rough idle
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rough idle
Have an issue with a 96 2.3L 5 speed with 156K on it. The idle seems to range a little up and down. The following parts have been changed:
spark plugs
plug wires
pcv valve
air filter
oil and filter
timing belt
I have cleaned the MAF and IAC. Checked for a vaccum leak and have not found one. Have went back and checked timing marks and they are right on the marks for both the camshaft and oil pump gear. If I disconect the IAC it drops the rpm down to almost stalling. If I pull the rubber grommet out of the air cleaner where wires run to the MAF the idle gets slower and rougher. Not sure what to check next. At times when pulling up to a stop light the idle will get very rough and occasionally stall. Sometimes when you go to pull out the engine will cough and then stall. Have checked fuel pressure and it is 30 pounds at idle and will climb when you accelerate. HELP!!!
When it is idleing you can go by the tailpipe and listen to it running and it will run smooth and then you will hear what seems like a late ignition on a cylinder. This is random and will occur when it is down to a slow idle.
When the truck wants to stall a couple of times I get a CEL and the code will show a P1443 (Low emissions purge flow) When I clear the code and it is running good (not trying to stall at stoplights the code will stay off. When the idling gets bad and it stalls alot at lights or stop signs the P1443 code gets tripped again and the CEL light comes on.
I am trying to avoid throwing parts at the problem, want to diagnose and fix, not just change parts until I get lucky.
spark plugs
plug wires
pcv valve
air filter
oil and filter
timing belt
I have cleaned the MAF and IAC. Checked for a vaccum leak and have not found one. Have went back and checked timing marks and they are right on the marks for both the camshaft and oil pump gear. If I disconect the IAC it drops the rpm down to almost stalling. If I pull the rubber grommet out of the air cleaner where wires run to the MAF the idle gets slower and rougher. Not sure what to check next. At times when pulling up to a stop light the idle will get very rough and occasionally stall. Sometimes when you go to pull out the engine will cough and then stall. Have checked fuel pressure and it is 30 pounds at idle and will climb when you accelerate. HELP!!!
When it is idleing you can go by the tailpipe and listen to it running and it will run smooth and then you will hear what seems like a late ignition on a cylinder. This is random and will occur when it is down to a slow idle.
When the truck wants to stall a couple of times I get a CEL and the code will show a P1443 (Low emissions purge flow) When I clear the code and it is running good (not trying to stall at stoplights the code will stay off. When the idling gets bad and it stalls alot at lights or stop signs the P1443 code gets tripped again and the CEL light comes on.
I am trying to avoid throwing parts at the problem, want to diagnose and fix, not just change parts until I get lucky.
Last edited by pike_hunter; Feb 1, 2006 at 08:48 PM.
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Joined: Jan 2004
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From: SW Va
Well pike_hunter I see you've been busy on this one.
Intermitent problems that won't hold still long enough to put your finger on them, are a bear to run down sometimes.
Seems the computer is unhappy with the evaporative emissions purge flow, when it sets the P1443 code, but the question is, is it because of the low idle speed/stall condition, thats occuring, because of some other reason, like maybe the EGR valve sticking from time to time, or maybe it's control, the DPFE acting out occasionaly, or maybe a sticking intake or exhaust valve????
SO, maybe a check & cleaning of the EGR valve & DPFE should be considered????
Could also be a sticking intake or exhaust valve, from deposits.
With this kind of mileage it's allowed to have some deposits. lol
You also might try running most of this tank of gas out, then before the next fill up, add a shot of Chevron "Techron Concentate", to a fillup with Chevron or Chevron/Texaco gas & do some spirited diving on that tank & see if that'll yield any positive results.
If so, then maybe input side valve deposits were part of the problem.
If not, at least you'll know the injectors, intake & combustion chambers should be clean & tidy.
For some reason I keep feeling it has something to do with the EGR system, but I can't point to any one thing, it's just a gut feeling.
Just some thoughts for consideration.
Intermitent problems that won't hold still long enough to put your finger on them, are a bear to run down sometimes.
Seems the computer is unhappy with the evaporative emissions purge flow, when it sets the P1443 code, but the question is, is it because of the low idle speed/stall condition, thats occuring, because of some other reason, like maybe the EGR valve sticking from time to time, or maybe it's control, the DPFE acting out occasionaly, or maybe a sticking intake or exhaust valve????
SO, maybe a check & cleaning of the EGR valve & DPFE should be considered????
Could also be a sticking intake or exhaust valve, from deposits.
With this kind of mileage it's allowed to have some deposits. lol
You also might try running most of this tank of gas out, then before the next fill up, add a shot of Chevron "Techron Concentate", to a fillup with Chevron or Chevron/Texaco gas & do some spirited diving on that tank & see if that'll yield any positive results.
If so, then maybe input side valve deposits were part of the problem.
If not, at least you'll know the injectors, intake & combustion chambers should be clean & tidy.
For some reason I keep feeling it has something to do with the EGR system, but I can't point to any one thing, it's just a gut feeling.
Just some thoughts for consideration.
Thread Starter
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Junior User
Joined: Jan 2006
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Thanks pawpaw!
I have been going over everything that I have done to date and found where I did something stupid. I did not catch the fact that the sprockets use two different marks for timing until I was doing some reading today at work. I had used the triangles for both the camshaft and the oil pump. I did not find any other marks when I did the timing belt. After looking at the technical section today I found what looked like two different marks on each sprocket and the instructions on this site list using a diamond for the oil pump sprocket. As soon as I got home I checked and fixed the timing belt timing. The rough idle is gone now but I have a bucking and jerking intermittently that has come back to haunt me. The 1443 is back and I suspect that I definately need the purge valve assembly. At this point and thinking of pluging the line off the manifold until I fix the bucking and then go pick up the purge assembly from the dealer and get it over with.
The bucking is intermittent and does it in different gears and speeds, but seems to be at lower rpms. Since the idle is now good and seems to be reasonably steady, I am looking for ideas on what to look for to cure the bucking and jerking. It is not near as violent as when I started working on the truck and it now longer seems to want to die, but it is rough when you pull out and the trucks jerks like you are flooring and then completely off the throttle repeatedly. Any help is greatly appreciated!
I have been going over everything that I have done to date and found where I did something stupid. I did not catch the fact that the sprockets use two different marks for timing until I was doing some reading today at work. I had used the triangles for both the camshaft and the oil pump. I did not find any other marks when I did the timing belt. After looking at the technical section today I found what looked like two different marks on each sprocket and the instructions on this site list using a diamond for the oil pump sprocket. As soon as I got home I checked and fixed the timing belt timing. The rough idle is gone now but I have a bucking and jerking intermittently that has come back to haunt me. The 1443 is back and I suspect that I definately need the purge valve assembly. At this point and thinking of pluging the line off the manifold until I fix the bucking and then go pick up the purge assembly from the dealer and get it over with.
The bucking is intermittent and does it in different gears and speeds, but seems to be at lower rpms. Since the idle is now good and seems to be reasonably steady, I am looking for ideas on what to look for to cure the bucking and jerking. It is not near as violent as when I started working on the truck and it now longer seems to want to die, but it is rough when you pull out and the trucks jerks like you are flooring and then completely off the throttle repeatedly. Any help is greatly appreciated!
