Help diagnose my misfire

[Jinks]

Haha, yeah i've only used it on fuel injectors before but figured it would work well for that. http://www.autozone.com/test-scan-a...l-tester/oem-6-pcs-noid-light-set/948078_0_0/

It has been there since i bought the car. At idle it isn't smooth, but stumbles, more noticable when it's cold. Warm idle still stumbling, driving it's doesn't jerk or anything just has hesitation. Did you look at the two videos i posted earlier?

I had the same issues and trust me it is extremely hard to find. It was the coil packs man. The rear coil packs. Unfortunately you can only check the primary windings, not the secondaries. FYI, if it is the coil packs, buy the Oem 130$ ones not after market. Your coil pack covers will not fit with aftermarket.

- - - Updated - - -

The rusted coil packs are your dead ringer here. Mine had the same. Which means at one point, they got wet. I recommend new coil packs, and new coil cover gaskets. A little Honda bond on the gasket will hold it in place and when dry, will not move from the cover. Chasing down fuel issues is irrelevant after seeing rusty coil packs.

 

[Old Guy]

Its a pain to do; but, you can check the operation of the coil packs by pulling the coil, put the spark plug in to the coil high voltage terminal and then hold the ground terminal of the plug against the engine while somebody cranks the engine. Do this in a dark area. If the spark only appears across the gap of the plug, the coil is probably OK. What you don't want is the spark appearing further up the long insulator nose of the coil indicating an insulation failure. No spark is equally bad! Do this with the connector to the fuel injector resistors disconnected. You really don't want the engine starting while you are doing the test.

Update:
Just for completeness, passing the above test does not absolutely guarantee that the coil is OK. As engine load increases, the density of the air fuel mix in the cylinder increases and the voltage required to fire across the gap increases. This is why sometimes an ignition related misfire will not occur at idle; but, will show up when the engine is under load. As the voltage required to fire across the gap increases, if there is an alternate lower resistance path along the insulator nose of the high voltage terminal of the coil, the current will take that path. Same thing with the test above. The spark may appear across the gap with the plug out in free air; but, back in the engine with the engine under load it could start flashing over internally.

 

[Larry Bastanza]

Here's my take on this: take into account each situation is different , but if I OR Larry B,I totally respect that guy can help we try
How many miles and Time/age are on the coils? If you plan on keeping the car , replace them, its a wearable IMO, 20 plus years old , how many heat cycles etc ...
The body of the rear bank coils rust up over time as most people dont cover the engine when they wash it, the small drain outs built into the valve covers is higher water just sits there and combine with old dried up and or missing coil cover gaskets furthers the problem, causing them to fail , I have only replaced one or two igniter packs in my career fixing these cars .

This is what I check next , First have the Fuel injectors ever been cleaned ? see attached sheet , Dripping is BAD , misfire/rough idle hello!, Also The TW sensor P/N 37870-PJ7-003 , located in the front bank cylinder head can be problematic , When was the last time , If ever , the Valves adjusted?

The early cars are senstive and problems can hide behind other issues/ lack of maintenace, bad prior repairs , I have seen it all over the last 20 years fixing NSX's

I recently had a NSX customer call me , the car was at the dealer , misfiring , THEY wanted to pull the motor, told him it had a " burnt" valve, Really???

Long story short , Compression and Leakdown were stellar, I sent the injectors out, the top Orings were dead also, new fuel filter , 3 rear bank coils , Valve adjustment, TW Sensor and Thermostat , gasket and Coolant , hadnt been done in years , although someone did all the hoses , When the valve covers were off I did check the Camshaft timing as I have seen a Few cars lately with the rear bank exhaust cam off 1 or more teeth off

Car ran Awesome

Car is still running great

Ben Daisy auto Pm or call me if needed 410-489-9334

Ben, could not agree more. Just yesterday I got a 1996 with 28K miles for service. The car would not even run going down the street, it was missing so badly. What I found was 3 bad coils. The owner said it was at the dealer and they replaced #5 coil. I replaced #1 ,2, and 4. Car hit the road like a rocket, no other work done yet. So let's talk about what a "bad" coil is. They are not electrically bad 99% of the time, in fact I can honestly say I never measured one that was electrically bad. What happens is the end of the coil(rubber cup) that fits over the spark plug deteriorates and becomes loose. When you have a coil out, take the spark plug and insert it. It should be tough to get in, and hard to pull out. So it needs to fit tightly over the plug. (It typically makes a popping sound if they are tight when you remove the plug.) When you get this "loose" effect, what happens is when the coil fires it arcs to the cylinder head bore in the head and does not fire the plug. So essentially the coil is firing outside the cylinder, aka misfire.

My $.02......

HTH
LarryB

 

[elijahcole92]

Ben, could not agree more. Just yesterday I got a 1996 with 28K miles for service. The car would not even run going down the street, it was missing so badly. What I found was 3 bad coils. The owner said it was at the dealer and they replaced #5 coil. I replaced #1 ,2, and 4. Car hit the road like a rocket, no other work done yet. So let's talk about what a "bad" coil is. They are not electrically bad 99% of the time, in fact I can honestly say I never measured one that was electrically bad. What happens is the end of the coil(rubber cup) that fits over the spark plug deteriorates and becomes loose. When you have a coil out, take the spark plug and insert it. It should be tough to get in, and hard to pull out. So it needs to fit tightly over the plug. (It typically makes a popping sound if they are tight when you remove the plug.) When you get this "loose" effect, what happens is when the coil fires it arcs to the cylinder head bore in the head and does not fire the plug. So essentially the coil is firing outside the cylinder, aka misfire.

My $.02......

HTH
LarryB

Well i went ahead and ordered 3 coilpacks for the rear, though i don't think that's the problem as i've moved them around, but definitely could be wrong

Last night i swapped my injectors from front side to rear and vise versa, didn't change anything. I also did a fuel pressure test that was around 42 at idle, and 50 with hose disconnected.

Coils will be here monday and i'm planning on pulling the valve covers to make sure everything is in time.

 

[Jinks]

Well i went ahead and ordered 3 coilpacks for the rear, though i don't think that's the problem as i've moved them around, but definitely could be wrong

Last night i swapped my injectors from front side to rear and vise versa, didn't change anything. I also did a fuel pressure test that was around 42 at idle, and 50 with hose disconnected.

Coils will be here monday and i'm planning on pulling the valve covers to make sure everything is in time.

Let us know what solves the issue buddy. I know these things are one huge pain in the ass with the early models. But once you get things all sorted out, you'll love your car. It's just testing you to see if you really love it.:smile:

 

[elijahcole92]

Coils didn't fix it. i began pulling apart my timing cover and such as i was going to replace tb/wp anyway and adjust valves, and i believe the timing is off..

At TDC (white mark on crank pulley aligned with cover mark) the front bank cams both line up and the 5mm pins go in. However on the rear bank, the intake cam lines up but the punch doesn't go in all the way, and the exhaust cam doesn't line up but the punch goes in all the way. So i don't know which exactly is out of time and how to set it and fix it.

the marks were also very hard to see, on some the groove was very small, on others larger, so i just marked it with white out.

Heres the front

rear, sorry couldn't figure out how to rotate it:

 

[Larry Bastanza]

Looks like the rear cam is retarded one tooth. This is typical of an inexperienced installation. What you need to do is once the timing belt is off, align it properly(rear exhaust cam that is). Once aligned install the belt on all cams and crank, EXCEPT the rear exhaust cam. ADVANCE the rear exhaust cam 1/2 tooth, install the belt. With the belt is in place you can move the cam back until the belt is tight, check the marks. This is all outlined in detail in the service manual. Move the cam with a 14mm wrench by turning on its mounting bolt to the camshaft.

LMK if you have any questions.

Regards,
LarryB

 

[elijahcole92]

Looks like the rear cam is retarded one tooth. This is typical of an inexperienced installation. What you need to do is once the timing belt is off, align it properly(rear exhaust cam that is). Once aligned install the belt on all cams and crank, EXCEPT the rear exhaust cam. ADVANCE the rear exhaust cam 1/2 tooth, install the belt. With the belt is in place you can move the cam back until the belt is tight, check the marks. This is all outlined in detail in the service manual. Move the cam with a 14mm wrench by turning on its mounting bolt to the camshaft.

LMK if you have any questions.

Regards,
LarryB

Larry,

thanks so much! i just wanted an expert opinion to make sure it was the rear off, since the punch fit fine and punch didn't fit fine for rear intake. I've been following the SM so i'll finish up today and check back Any idea why my compression test didn't show any difference between front and rear?

 

[Larry Bastanza]

mmm.... really? That is very odd. When you get done, BEFORE YOU PUT THE COVERS BACK TOGETHER, get me a pick of the cams, both front and rear sets. Frankly, the compression should be notable off between front and rear if the exhaust cam is off. Keep me posted.

Regards,
LarryB

Larry,

thanks so much! i just wanted an expert opinion to make sure it was the rear off, since the punch fit fine and punch didn't fit fine for rear intake. I've been following the SM so i'll finish up today and check back Any idea why my compression test didn't show any difference between front and rear?

 

[elijahcole92]

update:

got everything back together, marks are lining up here are some pics. I also did a leak down after a gear slipped some teeth just to make sure nothing was bent, on 85psi of air pressure all cylinders were between 22-17%. i couldn't go higher as my air compressor is messing up atm. Does that sound right?

Front bank:

rear bank:

 

[elijahcole92]

Well i believe it's fixed. Seems the rear bank cams were both off a tooth. Car purrs like a kitten now and drives much better. Time to put some miles on it Thanks to Larry B and others for all their help.