91 Accord low idle and missing
03-22-2014, 07:52 AM
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91 Accord low idle and missing
Folks.
OK I have read extensively on this forum and others about my issues. First off, I have no data to imply that the two symptoms are related but here is what the car is doing. I am getting occasional and sporadic missing. It is more noticeable at idle but I have felt it at speed 2-4K RPMs as well. Second issue, and perhaps more bothersome is I have a low idle. When I start the car it fires right up and runs about 1200 RPMs after a short while it gradually lowers RPMs to around 250-500 RPMs (note all RPMs are based on dashboard tach observation and not an electronic tach). The RPMs will fluctuate and sometimes drop so low the engine almost dies. The fluctuation is not really a flutter (constant up and down) listed in some threads rather, an occasional dip in revolutions. I have troubleshot the issue myself as well as broken down and taken the vehicle to two different shops (one a dealer and one independent). Neither shop could "find" the issue.
What I have done so far:
all vacuum lines have been replaced with Honda lines. vacuum line diagram followed carefully and only one line replaced at a time. Am certain I did not misroute any lines.
Fast Idle valve was replaced (by independent) to stop the flutter idle I previously had. New Honda part. Just for the heck of it, last night after a long drive I took off the feeder hose to the throttle body and plugged the lower hole in the throttle body. There was some suction! I understand there should be none. When plugged the car's idle dropped even lower. When upper hole (to IACV) is plugged, there is virtually no effect on idle, no suction detectable using my finger. Does this mean the new fast idle valve is bad? Also checked the internals of fast idle valve and the valve body is tightly seated.
Same independent shop also performed a valve adjust for me just as normal maintenance. The low idle started right after this procedure.
IACV replaced by me. no effect to any symptoms. New Honda part.
Checked TPS. reads .5v at closed and 4.5 v at full open, smooth voltage increase as throttle is opened. One gent at a local parts store suggested I replace the TPS in any rate. Have not done so yet.
Checked cam sensor per Honda shop manual, within specifications.
Flushed and bled (using the bleeder valve) coolant with new Honda brand antifreeze. System seems to be holding coolant well.
Honda dealer "suggested" I replace the distributor housing. They admitted it was a "guess" and was the "logical choice" based on their observations. I have not done so yet.
Not sure if it is relevant but I do have oil encroaching into one of the spark plug wells, even after the recent valve adjustment. Oil was present prior to the valve adjust as well. I cleaned the well prior to getting the valve adjust from the shop). I was hoping the upper seals (replaced as part of valve cover reinstall) would stop the oil. It now appears the oil is either because of an improper upper seal replacement (or perhaps complete lack of seal replacement by the shop...who knows) or lower seal is compromised. The reason I tell you this is, this could be causing the miss, or .....????
OK so there it is. I know it is a lot of information and possibly two different and completely unrelated problems. I am not adverse to putting more time and parts in the vehicle I just want to do it in an educated and logical manner. I will probably do all the work myself as I am not confident in the local shops due to their inability to find and fix the issues.
One last thing. I have owned this car from the day it came off the showroom floor so I have a really good feel for when things are amiss. Both shops said my idle was "fine". It actually is not fine it is lower than it has ever been I can see (tach) and feel it. Car has 280K miles on it and has always been well maintained either by my work or local shops depending on my time availability. Thanks for any suggestions!
Mott
OK I have read extensively on this forum and others about my issues. First off, I have no data to imply that the two symptoms are related but here is what the car is doing. I am getting occasional and sporadic missing. It is more noticeable at idle but I have felt it at speed 2-4K RPMs as well. Second issue, and perhaps more bothersome is I have a low idle. When I start the car it fires right up and runs about 1200 RPMs after a short while it gradually lowers RPMs to around 250-500 RPMs (note all RPMs are based on dashboard tach observation and not an electronic tach). The RPMs will fluctuate and sometimes drop so low the engine almost dies. The fluctuation is not really a flutter (constant up and down) listed in some threads rather, an occasional dip in revolutions. I have troubleshot the issue myself as well as broken down and taken the vehicle to two different shops (one a dealer and one independent). Neither shop could "find" the issue.
What I have done so far:
all vacuum lines have been replaced with Honda lines. vacuum line diagram followed carefully and only one line replaced at a time. Am certain I did not misroute any lines.
Fast Idle valve was replaced (by independent) to stop the flutter idle I previously had. New Honda part. Just for the heck of it, last night after a long drive I took off the feeder hose to the throttle body and plugged the lower hole in the throttle body. There was some suction! I understand there should be none. When plugged the car's idle dropped even lower. When upper hole (to IACV) is plugged, there is virtually no effect on idle, no suction detectable using my finger. Does this mean the new fast idle valve is bad? Also checked the internals of fast idle valve and the valve body is tightly seated.
Same independent shop also performed a valve adjust for me just as normal maintenance. The low idle started right after this procedure.
IACV replaced by me. no effect to any symptoms. New Honda part.
Checked TPS. reads .5v at closed and 4.5 v at full open, smooth voltage increase as throttle is opened. One gent at a local parts store suggested I replace the TPS in any rate. Have not done so yet.
Checked cam sensor per Honda shop manual, within specifications.
Flushed and bled (using the bleeder valve) coolant with new Honda brand antifreeze. System seems to be holding coolant well.
Honda dealer "suggested" I replace the distributor housing. They admitted it was a "guess" and was the "logical choice" based on their observations. I have not done so yet.
Not sure if it is relevant but I do have oil encroaching into one of the spark plug wells, even after the recent valve adjustment. Oil was present prior to the valve adjust as well. I cleaned the well prior to getting the valve adjust from the shop). I was hoping the upper seals (replaced as part of valve cover reinstall) would stop the oil. It now appears the oil is either because of an improper upper seal replacement (or perhaps complete lack of seal replacement by the shop...who knows) or lower seal is compromised. The reason I tell you this is, this could be causing the miss, or .....????
OK so there it is. I know it is a lot of information and possibly two different and completely unrelated problems. I am not adverse to putting more time and parts in the vehicle I just want to do it in an educated and logical manner. I will probably do all the work myself as I am not confident in the local shops due to their inability to find and fix the issues.
One last thing. I have owned this car from the day it came off the showroom floor so I have a really good feel for when things are amiss. Both shops said my idle was "fine". It actually is not fine it is lower than it has ever been I can see (tach) and feel it. Car has 280K miles on it and has always been well maintained either by my work or local shops depending on my time availability. Thanks for any suggestions!
Mott
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