Engine Miss

[SDHeights]

Picked up a nice Red/Black 93 the other day with a small handful of minor items to fix. The engine is missing, from idle on up while not under load. While driving, it is not really apparent, so it might not be missing while under load but can't tell for sure.

I have experienced missing in other cars with the exact opposite problem, where it misses under load, but does not at idle - this seems to generally be electrical issue as there is enough spark at idle, but not with higher volumes of fuel.

1) How can I identify which cylinder is missing?
2) What would be the first thing to try? Injector? Plug? Wiring? Other?

The missing seems very consistant time wise, so I think it's a cylinder issue versus some other issue that just makes the engine run rough.

Thanks for the help -

93, 64K miles

Jeff

 

[klr01tlr]

Hi, check if someone had previously detailed the engine compartment. They may have gotten moisture on the coils. They are very sensitive to missing even with a hint of moisture. Spark plugs may also be worn. Good luck!

 

[drew]

Get this fixed, or you will ruin the affected cylinder.

One by one you will need to pull the coil connectors, one at a time. On 5 of the 6 disconnections the engine should run differently (worse).

The disconnection in which the engine runs exactly the same (misses) then you found your problem child.

Test and swap coils, Does problem move or remain on that cylinder?
Pull and read spark plug
(hopefully you have solved the problem by now)
If not, take compression readings of all six cylinders.

Report back.

Drew

 

[SDHeights]

I've been working with some individuals on this via PM. I did the coil test and each introduced a distinct misfire, so I think it's actually not a misfire. After driving the car for a week or so, I have to re-characterize this as a chassis vibration at 1200 RPM and some smaller ones up in the range, all below 3K RPM, out of gear, clutch not depressed (i.e. just sitting in the driveway).

The engine itself sounds just dandy from the outside, even at 1200. But the whole chassis sets up a vibration that shakes the seats, steering wheel, exhaust, etc... From the inside, it sounds a little like a john deere because only the low frequency stuff is making it through.

Engine mounts? Timing belt?

Can anyone try to characterize for me what the "standard" engine vibration is like in these early cars?

Thanks,
Jeff

 

[drew]

Guess: Harmonic balancer. Very bad news if it goes...it can destroy your engine.

http://www.nsxprime.com/forums/showthread.php?t=33175

**

Something coming loose on the flywheel side?

**

I would also remove the belts for a few minutes so you can eliminate the accessories.

Good Luck

Drew

 

[SDHeights]

Found the problem - not an engine missfire at all. Timing belt was very loose. Did the belt, water pump and idler pulley. Sounds and feels much much better! There is still a broad spectrum of low vibration throughout the high idle range, but this I will buy as normal. The previous vibration was probably 5 times stronger and only at very specific RPM's (1200 was the worst).

Might be noteworthy to add this to the FAQ under engine idle related problems.

Thanks all -

 

[redshift]

There is still a broad spectrum of low vibration throughout the high idle range, but this I will buy as normal.

I don't have any vibrations.

Glad to hear you got the major stuff fixed though :biggrin: