5SFE severe misfire problem

[sergei]

Hi, I am trying to solve this problem for quiet a while:

5SFE with DLI (2 coils) misfiring badly.
The only time it is not misfiring when it is idled at 2000rpm. Blip the throttle it will misfire (ie running on 2 cylinders), give it full throttle it would misfire (and get up to 4000rpm max). Idle: runs on 2/3 cylinders (if it can sustain it). It also occasionally backfires in the intake.

Things I did:
New spark plugs (there were wrong ones in there, the 5SFE with DLI takes 2 pronged ones according to EPC).
Checked the leads (each around 1 to 2kOhm).
Measured secondary resistance on each coil 13.4-13.6kOh each way*(I will come to this later)
Check the timing (with bridged connector it fires about 10 degrees, in 2krpm range).
Checked cambelt timing (while was there replaced and reset the timing).
Visually checked the PCB on ECU (no leaky caps found or obvious problems).
No error codes except O2 heater circuit open (tried different O2 sensor - code went away, after clearing ECU).
Measured compression, even on all 4, but it read 16bars (!), either exhaust blocked or gauge out of calibration.
Unbolted cat. converter can see through it (no obvious blockage).
Ran with cat unbolted (muffler end).
Ran with O2 sensor out (in case there was blockage between manifold and cat. converter).
Checked the line and filter to the MAP sensor.

Now, back to coil resistance: I was under impression that the shared coil in DLI had a diode in series. Can anyone confirm if it is true for 5SFE?

[sergei]

Things I checked today:
MAP sensor: (varies the voltage depending on vacuum): 3.6V when not running, drops voltage according vacuum.
TPS sensor: 0.6V no throttle 3.6V full throttle.
MAP and TPS sensor supply 5V.
Checked if leads were in right order, 1 and 4 on first coil 2 and 3 on second. checks out with pics found in internet.

Tested it running again: got it to idle ok (after sparkplugs cleared), light to medium throttle OK up to 6000rpm, while medium to full throttle blips severe misfire.
No excessive smoke or fuel smell.

Things to check:
fuel pressure.
Put scope on crank and cam angle sensors.
Will try to spray additional fuel when blipping the throttle to see if it helps.
Completely remove cat converter pipe and run with open exhaust manifold to see if the cat is partially blocked (when blocked the OX sensor hole it made worse).
Get hold of another set of leads, crank and cam angle sensors, and coils from Pick-A-Part (if I'm lucky tomorrow). Another ECU?

I am driving blind here...

[Lloyd]

Cleaned out the line to the MAP sensor? Does it miss just after the initial blip and then clear itself, or does it consistantly miss and get to a maximum rpm kinda thing?

[sergei]

Cleaned out the line to the MAP sensor? Does it miss just after the initial blip and then clear itself, or does it consistantly miss and get to a maximum rpm kinda thing?

Cleaned the line, checked the MAP sensor filter/damper thing that is bolted on, blew through it with compressed air.

It misses on first start up, if gradually brought up to about 2000rpm it clears up, and if after that gently revved it revs to max without any miss.
At this stage it can be dropped down to idle and it will idle, mostly without missing. But once it starts missing on idle, it will be very difficult to clear it out. When it is revving at 2000rpm (at this stage without missing) and throttle applied more aggressively it will miss badly and backfire in intake.

[sergei]

I figured it out. All it took is daylight.
It is very simple problem.... I am a bit embarrassed for not spotting (or checking it). In hindsight I knew about it being very common...

Here it is:
Spark plug leads, specifically plastic tubes where blown through and bypassing the spark plugs.

Why did I not see it when I checked the leads: I was working outside in the darkness. Why did I not pay closer attention? No idea...

[Bling]

At least it was something simple

[sergei]

At least it was something simple

Yeah, now I have all this 5SFE junk that I got from pick-a-part:
4x injectors
Cam and crank angle sensors
map sensor
ECU
....
I guess I will clean them and put them on tardme.
I should quit doing favours to friends and working in the dark.
At least my lawns and hedges will be trimmed by said friend

[sergei]

Botched up the leads with 3 layers of epoxy and 2 layers of heat shrink. Seems to be working fine. Told the owner to get new set anyway.

[evil_si]

What was it doing when driving?
Bad hesitation when taking off

[sergei]

What was it doing when driving?
Bad hesitation when taking off

Yeah, pretty much.
It had wrong plugs, which I think contributed to the problem (or even killed the leads). These wastespark 5SFE require two ground tips.