2nd Generation Specific 1986-1992 Discussion

1990 turboII running rich and timing off, runs perfect on the road

Old 01-29-2012, 02:12 PM
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Default 1990 turboII running rich and timing off, runs perfect on the road

Sorry for the lengthy post. I have a 1990 turbo II and I have been a technician for about 9 years. I spent two of those years at a rotary shop. To drive the car it runs perfect, but at idle it is extremely rich and choppy and the timing shows about 20 degrees advanced and fluctuates back and forth some even though the idle is low, 500-700 rpm. Compression is about 95 psi on on all chambers. It has 86-88 turbo rotors because that was all I could find at the time.I smoke tested it for vacuum leaks and checked with carb cleaner while running. I have tested the map sensor, mass air, tps, crank angle sensor, and coils. I have swapped tps (for 1 that tested better), map sensor from a known good running car, a couple of crank angle sensors, and some different coils with no change. I have tested all the sensor wiring, they all have 5v reference, good ground, and good continuity on signal wires. I also cleaned an re-threaded all of the grounds under the hood. The coil wiring also tested good. The fuel pressure is correct at idle too. The engine is street ported with all emissions removed and open exhaust and intake. The only solenoids I'm running are boost control and pressure regulator control. My timing light has started flashing less consistently on L1 lately but the coils test good, I don't know how to test the igniters without the igniter tester mentioned in the FSM, which I don't have. I have also tried another ECU with no results. No codes stored except for removed emissions equipment. If I ground the initial set connector, it barely runs at all, extremely low and rough idle. Any ideas will be greatly appreciated.

Last edited by rotaryman13; 01-29-2012 at 03:05 PM. Reason: adding info
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Old 01-29-2012, 02:48 PM
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Default Re: 1990 turboII running rich and timing off, runs perfect on the road

Originally Posted by rotaryman13 View Post
Sorry for the lengthy post. I have a 1990 turbo II and I have been a technician for about 9 years. I spent two of those years at a rotary shop. To drive the car it runs perfect, but at idle it is extremely rich and choppy and the timing shows about 20 degrees advanced and fluctuates back and forth some even though the idle is low, 500-700 rpm. Compression is about 95 psi on on all chambers.I smoke tested it for vacuum leaks and checked with carb cleaner while running. I have tested the map sensor, mass air, tps, crank angle sensor, and coils. I have swapped tps (for 1 that tested better), map sensor from a known good running car, a couple of crank angle sensors, and some different coils with no change. I have tested all the sensor wiring, they all have 5v reference, good ground, and good continuity on signal wires. I also cleaned an re-threaded all of the grounds under the hood. The coil wiring also tested good. The fuel pressure is correct at idle too. The engine is street ported with all emissions removed and open exhaust and intake. The only solenoids I'm running are boost control and pressure regulator control. My timing light has started flashing less consistently on L1 lately but the coils test good, I don't know how to test the igniters without the igniter tester mentioned in the FSM, which I don't have. I have also tried another ECU with no results. No codes stored except for removed emissions equipment. If I ground the initial set connector, it barely runs at all, extremely low and rough idle. Any ideas will be greatly appreciated.

are the spark plugs good?? and what about the injectors?
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Old 01-29-2012, 02:52 PM
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Default Re: 1990 turboII running rich and timing off, runs perfect on the road

new plugs, injectors rebuilt several years ago, fouls plugs after about 20 minutes of idling
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Old 01-29-2012, 03:34 PM
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Default Re: 1990 turboII running rich and timing off, runs perfect on the road

The TPS needs to be adjusted with the car running, and should be set to read 1v at idle. I have seen that the recommended ohm range with the sensor disconnected does not always give you the proper voltage. The ECU needs the voltage to be right for the computer to read it properly.

Secondly, 4 stroke timing lights with adjustable advance read the advance as more than what it actually is on a rotary. The marks on the main pulley should line up with their corresponding coil on a regular timing light, or one with the advance set to zero.

There is a second clutch switch at the top of the clutch pedal that affects the idle timing. That should be tested. When mine failed, it left me with an idle that could not be adjusted to maintain a steady idle, no matter how high or low I set it.

95 psi is a littlle low, but not enough to cause plug fouling.

Ive never been a fan of the stock plugs, I always ran standard NGK's in mine. B9EGV all around when the motor was close to stock, and B11EGV all around with a heavily ported motor. Never fouled a plug with either.
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Old 01-29-2012, 05:27 PM
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Default Re: 1990 turboII running rich and timing off, runs perfect on the road

I have been setting my tps with the little 2 light box with the switch on and engine off, but I will try 1v at idle. I just have a cheap non-adjustable timing light. I have not heard of that clutch switch, but I will check it. My idle screw is pretty much non-responsive, other than I can make it idle even lower. Thank you for your time, I will try those things.
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Old 02-01-2012, 08:33 PM
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Default Re: 1990 turboII running rich and timing off, runs perfect on the road

Very possible that it is the timing...I did the same mistake with a timing gun...

Reason why you have to do it when the car is at normal op temperature is because of the resistance change with the sensor when it heats up.
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Old 02-01-2012, 09:26 PM
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Default Re: 1990 turboII running rich and timing off, runs perfect on the road

I am checking it at operating temperature, but thanks for the reply.
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Old 02-01-2012, 09:42 PM
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Default Re: 1990 turboII running rich and timing off, runs perfect on the road

Just to be clear, this thing runs extremely rich at idle! It will foul a set of plugs within 20 minutes if you don't drive it. The idle is really ruff because of all the fuel. But to drive it, it runs perfect. It starts every time whether its hot or cold and even with fouled plugs. You can clean the plugs, and it runs fine again.
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Old 02-01-2012, 10:46 PM
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Default Re: 1990 turboII running rich and timing off, runs perfect on the road

Heres a thought. Pull your PRC solenoid, and connect the vacuum hose from the FPR directly to a manifold nipple. The PRC solenoid effectively raises the fuel pressure when it activates by cutting the vacuum signal to the FPR and letting the FPR read atmospheric, regardless of manifold pressure.

I never understood its purpose, and after I pulled it, I never had a starting issue ever again, whether it was hot or you shut off the engine before it warmed up. It was impossible to flood once the PRC soleniod was gone and the FPR was plumbed straight to the manifold.
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Old 02-02-2012, 08:35 PM
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Default Re: 1990 turboII running rich and timing off, runs perfect on the road

I had the PRC solenoid removed, but I put it back because I thought that might be the problem.
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