I've been posting in a few threads related to this but not a lot of help in those. Trying for some "broader" help in case some in the know did not read those threads.

Quick details:

03 Max, SE, Auto 148k.

Solid car but noticed loud clunking when goosing it from a stop. Discovered bad engine mounts and replaced them. 3 Anchor, 1 OEM (driver side). After replacing I developed a rough idle. Not continuous, more like a pulsing. 2-3 sec idles smooth, 1-2 sec shudders, then smooth again. Really noticeable in part or neutral.

Did a full tune up, discovered LOTS of oil in 5th cylinder head. Plug submerged. Figured that as it. Replaced head gaskets and took car of oil leak in combustion chambers. Car idled better for a little while but returned to the same ole shudder.

I checked all the wires, as best I could when I had everything off the block for the head gaskets (did front and back). No "apparent" loose wire or disconnected vacuum hose.

Car does not seem to be running poorly. Gas mileage is still essentially the same as before engine mounts - maybe 1 mph better. Just an annoying vibration that drives me crazy.

No codes are coming up so thinking no issue with EGR, O2 sensors, plug wires, etc.

Lastly, I did opt for the non electronic front engine mount. Heard that can mess up your ECU if it goes bad. Wondering if disconnecting that might be giving me some issue with the ECU. Currently they wire harness is zip tied to a bracket near the plug wires and covered in elec tape.

Any thoughts or suggestions for investigation appreciated.

TMS

 

Have you changed out the valve cover gaskets? Highly unlikely to be the cause of the rough idle, but highly likely to be the cause of the oil leak submerging 5's spark plug. The factory gaskets leave a bit to be desired.

As far as the rough idling, I would check vacuum. Could be that you have a small leak causing the "pulsing" stumble that you're describing. Beyond that, I'll wish you luck and yield to those with more experience or more knowledge on this particular issue.

 

Yeah, I did new valve covers and gaskets at the same time. Even used liquid gasket in the corners, which I learned here. Oil in the cylinder head is no longer an issue - thankfully.

Any easy way to check vacuum? Is pouring water on them and listening for bubbles a valid option?

 

Mmmm, I typically use carb cleaner or B12 chemtool and spray it over all the vacuum lines. If the idle surges even a little bit, then you have a leak in that area or on that particular line. Doing it by the book requires using a fogger to see if any fog escapes.

I don't know that the soapy water trick will work on vacuum lines, as it will is pulling outside air in rather than pushing it out which might cause it to bubble up inside the line but might not bubble up outside where you could see it. It won't hurt to try it, but I'd use it sparingly, because water inside the engine isn't exactly ideal, and be sure you don't spray any electrics.

 

Get a can of starting ether and spray that on the hoses, connections, gaskets, etc. The engine will speed up if the ether is sucked in.

 

I have disconnected the electronic mounts on my 2000 SE. No issues, no CEL. From what I remember the ECU controls, but does not monitor, the mounts (it may be worth checking the FSM).

 

If you're using carb clear to check leaks do it with a cold engine. You don't wanna start a fire. You could also blow cigarette or cigar smoke in one of ur lines and see if anything comes out anywhere. Never tried it but I've seen it done. Let us know what it was when you end up fixing the problem.

 

The rough idle :
Check for vacuum leak, and torque of the bolts of intake manifold.
My personal preference is to replace the 1,3,5 ignition coil with OEM Genuine nissan. The 2,4,6 which ever brand, since it easy to remove and replace it.
5th generation : the front right engine mount is electronic (soft :idling harden:cruising). Most of the thread I read they suggest the oem engine support for front right engine to solve the rough idling. The aftermarket electronic mount failed to function as OEM. You can use the aftermarket for the front engine mount (passenger side) rear mount and the transmission mount. Those mounts are not electronic.
Install a PCV oil catcher.

 

Well, I sprayed about 1/2 can of carb cleaner on every vac hose I could find and nuthin. Even took off the Air filter intake to get way down into the engine to spray all the small vac hoses. So at this point, given the fact that it was NOT doing this before the new engine mounts, and I did not go back with an elec mount in the front, I think I'm going to go OEM for the front electronic mount and see if that is my issue.

Unless someone has another suggestion?

 

Nuthin to worry about shell out the money for TWO elecronic mounts and tell us if it fixed the problem since you ruled out a vac leak...

 

Can you clarify the TWO elec mounts comment? On my 03 there are 4 mounts. Front of the engine (elec), two on the sides of the engine. Passenger side was replaced with Anchor, driver was replaced with OEM (Local parts store did not have that in stock) and there is the trans mount (behind engine just above the muffler). The only one that had a wire was the front mount. Which other one is electronic?

TIA

 

Since i have a 2k mine had both mounts on the center beam electronic,idk if one of yours was removed before you got the car or 5.5 gens come with only one electric one...the only issue i had when i changed mine was the trans mount the aftermarket mount was made out of sheetmetal and the oem of beefy alloy so washers were needed.....

 

Just checked OEM and the 5.5 only has a front elec mount. Must have changed between model years. Shew! Thought I was losing my mind.

Off to Courtesy to order. Will let you knows know what happens after I replace it.

 

You never really mentioned that you changed your Valve covers in your initial Thread....So I'm curious how old your plugs are? I'm sure it's a coilpack/sparkplug issue.....I would advice you going OEM and definitely staying away from that Duralast crap.....Check your coilpack boots for holes where you might be experiencing vlotage leakage to ground!

 

Well, believe it or not, I changed the front engine mount to OEM electronic and now my car purrs like a kitten. Odd thing is, Nissan service manager assured me that going non electronic was fine. Guess he was wrong, eh?

$900 later in mounts, plug, valve covers and struts (to be done this weekend), my car should be like new.

This is one for the "scratch my head file."

Thanks for all the suggestions.

 

I suspected coils but never coded and ran diagnostics - nuthin came up. Compression was good too. Ive had coils go bad before and it was much more noticeable than this. I read on MF that the electronic mount really only engages in first gear, which explains why I did not have problems at higher speeds and/or fuel issues.

In the end it ended up being the mount itself. I would have done OEM to begin with but my deal was out of stock. Live and learn. Order a head of time.

 

This is interesting because I've read several posts that say to disconnect the electronic mounts to avoid frying ECU. I need to change my mounts, so I'll be putting the same that is in there now, oem electronic. Maybe it was the aftermarket stuff that was causing the fried ECU's? Good thread because I was wondering about this same thing.

 

5th gen issue.