LS430inDE.

Boy do I feel like an A$$!

My 05 has about 140k on the ticker. Car was running smooth as can be. No problems AT ALL. Well, I do have a tempermental tilt/telescope wheel, but that's not why I'm posting.

I was planning on doing the plugs at 150k miles, but had nothing going on tonight, so I said, what the heck. Let's do the plugs NOW.

I had no issues removing the Denso IK30 'iridium power' plugs that were installed probably 60k+ miles ago? There was some dark wet looking 'oil' on several of the plug's threads which I thought was odd. I replaced the Denso's with NGK 'Laser iridium' #4589 (IFR6T11). They were pre-gapped, and I measured/confirmed each one about .04x".

While I had the engine cover off, and the airbox hoses & plumbing off, I also decided to change out the PCV screwed into the drivers side valve cover. I had to take the oil fill neck off to get a wrench on the PCV. I replaced the PCV without issue.

I also sprayed the hell out of the intake/butterfly valve while all the plastic air plumbing was off. I didn't have intake or carb cleaner, but used Mass Airflow Sensor cleaner! (I was thinking it's ok, as it's not as 'strong' as carb cleaner???

Anyway, I took my time and replaced all 8 plugs. They all extracted fine. The clips connecting to the coil packs are a ***** to squeeze and pull off, but besides that, no issues.

I also coated the porcelain body of all the plugs with dielectic grease, along with a light coat on the rubber shaft of each coilpack.

It took every bit of 3 hours, but as I mentioned, I was taking my time, and just having a good ole time by myself and the radio and a bottle of WATER.

So.........I put everything back together, and triple check for tools, electrical connections not made, hoses not connected, etc. We are good to go.

I attempt to start the car and held the key cranking, for 5 seconds, and she doesn't start. Ok. Understandable. (I had sprayed the hell out of the butterfly/intake, although it was 2 hours previous.) I took a breath and cranked again for 5 seconds. She still didn't start. NOW I'm getting worried. I take another breath and cranked again for 5 seconds. Presto. She's running. ROUGH, but she's running.

I gave it about 3 minutes to work all the cleaner through the system, and within 10 seconds of running I throw the check engine light and check VSC!!!! WTF!!!?

Ok. So I keep letting her run for another 2 minutes, and while the real rough idle went to a simple rough idle, I'm f-ing PISSED OFF at what is happening?

I let her run for another minute although it seems like hours, then shut her down. SOMETHING IS WRONG. I take the engine cover off and tug on all the coil pack electrical connections. They are all secure. SO NOW WHAT? I think----disconnect the battery. Wait 5 minutes then reconnect and re-start, and see what we get?

Now, instead of what feels like running on 6 cylinders, it's slightly better feeling like running on 7 of 8 cylinders.

So, I have a scanner for the code, but it's at MY place and I'm doing the work at my GF's house in her garage. So, I can't scan for anything now.

Do you guys think I'l smoke the cat if I drive ~20 minutes and park it? What do you guys think it could be? I tried the obvious, loose or disconnected coil pack. No dice. Thought maybe I broke a wire in the harness to the connector? I don't think so. Could a coil pack just stop working after I gently placed it on the garage floor? I didn't drop any, etc. I was gentle. All the coil packs are the originals, mind you. But WHY, if it's a coil pack would it go bad NOW? The NGK's are the correct part #, so that's not the issue.

You guys have any other ideas? It's a real PITA to disconnect 1 coil pack at a time to see if there's any difference in how rough she idles. I get a little weirded out too, intentionally 'failing' a cylinder, because I know if she runs rough for a long enough time, I will smoke the cats!!!

And it's midnight too. This really SUCKS.

campisi

"Car was running smooth as can be. No problems AT ALL."

Clear case of If it ain't broke, fix it till it is. Go back and redo and recheck everything. Next time don't 'fix' stuff just because.

LS430inDE.

Thanks for your help.

ISFPOWER

iTrader: (20)

similar issue happens with the vq35de motor , if you open and close the throttle body butterfly without having the the battery cables off, you end up buying a new throttle body. Not sure if thats what happened to you.

LS430inDE.

Oh WOW. I did not have the battery disconnected when moving the butterfly valve.

I have re-checked everything on the driver's side and all appears ok. I even started the car with 1 coil pack connection disconnected, and feels like running on 6 cylinders. While running, I reconnect the disconnected COP and then smooths out to running on 7 cylinders. As stated, I did the drivers side bank.

I disconnected the COP on passenger side closest to the firewall (no idea cylinder #), and started again and felt like 6 cylinders. I then reconnected and smooths to 7 cylinders.

I just took a break to see if anyone had posted. (I knew there'd be a 'few' in the crowd like campisi, but never imagined they'd be the FIRST to respond).

Any idea what a new throttle body costs? Thanks so far.

LS430inDE.

So I rechecked all the connections on the passenger side. When 1 COP is disconnected, engine runs like REAL crap like 6 cylinders. I reconnect, and engine improves slightly.

I disconnected both battery cables and completely disassembled the throttle body from the intake. I cleaned all the carbon off the back side (wasn't that bad) and what remained on the front side. It was pretty interesting to see the intake/plenum on manifold? with the throttle body removed. I don't do this every day nor every year. First time for me taking off a throttle body.

Anyway, I thought I found the culprit when I removed the throttle body and some light red liquid dribbled out. Unfortunately, it wasn't the culprit. It simply was coolant dribbling from a couple of the small rubber hoses going to the throttle body.

I reconnected everything, crossed my fingers and started her up. She started right up and came to a high idle at 1,200rpm, but was still missing. She slowly came down in rpm's, and I'm calling it a night.

So, possible solutions so far are to replace the throttle body. I'm thinking of replacing ALL the COP's just to do it. The OEM Denso's can be had at RockAuto for $51/each before 5% discount code.

Any other takers?...

Johnhav430

Keep us posted would like to know what caused the issue...I can't see a plug replacement causing a smooth motor to go rough, that's just me. I have heard stuff where people say only use the OEM plugs, that was the case with my Maxima. With my BMW, I used the Bosch version of the plugs, as BMW cost $3 more ea. but they both have the same p/n on them, so I installed green Bosch instead of blue OEM, did not experience any improvement nor detrimental behavior, and they get replaced every 45k on the 335i...could your issues be PCV or TB related? I'm just guessing...good luck. My Maxima has a throttle position sensor that goes bad, just grasping at straws...and that throws a CEL....

rkw77080

Sorry to hear about your trouble.

Here are my suspicions... It sounds like the problem is with the "vacuum" system rather than "electrical" system. Forcibly moving the butterfly valve can damage its motor or gears, but I don't believe you have done that. Pull the DTC which can also narrow the problem area. Please let us know which DTC you are getting.

So at this point, we should not introduce any new variables into our troubleshooting effort. Instead, review what has been done so far and determine which of those activities possibly contributed to the problem. My first thought was the ECM. By installing a new PCV and new spark plugs to replace old ones with dark and wet oil stains, you are making huge changes that your ECM has to learn to deal with. This will take a bit of time, the ECM maps all its inputs to various driving conditions to optimize vehicle performance.

But I think there is more... I would inspect all rubber hoses that you've touched to ensure proper re-installation. Inspect nearby hoses that you may have disturbed, and last by not least, inspect for cracks in the hoses.

RushNatU

Sounds like a vacuum leak...need to check codes

tradosauru

Way to be an a$$. Nothing wrong with changing the plugs at 60,000 miles.

bmore430

Any of the hoses you removed possibly split or hairline Crack causing vacuum leak?

Bad or cracked spark Plug?

Don't see how a coil could have magically gone bad if the car was running well.

tradosauru

I would use a torque wrench to make sure that all spark plugs are seated at the same depth. Sometimes installing a spark plug can hit rusted threads and catch making you think that the spark plug is seated. Use 20 ft-lbs. Before that though take each spark plug out and look at the end of the spark plug and make sure you didn't bend the tab when installing. I've done this on another car and now I'm very cautious when installing spark plugs.

After that and you verify that all vacuum tubes are installed I would check the spark plug coil on plug wires to make sure you didn't accidentally pull one out. Follow my old thread to see how this happened to me. https://www.clublexus.com/forums/ls-...plug-wire.html

LS430inDE.

I just woke up. Thanks so much for the suggestions guys. I do have a scanner, but it's at my place. I'm doing the work in my GF's garage and there's no way I can get my scanner, just yet.

It's interesting you guys are leaning towards a vacuum leak or hose. After I did all my work, I tried starting her up, with the airbox off along with all it's plumbing. My intention was so that I could spray some mass airflow sensor onto the butterfly valve, while she was running. She simply does NOT like having the airbox off & plumbing disconnected. She would NOT stay running with it off. That's when I put the airbox & plumbing back on, and she stayed running. Rough, but running.

I didn't tell you guys I tried driving around the block before going to bed. She has what seems like 75% power? In other words, it seems like (according to lack of power), that she has more than 1 suspected bad plug/COP. At stop signs she was idling almost at 500rpm? So low, I thought she was going to stall. I placed in neutral at the stop signs and rpm's increase, but you can tell she's still 'missing'.

I didn't use a torque wrench but know that I cranked each plug greater than 20ft/lb if that is the correct spec. All the plugs were easy to insert and tighten. I tightened by hand, at least 5-6-7 revolutions, until I had to put a ratchet to firmly snug each plug. I gently placed each plug into the plug socket and carefully placed in the tube leading to the cylinder head. The plug never slipped out of the socket and never banged, so I honestly don't think the gap is closed. The ground of the splug are actually really hard to adjust. (I didn't make any adjustments to these platinums, but know the ground is very solid and not easily adjusted/moved). I tightened by hand, at least 5-6-7 revolutions, then I put a ratchet to it to firmly snug each plug.

I think you guys might be onto something with a vacuum issue. As I mentioned, she would NOT stay running with the airbox & plumbing disconnected.

I'm getting some coffee and will be back. Thanks guys.

Gronemus

He was doing preventative maintenance as he should have been doing. The Denso IK30 plugs that he was removing have a much shorter service life than the Denso SK20R11's or the NGK IFR6T11 plugs normally called out for this car.

I would keep on double checking your work with the remaining plugs that you haven't taken out yet and then start looking for cracked vacuum lines as others have suggested. I would think that a broken vacuum line large enough to cause an engine stumble would be easy to hear though.

Does your GF have a car? Would be nice to get that code fished out but I wouldn't drive the car 20 miles in it's current condition. Good luck and keep us posted...

LS430inDE.

GF has a car but she went to her sisters for the night. She'll be back in about 30 minutes and we'll get my scanner.

In the meantime, I examined best I could all the hoses that I disconnected and around where I worked. There is no hissing or anything that sounds out of the ordinary.

There IS a cracking vacuum hose on the smaller diameter of the 2 hoses connecting to the air box 'resonator'? There are supposed to be 2 rubber vacuum hoses which connect to this resonator. One larger rubber hose goes from it, to the top of the passenger side valve cover. It has a double layer of rubber, and it appears fine. The smaller diameter hose goes down and not sure where it connects to. Only the END/EDGE of this smaller hose is split. The split is at the very end of the hose where it connects to the resonator. The pressure squeeze clip that holds it in place is about 2mm away from the split end. I don't think that simple split end is the culprit. Regardless, I'm attaching a pic pointing to both the hoses I'm talking about...