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TBI thermostat/tune question or 2...

shovelbill80

shovelbill80

1/2 ton status
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i just got this '90 and have never owned a fuelie anything. my friend, the PO, put a 180 thermostat in her and i was wondering if this can fool with the computer thinking it's still warming up always.....i just put 2 "fill ups" through it and all i come up with is 5.9 MPG in the city. granted i've warmed it up some after i got this remote starter gismo, but 6 mpg is beyond your average abysmal...

i need to do a complete tune up too. he changed out tons of crap before i got it and it still has a little "pulsing" at idle every now and then too. he chased a vacuum leak and so did a mechanic friend, but didn't find anything. more fun for me. she WILL be a great truck one day.

i've read some guys say it doesn't matter which thermostat they run. any and all advice would be greatly appreciated before i start a big search about getting this running really well. she always starts has really good strong power for having 164,000 on the clock.. blows some oil smoke when starting cold though, goes away after a few seconds.....thanks, Bill

edit: so you know....has 3.73's and 31"
 
The TBI trucks are supposed to use a 190-195 degree thermostat. If you run something cooler, you'll get less efficiency.

The truck I just bought had a 160. I put in a 195 and it runs a LOT better. Plus the heater works better. :)
 
Proper thermastat for the engine will help. But that little blue smoke is messing with your O2 sensor. So try a new O2 sensor and check your milage on the first tank.

I grew up across the river from you and know what the city driving is like. Cold weather kills fuel milage...
 
thanks Jesse....i'll be getting the 195 today if i can

Eagle...when i go to the auto parts store i'll pick up an O2 sensor also. i know he replaced it somewhere down the road, but i need to do any and everything again to be sure. i bet you don't miss the city "driving" either. thanks.
 
I left NJ in 1981 to travel the US, it was only two weeks before I knew I was never going back... went back last year 2009 to get my mom after my sister passed away. Sorry, don't miss it! Never forget the smell of Newark Airport when they opened the door.... :doah:

If it is tuned properly, no codes set and a recent O2 sensor you may be able to clean the O2 sensor with appropriate cleaner from auto parts store. But that little puff of blue at startup leaves residue on O2 each time. Also outside of O2 needs to stay clean and can not be covered with oil and grit... going a step farther that little puff of blue is probably not doing your cat converter any good either...

shovelbill80 said:
thanks Jesse....i'll be getting the 195 today if i can

Eagle...when i go to the auto parts store i'll pick up an O2 sensor also. i know he replaced it somewhere down the road, but i need to do any and everything again to be sure. i bet you don't miss the city "driving" either. thanks.
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That reminds me, I was talking to my father in law about my truck smoking and he said to get some CD2 to help. Well, I was Googling around and found this interesting write-up about the PROPER application of CD2 and how to stop the smoking:

http://www.mikebentley.com/oilburn.htm

The good part:

First, check for and correct any oil leaks around valve covers and oil pan. Tightening bolts may do the trick. If not, install new gaskets or have the work done. (This procedure won't stop leaks.) If front or rear engine-bearing seals leak, add a can of "Bearing Seal Additive" after Step #2. Chances are it will stop or vastly minimize the problem at low cost. (It did for me.)

Okay, here are the 3 Steps:-

1. Drain engine oil and replace oil filter. You've probably been using a multi-grade 10-30 or 10-40 weight oil. Or a straight 30 weight oil. Regardless, replace that oil with one grade heavier, single-weight of oil. During warm months, use 40 weight; in the winter (depending on how far the mercury dips in your part of the country) use 20 or 30 weight. Slightly thicker oil won't hurt that worn engine, and if your battery is good, it'll turn over fast.

2. Add two cans (30 ounces) of Alemite CD 2 for Oil Burning, which replaces one quart of the oil you would normally use during an oil change. (If capacity with new filter is less than 5 quarts, use one can of the Alemite.)

3. Drive vehicle at town-speed, 20 to 35 miles per hour, for at least 50 miles (a 100 mile distance is better), before opening it up to expressway speeds. That's all there is to it!

Steps #1 and #3 are the real secret, assuring success when the "usual" additive treatment helps little if at all. Here's why, as my mechanic friend explained it to me:-

The Alemite contains a substance that builds-up between ring and cylinder wall, forming a tough, long-lasting seal. Problem is, standard 30 weight (in moderate clime) and multi-grade oils are too thin; they don't have sufficient "body" to prevent most of the sealer from blowing past rings BEFORE it can do its job. A heavier, single weight oil retards the blow-by and speeds-up the seal formation.
Driving at moderate speed for the first 50 miles or so, also helps accomplish fast seal build-up. Use a heavy foot on the accelerator immediately after treatment, and the fast-moving pistons pump much of the oil and sealer out the tail pipe.

The sealing compound, after setting-up, isn't as hard as steel. So, to prevent seal from deteriorating, add one can of the Alemite when changing oil thereafter. You might get away with going back to a thinner or multi-grade oil. But, why bother changing a winning combination!
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I just replaced my 195 t-stat the other day, i recently moved back to Northern indiana from Arizona, and since i had the cooling system set up for max cooling in the Arizona heat, now it's over cooling, even with that 195 t-stat. I replaced it as it seemed like it was just opening too soon, running about the 170 area, and so far it's running warmer, but still not at the normal spot i like to see it at.

I was at Napa the other day to get that stat, and he told me there was a 205* t-stat available, i'm seriously thinking about going with that one, seeing that i have a 4-core radiator & heavy duty fan clutch, i think it may work fine.

Yes, the lower t-stats in these or any fuel injected motor will make the computer think it's still under normal operation temp, and keep it in "cold mode" or choke style setting for carb'd motors, feeding more fuel.

I ran a lower t-stat on a Camaro i had several years back because overheating issues, yeah it ran cooler, but also lost some fuel mileage from it.

If your cooling system is good, clean and works the way it's suppose to, you should have no problem running a 195* t-stat, and being that you're on the east coast in a similar cold weather climate, if it still doesn't get warm enough for ya, consider that 205* unit, i'm going to try it out this week and see how it goes.
 
That little puff of blue isn't anything more than umbrella seals. I wouldn't start mucking with additives and snake oils, just replace the umbrella seals when it gets excessive. That puff of blue should be trademarked by GM...I had an 88 round body pick-up I bought brand new, and it started with that little puff of blue at start up with less than 40K on the clock. :rolleyes:

My TBI 350 in my 90 Blazer has 263K on it. I get a small puff at start up and that's it. Hammer down, no blue at all. i changed the oil 3000 miles ago, so I'm due, just checked and it's less than half a quart down.

I'm pretty sure some bonehead swapped a 160 T-stat into mine, or removed the T-stat altogether. Temp never sees higher than 165 or so. My mileage on 31's with 3.08s was ~13 or so. That was 60% highway though, and what I call light city driving. When I'm running across town it's usually at 2:00 am or so, the lights are favorable and there really isn't any stop and go.

With the 35's and 3.42's I think I'm down to 11.5 mpg. I'm about to put in a 195 T-stat, I think I can get it back up to 13 ish again. It should have been pulling down closer to 15 with the 31's...

Rene
 
Eagle....sorry bout your sister. Newark always sucked.

thanks guys.....i'm waitin for a check to clear to get the stuff. is there and anti seize stuff on that O2 sensor? mine sure looks like it's rusted on pretty good. i hope these things don't break or strip very easy :rolleyes:

when the oil smoke get to be a concern i guess it'll be time to do a complete motor.....a torquer truck type roller cam motor with different heads. i'm thinking on getting some flow matched injectors, adjustable regulator and gage over the winter too. the exhaust has been changed from the converter back a while ago and in the spring i'd like to do the y pipe, maybe headers. eventually i'd like to have 200 hp and 300 ft lbs at the wheels, that should be just fine for me....and like 18 or better on the highway.
 
Honestly, if you're not getting any fault codes saying your O2 sensor is getting a funky reading, i wouldn't be too worried about it. From what i understand all they are is a little pyrometer, sensing exhaust heat temp and adjusting the air/fuel ratio accordingly.

I have driven my '89 when it had it's original motor for about 4-5 years with a motor that would smoke quite a bit at start-ups, and sometimes would start to smoke alittle on extended idle times. Never had an issue with the O2 sensor. Now i can see definately over time it would cause problems with a cat maybe, and it will build up some carbon on the seosor too, but from my experience, it never failed, or affected the way the truck ran from all of that.

BUT, as soon as there is a fuel delivery problem, even a slight one, that O2 sensor is faulting out reading usually a lean condition.

I'm not claiming to know everything about the sensors and how exactly they work, but i did stay at a Holiday Inn Express last night


Just an opinion from me, :D
 
i have last years emmissions ticket on the truck, i'll scan it in later. seems like it did really good too...i'm going to run it again as i need to inspect it anyway and see what i see. it pretty much sat for the last year, not going very far.

Eagle. i think with some little mods, 33's and 3.73's 18 on the highway is not out of the ball park based on what i've read.....my '85 with 35's, 4.10's and a 305 was getting around 17 as i remember......eventually we'll find out if it's possible. 10 in the city would be a stretch, but that's what i'm shooting for.
 
Yeah but your talking NY City, if you just stay in the city I could see 10 MPG. But those long parking lots to commute are horrable. Do they still call the Long Island Expressway the longest parking lot in the world?

I have a 2wd Suburban that get's 11 here in Idaho winter city warmup driving and it does get 17 hwy.
 
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