32 MPG after tune-up

[LV2XLR8]

Hey all. Before I took a trip to SC, I changed my wires, plugs, and all three coils and fuel filter and I was suprised to notice that I used almost 9.5 gallons after 300 miles. WOW. I quess I needed a tune up.

[nikon]

what year is your car???

[BobsSilverSix]

Dude it's a 97 3.8, it's in his profile....

[CamaroRob97]

Ya I get about the same MPG 30-33. Do your PCV valve also, so you could say you did a complete tuneup.

[Jaymatic]

how in the world do you guys get this gas mileage. My car is stock and I'm lucky if I get 24 MPG. I don't drive hard either.

[mAsKeD_mUlLeT]

after i got a tuneup i'm getting about 19-20mpg. i used to get 17mpg.

[nikon]

Originally posted by BobsSilverSix:
Dude it's a 97 3.8, it's in his profile....

very sorry "dude" did'nt think to look that far I was only looking in the sig ;)

[smiley49]

My car is stock and I only get 14 mpg...

[Dan Vincent]

You guys with A4s, make sure you aren't getting the infamous torque converter clutch isolator valve wear... causing your TCC to not lock up. If you've got 3.42 gears, standard tire height (IE stock tires/rims or taller rims with lower profile tires) and an A4, your car should be just around 2000-2100 RPMs on a flat surface cruising at 65 MPH. If you're at around 2500 RPMs, your TCC isn't locked and you're wasting fuel (as well as overheating your tranny). This is common on the 4L60E and it's a (relatively) easy and cheap fix for a tranny shop (I paid $316). After getting the fix done, my TCC is locking up again and my highway gas mileage is getting a LOT better (went from an average of 22 MPG to 28+). For reference, my car has about 64,600 miles on it. There's no set time for when this happens - I've read about guys who had it at 40K and guys who didn't get it until 90K. Usually you'll notice this on very long trips where you'll get a SES with a P1870 code and a harsh 1-2, though I wasn't always getting those.

Things like plugs, wires, O2 sensors, etc all affect gas mileage, so does a new air filter (if your paper one is old, I use a K&N), PCV, etc. Cars with 3.42s will get slightly worse mileage than ones with 3.08s, but it won't be a huge difference. Severe drops in gas mileage can usually be attributed to these previous things.

[ May 22, 2004, 04:13 PM: Message edited by: Dan Vincent ]

[SD6]

32mpg on the hwy for me. 5th gear is my friend with these gas prices.

[LV2XLR8]

I think my intake and exhaust actually help my hwy mpg cause of the increased air volume. My city is horrible though like 12 or less but I drive in Atlanta.

[Turbo V6 Camaro]

27 average most i eve go was 36MPG high way....thos days are over

[Blue Flame V6]

I got 36 mpg running between 75-85 mph the other day when I went to the Kidrock concert in Wichita, don't know how but hey I was happy. The best I ever got was 42 mpg following my dad with our car trailer but that is the reason because I was riding his draft.

[Christian]

Originally posted by Dan Vincent:
You guys with A4s, make sure you aren't getting the infamous torque converter clutch isolator valve wear... causing your TCC to not lock up. If you've got 3.42 gears, standard tire height (IE stock tires/rims or taller rims with lower profile tires) and an A4, your car should be just around 2000-2100 RPMs on a flat surface cruising at 65 MPH. If you're at around 2500 RPMs, your TCC isn't locked and you're wasting fuel (as well as overheating your tranny). This is common on the 4L60E and it's a (relatively) easy and cheap fix for a tranny shop (I paid $316). After getting the fix done, my TCC is locking up again and my highway gas mileage is getting a LOT better (went from an average of 22 MPG to 28+). For reference, my car has about 64,600 miles on it. There's no set time for when this happens - I've read about guys who had it at 40K and guys who didn't get it until 90K. Usually you'll notice this on very long trips where you'll get a SES with a P1870 code and a harsh 1-2, though I wasn't always getting those.

I am having that EXACT problem man, care to elaborate a bit more on what's going wrong? I thought I had a soleniod going bad or soemthing. But this is the reason that I LOVE these forums man, no kiddin' [img]graemlins/bowdown.gif[/img] . You say it may run about 300+ to get it taken care of right? At the tranny shop, what are they actually doing? A conversion? An installation? Any help on this is appreciated Dan, or any of you guys that know, thanks!

[Dan Vincent]

What happens is you bring your car to the tranny shop, they hook it up with the scan tool, and drive for a bit. Watch the torque converter slip and TCC apply duty cycle. If the TCC apply duty cycle is very high and the slip is very high, the TCC isn't applying. Note that the car has to be warm enough for this to happen (it took my car about a half hour to 45 mins worth of driving for it to stop applying).

What happens is the TCC regulator/isolator valve in your valve body is not a straight on-off mechanism. It's pulse-width modulated for a soft apply (so that you don't feel the TCC engage). This PWM of the hard aluminum valve wears the soft aluminum valve body, causing the tranny oil to leak past the valve, causing no apply or slippage. The PCM sees this and thinks the converter itself is dying, shifts the line pressure to max and flips the P1870.

It's a relatively simple fix. The shop removes the valve body, reams it out with a sonnax reamer, and installs a Sonnax TCC regulator/isolator valve fix kit. The kit is about $40-$50 and the reamer is about $100 (most tranny shops should be doing these repairs and should have reamers already).

Here's a link to the Sonnax valve kit:

http://www.transmissionspecialty.com...54-03K-04K.htm

Mike at Aamco in Westfield, MA quoted me about $350 and charged me $316. Sadly, you're in AL, but ask your buddies for a reputable tranny shop. This is bread n butter work for most tranny shops, so it should be relatively quick for them. They'll give you a new filter and fluid too, gasket, etc.