be OK w/ factory pipe as long as it is 2 3/4", some got swapped to smaller pipe.

The Y pipe plus tbi mods helped mine alot. I did injectors then too so I bet that didn't hurt.

source unknown
 
Going to have to try the 3 wire on a 93 454...
 
So now that I have spent countless hours fixing this truck up, I am starting to look at diesels. A nice 1999 6.5 TD K2500 suburban has come up for sale near me, I can probably buy it for close to what I can sell this truck for.

I'm a little hesitant though, have never owned a diesel. Mainly I am interested because they get better MPG and probably would do a much better job towing a car hauler than my 5.7.

http://greensboro.craigslist.org/cto/4442895193.html

Good deal? I am getting the details from the owner and might go check it out in the next few days.
 
Diesels getting better milage isn't a good reason to switch anymore. With diesel being more expensive than gas, and the added costs of maintence on top of it, diesels only make sense if your going to use them for towing alot. I know in hindsight now I wish I would have sold my BURB, bought a 1500, and did a 6.0L swap in it, or just have bought a newer BURB or truck with an LS engine in it. The newer trucks get alot better milage than the old TBI's did, have ALOT more power(nearly double), run forever, and don't cost much to maintain.

And for $3600, I would be asking him what is wrong with it, and having it checked out CLOSELY to make sure it is in decent shape. Even ROUGH 6.5 BURBS are fetching that kind of money, and decent ones on EBAY are going for ALOT more than that. Chances are for that price he is trying to ditch it for a reason.
 
THEFERMANATOR said:
And for $3600, I would be asking him what is wrong with it, and having it checked out CLOSELY to make sure it is in decent shape. Even ROUGH 6.5 BURBS are fetching that kind of money, and decent ones on EBAY are going for ALOT more than that. Chances are for that price he is trying to ditch it for a reason.
Click to expand...

But the ad says it was well maintained!!

I'll definitely not rush into a purchase. I did pick my burb up for $1800 though. Some deals are out there to be had.
 
I ordered a chip from Brian at tbichips.com

Also going to do intake and exhaust. Specifically replace the cat and Y pipe. I ditched the stock baffle and going to put a different intake on there that still routes to the fender 'cold air" thingy.

Let yall know how that does.
 
Interesting read. My first truck was a 94' silverado K1500 with the 350tbi and the stick NV3500 transmission. The only major issue I had with the truck in the 3 years I owned it was a leaky gas tank.
Wish I would have known about the sensor. I basically got 12mpg everywhere. It had some high gear in it, at 55 it would run almost 2k rpm.
 
Time for exhaust on this truck. Any recommendations for an inexpensive, quiet muffler? Going to do a new cat, muffler and maybe y pipe


Sent from my iPhone using Tapatalk
 
I used to like a flow master 50 on my v8 jeep. But probably need something quieter. The truck's main mission is now towing around a 24' boat that weighs 6000lbs.


Sent from my iPhone using Tapatalk
 
Look at JONES FULL BOAR mufflers. They make copies of FLOWMASTER and MAGNAFLOW for less than half the cost of the name brands. There MAGNAFLOW copies are even made of stainless just like MAGNAFLOWS are, and they don't sound half bad. Heres a video of a set I put on a CORVETTE awhile back. Keep in mind this is not a stock engine by any means, but it gives you an idea of the sound, and it was very quiet inside the car.

Open pipes.
JONES FULL BOAR MAGNAFLOW copies.
 
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