North American Turbocoupe Organization



Bought another 87 Turbo Coupe, need help please
BigKeyserSoze Offline
Member
#1
Good afternoon everyone! I haven't been here in a while, but in high school I drove an 87 turbo coupe. A few years ago, I bought a junked out 87 turbo coupe and turned it into a 24 Hours of Lemons/Chumpcar car, and raced it with some success.

I was given the opportunity to save a reasonably clean 1987 this week and could not say no. It is an automatic, 64k miles, but does not run right. The seller claimed to be a mechanic, and it looks like someone has tried to fix it, but without luck. The car has sat for a while, and had almost no gas in it. I just put 5 gallons of 93 in it, but have not tried to restart it.

It feels like it is running on two cylinders, it runs rough when trying to rev, even in park. It doesn't make enough power to even drive it up on my trailer. I pulled the spark plugs out, and all 4 of them are super black, the electrode, the end, all of it. The plugs were some expensive Bosch platinum plugs with part number Hr8dpx on them. The wires appear clean and newer, cap and rotor look ok. The firing order looked ok, 1,3,4,2 if going clockwise.

What plugs (brand and part number) should I put back in it? Any thoughts on what might be making the plugs so nasty rich? It does not appear to have any significant vaccumn leaks, and the car is not otherwise molested.

I should mention that from just behind the downpipe back, the exhaust was hacked all the way off. I did not look to see whether the oxygen sensor was on or not. My recollection was that even if the oxygen sensor was off or bad, the car would run ok, but feel free to correct me.

I would appreciate any help. There was a time in my life where I knew much about the TurboCoupe, but having not owned one in a while, I'm rusty with it.

-Scott
1987 Turbo Coupe
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Jeff K Offline
Administrator
#2
NGK 2238 plugs.

OBDI isnt smart enough to know the O2 sensor isnt there. PCM reads zero O2 voltage as super lean, and maxes out long term fuel trim on the rich side to try to compensate for the perceived lean condition. O2 sensor isnt in the DP, it is in the turbo exhaust elbow. If the O2 is there, be sure the orange ground wire is connected to the turbo inlet bolt. If not there, it will lead to super rich condition.
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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BigKeyserSoze Offline
Member
#3
The 02 is there and has the orange wire hooked up. I changed the plugs with Motorcraft SP-447, absolutely no change. I ran KOER codes, the engine was not warmed up well. Codes were 12 (idle speed control), 21 (engine coolant temp sensor), 25 (knock sensor), 34 (vaccumn delay valve), 42 (heated o2 sensor) and 76 (vane air meter). Of that list, I can't imagine anything except possibly a bad vane air meter making it run this bad. It looks like someone changed the timing belt at some point, if they are off a tooth on the belt, would it run at all? This thing will idle, actually pretty smoothly, but won't rev, even in park, at all. Literally won't rev above 3000 rpm no matter what. Any chance it is a bad computer?
1987 Turbo Coupe
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BigKeyserSoze Offline
Member
#4
PS I had already bought the Motorcraft 447 plug before I saw your recommendation for the NGK 2238.
1987 Turbo Coupe
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Jeff K Offline
Administrator
#5
Are those Motorcraft plugs Platinum plugs?? These motors run like total CRAP with Pt plugs. Use only "old style" copper plugs.

Was the code 42 a CM code or a KOER code? COde 42 indicates rich condition the long term fuel trim can not correct for. Pull vac line off FPR and see if there is gas in it or if it smells like gas. Blown FPR diaphragm allowing raw gas into the intake is a relatively common issue.

Unplug the VAM and see how it runs but do NOT get into boost. Ignore any VAM related codes that pop up. Unplugging the VAM puts the PCM in a pseudo speed density mode. Can also monitor VAM volts with key in RUN and opening / closing the VAM door to see if voltage changes smoothly from around .3 V with door closed to about 4.5 V with door fully open.
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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BigKeyserSoze Offline
Member
#6
The plugs were old style copper. No change in how it ran.

The code 42 was a KOER code.

Today I checked cam timing, it was fine. Compression around 140 on all cylinders. Makes 40 or so pounds of fuel pressure with engine off and key cycled forward, so that is ok.
We were trying to run it today with the intercooler off just so we could watch things happen, it runs exactly the same with the intercooler on and off, even with no hose joining the turbo to the intake. It changes nothing to unplug the VAM. The new plugs are black and fuel soaked when you pull them out. I'll pull the vac line of the fuel pressure regulator and do as you say, if that is a common problem, maybe that is what is happening here, although I'm trying to think about how a blown diaphragm would allow raw fuel into the manifold. I wouldn't know how to monitor the VAM voltage, just poke a pin into two wires and measure?
1987 Turbo Coupe
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Jeff K Offline
Administrator
#7
Blown FPR allows fuel to be sucked into the intake thru the vac line on the FPR.

Monitor VAM volts between the BK/W wire (signal return, negative) and W/BK wire (VAM output, positive). Also verify 5 V VREF going to the VAM.
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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BigKeyserSoze Offline
Member
#8
Wouldn't pulling the vac line off the FPR and running the car be a way to see if its blown? With the vac line off, if it was sucking gas, it wouldn't be anymore. The fuel pressure would be a few pounds lower, true, but that wouldn't be enough to make the car idle badly I wouldnt think. Which wire would I measure the 5v VREF from? Thanks again.
1987 Turbo Coupe
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BigKeyserSoze Offline
Member
#9
I pulled the vac line off the FPR today and ran the car, no change still, still runs like death. Will test the vane meter next, starting to wonder if it has a bad computer.
1987 Turbo Coupe
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Jeff K Offline
Administrator
#10
If the PCM fails, it usually results in failure to output codes, and/or fuel pump runs constantly whenever the key is in RUN even with the engine not running, and/or the primary engine cooling fan runs constantly whenever the key is in RUN.
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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