Rough Idle In Gear and While Accelerating
#1
09-13-2019, 09:02 AM
Rough Idle In Gear and While Accelerating
Vehicle: 1992 F250 7.5L 460 Motor, automatic transmission
Issue: When first started the engine runs at low idle for the first 1-2 minutes and then smooths out. When the truck is put in drive the idle again drops and runs rough. When driving the engine begins to sputter and sounds like a miss fire. This occurs when accelerating slowly (does not occur when you hammer on the throttle to accelerate). When you come to a stop the idle again drops very low and runs rough, until the the truck is put back in park and then the idle evens out again.
New Parts: Fully rebuilt motor within the last 5 miles (bearings, cam, lifters, oil pump, etc, all internals re built). Just prior to rebuild the truck had new wires, cap and rotor, MAP sensor, Fuel Pressure Regulator, ERG Control Sensor, fuel filter, starter solenoid, rebuilt fuel injectors and new o rings, ignition coil
Items Checked so Far:
Thoughts and Ideas would be really helpful. I really need a list of potential things to check, because at this point (according to all repair manuals) it could be anything???
Issue: When first started the engine runs at low idle for the first 1-2 minutes and then smooths out. When the truck is put in drive the idle again drops and runs rough. When driving the engine begins to sputter and sounds like a miss fire. This occurs when accelerating slowly (does not occur when you hammer on the throttle to accelerate). When you come to a stop the idle again drops very low and runs rough, until the the truck is put back in park and then the idle evens out again.
New Parts: Fully rebuilt motor within the last 5 miles (bearings, cam, lifters, oil pump, etc, all internals re built). Just prior to rebuild the truck had new wires, cap and rotor, MAP sensor, Fuel Pressure Regulator, ERG Control Sensor, fuel filter, starter solenoid, rebuilt fuel injectors and new o rings, ignition coil
Items Checked so Far:
- Timing just set to 10 BTDC without Spout connected
- IAC valve checked and cleaned
- TPS Sensor checked
- Cylinder Pressure Check
- All fuses under hood and in dash
- Pulled all codes both in a cold condition as well as as at operating temperature. Code #11 was the only one, indicating everything is fine
- Just filled both tanks with new fuel and put in fuel dryer to ensure new good fuel.
- Coolant Temperature Sensor - Dash temperature gauge reads 0 constantly
- I have a squealing from what i assume is the idler pulley
Thoughts and Ideas would be really helpful. I really need a list of potential things to check, because at this point (according to all repair manuals) it could be anything???
#2
09-13-2019, 09:31 AM
You know this is no fun because you spent all the money on everything you did.
Something I find puzzling,
You are getting a clear code and yet the coolant temp sensor seems to have a problem, providing it is the sensor, and not the gauge. On those vehicles the temp gauge controlled the voltage to all the other gauges for them to work correctly.
If the coolant sensor is operating out of range it will not throw any code and will still affect performance. If any doubt, replace it.
don't know how you checked the TPS (throttle position sensor) , would you tell us how you did that?
The ECM (Computer) provides a 5 volt reference voltage for the sensors to work and sometimes if that voltage is off due to a poor connection ,some of the sensors will not provide correct info to the ECM and it will not be bad enough to cause a code to be set and will still cause multiple problems.
Something to check, make sure the EGR valve is not stuck slightly open with carbon, that can affect idle and acceleration.
Something I find puzzling,
You are getting a clear code and yet the coolant temp sensor seems to have a problem, providing it is the sensor, and not the gauge. On those vehicles the temp gauge controlled the voltage to all the other gauges for them to work correctly.
If the coolant sensor is operating out of range it will not throw any code and will still affect performance. If any doubt, replace it.
don't know how you checked the TPS (throttle position sensor) , would you tell us how you did that?
The ECM (Computer) provides a 5 volt reference voltage for the sensors to work and sometimes if that voltage is off due to a poor connection ,some of the sensors will not provide correct info to the ECM and it will not be bad enough to cause a code to be set and will still cause multiple problems.
Something to check, make sure the EGR valve is not stuck slightly open with carbon, that can affect idle and acceleration.
Last edited by hanky; 09-13-2019 at 09:34 AM.
#3
09-13-2019, 10:04 AM
Hanky,
Coolant Temp Sensor - I plan on replacing it this weekend, will post results on Monday.
TPS - I followed a Haynes manual for testing procedures. I will test again this weekend and post recorded results on Monday.
ERG - how do you properly check this. I see a lot of threads that lead to this as a possible issue. I just dont know the proper procedure to confirm, as many descriptions do not agree on how to test
Coolant Temp Sensor - I plan on replacing it this weekend, will post results on Monday.
TPS - I followed a Haynes manual for testing procedures. I will test again this weekend and post recorded results on Monday.
ERG - how do you properly check this. I see a lot of threads that lead to this as a possible issue. I just dont know the proper procedure to confirm, as many descriptions do not agree on how to test
#4
09-13-2019, 01:11 PM
At this point we are not concerned with testing the function of the EGR valve assy.
What we want to confirm is, no exhaust is getting into the intake altering the mixture to the engine.
If you carefully remove the 2 bolts that secure the EGR valve to the manifold and look underneath the mounting. You will see a hole where the pintle(stub) of the valve lifts up and allows exhaust gas to go into the intake. Sometimes a piece of carbon will get trapped in that opening and prevent the pintle from coming all the way down and closing the opening. A slight tap with a mallet will shock the carbon and usually break it loose and allow the pintle to close completely. You should really replace the EGR valve mounting gasket, but if you are careful when removing the valve assy , you may be able to reuse the gasket.
If the valve doesn't open when vacuum is directed to it , it concerns emissions , but not idle quality. Before moving on , lets see what you find and what result you get. You can temporarily remove the vacuum hose from the EGR valve and plug it to confirm no vacuum is getting to it at idle.
I inquired about the TPS because you cannot always get a good reading of the TPS with a digital meter.
What we want to confirm is, no exhaust is getting into the intake altering the mixture to the engine.
If you carefully remove the 2 bolts that secure the EGR valve to the manifold and look underneath the mounting. You will see a hole where the pintle(stub) of the valve lifts up and allows exhaust gas to go into the intake. Sometimes a piece of carbon will get trapped in that opening and prevent the pintle from coming all the way down and closing the opening. A slight tap with a mallet will shock the carbon and usually break it loose and allow the pintle to close completely. You should really replace the EGR valve mounting gasket, but if you are careful when removing the valve assy , you may be able to reuse the gasket.
If the valve doesn't open when vacuum is directed to it , it concerns emissions , but not idle quality. Before moving on , lets see what you find and what result you get. You can temporarily remove the vacuum hose from the EGR valve and plug it to confirm no vacuum is getting to it at idle.
I inquired about the TPS because you cannot always get a good reading of the TPS with a digital meter.
Last edited by hanky; 09-13-2019 at 01:19 PM.
#5
09-16-2019, 08:27 AM
Well i fixed up one issue and gained another.
First thing i did was put about 25 miles on the truck (while it was running rough). Then i pulled codes again. The second time i pulled codes i got a 21 (Engine Coolant Temperature (ECT) sensor out of range – ECT). I replaced the coolant temperature sensor and drove it. After a few miles the rough idle was better. I didn't feel like it was going to die every few seconds. So i went on another trip to town. This time when i went to town i have absolutely no power when i hammer on the gas. I can drive and accelerate slowly, but the minute i press down on the pedal the truck just stays the same speed, it doesn't even accelerate.
Other notable issues im having:
Im chasing something here. General themes from reading other posts are ECM, Catalytic Converter, fuel pump... any thoughts help or advice would be appreciated
First thing i did was put about 25 miles on the truck (while it was running rough). Then i pulled codes again. The second time i pulled codes i got a 21 (Engine Coolant Temperature (ECT) sensor out of range – ECT). I replaced the coolant temperature sensor and drove it. After a few miles the rough idle was better. I didn't feel like it was going to die every few seconds. So i went on another trip to town. This time when i went to town i have absolutely no power when i hammer on the gas. I can drive and accelerate slowly, but the minute i press down on the pedal the truck just stays the same speed, it doesn't even accelerate.
Other notable issues im having:
- Starting is difficult. I tested the battery and alternator, both test good. I suspect the starter and a new one is on the way.
- Power during acceleration is non existent (see above description)
- Speed gauge bounces 10 MPH when im traveling between 50 and 60 mph? No idea
- Replaced all spark plugs
- Replaced coolant temperature sensor
- Tested the erg with a vacuum. holds a vacuum and confirmed the spindle rod moves when actuated. I actuated it a number of times to be sure.
- Timing was re-checked and st confirmed at 10 BTDC
Im chasing something here. General themes from reading other posts are ECM, Catalytic Converter, fuel pump... any thoughts help or advice would be appreciated
#6
09-16-2019, 08:36 AM
Oh... i will say i relaized you had said that the volt meter was not always the best way to test the TPS. As i continue to have problems i want to make sure i test it properly. WHat is the correct method to test the TPS?
#7
09-16-2019, 03:55 PM
With a scope. A scope will catch and graph the entire range What we want to confirm is it doesn't drop out at any time..
What you did with the EGR valve only shows that it opens, but does not show or confirm that it is closing completely. That is what is important here.
Also , remove and plug the vacuum line to the EGR valve and that will prevent it from opening when it is not supposed to.
If no change is noticed , reconnect the vacuum hose.
What you did with the EGR valve only shows that it opens, but does not show or confirm that it is closing completely. That is what is important here.
Also , remove and plug the vacuum line to the EGR valve and that will prevent it from opening when it is not supposed to.
If no change is noticed , reconnect the vacuum hose.
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