North American Turbocoupe Organization

Poor Fuel Economy
I recently purchased a 1988 Turbocoupe. It has about 94k miles. It had several oil leaks which I have mostly fixed (oil pan, valve cover & transmission pan gaskets). I also replaced the oil pump, EGR valve, wires & plugs and air filter. However, it has only been getting about 9-10 mpg in mostly city driving. Other posts that I have read usually get about twice that. What are some of the possible causes of this and where do I go from here?
P.S. - It also idles rough, though it doesn't stall. Driven real easy.
Thanks for all the input, will try ASAP.

Pete D Offline
Jim, Welcome to the board.
Pull the vacuum line off the fuel pressure regulator and see if there is gas or the strong smeall of gas in the line. If the smell is faint, then run the fuel system diagnostics:

Have you pulled the codes yet?
Let us know what you get in each phase of the test.

Did you use the Motorcraft EV-127-A valve, Ford P/N: E5ZZ-6A666-A. Other brands do not keep boost out of the crankcase which can cause leaking gaskets.
Pete Dunham


Jeff K Offline
Is the CEL on? If running rich enough to get that horrible mileage, it should be on. If it isnt, are you sure the CEL even works? Common for the PO to pull the bulb out if it is on when trying to sell it.

I assume you have an auto tranny?? If so, here some possibilities:

Brakes dragging. Common for the rears to get hung up (frozen caliper pins) of siezed park brake cables keeping rears on.

Is the tranny going into OD?

Bad 02 sensor or orange 02 ground wire at turbo inlet disconnected (this should turn on the CEL)

Is all your driving very short trip on cold weather? Long warm ups? That kills mileage.

Is the engine getting to operating temp?

Are you driving it like you stole it?
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
05 Taurus SEL Duratec daily driver
04 Taurus Duratec (wifes car)
02 Pontiac Grand Prix GT
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized

Kev Offline
Posting Freak
By the way,
PO means Previous Owner
CEL means Check Engine Light.
O2 means oxygen
1988 TC 5spd

tr_guy79 Offline
Senior Member
When having "fun" my TC will definately drop into the low teens on MPG. A highway run will definately give you a more accurate idea of fuel comsumption.

If you are driving it "normal" and returning that type of mileage, then there is definately amiss...

A good checkup on any newly acquired TC is to:

1. Pull Codes and fix any problems
2. Make sure tranny is locking and going into OD
3. Check FP (AZ rents the tool. It's EASY to do 39psi @ idle)
4. Check for boost/vac leaks
5. Set base idle (800rpm, warm engine, IAC disconnected)
6. Check TPS voltage (.96V @ idle)
7. Check timing (10-12* spout out)
8. If original, replace HEGO sensor (O2 sensor)

I have done all but #8 on my '85, and everything FAILED except #1,2,and 7

Good luck, and keep us posted

3rd Annual Philly Tri-State NATO Meet -

'87 - Range Roller 4* adv / 50 trim t04e / Ported E6 / Gutted Knifed intake / Stinger 3->2.5" / Adj. Cam Pulley / Warlboro 255

To Do: PIMP/MS2, FMIC, Bigger Inj

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