Code 21 no engine light on though?

[93_jdm_fd]

I thought just for fun I will check my car cold(when I have my misfire problem), so I drive maybe 3 min to get my morning coffee. Get out jump the two terminals and start counting blinks, I get code 21. Which is ignition fault. Could mean coils, plugs, ignitor or even coil pack wire harness. What I don't get though is why didn't my engine light come on if there are codes being stored?

[bobbo]

You need to put the jumper in or hook up to Consult to get the codes.
Give us some more info on your misfire.
Check plug gap and coil resistance but it's most likely your ignitor.

[93_jdm_fd]

It idles like an old 350 with a big cam. I have many coils that I have been swapping around and nothing seems to change as far as checking them while unplugging one at a time while running. They all make it drop idle while being unplugged.

I put new plugs in a few weeks ago, gapped from 1.1 to .6mm and all gaps seemed the same. I left them at 0.8mm just cause that's what everyone seems to run for a gap. I have to turn the idle up to 1200rpm just so it's not shaking parts loose while I'm sitting in traffic. I seem to have no issue with boost or vacuum leaks.

This has been on going for the 8 months that I've been driving it. Runs and drives great but has a really shitty cold start idle and when warm it's still lumpy but the needle is steady, stock cams and good compression.

[judasentinel]

Code 21 does NOT correspond to ANY faults AFTER the ignitor. If a plug is faulty, a coil or coils misfire, or the coilpack harness is shot, you will not get code 21. That code comes only when the ECU is unable to get the required signal from the ignitor.

Codes in our ECUs are not about mechanical fault per se, but about the electrical connections between mechanical or electrical components. For example, take the MAFs. If one of your MAFs is giving faulty airflow readings, you wont get an error code. But on the other hand if the MAF wire is broken, you will get a fault code.

So if you are getting code 21, check your wiring and/or ignitor. I think your small block chevy-styled idle is being caused by one or more of your cylinders not getting spark due to the ignitor or the wiring before it.

[markdett]

Ignition primary code is 9 times out of 10 because of faulty coil(s).

[93_jdm_fd]

I realized yesterday that I got the code 21 because when I removed the coil pack cover I tried starting the engine with the ignitor unplugged and that's why I code that code. I cleared the codes and did my road test again while cold and got the bucking, popping thing going, pulled over checked for codes and of coarse code 55.

I'm going to pull the coil harness out today and see if I can find a problem, reinstall the old coolant temp sensor and go from there. If I had one or more coils failing I would get hesitation during boost and I have no problem at all, only rough lumpy idle. Moving back to Edmonton next month and my brother has a gtr so I'm going to have to start swapping parts over to eliminate this problem.

[Skym]

Code 21 = no ignition signal (as far as I know it's same on any Nissan). That probably means a wiring problem on looms or wiring falling out of ECU plug (it does happen if loom is pulled on instead of plug), etc.

Here's the diagnostic tree you follow for Nissan Altima (look in Skyline manual, as it should have a similar tree with correct pinouts) -

http://autorepair.about.com/library/images/bl379a-lib.htm

The ignition barrel / switch does playup on Skylines, so could be the cause. The ignition fuse does blow if there's no earth on ignition module.

[93_jdm_fd]

I had the ignitor unplugged while I was trying to start it that's why the code was there. So I'm back to square one with the lumpy idle. I thought if I had codes stored the light would turn on like most cars today. I didn't know you had to check every other day to see if codes are being stored.

I just happen to check that day and found the code 21 and thinging great at least I can start there but, then realized that I had the ignitor unplugged with the key on and that's why the code popped up. I checked again today after resetting the ecu and just code 55.

[Skym]

If rpm goes up, down at idle, o2 sensors (no error code will show up on ECU, so hard to diagnose). Even the light missfire at idle can be due to o2 sensors making engine go lean (lean missfire). Unplugging o2 sensors will stop both from happening and idle probably will be glass smooth (not a good idea if intake manifold or exhaust manifolds are leaking via gaskets). Sometimes oil is too thick thus causes the rough idle (it did on my car when running 10w60 oil and 10w40 oil fixed the problem).

Only other things I can think of at this moment in time is camtiming is incorrect (out by a tooth or two), CAS is set incorrectly or have cams that you don't know about.

[93_jdm_fd]

On my lunch break today I warmed it up and tested the 02 sensors by watching the blinks while in diag mode, the blinks were steady back and forth which I guess means air/fuel is good. Both sensors are brand new any as of last months parts list. I didn't try unplugging them while it was running to see if it made a difference.

The CAS timing is dead on via my timing light(4 mark from the left) 20degrees, I finally just got a cam cover and installed it. I will remove it again and check actual timing marks on cams. The only thing I did was install new valve seals but place all valves, buckets and shims in one of those trays that are made for rebuilding engines. I bought the engine blown and rebuilt it so I have no clue how it ran before as far as valve lash(to tight to loose). I am going to chech valve clearances this weekend. If one was tight that would cause my misfire at idle.

[93_jdm_fd]

Just run it at idle with the 02 sensors unplugged and it seemed to run better or least there was a change in the way it sound and it did sound better. So two new aftermarket garbage sensors? I got them for a 96 maxima and swapped over the connector ends. Maybe I will just put the old ones back in.

[alliedelectricals]

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[93_jdm_fd]

Finally found the problem. I checked all the valve clearances and have 4 of the 12 exhaust valves open, I cannot get a 0.05mm feeler gauge between the lobe and the valve bucket. The cylinders that when I unplugged either a coil or injector on and felt no real change are the cylinders with the tight valves. One valve on cylinder 2, both valves on 5 and one on 6. That would explain the shitty rough idle and why I cannot set it to 900rpm without the engine shaking the mounts loose.

I had all the valves out to replace the seals while I was waiting for the block to come back from the machine shop and put all the valve, shims and buckets in a tray and reinstalled everything from where it came from. I was going to check clearances while I had it out and on my work bench but didn't have two sets of feeler gauges. I got the block back the next day and figured it should be fine, lol. Someone must have already had the cams out before and dumped everything upside down, just chucked everything back together and that was it. I bought the engine with a blown bottom end so I just assumed the head was never touched.