5.9L engine idle problem
#11
01-03-2011, 04:31 PM
Grand Champion
#12
01-10-2015, 04:42 PM
Hello everyone,
So here's my problem, i'm taking my truck to a mechanic in afew days to try and get this fixed but from searches on the internet i've found alot of people with this happening and in every case it seems they've done something different to fix it or couldn't get it fixed and alot of them complained about the end cost after a mechanic went through and replaced part after part.....so here's the problem, i bought my 99 ram 1500 5.9L 4X4 recently and drove it home with no problems (200miles) a day or two later i had it running at idle and all of a sudden my idle drops to about 5 or 600rpm and it sounds really rough like it struggling to stay running.....i reved it up once or twice and it went back to normal idle...around 900rpm i think, so i didn't think much of it.....well later on i was driving and came to a stop and while sitting there idling it suddenly dropped down to the 5-600rpm ranged and was idling rough, engine shaking ect and the light turned green...now i went to take off and the engine was stuttering and cutting out and i started to slow back down to almost a standstill, at the same time i heard popping or backfiring into the air cleaner i believe...i stepped on the peddle to the floor and it cut out for a second then the engine roared to life and i got upto speed (35mph)....now the CEL has come on and i've read the codes and it says its running rich and the O2 sensors are bad, we cleared teh code and i continued driving it....it still does it completely randomly and usually does cause the CEL to come on again.......now i went through and replaced plugs, wires, cap, and rotor....exhaust seems to have good pressure comming out the pipe but it still seems to do this...its completely random....does it when its warmed up or when its cold.....might do it once in 40 miles of driving or several times...there's no pattern........i should also mention it seems like its getting really poor mpg....i havn't done the math to see exactly what my mpg is but i can put half a tank in it and drive it alittle around town and go home and i'm almost back on E again.......... dont know if this is part of the problem but i've noticed that to hit hiway speeds (70mph) i seems like i gotta have the peddle to the floor........anyway, i just want some idea of what it might be so that i can point the mechanic in the right direction without costing me an arm and a leg in parts tryin to fix this......mechanic looked at it once and because it didn't throw a code and when he test drove it afew miles it didn't do it he thought it was fixed........PLZ HELP!....ty.
So here's my problem, i'm taking my truck to a mechanic in afew days to try and get this fixed but from searches on the internet i've found alot of people with this happening and in every case it seems they've done something different to fix it or couldn't get it fixed and alot of them complained about the end cost after a mechanic went through and replaced part after part.....so here's the problem, i bought my 99 ram 1500 5.9L 4X4 recently and drove it home with no problems (200miles) a day or two later i had it running at idle and all of a sudden my idle drops to about 5 or 600rpm and it sounds really rough like it struggling to stay running.....i reved it up once or twice and it went back to normal idle...around 900rpm i think, so i didn't think much of it.....well later on i was driving and came to a stop and while sitting there idling it suddenly dropped down to the 5-600rpm ranged and was idling rough, engine shaking ect and the light turned green...now i went to take off and the engine was stuttering and cutting out and i started to slow back down to almost a standstill, at the same time i heard popping or backfiring into the air cleaner i believe...i stepped on the peddle to the floor and it cut out for a second then the engine roared to life and i got upto speed (35mph)....now the CEL has come on and i've read the codes and it says its running rich and the O2 sensors are bad, we cleared teh code and i continued driving it....it still does it completely randomly and usually does cause the CEL to come on again.......now i went through and replaced plugs, wires, cap, and rotor....exhaust seems to have good pressure comming out the pipe but it still seems to do this...its completely random....does it when its warmed up or when its cold.....might do it once in 40 miles of driving or several times...there's no pattern........i should also mention it seems like its getting really poor mpg....i havn't done the math to see exactly what my mpg is but i can put half a tank in it and drive it alittle around town and go home and i'm almost back on E again.......... dont know if this is part of the problem but i've noticed that to hit hiway speeds (70mph) i seems like i gotta have the peddle to the floor........anyway, i just want some idea of what it might be so that i can point the mechanic in the right direction without costing me an arm and a leg in parts tryin to fix this......mechanic looked at it once and because it didn't throw a code and when he test drove it afew miles it didn't do it he thought it was fixed........PLZ HELP!....ty.
Was there ever a solution found for this. I have an 01 5.9 magnum and it's doing almost the exact same thing. It randomly cuts out and while it's doing that you can hear a small backfire through the throttle body. Let me know. Thanks.
#13
01-10-2015, 05:07 PM
Grand Champion
#14
01-10-2015, 06:07 PM
I knew it was almost 4 years old. That's the main reason I asked here. I guess the symptoms are the same except the lack of power wile it's not cutting out. As of now it has new plugs, wires, cap and rotor, and fuel pump assembly.
#15
01-10-2015, 07:03 PM
Grand Champion
His inability to discern a pattern doesn't really mean that there wasn't one. The pattern is very predictably this: Any time the exhaust stream is running (relatively) cool the engine runs like crap, and any time the exhaust stream is running relatively hot it runs much better. Higher RPM or higher load will heat the exhaust, idle or cruising at highway speed will cool it. The root of it is that these sensors have a certain minimum operating temperature below which they are inaccurate, and as they age that minimum temperature increases, eventually to the point at which this symptom picture appears.
The loss of power comes about due to the fact that the typical failure mode of an oxygen sensor is a false rich reading, which causes the PCM to run the engine too lean. Which is also what causes the low and usually lumpy idle, usually with a sucking sound in the intake while the idle is low -- the sucking sound is coming from the IAC being wide open as the PCM tries to get the idle speed up to target.
Something else to consider is that oil fouling/carbon build-up on the sensor will present in much the same way because the sensor, being coated, sees a lot less of the exhaust stream and will again deliver a false rich reading. So check out the plenum gasket while you're at it. If it's found to be compromised, you'll want to fix it right away and also test the catalytic converter for clogging. With luck, if this is what's going on, you'll catch it before the converter failure causes a cracked cylinder head.
Last edited by UnregisteredUser; 01-10-2015 at 07:07 PM. Reason: Added the afterthought
#16
01-10-2015, 08:10 PM
That makes it easy, since the OP's symptom picture included diagnostic codes indicating failed oxygen sensor(s). By the time the PCM sets that code your sensor has been failed for a long, long time. Even without the codes the OP's symptoms point at the O2 sensor.
His inability to discern a pattern doesn't really mean that there wasn't one. The pattern is very predictably this: Any time the exhaust stream is running (relatively) cool the engine runs like crap, and any time the exhaust stream is running relatively hot it runs much better. Higher RPM or higher load will heat the exhaust, idle or cruising at highway speed will cool it. The root of it is that these sensors have a certain minimum operating temperature below which they are inaccurate, and as they age that minimum temperature increases, eventually to the point at which this symptom picture appears.
The loss of power comes about due to the fact that the typical failure mode of an oxygen sensor is a false rich reading, which causes the PCM to run the engine too lean. Which is also what causes the low and usually lumpy idle, usually with a sucking sound in the intake while the idle is low -- the sucking sound is coming from the IAC being wide open as the PCM tries to get the idle speed up to target.
Something else to consider is that oil fouling/carbon build-up on the sensor will present in much the same way because the sensor, being coated, sees a lot less of the exhaust stream and will again deliver a false rich reading. So check out the plenum gasket while you're at it. If it's found to be compromised, you'll want to fix it right away and also test the catalytic converter for clogging. With luck, if this is what's going on, you'll catch it before the converter failure causes a cracked cylinder head.
His inability to discern a pattern doesn't really mean that there wasn't one. The pattern is very predictably this: Any time the exhaust stream is running (relatively) cool the engine runs like crap, and any time the exhaust stream is running relatively hot it runs much better. Higher RPM or higher load will heat the exhaust, idle or cruising at highway speed will cool it. The root of it is that these sensors have a certain minimum operating temperature below which they are inaccurate, and as they age that minimum temperature increases, eventually to the point at which this symptom picture appears.
The loss of power comes about due to the fact that the typical failure mode of an oxygen sensor is a false rich reading, which causes the PCM to run the engine too lean. Which is also what causes the low and usually lumpy idle, usually with a sucking sound in the intake while the idle is low -- the sucking sound is coming from the IAC being wide open as the PCM tries to get the idle speed up to target.
Something else to consider is that oil fouling/carbon build-up on the sensor will present in much the same way because the sensor, being coated, sees a lot less of the exhaust stream and will again deliver a false rich reading. So check out the plenum gasket while you're at it. If it's found to be compromised, you'll want to fix it right away and also test the catalytic converter for clogging. With luck, if this is what's going on, you'll catch it before the converter failure causes a cracked cylinder head.
#17
01-10-2015, 08:12 PM
#18
01-10-2015, 09:14 PM
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#19
01-10-2015, 09:17 PM
Grand Champion
It was suggested above that you might try cleaning the thing, and it might sometimes work for a while, but it's much better to replace the sensor if it's failing. The risk is that most folks would be happy to call it a win if the symptoms mostly disappear, but if the engine is still running lean it'll accelerate the wear of the expensive parts in the combustion chambers. It'd actually be better, if the part has failed, to just leave it unplugged until you can get another installed. Running a tad rich, with no catalytic converter to be harmed by it, isn't really a problem.
#20
01-10-2015, 10:26 PM
I have extensivly cleaned the TB. I took it off and cleaned all through it and put a new base gasket under it. We'll unplug the 02 sensor and see where that gets us. I hadn't even thought about the MAP sensor. Where is it located exactly? I can't remember seeing one on the side of the intake anywhere.