North American Turbocoupe Organization



Rebuilt Engine-MAFI Seems To Be A Problem
Randy Wilhite Offline
Junior Member
#1
Hi folks. 1987 TC with T5 trans. Removed original engine with 166,200 miles that was smoking blue smoke, especially under boost, otherwise it ran really great. Had engine remanufactured, original IHI turbo rebuilt by Evergreen and reinstalled in car. Hooked everything up, got timing set to 12 degrees BTDC. Ran car enough to get up to normal operating temp, at which point it started pumping out large clouds of black unburned gas exhaust smoke. Also started running really rough.

Could not get engine to restart unless I blocked open the Mass Air Flow box vane. Then it ran but also roughly with lots of black smoke. Unhooked MAFI electrical connector and it would not start with or without MAFI flap blocked open. Re-connected MAFI electrical and again it would restart, but black smoke and very rough running.

Every single intercooler and turbo hose is clamped tightly. Fuel pressure is 40 pounds at idle.

Will not run with IAC electrical disconnected but with the IAC reconnected it does run but requires bottoming out the idle adjustment screw.

Ideas, suggestions, thoughts?
Original owner 1987 Turbo Coupe 5 speed.
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Scott Mabe Offline
Member
#2
Possibly fpr? Pull the vac. Line to fpr and check for fuel.
1987 Turbo Coupe
1988 Thunderbird parts car/ possibly street/strip car
1990 F-250HD 460ci
2001 Pontiac Montana (wife's ride)

-PLEASE FORGIVE TYPOS, I USE SWYPE ON MY PHONE-
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Jeff K Offline
Administrator
#3
Measure VAM volts between BK/W and W/BK wires at the VAM. At idle should be close to 1 V or a little less. Anything over 1.5 V and it will be pig rich.
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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Randy Wilhite Offline
Junior Member
#4
Jeff, thanks so much for your reply. I checked the voltage at the VAM connector by back probing the harness side of the electrical connector. At idle (such as it is) I get a reading of 3.64 volts - assuming my meter connections are correct with the black/white wire being negative and the white/black wire being positive.

Just to be clear, this reading is with the VAM vane propped half way open with a wrench, which is the only way the thing will start and idle. As soon as I remove the wrench, which allows the vane to close, the idle goes up, the engine seems to smooth out for about two seconds and then dies. Will not restart until I prop open the vane again.

Since the reading of 3.64 volts is way over the desired .9 volts or so, how do I get the right volt reading to the electrical connector to the VAM?

Scott, also thanks for your reply. My understanding of the FPR (fuel pressure regulator)is that if it is bad, the fuel pressure at the injector rail Shrader valve will be high - in the area of 60 pounds or so. Mine reads 42 pounds, so I have to assume the FPR is working. Is that correct?
Original owner 1987 Turbo Coupe 5 speed.
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Scott Mabe Offline
Member
#5
From what I've seen you can have correct fuel pressure but the diaphragm can leak letting fuel be pulled directly into the intake.
1987 Turbo Coupe
1988 Thunderbird parts car/ possibly street/strip car
1990 F-250HD 460ci
2001 Pontiac Montana (wife's ride)

-PLEASE FORGIVE TYPOS, I USE SWYPE ON MY PHONE-
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Pete D Offline
Administrator
#6
"Since the reading of 3.64 volts is way over the desired .9 volts or so, how do I get the right volt reading to the electrical connector to the VAM?
Propping the door open increases the voltage artificially, ie you don't know what your true idle voltage is, yet.

You should be able to check it with the engine not running. Do as Jeff described above, with the key in RUN, engine off
Pete Dunham


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Jeff K Offline
Administrator
#7
VAM volts with key on, engine off should be around .35 V. Pushing the door open by hand should result in volts increasing smoothly up to around 4.5 V.

If you have an LA series or 8UA PCM, the engine should start and run fairly well with the VAM electrical connector removed. SInce yours doesnt, it sounds like the problem isnt the VAM.

Have you checked the FPR vac line for gas or even strong gas smell yet as Scott suggested? I have had leaking FPRs on a few Fords and recently on my Grand Prix GT.
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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shorangerbird Offline
Member
#8
-maybe check the IAT sensor in the center of intake?? mine was kinda doing the same with running like crap and blowing out black smoke, but it wouldnt stay running though. connector was corroded. cleaned it, cured what ailed it. ran fine after that....
'87 Turbo Coupe...538 actual miles...
'86 Turbo Coupe 5sp Ca. car 74k.....
Thinning Down the Herd......
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Randy Wilhite Offline
Junior Member
#9
Okay, boy I don't know why I could not figure out that the VAM door being open increased voltage readings, but I didn't.

With the VAM flap being closed, I get a reading of .23 volts. If I push the door open with my finger, the voltage reading goes up to a maximum of 4.5 volts, smoothly and with no drop outs.

Tried starting it with the VAM electrical connector disconnected and would not start.

I checked the Throttle Position Sensor (TPS) as described in the tech procedures on the board and the closed throttle reading is .94 volts. As I moved the throttle open it smoothly increased and decreased with no noted drop outs.

I checked the fuel pressure regulator vacuum line and saw no gas in it. Just to make sure I have the right thing, I am talking about the vacuum actuator on the left side of the fuel rail as I am standing at the driver's side fender looking at the intake manifold - it has a small diameter vacuum line going to the intake manifold vacuum port.

Engine will not start at all, although it sure acts as if it wants to.

Any other ideas, thoughts or suggestions?
Original owner 1987 Turbo Coupe 5 speed.
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Pete D Offline
Administrator
#10
Your TPS sounds OK. You got the fuel pressure regulator. near the front of the engine,on the fuel rail. Check for either visible gas or the STRONG smell of gas. A faint gas smell is OK.

Long shot but did you replace the spout after setting timing or set timing with the spout in place?
Pete Dunham


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