RX400H pulsing surging at all speeds after replacing...

[B.I.L.sRX400H]

Valve cover gaskets, spark plugs, and air hose between the two resonators.

It's my Brother In Laws (hence the username) car, and he said it wasn't doing this before hand.

No CEL or other indication it has any malfunctions.

It isn't jerky or anything, or affects speed, but can feel slight 2 or 3 pulse surges.

Neither I nor my bro in law are in the know of hybrids, he keeps wanting to say transmission but I feel it's something to do with the hybrid drive based on little more than a hunch. I'm way more a "car" guy than he though.

Searching prior to joining/posting this I'd searched and found a few threads of people experiencing this at highway speeds but we're experiencing this from 20ish to at least 50ish, maybe faster. Seems the consensus in the found threads was either they weren't experiencing it, or chalking it off to the "hybrid experience".

Any input ot advice on things to check appreciated.

Thanks!

~T

[RX400h]

How many miles are on the odometer? 
It looks like the pulsing/surging occurred after the work, so I would not assume that the issues are NOT related to the service work. Who did the work? We had our sparkplugs replaced at 120,000 miles (Toyota dealership) and the valve cover gaskets, a year later (independent shop). Our RX now has 135,000 miles or so on it and we've never experienced any surging or hesitation of any sort.

[B.I.L.sRX400H]

I performed the work, he'd brought it in to his local garage for a service and they told him about the valve cover gaskets leaking. Was going to cost a little north of $600 which my bro in law doesn't have. I'm not a mechanic but have done plenty of engine/mechanic work throughout life.

It's got 187k on the odo. So while you may haven't experienced it personally, certainly you've seen posts on it in years past. I recall seeing your replies In threads I found before joining.

No CEL or any warning lights are on, and he does say it runs better after. Could be the new plugs or replacing the air hose that was badly cracked to the point of almost breaking into three pieces.

I have an OBDII scanner that can be used for real time monitoring, going to take it for a spin tomorrow while monitoring and see if I notice anything peculiar.

Also, even double checking as I reassembled that everything was getting reconnected properly, I'll triple check tomorrow as well. Although, if it was something left unplugged/disconnected or lose, I'd expect a CEL trigger.

[RX400h]

I would think that if you changed air flow in any way, that the engine's ECU would have to relearn its outputs. How long has it been since you did the work?

Did you use OEM plugs? Not doing so could result in less than desirable performance. 

[B.I.L.sRX400H]

3 hours ago, RX400h said:

I would think that if you changed air flow in any way, that the engine's ECU would have to relearn its outputs. How long has it been since you did the work?

Did you use OEM plugs? Not doing so could result in less than desirable performance. 

I did the work over this past weekend, and during disassembly found the fractured hose and luckily found it in stock at a nearby Lexus dealer.

I looked in the manual online and didn't see a specific plug mentioned but did recommend iridium so we went with NGK iridium plugs.

So results from today: I have an OBDLink LX scanner and use it with their OBDLink app on my Android tablet. It didn't identify any codes, and driving around for a while, other than erratic RPMs didn't see anything that looked "out of ordinary"

After getting back home I was going to try buying the Toyota extended codes for my scanner and decided if I'm going to do that, I'll do it on my PC so it's attached to that account vs Android which is more likely to change.

So I went out and connected the scanner with my PC (different app, better apparently) and it found a pending code P0305 Cyl 5 misfire. This definitely seems to be what could be the cause, I'm just surprised it didn't activate the CEL as I've seen misfires do frequently in other vehicles.

So I also reset the ISC which I found is recommended after disconnecting the battery. This did seem to smooth out the RPMs as it wasn't jumping around so much after.  Is there a reset procedure for the ECU?

Now to track down the cylinder numbers, for the love of God please don't be the back bank...

Edit: So I just found cylinder 5 is the back bank driver's side most cylinder. I'm going to see if I can get my hand in to check anything but suspecting I'll have to disassemble again. If so I'm thinking the coils should be changed for good measure. Any recommendations for a good OEM equivalent? Disregard, just ordered 6 Denso 6731301

One of the plugs box's had been opened and I'm fairly certain it was that one that got it so going to get a new plug as well just to be thorough.

[RX400h]

Those are good coils ($53.79 at rockauto.com). I've replaced the 12V battery every 5 years or so and never had to reset anything except the windows and radio stations. 
The spark plugs you used should be okay. I see that there is an NGK 94279 "Ruthenium HX High ignitability plug at rockauto. It is $8.55 each. Supposedly, it offers "maximum durability and ignitability"

[B.I.L.sRX400H]

12 hours ago, RX400h said:

Those are good coils ($53.79 at rockauto.com). I've replaced the 12V battery every 5 years or so and never had to reset anything except the windows and radio stations. 
The spark plugs you used should be okay. I see that there is an NGK 94279 "Ruthenium HX High ignitability plug at rockauto. It is $8.55 each. Supposedly, it offers "maximum durability and ignitability"

Yeah, NAPA had those coils listed as an OEM but ended up getting them on Amazon at pretty much the same price as RockAuto. I would have gone through them but was looking for an arrival by the weekend. Which of course Amazon stated delivery today, Saturday, but now has been delayed until tomorrow.

RockAuto is great, I use & recommend them whenever I can.

The plugs used are NGK Iridium IX, not sure how they compare other than price wise, RA is about $2 bucks cheaper.

I was hoping to get going today but waiting until tomorrow, once it's status is out for delivery I'll start the disassembly.

Also ordered some new coil plugs/connectors, 3-4 out of 6 snapped right off when disconnecting, super brittle. Seems like a bad choice of plastic for those connectors...

I'll update once done unless something pops up in the meantime.

Thanks!

[B.I.L.sRX400H]

So the coils actually ended up being delivered yesterday (Saturday) and after lunch I started disassembly in anticipation of their arrival but didn't end up getting delivered until well after dark.

I pulled the #5 plug, did a quick glance, wiped it off and gave to my brother in law to exchange. He had to go to three stores to find one lol. Any way, the first one the guy noticed the ceramic isolator had two cracks in it running the length of it and was asking if I'd used the right sized socket or over torqued it! I mean, the socket either fits or doesn't, can't really use a wrong sized socket there, and how much torque would it take to fracture the isolator?! I don't think that's possible...

Only about 35 here this AM, going to wait until noonish to install the new coils and reassemble. Just wanted to share about the plug.

[B.I.L.sRX400H]

Success!! Don't know if it was that plug or the new coil, but runs like a top now.

Hopefully the cracked air hose replaced also will resolve the periodic 0171 & P0174 codes.

Also, putting the vehicle in Drive, it doesn't seem to engage as it will roll back even on a very modest incline. I'll tackle that later, he's already gotten enough free labor out of me lol

Thanks for the replies and to all those that sent positive thoughts my way!

[RX400h]

That's great! Patience and persistence are the keys!👍

[BobbyWeir]

I'm looking at purchasing an 08 400h with a little over 110000. Feeling better about buying (given current used car market) . Thanks. 

[RX400h]

Ours has more than 136,000miles on it and still running great.