Plagued with horrible miss firing even after Nico search

[PauleyDucati]

Afternoon everyone. This is going to be a long post but hang in there please!

About a year or so ago my '99 Q started miss firing on cyl 5 i later found out. I tried new plugs which did nothing so I searched on Club Nico and discovered issues were reported with the coil packs so I bought a set of coil packs and another set of new plugs, put them on and once the ECU adjusted, the miss fire stopped.

About 6 months later it started again. I bought ANOTHER set of new plugs and decided to try and swap in one of my old coil packs in place of the new one just to see if I bought a faulty one. This fixed the problem again but for a shorter period of time, about 2 months or so when the miss fire started up again. (Keep in mind not once through the previous time frame had the check engine light come on, I thought the previous owner had somehow covered it up and was worried I bought a problem car). Once the miss started again after the two months it FINALLY threw a check engine light so I scanned it and along with the knock sensor codes it said "O2 bank 1 sensor 2 high voltage" and also the miss fire had moved from cyl 5 to cyl 4. Since swapping the coil worked temporarily last time I did it again and it worked again this time for an even shorter period of time of about 1 month. It started again so I scanned again, same problem with O2 sensor, this time it had an "EGR malfunction" code. I bought a new EGR valve and noticed one of the lines was just severed so I left the old EGR valve in and repaired the severed line. The car ran great for about ten minutes before the miss firing started again.

Ever since I fixed the severed line, the car has not thrown a code in about a month of driving yet it BARELY runs (I know it shouldn't be driven but I just got laid off and I have no other form of transportation). Last night after replacing all of the serp. belts, I threw in a new set of platinum plugs just because I'm almost out of ideas, I discovered oil in the plug holes on the driver's side cyl bank coming from leaking valve cover so clearly I need to replace the valve cover gaskets now... Once I put new plugs in and cleaned the oil out, the car ran absolutely beautifully, I was ecstatic that I thought I finally found the issue. I could actually accelerate for the first time in a year...then within 15 minutes it went back to it's normal miss firing and barely runs now. I don't think it's possible for oil to leak into the spark plug wells that fast considering the small amount of leakage that was going on...I'm at a loss and about to drive the car into a wall. I can't take it anymore and no one I know has ANY advice what so ever. I've spent hours online searching but found nothing, any help would be appreciated. I LOVE this car with all my heart but if I can't find a solution before it starts warming up, I have to sell it because I feel betrayed and cheated by the car lol.

THANKS!

[Q451990]

Does your miss go away when the car is cold, and then come back after it warms up? It seems like every time you mess with the car, it runs well, and then goes back to it's old ways... your "barely running" description doesn't match a single cylinder misfire in my experience. I'm wondering if you don't have an electrical harness issue that's getting fixed when you move some wires around, and then
comes back later... causing multiple cylinders to go down at the same time.

Just for clarification... where these new coil packs OEM Nissan ones, Hitachi brand, or something else?

EGR malfunction is typically a carbon clogged port leading into the intake from the EGR valve - but it shouldn't cause a misfire.

Heath

[paranoidjack]

Does your miss go away when the car is cold, and then come back after it warms up? It seems like every time you mess with the car, it runs well, and then goes back to it's old ways... your "barely running" description doesn't match a single cylinder misfire in my experience. I'm wondering if you don't have an electrical harness issue that's getting fixed when you move some wires around, and then
comes back later... causing multiple cylinders to go down at the same time.

\

Heath nails it - the same thing I was thinking the whole time I read your post - this problem seems electrical, but clearly for something that wouldn't trigger the CEL. I am currently fighting some gremlins in my MAF wiring harness - I believe yours is elsewhere, but Heath is dead nutz I think.

[lamsv]

Was there any oil on the coil packs/plugs when you swapped them? I have the same misfire. It happens 1 out of 4 times I start the car, and goes away after 1-2 minutes. I have a leaking valve cover gasket, which is putting a small amount of oil down in the spark plug hole, causing the plugs to foul until the heat gets high enough to burn the oil off. Hence, why the rough idle always disappears. I hope anyways!

[maxnix]

EGR malfunction is typically a carbon clogged port leading into the intake from the EGR valve - but it shouldn't cause a misfire.

Heath

You mention neither mileage nor condition nor maintenance history beyond the ignition coils and sparkplugs.

If you have read enough of the previous posts, you also know that the EGR tube from the EGR valve goes into the plenum and must be cleaned with plenum and solvents every 100K or so depending on how clean it was when reassembled. Time to read ParanoidJack's plenum job thread and prepare yourself.

[PauleyDucati]

I appreciate the responses guys! I've only had the car for a little over a year and I do regular maintenance the way it should be done but I havn't a clue what the previous owners have done. I know the first owner took care of it, the second owner I'm going to assume did NOT do what should have been done.

It now has 155,000 miles and it's a 1999. This past time when I changed the plugs there was a small amount of oil in the plug ports in two of the four cylinders of bank one, and yes it was coming from the valve cover gaskets so that's one more thing I have to add to the extensive list and from what a couple friend's say that have Q's and what I can see is it'll be a big job and I'll need a lot of patience lol.

Less than a month after I bought the car, the alternator caught on fire for a few seconds until I could put it out with apple juice (all I had in the car at the time) and disconnect the harness from it. I bought a new one (well of course nothing is new anymore so rebuilt) that died a few weeks later, got another one that's been fine since. The miss firing didn't start until a few months after that but now that you mention harness issues, I could see something getting singed inside that plastic shroud that runs near the alternator. Wiring scares me especially in this car because there are so many that go everywhere I wouldn't even know where to start. I'm good with a wrench but I'm far from experienced with that caliber of electrical work. My experience goes no further than accessory and stereo install

The coil packs I bought were from a used Q with around 60,000 miles. Since the economy is so effed up I wasn't able to scrape together the $1200 needed for a brand new set unfortunately. I have a feeling I'll have to find a way to buy a brand new set anyway but before I drop that much money blindly I want to be 110% sure it will fix my issue.

When I checked the EGR valve I noticed that metal line going from EGR valve to the other valve behind the engine was severed at the rubber connection hose so I cut a new piece of hose and repaired that. Ever since then, the car stopped throwing the SES code. It's seems like the car has the most trouble accelerating at low RPMs. When I manually shift through the gears, the car will actually accelerate fairly normal. Also, it seems like if I let the car warm up for a length of time before I drive it, it is worse than if I just jump in and go with the engine not in full operating temp. yet... I've never been so frustrated and angry with a vehicle issue before in my life and it's really getting to me. I love this car so much I don't know that I could ever sell it. if it comes down to it I might have to try to get a loan for a second car and keep this one as a project. I had to give up on one dream when I sold my bike, I'm not sure I could give up on this one too you know? Never surrender!!!

I'll have to check into the plenum job you suggested, that's a new issue to me. The car, physically looks stunning. It's in excellent condition given it's age and the fact that Nissan paint appears to be just as resilient as GM's paint was on my Vibe...horrible. Unfortunately, a couple weeks ago someone sideswiped me and didn't leave any note so I'm working on getting insurance claim settle so I can have the door skins replaced. Before that though the car looked great inside and out. Ten thousand times better than any other Q I've seen in my area (most are completely destroyed around Detroit area).

Thanks again for the comments, this site has been a great help to me so far in the vast amount of work I've already put into this car so thanks a lot for that! I had big plans for the Q too but getting laid off and this miss fire problem certainly put a stop to all that lmao!

[PauleyDucati]

I finally met someone around my area with some new suggestions and they mentioned ECU or ignitor chip. I can't find much on the ignitor chip so far except from all the SR20 swaps on here but I'm going to keep looking and call my old shop to check on AllData.

Thanks!