Runs rough
08-26-17, 08:30 PM
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R.E.X
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Runs rough
Hello, I need help with my 1988 convertible, Runs great cold, starts to run rough after driving 20 min or so. Idle drops to 500 rpm's and has very low power. Replaced TPS and calibrated, fuel filter, fuel, plugs. No change, While running it at times clears up and runs great even when warm but after turning off and restarting the eng goes back to rough low idle and very low power. Help Please
08-27-17, 10:16 AM
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What do your plugs look like? Does it smell like it is running rich? One though could be the temperature sensor or wiring for this sensor. The gauge uses a different sensor to what the computer uses, if it is not sending the correct signal, for example its always telling the computer the engine is cold, the computer will inject extra fuel, which makes it run good when cold, but overfuels when warm. It will also prevent the computer from going into closed loop as it has to get to a certain temperature to do this. With it intermittantly working fine, I wonder if you have a bad connection, or wiring for this sensor, usually the sensors work, or not at all, where a bad connection can. I would pull the plug off the sensor, look for corrosion, or some signs of problems. It is the one on the back of the thermostat housing, 2 wire plug.
08-27-17, 10:33 AM
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Thank you for you suggestion, I check that. I did make a code reader out of LED lights but the only time it will light is code is when the eng is running rough, not when the eng is not running or when running fine. The code that flashed is 1 long light (2 sec ) the a 2 sec Pause the repeat. Poss 02 sensor ??????????
08-29-17, 08:12 PM
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Runs rough hot
Eng runs rough hot. While running I unplug the trailing coil and no change. When I 0lug the coil back in the tachometer does not work and there is still no change. If I turn off the eng and restart it there is still no change but the tachometer starts working again. The coil does have spark also after restarting. Can the coil work but be to week to function correctly?
Any thoughts from any one?
Any thoughts from any one?
09-02-17, 08:43 AM
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I dont think an oxygen sensor can cause this. My S4 NA when I got it had no connector on the oxygen sensor, I repaired it with a crimp on spade connector, and for 3 months before I switched to a standalone ECM, I had a wideband o2 sensor installed in the stock 02 sensor, and had the sensor unplugged from the computer, and I noticed no driveability changes at all.
As for your trailing coil, I think that sounds normal, the engine will run fine without the trailing coil, when you un plug them, it probably shuts down the coils to protect them. The tach is driven off of the trailing coils, so if the coils dont fire, the tach does not get a signal.
The computers in these cars are pretty dumb, so incorrect signals from a sensor can cause the ECM to do dumb things and it doesnt know any better. Looking at the code, does sound like an O2 code. What you could do is just unplug the sensor, see if anything changes. IF the computer does not see the sensor, it defaults to a normal value so you can drive the car to a repair shop. I would also try unplugging the water temp sensor under then thermostat, once the car is warmed up, this will default to a 180f coolant temperature (making the car hard to start cold, but normal when hot). I would also try the same for the intake air temp sensor in the intake manifold plenum, on the drivers side of the plenum, just unplug it while idling, give it a couple seconds, if the idle improves, that is likely the issue.
I doubt the air flow sensor is at fault, as this sensor is used when the engine is hot and cold, I would assume you would see poor running regardless of engine temp.
Also, do you have full emissions on this car still? Could be a vac leak before one of the solenoids, so its only there when a solenoid is open, but again, I dont think it will affect power much, just mostly idle, unless the leak is huge, which I dont think it will idle.
As for your trailing coil, I think that sounds normal, the engine will run fine without the trailing coil, when you un plug them, it probably shuts down the coils to protect them. The tach is driven off of the trailing coils, so if the coils dont fire, the tach does not get a signal.
The computers in these cars are pretty dumb, so incorrect signals from a sensor can cause the ECM to do dumb things and it doesnt know any better. Looking at the code, does sound like an O2 code. What you could do is just unplug the sensor, see if anything changes. IF the computer does not see the sensor, it defaults to a normal value so you can drive the car to a repair shop. I would also try unplugging the water temp sensor under then thermostat, once the car is warmed up, this will default to a 180f coolant temperature (making the car hard to start cold, but normal when hot). I would also try the same for the intake air temp sensor in the intake manifold plenum, on the drivers side of the plenum, just unplug it while idling, give it a couple seconds, if the idle improves, that is likely the issue.
I doubt the air flow sensor is at fault, as this sensor is used when the engine is hot and cold, I would assume you would see poor running regardless of engine temp.
Also, do you have full emissions on this car still? Could be a vac leak before one of the solenoids, so its only there when a solenoid is open, but again, I dont think it will affect power much, just mostly idle, unless the leak is huge, which I dont think it will idle.
09-02-17, 02:50 PM
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> Things I have tried : Put trans fluid in the rotor housings and let it
> sit for 36 hrs. The eng started up and ran great for 20 miles. Turned the
> eng off for 15 to 25 minutes then restarted. The eng started running rough.
> No power, idles at 500 rpm's and will not clear up. While the eng was
> running rough I removed a plug and added trans fluid one rotor at a time to
> assure there is not a compression issue. Each time I restarted the eng,
> other then a lot of smoke for a moment no changes. I replaced the 02
> sensor, no change, unplugged the tps no change, unplugged the BAC no
> change, Sprayed the complete eng down with carb cleaner looking for a
> vacuum leak no change.
> This eng runs great cold and continues to run great until it is shut
> down. Sits for a short period of time then runs like dirt. I am at my witts
> end
> sit for 36 hrs. The eng started up and ran great for 20 miles. Turned the
> eng off for 15 to 25 minutes then restarted. The eng started running rough.
> No power, idles at 500 rpm's and will not clear up. While the eng was
> running rough I removed a plug and added trans fluid one rotor at a time to
> assure there is not a compression issue. Each time I restarted the eng,
> other then a lot of smoke for a moment no changes. I replaced the 02
> sensor, no change, unplugged the tps no change, unplugged the BAC no
> change, Sprayed the complete eng down with carb cleaner looking for a
> vacuum leak no change.
> This eng runs great cold and continues to run great until it is shut
> down. Sits for a short period of time then runs like dirt. I am at my witts
> end