Poor Gas Mileage


New Member
Jun 6, 2001
OK Guy's,

I haven't posted for a few weeks. Been busy with summer visitors and house work.... Anyway here is my problem. I have the rough idle issue worked out on the 83 T-Type (N/A 3.8 w/2bbl) but the gas mileage is terrible. I'm only getting 13MPG around the city. I did some research and found that a 1983 with this engine was rated at 20MPG in the city. I'm looking for any ideas as to why the mileage is so bad.

Any and all input is appreciated.


Greg Adams
87 GN
83 T-Type
Could be a dirty air filter, incorrect timing, emission system not working properly or a comination of all three.
What has the problem with the rough idle?
Just an FYI, I've been getting 17-18 MPG with my '83 TR on mixed city/highway driving.

20 MPG might possible if you never opened the secondaries.
Hey Rich,

My swapped 3.8 gets 19.30 on the highway. I religiously keep track of it. Max capacity of 15 Gals in the tank. And this is with the Q-jet. I don't always use the A/C. And I only floor it just to prove a point at times. (Jap cars ya know..).

Something is wrong with his car. The min gas milage he should get even if its poorly tuned is 15MPG with a duel jet. Less then this and something is truly wrong here.

Do you smell gas when you first start up the car? Even a slight trace of the smell of gas is a fuel leak.
No smell of gas but the car has no pick up at all. I'm going to start with the timing and be sure that the Vaccume advance is working correct. What about a clogged cat? Like I posted before the previous owner removed all the turbo parts and coverted it to a N/A 2 bbl. I'll start the trouble shooting process and keep you all updated.

Thanks for the input so far..keep the ideas coming.

Rich, Tug,

After I read Tugs thread a month ago and looking at his pics, I noticed that the distributor was dropped in rather awkwardly.

Last year, I was having problems with my computer system on my '81 and decided that I might rid myself of it if I could'nt troubleshoot the problem. I went out and got myself an earlier
non-EST/HEI distributor and an earlier non-TPS Q-jet. I rebuilt both to new conditions. However, I was able to troubleshoot and fix my computer problem. I kept the earlier units thinking that someday I might run an experiment with them.

Tug, after reading your thread a month ago I was inspired and tried the modification. These were my findings:

Some Earlier pre-1981 V-6's did not come with an air pump. HEI distributors that came on these V-6's were vacuum controled. Thus, the bracket assembly that holds the later air pump would obstruct an HEI distributor's diapragm resulting in limited adjustment, (if any), on the timing. That is why the air pump and assembly on Tugs 83 is missing, (or removed altogether).

Even with this though, the earlier HEI distributor cap and no. 1 plug is not in the same place as the later '81 and up EST distributors. This would mean that the possibility that the distributor was dropped in the wrong place is evident in Tug's 83. One must know how to modify this properly. On my experiment I had to file a new notch on the earlier distributor and I used the later '81 distributor cap so that it would fall in the exact place as was meant to be on the later V-6's. I got everthing running smoothly and perfectly tuned. But my final thought on this experiment was that the EST/HEI distributor system was vastly superior to the earlier vacuum controled type HEI distributor. It responds smoother and faster then the vacuum/HEI's.

Tug, if you still have the wiring and computer on your '83 only that it was disconnected and not butchered. Then get yourself the later EST/HEI distributor, later TPS control carburetor, and install the coolant sensor on the intake. (And hopefully the oxygen sensor is still attached on the exhaust manifold).You will never get that V-6 to run properly without it. Reverting that V-6 correctly to an earlier system is time consuming and very much involved.
WOw Freddie...That's alot to digest right now...I do have all the wiring and computer and distributer that was removed from the car. I'll have to take a look at the parts and see what condition they are in. If I have to do that much to get this thing running correct what do you think about going for a SFI setup like the 86/87"s?

i just wanna know what the hell the guy was thinking takin off the turbo? if u have it.. put it back on.. where in seminole Fl do u live? i live in Palm Harbor about 10 Min away from Clearwater.. maybe we can get together and i can give u a hand. ive become real freindly w/ my 3.8 2bbl. i can prob help u. i hate my gas milage also... city driving it sucks.. but when i go travelin to sarasota to visit family... i get great milage.. ill get 200 miles to a 1/4 a tank. i ove it. i ahve a 85 N/A Regal. 93k mile and she runs like a charm.let me know.....

Rich would probably be better at answering the SFI question.

This I do know, a used computer controlled dueljet would probably run you $20-25 at a boneyard. A rebuild kit for the Dueljet would run you about $15-20. A used EST/HEI distributor would run you about $20-25. A new 7-pin module for the distributor cost about $18.00-23.00, (if you need it). New later distributor cap and rotor $20.00. New coolant sensor $20.00. So bringing it back up to the '81 and up CCC type system could run you about $150.00.

The computer is located in the interior on the right side passengers leg area below the glove compartment against the wall. (Hopefully its still there, if it is'nt boneyards charge about $35.00 for a used one. BUT IT MUST BE THE OEM TYPE FOR YOUR VEHICLE! I'm sure the turbo computers are probably rare, so let's hope you still have the original. And that right there is half the job!). If you go this route it still can be tricky. Computer troubleshooting can be frustrating at times. But after you plug together all the parts and turn it on and it works and it does'nt throw any codes, your done!:)
Originally posted by b4black
Just an FYI, I've been getting 17-18 MPG with my '83 TR on mixed city/highway driving.

20 MPG might possible if you never opened the secondaries.
I get about the same with a multi miss + other problems and my lead foot. My highway driving is more like city driving expect I get up to 65 - 70 at times.