Our '94 with fewer than 20k miles has developed a miss especially at low RPM (even at idle). While it accelerates fairly well, the miss is profound under any degree of strain. It has developed very quickly and appears to be getting rapidly more serious to the point that it may simply quit completely. HELP!
'94 Engine 'miss'
- Thread starter Espritman
- Start date
I doubt that anybody could correctly diagnose your problem from the information you have provided. Given that, I had a similar problem with my 94 early last year with 40,000 miles on the odometer. After checking multiple possible gremlins like throttle body, coil packs, bad / old fuel, loose wires, etc. My problem was solved completely with a new set of plugs. It has been over a year now with no further problem.
The best advice I can give is to get the car to somebody that knows what they are doing and let them figure it out.
Good luck!
Norm
The best advice I can give is to get the car to somebody that knows what they are doing and let them figure it out.
Good luck!
Norm
As Norm notes, so many possible causes.
Your car is pre OBDII; but, my recollection is that the pre OBDII cars still had error codes; but, not the mis fire codes that are present on the OBD II cars. The pre OBD II cars have ignition output failure code(s). The first step would be to confirm that you don't have any codes. In the absence of codes, the easier things to check are the condition of the ignition coils and spark plugs. Pull the individual coils and examine for signs of tracking (electrical flash over) along the nose of the coil. Any signs of tracking and the coils should be considered a candidate for replacement. If there is any signs of existing wetness or previous wetness on the nose of the coils' you can try cleaning them with an electrical cleaner; but, they may be candidates for replacement if they have been exposed to moisture. If any of the coil noses show signs of moisture, the accompanying spark plug should be replaced. If the spark plugs are greater than 5 years old or you don't know when they were replaced, consider possible replacement.
Since your misfire occurs at idle, with the engine running you can try the disconnect the coil trick to try and locate the cylinder (hopefully just one cylinder) with the misfire. This trick works best if the misfire is bad -disconnecting the bad cylinder does not make much difference to engine operation where as disconnecting a good cylinder makes a significant difference. If the misfire is mild, you may not be able to identify a difference between a good and bad cylinder. If you think you have found the cylinder with the misfire, try swapping coils with another cylinder. If the misfire moves with the coil, then the problem is likely the coil. If the misfire stays with the cylinder, it is something other than the coil.
Check the condition of the grounding on the ignitor module. The only practical way to do this if you don't have test equipment is to disconnect the ground connection, make sure it is clean and re attach.
If there is a chance that the engine is running rough as opposed to a true misfire, cleaning the throttle body may help (do a search, there are a number of threads on Prime dealing with this).
Beyond these simple things to check, things get more complicated and it may be, as Norm suggests, time to send it off to a good service tech.
Your car is pre OBDII; but, my recollection is that the pre OBDII cars still had error codes; but, not the mis fire codes that are present on the OBD II cars. The pre OBD II cars have ignition output failure code(s). The first step would be to confirm that you don't have any codes. In the absence of codes, the easier things to check are the condition of the ignition coils and spark plugs. Pull the individual coils and examine for signs of tracking (electrical flash over) along the nose of the coil. Any signs of tracking and the coils should be considered a candidate for replacement. If there is any signs of existing wetness or previous wetness on the nose of the coils' you can try cleaning them with an electrical cleaner; but, they may be candidates for replacement if they have been exposed to moisture. If any of the coil noses show signs of moisture, the accompanying spark plug should be replaced. If the spark plugs are greater than 5 years old or you don't know when they were replaced, consider possible replacement.
Since your misfire occurs at idle, with the engine running you can try the disconnect the coil trick to try and locate the cylinder (hopefully just one cylinder) with the misfire. This trick works best if the misfire is bad -disconnecting the bad cylinder does not make much difference to engine operation where as disconnecting a good cylinder makes a significant difference. If the misfire is mild, you may not be able to identify a difference between a good and bad cylinder. If you think you have found the cylinder with the misfire, try swapping coils with another cylinder. If the misfire moves with the coil, then the problem is likely the coil. If the misfire stays with the cylinder, it is something other than the coil.
Check the condition of the grounding on the ignitor module. The only practical way to do this if you don't have test equipment is to disconnect the ground connection, make sure it is clean and re attach.
If there is a chance that the engine is running rough as opposed to a true misfire, cleaning the throttle body may help (do a search, there are a number of threads on Prime dealing with this).
Beyond these simple things to check, things get more complicated and it may be, as Norm suggests, time to send it off to a good service tech.
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Take out you spark plugs and examine them. It is highly possible that the color of one of them is different so you can narrow the problem to that cylinder (spark plug or coil). This is the first thing I would do before thinking of another problem (injector, fuel pump, ...).
Thanks very much for your guidance. I appreciate your taking the time.
The issue has since advanced to the point that the car stops completely, rests for a minute or so then restarts. That suggest to me that it is not an individual cylinder issue. Does this development help with further suggestions?
The issue has since advanced to the point that the car stops completely, rests for a minute or so then restarts. That suggest to me that it is not an individual cylinder issue. Does this development help with further suggestions?
It sounds like you could have a "bad fuel" issue. (moisture and dirt can plug things up and then settle out to allow a restart) Did the problem start after a recent fuel purchase?
Norm
Norm
I had a similar problem where anything under 3k rpm it spit and sputtered. New coil packs and plugs solved that issue and before putting the car back in storage it ran much better.
Sounds a little more like a fuel starvation issue rather than an ignition induced misfire. However, I would expect you to be triggering lean fuel mix trouble codes. A fuel pressure check would be in order. A number of potential causes including failing fuel pump, plugged fuel filter .... Best to test first.
An old mechanic once told me you need compression, fuel, and a spark to have an engine run.
Let's assume you have compression.
Your engine has error codes which will help diagnose your spark situation.
As Old Guy suggested, have you checked your error codes?
This may help determine if you have a coil, igniter, O2 sensor etc. issue.
If it's not electrical then it has to be fuel delivery.
When was your fuel filter last changed?
Can you hear your fuel pump start up?
Have you had your injectors cleaned and re-calibrated? (RC Engineering)
Send us your error codes and more fuel system maintenance info.
If you can't access your codes, or don't have any maintenance records, it might be easiest to take your car to a dealership with an NSX tech
Let's assume you have compression.
Your engine has error codes which will help diagnose your spark situation.
As Old Guy suggested, have you checked your error codes?
This may help determine if you have a coil, igniter, O2 sensor etc. issue.
If it's not electrical then it has to be fuel delivery.
When was your fuel filter last changed?
Can you hear your fuel pump start up?
Have you had your injectors cleaned and re-calibrated? (RC Engineering)
Send us your error codes and more fuel system maintenance info.
If you can't access your codes, or don't have any maintenance records, it might be easiest to take your car to a dealership with an NSX tech
Thanks to each of you respondents. You've given me a nice long list to pur
sue.
Bob
sue.
Bob
@ Espritman - one more thing to check for - the main relay. I had a weird misfire on my 92 - after recent service of 90k (new plugs, cleaned and balanced injectors, timing belt, valve adjustment, fuel filter etc. etc.). Wouldnt happen often, but once in a while and very sporadically. Sometimes also at low rpm. Replaced the main relay, and since then no problems. Also starting the car has been smoother - after a long drive, sometimes it would take 2 tries for the engine to "catch". With the new relay, it has started every time on the first try.
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