North American Turbocoupe Organization

Idle, "clattering" and mileage problems
Evedell Offline
Junior Member
Just picked up my 87 TC 5-speed (120k) up from Blood Enterprises, who did a drive-ability inspection. Great guys down there, and I recommend them to anyone in the Pacific Northwest. In any case, I came in with the following concerns:

-Poor mileage - bad in the summer, worse in the winter (routinely 14-17 mpg)
-"Clattering" noise under load, not sure if it's pinging or what, but it was concerning.
-Hanging throttle - every 2nd or 3rd time I drive the car, the throttle likes to climb, usually building up to 3k and stays there. I can shut off the car and restart it, and it usually takes car of it. Sometimes, it goes away on its own, and, rarely, I can floor the throttle for a second and it kicks down.

When I got it back, I got this report:
"test drive, monitoring with scanner, o2 sensor input to ecm, ect, and vat all operating correctly, timing and timing control appear to be ok at this time, check for clattering, none present, throttle has not stuck, visually inspect, throttle bushings have some play, suspect they are the reason for the sticky throttle, recommend replace the throttle body and recheck."

Unfortunately, they weren't able to replicate the idle hang or the clattering noise, but that's to be expected (my car is a fickle beast). Going with their advice, what's the recommended replacement for a throttle body? Should I find a NOS unit, a rebuilt unit, or are there any swaps that people have done that work better? Addressing the mileage issue, I have more or less run out of ideas. I've tried different gas stations, played with the regular-premium switch, drove like a granny, drove like a pissed-off teenager... Doesn't seem to affect it in any way.

To summarize...
-Rebuild, replace, or swap throttle body?
-Mileage sucks, what do I do?
-How do I know if my car is pinging?

1987 Turbo Coupe, T5, Stock 2.3t
converted shocks/struts

Not B Anymore Offline
You shouldn't really be getting pinging if the knock sensor is hooked up.

There is no direct bolt-on throttle body that I am aware of. People swap in SC or 'stang TB's, but some form of modification is required to make that work. There was an old post on here about someone who had a bushing fit to their TB because it was worn. That's all I remember about it at the moment - I'll try to find the post.

I don't think the idle climbing has anything to do with the throttle bushings though. Seems more like a control issue than a mechanical one. You might think about cleaning the IAC and double checking your base idle and TPS voltage. There is a tech article on how to do it.

Hopefully someone will chime in here who can help more...
Brian Leavitt
'86 TC 5-Speed -- MS2x w/COP | 83 lb. injectors | T3/T4 50 Trim Stage 3 .63AR | Full 3" Exhaust - No Cat | Motorsport FMIC | Ranger Roller | Ported E6 | Walbro 255HP | Kirban | 20psi | 120-amp 3G | 8.8" 3.55 rear | '03 Cobra Wheels

Pete D Offline
I agree on testing he TPS and clean the IAC. A bad TPS could cause the hanging idle but it's not the only possibility. I'd also recommend you pull the EEC codes. There are 2-3 articles in the Tech Articles (links on the right of this page)

On the fuel mileage, how long since a good tuneup with the right parts Motorcraft wires, Autolite 764 copper plugs or Motorcraft AGSF32-C plugs and a good grade of cap and rotor

Clattering noise: Not enough info. Any idea what part of the car or engine it's coming from. Need more info. Does it happen hot? or cold?, only hot? High load? low load?. Are you using high test gas. Can you hear it just reving the engine in neutral, under the hood

Pete Dunham


Jeff K Offline
Hanging high idle is often caused by TPS base voltage over 1 V, and not a mechanical problem with the TB. Is the CEL on? Does the CEL work? (Does it come on when the key is turned to RUN without starting the engine?
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

w60 Offline
Senior Member
Around town my t-bird gets about 15 mpg and my CR/V gets about 17. On the highway my CR/V gets 23 and my t-bird gets upper 20's to 30...for what that's worth.
White 88 TC Auto Trans
White 04 Honda CR/V
Blue 74 Honda Trail 70

Pete D Offline
In mixed driving I get 16 -21 and on long trips I get 25-29 in an 88
Pete Dunham


Sean Offline
......I get 10-15mpg in town....and 20-22 on the highway......but my "highway" driving is 85+, and my city driving is stop and go with a lot of WOT....
1988 Thunderbird Turbo Coupe
160 amp 3G and upgraded charge/power supply cables.

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