360 - Misfire Problem - Suggestions?

Hmm.....

I was intending to revisit this thread to say that I'd done a few additional tests since first posting the fuel pressure results above and that I'd found that pressure is actually ok, but when I saw Eric's post above I thought I'd just check the OBD status and report.

What I'm seeing now on the OBD is .....

ECU11 (which I believe is 1~4) is at 11.7% and
ECU14 (which I believe is 5~8) is at 17.2%

Historically LTFT has tended to be in the 10%~14% range. I haven't seen a number as high as 17.2% previously. Also, the car hasn't been driven for more than 200~250 miles since the last reset. To achieve a +17% over such a short period seems a bit worrying?

As I said above, I have tested both sides twice more since the first test.

Test 1 - 50 psi on 1~4 and 40 psi on 5~8 (I tested the 1~4 bank first on this test)
Test 2 - 45 psi on 1~4 and 50 psi on 5~8 (I tested the 5~8 bank first on this test)
Test 3 - 50 psi on both but the 1~4 bank was a bit slow to build to that pressure while the 5~8 bank went straight up.

The manual says that pressure should hold at about 2.75 bar / 40 psi for an hour after turn off. I've no problems achieving that hold but can also state that even 24 hours later I've still 35 psi (which seems a little unlikely). I've found that when I disconnect the pipe from the fuel rail that the pressure gauge does not fall back (even though a certain amount of fuel does dribble out). I have to disconnect and reconnect the pipe from/to the gauge quick-click connector several times in order to relieve the pressure. It seems that the gauge is capable of holding pressure on it's own accord and can therefore only be relied upon to give a reading of peak pressure and not the leak down test.

I've re-set the ECU and will test both sides again tomorrow and then drive a bit and see what it reports.

p.s. The car is starting, running and pulling fine by the way!

 

Ok, update time.......

Powered down ECU overnight. Connected fuel gauge to Bank 1~4 and turned on the ignition. Fuel pumps prime and throttle bodies do their bit - not a gig from the gauge. Turned ignition off and then back on again, still not a gig from the gauge.

Started car (no problem) and by the time I got back to the engine bay the gauge was reading about 40 psi and made it's way up to 45 psi after a short time but didn't go any higher.

Disconnected gauge and attached to Bank 5~8. Turn on ignition and gauge lifts relatively slowly to settle at about 30 psi. Start engine and it's up to 45 psi pretty quickly and moves on to 50 psi after a short time.

At this stage I will say that the fuel pressure gauge is not an expensive, professional piece of kit. I bought it on ebay with a super-wide variety of connectors and pipes for Stg£60. It definitely does not release pressure so it is not capable of "live monitoring" because all it does is register peak pressure but, that said, I've no reason to seriously doubt it's ability to measure with reasonable tolerance.

Went for a 70 mile drive. Stopped after 23 miles and checked OBD. Found Bank 1~4 LTFT at 19.50% this is higher than I've ever seen it. Checked Bank 5~8 and it's at 4.7%.

Left the OBD logging 5~8 and drove on for 11 miles by which time the LTFT had moved on out to 7%. Air Flow Rate (AFR) recorded 5.25 g/s at idle, 4.25 min, 19.21 average and 99.21 max (RPM max this run 6541).

Left the OBL logging 1~4 and drove on another 21 miles by which time the LTFT had moved on out to 20.3%. Air Flow Rate (AFR) recorded 5.75 g/s at idle, 2.75 min, 18.20 average and 103.50 max (RPM max this run 7951).

On return home Bank 5~8 LTFT is sitting at 10.90% and Bank 1~4 is at 21.1%.

Eric, I know you live and breathe this OBD stuff. There's lot's more data available but I don't know how to interpret most of it. If there's anything you feel might be useful to post up let me know and I'll see if I have it logged.

The car seems to me to be motoring fine. The only thing I will say is that I've always felt that the throttle/engine response anywhere below 4.5k is a little underwhelming on this car. Unfortunately I don't have any experience driving any other 360 ever so I've really nothing to compare it with.

I'll pull some plugs in a wee while once she cools down but in the meantime any thoughts or comments most welcome!

 

Oh!....... and while out I ran over a young Deer. Thankfully someone else had already done the job of laying it flat-out on the road but even a dead young deer is a challenge for the limited ground clearance of a 360.

Fortunately the only evidence is a tuft of hair snagged where the centre under-floor joins the front-floor and rather a lot of dried blood all the way back.

Glad it wasn't standing there when I came upon it.

 

Surveyed the Deer remnants.....

Tuft of hair snagged in the underfloor.

Clean up required from just behind front axle right to the very back of the car. Yuck. I seem to have lost one of the two bolts at the rear of the undertray (might have simply loosened out) and the other one has been pulled half out. Not the worst damage to report but I'm hoping the receivers for the bolts haven't been pulled from the chassis.
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Now to matters more technical.

Fuel pressure gauge still showing 40 psi two hours after having been disconnected from the fuel rail.

Two phone-camera shots of plugs. 7 - 5 - 4 - 2 (left to right) one with flash one without. Probably a little lighter than usual but it was a relatively clean drive on open roads with very little slow-down time as I approached home. No ridiculous difference to my eye......
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Photographs aren't all that clear, I can't get a 0.70mm feeler blade into any of them.

I had another look at the plugs today in daylight. They all look fine to me, actually better than I have ever seen before from this motor. I've taken plugs out after track days and they've never really been light tan as I would like to see. If it wasn't for the puzzling results from the pressure gauge and the high LTFT figures I wouldn't have a concern in the world!

 

Hi all, the issue now is so like the last time I can cut and paste most of it!

"Hi All,

The car (2000 Yr with 52k) developed a misfire the other day. I was able to establish that the cat on the 5~8 bank was a lot hotter than the 1~4 bank. Slow down flashed briefly a few times and the CEL lit up.

Pulled code - P0152 which is an O2 sensor circuit (upstream bank 2 sensor 1) high voltage.........."

Problem on this occasion is the #6 plug (#5 last time) and we're 2300 miles down the road.

This happened after a half-day on track, followed by a 100 mile run down the country at modest but pretty steady speed followed by a high speed blast over the last four miles. The car was then parked up for three days/nights and was misfiring when I started it. I thought maybe a fouled plug and stopped about seven miles later and waited 10 minutes to see would the heat soak cure it. No joy. Cat was already glowing nicely around the outlet of the second o2 sensor. Drove on and a few minutes later the CEL lit and not long after that I got the flashing slow down warning.

Using an IR temp gauge I can quickly establish that #6 wasn't firing and with a quick swap out for an old plug I'm back in business.

Looking back on my records of the previous very similar problem I now realise that there are other similarities. I had used the car for a full day on track a month prior but now that I check the mileage there was only 40 miles recorded between completing the track day and when the original misfire developed. (I was on holidays before y'all jump on me for not using it )

The plugs are NGK PMR8B. I wondering if perhaps they're getting glazed by long hot running on track. The appearance of the insulator on the plug is yellow-tan and somewhat shiny also.

Thoughts anyone? Thanks in anticipation.

 

I know! Poor wee thing took out a couple of the riv-nut underfloor anchors from the chassis too. Still, not too bad all things considered.

I'm leaning towards extended track use causing the problem and contemplating the next cooler plug in the same range ...... NGK PMR9B. Problem is I don't want to find myself fouling them when pottering around town.