'94 maxima rough idle, stumbling

[canucklehead]

Just noticed my '94 maxima VG30E was idling rough and feels almost like it has a miss, or a cylinder isn't working. This happened right after filling up fuel, which could be a coincidence. Also, fuel consumption suddenly seems bad.

I'm going to start with a new fuel filter, then I'll try a set of platinum plugs. I'll report back what i find. Air filter is a K & N and was cleaned about 10,000 miles ago, but I'll look at it. Man, it costs more to buy a K&N cleaning kit than a new paper filter costs!

Any other ideas?

I pulled the plastic cover off of the distributor and I noticed a thin wire with a female blade connector that slides onto a male blade connector on the distributor. it was badly corroded, so I soldered on a new connector and felt like a genius for finding this problem.....except it seems to have made no difference. Could just be a ground connection of some type??
Modified by canucklehead at 12:13 AM 12/24/2008

[MinisterofDOOM]

I had a very similar rough idle issue with my VG Maxima that turned out to be a cracked distributor cap. If all your plugs check out, I would start there.

[canucklehead]

I didn't realize these had a distributor cap! I thought it was some kind of electronic ignition system with coil packs. If i have a distributor, then there should be a cap & rotor as part of my maintenance aswell, shouldn't there?

I only noticed the plastic snap on cover.

** I have edited my original post to correct my reference; it was the distributor I fixed the wire on.
Modified by canucklehead at 12:15 AM 12/24/2008

[MinisterofDOOM]

Yeah, the SOHC VG still has a mechanical distributor--cap, rotor, and all. The DOHC version has electronic coil-on-plug, though.

The distributor is hiding under that kinda-rectangular black plastic "ECCS" cover on the passenger side of the engine bay.

[canucklehead]

You are most correct. For some stupid reason, i thought that was the coil. I found the coil too! I'll replace the cap and rotor soon. what I referred to earlier as the coil pack with the wire i repaired, was in fact, the distributor.

so I just walked in the door from changing the spark plugs and fuel filter. i never let it warm up long enough to see if it's fixed the problem, but I don't think it did. But i just have to say, that's about the easiest, most accessible tune up I've ever done. Plugs are dead simple to change, there isn't one that is the slightest bit tough to get at. the fuel filter,dist. cap & rotor are all simple to get at. One thing i have heard is that the timing belt is a 6 hour job on this car. Considering it is maintained/replaced at 100,000Km interval (same as a set of platinum plugs), you'd think they might have designed that part to be easier.

so the auto-parts place told me I needed BKR6E plug, but the maxima manual says BKR5E. The ones I took out were 5's. I ended up putting in platinum plugs, and used the 5 instead of the 6. Anyone experiment with plugs? My old ones looked perfect for having 55,000 miles on them (87,000Km).

[MinisterofDOOM]

Timing belt difficulty was kind of a no-choice deal. The FWD layout doesn't leave a lot of room, even with the Maxima's unusually wide engine bay.

I've always had the dealer change the timing belt for me, simply because I don't feel like dealing with it. Timing belt, water pump, and any other items in the area that might need replacing all at once.

You may want to check with a dealer regarding the 100,000km change interval, too. Nissan has gradually increased the interval over the years as their belt designs have improved. I think it was 105 thousand MILES with the final Frontier belts in 2004 (same basic motor). If you have a newer belt, you might be able to go longer before another replacement is required.And, for what it's worth, my second belt went for about 130,000 miles (aaaah!) without breaking. Not a chance I'd recommend taking, but I think the 60,000 mile/100,000 km recommended interval is a little on the conservative side. Maybe for the best, though, since belt failure will almost assuredly destroy the motor.

[canucklehead]

well, i replaced the plugs with platinum ones, I replaced the fuel filter, distributor cap & rotor. I also re-set the timing, altho it was still within spec. It still gets an occasional stumble on low idle, but is running WAY better. much more responsive and peppy. the idle issue is so minor, I don't think I'll worry about it. and it's intermittment. maybe I just have some cruddy gas to burn out.

[canucklehead]

hmmm, this stumbling idle is wierd. It only stumbles every 5 seconds or so. Maybe a sensor of some kind and the information doesn't get processed correctly? if it was mechanical, I would expect it occur more regularly.

Even though I have better performance, I'm not sure my mileage is better. We've had a lot of snow and cold weahter, so maybe I'm using extra fuel for that. I'll wait for the rain to return, then compare my mileage. I was hoping the overdue tune up would improve my mileage.