Misfire Coming On Boost

[Rolls]

CAS is a possibility, get a consult cable and check for error codes.

[DVS JEZ]

when u were tuning the safc did you have a wideband connected and read the afr's?

have you checked your catalytic converter

[No Crust Racing]

No consult port on ca's, only ecu diag LEDs which are showing clear.

Update time: removed fuel reg vac hose and blocked, went for a drive. Only had it miss a bit a few times but I put this down to the temp tonight, even colder than last night.

Not goin to do any more drive testing at night as I can't get the car hot enough without flogging it and I'm risking defects etc by being out in it as it's track modified but street reg'd and only rarely street driven.

Still showed the same doughy/bog down behavior once warmed also.

When I got back I also tested the resistance across the engine temp sensor as per service manual. Got .386k ohms. Manual says .2 at 80 degrees, the car was a bit cooler so higher resistance seems right. FYI it should be 2.5k ohms when cold and gets lower as the temp rises.

Next step is pull the cas ad test it, then I might drive it and heat soak the engine bay/cas a test it again.

I have access to another ignitor so will look at that over the weekend. I know I had some bad misfire in my 33 from this but this feels different and the ignitor is not on the rocker in a ca.

Sorry for typos, on the iPhone.

[DVS JEZ]

Checked ur cat?

What fuel pump?

[No Crust Racing]

Forgot to add, safc is on zero adjustment atm, ecu is tuned. Cat is.... Track modified.

[No Crust Racing]

Stock pump

[DVS JEZ]

Get a new fuel pump or atleast test it on a dyno under

Full load. The pump is very old. U may be getting a lean pop due to a weak pump.

[No Crust Racing]

If it was a fuel pressure issue I'd of thought it would show up with the regulator test, the service manual has that as a step to rule out the pump for misfire, lack of power, or surge issues. The next step in the FSM is to check the CAS itself and then check timing. So I'll rule those out first.

I'll need some bits to do timing though, I have access to a timing gun but I can't see a way to get a signal for it without running a spark plug lead between the coil and plug so I can clamp onto that. The manual has other ways but involves specific Nissan tools.

[DVS JEZ]

Just get an old lead between the coil and th plug. Works a Well and is cheap.

Can u post up a screen shot of the reg test to diagnose fuel pump please. Curious to see it

[No Crust Racing]

The mate with the timing gun has a carby V8 so I might be able to pilfer one of his leads too.

[No Crust Racing]

OK Update time. I had a few mins last night so I pulled the CAS to test. A few things to note.

1) The CAS and timing cover had paint pen marks on them, so it's been off before, the exhaust cam gear also had paint pen marks on it so I will deffo check timing as it's been adjusted before either when tuned or when timing belt was done.

2) According to the Service Manual, the CAS should read between 0 and 5V on pins A and B (see attachment) and the injectors should fire when rotating the shaft. I quadruple tested both pins and got between 0 and .3 on A and between 11.7 and 11.9 on B. That seemed very far off which is why I quadruple tested. I did however get 0-5V on pin D (I quadruple checked the plug orientation to be sure i was testing the right pins). So either my CAS is wack or the service manual is asking you to test the wrong pins. The injectors could be heard firing also so that's good.

I dropped down to a workshop this morning where a mates car is getting a rebuild and borrowed his CAS and Ignitor. Will check both of those and timing this weekend.

I'll re-gap the plugs back to .8 for testing too as a few CA owners have suggested coppers at .8 is the way to go, no harm in trying. I will do that after the above.

[No Crust Racing]

Just get an old lead between the coil and th plug. Works a Well and is cheap.

Can u post up a screen shot of the reg test to diagnose fuel pump please. Curious to see it

Sorry mate only just saw this.

The step is as simple as disconnect fuel reg, does the problem improve? Yes? If so measure fuel pressure. I didn't follow on with the fuel pressure step as my problem did not improve.

Grab a copy of the manual here.

http://180sx.strent.net/documents/S13.CA18.Service.Manual.pdf

[No Crust Racing]

Update:

Tested another CAS, exact same readings as mine. Interesting to note that pins D and C in the above picture are what actually register 0-5V, they must have gotten it wrong in the manual. I have mega ultra quadruple checked. Two CAS' same results.

Something else I noticed when putting things back to how they were is that I didn't actually disconnect the fuel reg (face palm) I had disconnected something else sitting just above it, very similar looking and a bit larger. I realised this when I was reconnecting it and thought it seemed odd that it wasn't ON the friggen fuel rail.

So I will test that properly tomorrow.

I also have the Ignitor to test (possibility as I don't run heat shields on the turbo and the ignitor is on the passenger side strut from factory and will gap plugs back to .8 as well. Will do those things one at a time though so I can be certain if something fixes it.

Cheers

[DVS JEZ]

Let us know how u go

[GTR260]

Update:

Something else I noticed when putting things back to how they were is that I didn't actually disconnect the fuel reg (face palm) I had disconnected something else sitting just above it, very similar looking and a bit larger. I realised this when I was reconnecting it and thought it seemed odd that it wasn't ON the friggen fuel rail.

So I will test that properly tomorrow.

That thing u disconnected is an actuator for the secondary throttles inside the runners

[No Crust Racing]

Update: Got it hot enough to miss consistenly and tried properly disconnecting and blocking the fuel reg and tried the other ignitor both without success.

Also was very slow to make boost and wouldn't make full boost with the reg disconnected.

Tomorrow weather permitting I will gap the plugs at .8 and try again. Heat is definitely a factor, once the bay is nice and soaked. I also found a big ass exhaust leak at the dump.

[No Crust Racing]

Double update time

Gapped the plugs back to .8 and tested, no change, if anything it seems worse on a wider gap. The miss is bigger and last longer.

Had another fiddle with the SAFC, and found that after removing about %20 from the map in the problem rev range it stopped missing completely, I also noticed that it was very slow to build boost due to this (SFA fuel = SFA exhaust gas and no spool)

I richened it up 20% and tested again, missing like a bitch. Big black puffs of fuel out the exhaust. So I suspected either a leak in the cooler piping somewhere.

Removed both head lights, took off each piece of cooler and induction piping, inspected, adjusted and re-tightened all clamps. Check multiple vac hoses, cable tied anything that looked remotely suspicious. Went for another test drive. Still missing and quite noticeably too, again larger gap seems worse than when it was on .5

I am yet to check the timing but does anything think this could actually be a timing issue? I dont want to go borrowing a gun if there's no point.

I don't think a fuel pump is the issue as there appears to be plenty of fuel in the map, the car sometimes backfires too, over-fueling I would think. I also noticed some oil build up in the cooler core, assume from tiring turbo, can the mix be that oily that it won't ignite?

Rapidly running out of ideas and patience

[Rolls]

As you found out rich mixtures compounds the problem as it makes weak spark even more likely to miss.

Get it on a dyno and get it tuned properly, don't do it yourself as you will probably lean the motor out and kill it. Get new coils as well, guaranteed to fix the problem. It is 99% of the time a combination of weak spark and too rich making weak spark even worse. Small plug gap makes the spark stronger which is why it seems to help.

I need a generic post for these threads, it is almost always this and this is always the fix. Check out the massive misfire from 4500 to 5000rpm thread. It'll be a combination of coils + plugs + too rich.

Edited July 31, 2011 by Rolls

[No Crust Racing]

I'd normally agree with you having helped a number of mates sort these issues myself.

Which is why one of the first things I did was try different coils from a known working engine (CA18 with T28 making 180rwkw, Z32 etc) and a diff coil pack loom. Then different plugs. So if it was a spark issue you'd think it would have got better with different coil packs.

Besides a big ass air leak from somewhere, what else could cause it to overfuel? The reason I ask is I don't wanna throw down a few hundred on coil packs that don't fix the issue.

[Rolls]

Besides a big ass air leak from somewhere, what else could cause it to overfuel? The reason I ask is I don't wanna throw down a few hundred on coil packs that don't fix the issue.

If you have changed to known working coils then I'd say you can be fairly sure that isn't the issue, but the fact that gap makes a big difference suggests it is now primarily overfueling. Overfueling on its own can cause a misfire, I know because it happened to me. Was running sub 10:1 around 9:1 at peak torque which caused a rich misfire, was a tomei remapped rb20 ecu (car had a bunch of tomei stuff in it) but it was designed for jap fuel, had so much timing they had to retard the cas to get it to not ping.

Solution was mapping a new ECU from scratch (before nistune etc) which fixed it as the tune was just simply not designed for our conditions.

Sounds like you are running a stock ecu with some minor changes via the SAFC. Stock tune with extra boost, bigger exhaust and intercooler etc means you can be seeing almost 100% as much air as the stock tune was meant to cope with, the factory tune then goes massively rich and retarded to make sure the motor doesn't go pop, sub 10:1 is quite possible if it is a cold night with >12psi and lots of engine flow mods (intake/exhaust etc).

As seen taking fuel out via the SAFC fixes the issue, the issue with doing this not on a dyno is you could be massively leaning the motor out making it detonate, you need a wideband and a dyno to do it properly. The other issue is you still have the retarded stock ignition maps, though if you are bending the afm signal perhaps it will fool the ecu into using lower load cells with more appropriate timing, I'm not sure. Ultimately I would recommend a nistune and a proper dyno map, if you want to do it on the cheap get a tuner with a dyno and wideband to tune the SAFC properly, you've seen it yourself, it will fix the issue.

Good luck!

Edited July 31, 2011 by Rolls