Misfires and an intermittent Check Engine Light
 

I'd like some expert insight into some engine problems that cropped up in the past couple of days please. My X3 was driving perfectly well, until I noticed a rather spluttery misfire when I took it above ~3000rpm or so. The currrent conditions are:



-The aforementioned misfire, only really evident from 3000rpm to redline. It's not a consistent 'dakka-dakka-dakka' misfire, it's more of a random staccato type deal.

-Check engine light appears now and then, it remains steadily on for a minute or so, then turns off again

-Intermittent engine cutout. Cruising down the freeway, the engine will shut off completely for ~0.2 seconds, then kick back in again, usually triggering the CEL.



I followed my hunches and replaced the crank angle sensor, cam angle sensor, and tested the TPS. Visual inspection of the wiring harness seems okay. Visual inspection of the fuel pump seems okay with an unclogged mesh bag. I can't get the trouble code(s) because this is an OBD1 95 accent with a newer dohc engine swapped in - the diagnostic port don't worky no more.



Thanks for reading. I'm going to start looking through hmaservice and test the coil packs/splugs this afternoon, but I'd value your input on this.

Never mind, it ~was~ the coilpack for cylinders 2 and 3. Too bad I tore apart the dash before testing spark...





I swear that DOHC alphas consume coilpacks, this has got to be the fourth or fifth coilpack that's died on me in my time of owning various X3s and LCs. :nuts2:

ever considered swapping to a gm style coil pack?

iv had mine failed 3 times. and building it (removing and seat reseating/cleaning bolts below as worked. without buying replacements.

I had not. I'll actually look in to that one, 3800s are cheap as dicks around here and they all use waste spark. Nice one :beercheers:





Yes, I had one get pretty grimy under there too. But the main part of the coil pack is what seems to go for me, despite how deliciously clean I can make the contacts. I'd like to cut open the plastic wad and see what's up inside of there. However, I think that would probably prohibit any further repairs to said coilpack. :Shifty:

Update: no it wasn't the bloody coilpack. Although it revved okay in the garage after doing the coilpack, it's now behaving in the exact same way as it was to begin with.



Tried disconnecting the MAP sensor, then the ISC valve. They made no difference to the problem.



Anyone got ideas here?

plug wires were cause of my last rough running/cel. Intermittent makes it funny though. Hate to suggest it for fear of a jinx but . . . do you have a compression tester?

Okay. Tested current draw of the fuel pump, it kept running strong with a steady 4.5-4.8 amp draw. Even when the engine was 'off'. Tried disconnecting the FPR vac hose, that also made no difference.



I've also had trouble with splug wires in the past, but it's not them. I'm getting healthy spark at the plugs. I don't own a fuel pressure tester nor a compression tester - the thought did cross my mind but it's not quite exactly the issue here.



I have a spare 02 sensor, I'll throw that in tomorrow. If that doesn't work, I'll get a dashboard loom from a busted X3 and convert to OBDII so I can get dem trouble codes.







This is seriously the worst timing for my DD to break down. :chairhit:

If the idle is also not great, check the timing and the timing belt.



I'm having trouble thinking about it just now but shouldn't the car run worse if the FPR vacuum is disconnected? If that made no difference then _______

Okay. It was actually the MAP sensor. Who would have guessed?



I got to the point where I'd exhausted rationality and started swapping sensors with my spare engine. It wasn't the fuel pressure regulator nor the 02 sensor.



The MAP sensor is from an LC so I still have a CEL, but it's running fine. I'll get an X3 unit tomorrow and report back. Thanks for the replies :thumbup: