North American Turbocoupe Organization



OK, guys, here is a strange one
Jeff K Offline
Administrator
#1
The 88TC has been running great for several months and several thousand miles. Today, my daughter and I took a trip to visit some friends about 100 miles away. On the way home, traffic was light, and I was crusing at 75-80 mph all the way home. My 12 year old daughter likes to watch the A/F gauge bounce around in closed loop and she asked me why it stopped bouncing when we went over 80 mph (2900 indicated RPM). I tried to explain how the EEC went open loop at higher RPMs, etc... (I will turn her into a gear head if it kills me...hehe). Well getting into town, we slow to 60 to 65, and she notices the A/F gauge was not bouncing, but sitting right in the middle. A little time after she mentioned it, the CEL came on. No effect on how the car ran, though... A quick WOT burst up to 80 mph made the A/F go full rich, as always. After about 2 minutes, the CEL went off, and the A/F gauge started bouncing again, indicating closed loop operation restored. As soon as we got home, I ran the codes. KOEO: 28 (VAT code expected because it is 20 deg out today), continuous code 42: rich when closed loop expected. This obviously is what triggered the 2 minute long CEL. KOER: 25 (KS, expected) and 28 (VAT, also expected). Drove it around a little after the code test, and all seemed normal. I am leaning toward a EEC glitch as the cause of the CEL. I will check the TPS and VAF voltages to be sure they increase smoothly one of these days, just in case there is a problem there. BTW, fuel pressure is at 43 psi with vac hose off, and the regulator is good (fairly new Kirban AFPR), and 02 sensor is only about 8K miles old. Anyone have any other ideas???

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Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 20 psi, forced air intercooler, water injection, bypass valve, Ranger roller cam, subframes, etc., etc.. // 86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP nitrous, ignition, gears, suspension, etc., etc.... // 91 Escort: Bone stock winter car // 00 Windstar (wifes vehicle)
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
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Pete D Offline
Administrator
#2
Connector at O2 loose?? EEC brainfart?? [Image: biggrin.gif]

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NATO Member
88 TC X 2, 86 SVO, Main TC with K&N, 3"DP to 2.5"duals through Dynamax, Ric valve at 17+ and disconnected KS.
Elite Bodega 16" chrome wheels. Autometer pod w/ A/F and Vac/boost gauges.140 mph Motorsports Speedo New engine: Total Seal rings and TRW pistons, ported and polished head w/ cc'd chambers,1.59"exhausts, SS valves, gutted upper, knife edged lower, A-230 cam, Race Engineering Adj Cam Sprocket, Crowlers, ARP head studs, and rod bolts. Walbro 255 HP pump and Kirban adj FPR, T-3. Centerforce II, KB subs and jack rails.
Pete Dunham


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Jeff K Offline
Administrator
#3
Ya, I am going to check the 02 connector, but I am leaning toward the EEC brainfart theory myself. Maybe the EEC felt it had to make corrections to the long term fuel trim for some stupid reason.

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Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 20 psi, forced air intercooler, water injection, bypass valve, Ranger roller cam, subframes, etc., etc.. // 86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP nitrous, ignition, gears, suspension, etc., etc.... // 91 Escort: Bone stock winter car // 00 Windstar (wifes vehicle)
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
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Dan E Offline
Posting Freak
#4
Geez, I was afraid to even suggest an answer...I mean when you are stumped Jeff, I feel like my God...who else would know the answer ? (I mean that with honest respect...).

My first thought was also the O2 sensor but...

Sometimes I feel that the EEC "learns" and adapts to periods of constant speeds and if you were in an extended period of time at one speed and A/F mixture...maybe it got "stuck" at that point. Just a hairbrain idea...

Maybe clearing the codes and/or disconnecting the battery for a while to re-set the EEC may have an effect ???
Dan Eaves
88TC 5spd Vermillion Red, Polished...everything...
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segfaultxr7 Offline
Posting Freak
#5
Jeff, I have the exact same thing happen sometimes if I run the car hard for a while and then coast. There's a stretch of interstate that is uphill for about 5 miles, then one exit is downhill for about one mile. Sometimes if I get off that exit, the check engine light will come on as I'm coasting downhill, then it'll shut off a few mins later. It's always a 42. I have a new O2 sensor and FPR, BTW.

Come to think of it, this almost always happens not long after I have disconnected the battery. Have you unhooked yours recently? I think you might be right about the EEC thinking it needs to make corrections. In my case at least, the EEC would still be making air/fuel ratio adjustments and running it in open loop so much might confuse it.
88 TC 5-speed
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Jeff K Offline
Administrator
#6
Good thought about the battery. I havent disconnected it recently, but it is about 5 years old, and the car does crank a bit slow in cold weather, especially after it has sat for several days without running. Maybe the batt voltage drops low enough when cranking the cold motor that the EEC keep alive memory resets, and then the EEC has to learn new fuel trim correction factors?
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
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Walsted Offline
Posting Freak
#7
Quote:Maybe the batt voltage drops low enough when cranking the cold motor that the EEC keep alive memory resets, and then the EEC has to learn new fuel trim correction factors
Judging solely from the tripminder display, my EEC dumped everything when I had to jump-start my wife's car one morning. MPG went down to 19 for a tank and gradually improved back to normal with no changes to the car's set-up, so I assumed it was an EEC loss of memory due to the jump-start. If your battery is a bit old and tired, I could see it doing the same.

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Mike Walsted - Nato member
1986 5-speed TurboCoupe .
Mike Walsted - Sold my 1986 5-speed TurboCoupe
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TurboCoupe50 Offline
Posting Freak
#8
Jeff, for some reason Ford dropped the CEL in the 49 states TC's for '88. The CA and CDN cars still had it, now maybe we know why. There has been no CEL's on the eight '88s I've oned but the two '87s did have it.

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Two 1988 Turbo Coupes ..... yea one of em has a 5.0 And runs 13.3s
1988 Turbo Coupe331 AOD

1972 Comet GT

1969 Fairlane Cobra 428CJ 4-Speed
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Dan E Offline
Posting Freak
#9
Tom:

Are you saying that the CEL's on 88's just weren't hooked up or they were missing entirely ?

My 88TC has a CEL that comes on then goes off during KOEO or KOER.

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Dan Eaves
88TC 5spd, Crower 5.5" Sportsman Rods, Short Wiseco Pistons bored .030" Over, Ported Head with Polished Combustion Chambers, Gutted & Polished Upper, Ported & Polished Lower, Polished T/B, Ported E6, SVO T3 .63AR Turbo, Bosch Bypass Valve, 3" DP w/No Cat, 2 1/2" DynoMax single cat back w/DynoMax Super Turbo Muffler, RR Cam, K&N in Fenderwell, Gillis Boost Valve, Centerforce I Clutch, Removed A/C, Polished Wheels, Polished Valve Cover, Polished Crank and W/P Pulleys, Walbro 255LPH HP Pump, Kirban Adj FPR, and the DAMN Heater Core is new too !

NATO MEMBER (Vice Chairman...if it's a vice...I deal with it)
Dan Eaves
88TC 5spd Vermillion Red, Polished...everything...
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Jeff K Offline
Administrator
#10
Well, it has been 2 days since the CEL episode, and the car has been running perfectly ever since. The A/F gauge has been behaving normally, bouncing rich / lean several times a second as usual. Ran the codes again tonight (from the drivers seat, of course... didnt even pop the hood) after I pulled in the driveway after work, and everything is normal, except for the 28 and 25 which I expected. My conclusion: As Pete put it, EEC BRAIN FART. [Image: smile.gif] [Image: smile.gif]

Tom... very interesting about the lack of a CEL in some 88s. I think I'll start a topic on this surveying memebers and see how many have a functioning CEL.

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Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 20 psi, forced air intercooler, water injection, bypass valve, Ranger roller cam, subframes, etc., etc.. // 86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP nitrous, ignition, gears, suspension, etc., etc.... // 91 Escort: Bone stock winter car // 00 Windstar (wifes vehicle)
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
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