nsghtbrwry

Hey guys, so I ran into a problem on a client's '01 RX300 that I thought I'd share here for your benefit, since my confirmation came from testing the problem on my '01 ES300.

So this guy came to me with a P0330 (knock sensor bank 2), P0300 (random misfire), and P0302 (cylinder 2 misfire). After a little of this:
(just kidding)

...I did the knock sensor along with all the fixin's (harness, bypass hose, intake gaskets, valve cover gaskets/spark plug tube seals, washers on VC bolts). We figured the P0302 could be a red herring, and doing the knock sensors might take care of it. Nope, only the knock sensor code disappeared, and it kept misfiring at idle under light load (in Drive).

He told me it originally started misfiring during a cross-country trip, and he replaced the front bank of spark plugs with ones recommended by the local AutoZone; later he replaced the other three, the cyl 2 injector (reman Denso) and all the coils (Chinese coils from eBay, "Orion Master Tech").

He tried swapping coils and plugs between cyls 2 and 4, to no avail. When it got to me, I tried that stuff again, and also checked the compression (140 in cyl 2, 155 in cyls 4 and 6), swapped fuel injectors between 2 and 4, checked fuel pressure, checked the wiring from the coils to the ECU...no change, still P0302.

I swapped the coil from my ES (OEM Denso) onto cyl 2...same. Finally, I noticed there was a hole in the end of the plug (where the coil contacts it). Took it out and there it was, stamped "GERMANY" on the collar. Pulled it out of the spark plug socket and "Bosch Double Iridium." The peg on the end had a threaded hole - I guess it was for an application where a coil pack screws into it to make good contact; but with the stock setup, where the coil pack pressed down on the end peg, the hole means that much less surface area to let the electricity through (that's my theory, anyway).Plugs were 100 miles old.

When I put the Bosch plugs in my ES, it started misfiring exactly the same, but threw both P0302 and P0304. I tossed three NGK 4589's on the RX's front bank (RockAuto lists these as the OEM plug), and the misfire disappeared.

Of course, I told the owner not to trust AutoZone employees, whatever the computer says fits the car is based on if it has the right thread. Plus all the anecdotes spread out across car forums of Bosch plugs causing problems outside of cars where they were specc'd. Hell, I'm working on a BMW N51 engine lately, and they even switched to an NGK Iridium IX for the OEM plug (again, according to RockAuto).

Well, hope this helps someone. Oh shi-...I forgot to pull that Bosch garbage out of my baby. BRB

Hayk

iTrader: (1)

Nice work, thank you for sharing your findings. Would you happen to have a picture of the hole on the end of the plug you mentioned?

nsghtbrwry

Sure, if I can find the plugs...otherwise I'll post up a stock image when I get a chance.

Lol, I got another one in today with the same problem! Already has OEM plugs, so I'll start a thread in the RX forums for some help.

spineman

I got a P0300 code on wife's RX450h yesterday. So what plugs should I get? Are the chinese coils ok if they are the problem?

Oro

CW is to get either the Denso "Long Life" Iridium or the NGK "Laser Iridium." These are the thicker wire, longer-life iridium plugs. They make thinner wire Iridium variants for performance applications; I would avoid them in your application.

An alternative you can try is the Autolite Iridium. Last time I went to get plugs, I saw some for our ES at RockAuto quite cheap, especially after rebate. After doing a lot of research into their reliability and factoring the cost difference (~$10/6 vs $75 for the NGK), I tried them. Two years and 30k miles later and they work great. I'll do it again in my Acura SLX when the time comes. But if you don't want to try that or they aren't as compelling a deal on your vehicle, go with one of the two above.

I, also, haven't been able to get Bosch plugs to run well in even German cars. The Platinum +4 has to the worst "premium" plug design, ever.

skeeter55

Bosch plugs have been a problem that I have monitored also

spineman

I see you can get OEM Denso for $50 on Ebay. I'll probably go that route. Hopefully I get get to back 3 cylinders.

HomerJay

Check RockAuto they sell Denso plugs cheaper than that. Also don't forget an additional 5% off when you check out. Get the most recent 5% discount code and paste in "How Did You Hear About Us?".

spineman

The OEM Denso on RockAuto are 9.62 a piece. That's more than ebay??? Got 6 on ebay for 39.99 free shipping

nsghtbrwry

Well, if you're sure that the plugs from eBay aren't fake...

That reminds me, sorry about the delay - I totally forgot to post a pic of the plug end that I think is half the problem.

spineman

https://www.ebay.com/itm/New-Genuine...!US!-1&vxp=mtr

They look real to me. 99.9% positive feedback What do you think?

LeX2K

That's 60-80% less than places like Rockauto, suspicious. BTW Ebay reviews are useless they are not necessarily reviews from a specific listing, or sometimes they are for a different product.

Billybon

I'm new to just comment on "the hole" in the spark plug for those who don't know.
The hole in center = Terminal Type: Removable Nut.
When I was a kid, we had a lawnmower that the magneto wire terminal fit on the threaded stud and the nut secured it onto the plug.
And now I have a Honda outboard motor 2001- 90hp and the spark plugs used on it, are used with OUT the nut on the plug when I attach the plug wires (no nut on plugs).
So the O.E. plugs were NGK DR7EA, but I crossed to a Bosch plug that use 'silver' instead of the standard used 'copper' center core, Bosch 12mm #7701 (silver) with a removable nut. The 7701 are used on Farrari car.
I hope that broadens your knowledge some.