Blkongray

Hey All, I'm hoping someone has some insight on a misfiring problem I've been experiencing on my 1999 2WD RX300 (136K on the odo). A week or so ago my wife and I were on our way back from the Salem area and out of the blue the engine started to hesitate and sputter/studder with a flashing CEL on. Once I got home, I pulled the code: P0300 & P0303, so my first thought was the coil pack on #3. So I bought a replacement coil but had the same problem. Then I got more codes: P0305, P0171 in addition to the P0300 and P0303. I thought i might have gotten some bad gas, so I ran out the fuel and filled with quality midgrade fuel. Same problem.

Long story short, here's what I've done to the engine, but I'm still sproadically getting a P0300 & P0303. There will times when the engine runs flawlessly, and other times when it sputters, and studders. It has crisp acceleration when not sputtering, it's still getting good gas mileage, the sputtering is pretty minimal, but I just can't find the root of it. Oh yeah, here's the list of what's been done so far:

Cleaned the MAF (with spray automotive electronics cleaner; didn't touch)
Replaced all plugs with properly gapped NGK Iridiums
Replaced a coil pack and then rotated them
Ran some fuel injection cleaner through a tank of gas
Replaced the 'right' side (rear bank) Oil Control Valve
Checked all lines on intake and put in new air filter

Now it's still sputtering sporadically, and I'm getting P0300 and P0303 repeatedly with no other codes. I'm starting to think it's a mechanical problem, like a faulty fuel injector, because there are times I'll feel a slight sputtering, but the CEL won't turn on.

I haven't pulled resistances on the injectors yet, and the reason I haven't is because the sputtering is so sporadic... there are times when everything works perfectly, and I would think electrical operational values would read in the 'normal' range if taken static, especially if the problem was mechanical. I really need to tap into the engine's operation with a scope or diagnostic software so I can watch it live and see where it's faulting. At this point, unless someone has experienced this kind of problem before, I'm probably going to resort to taking it to my shop for a diagnosis.

Again, at this point I'm thinking a faulty fuel injector. Anyone else have any ideas?

Thanks in advance!

Lexmex

I posted recently about P0300, https://www.clublexus.com/forums/sho...00#post3628294

This is one situation where if I can't see it up close, not much help I can give.

thomas1

You know, maybe one of the coil packs has corrosion on it where the spring contacts the spark plug, did you shine a flashlight up the boot and look at the condition of the spring contact? Some anti-corrosion electrical contact cleaner could be a plus... Maybe the IAC is sticking momentarily and causing the stuttering... just some thoughts...

BCP43002

From the Lexus repair manual comes these possible causes for that code:

Open or short in engine wire

Connector connection

Vacuum hose connection

Ignition system

Injector

Fuel pressure

Mass air flow meter

Engine coolant temp. sensor

Compression pressure

Valve clearance

Valve timing

ECM

RayN

When the hesitation happens when the car warms up or from cold to warm? If it only happens when its warm and sometimes, it could be your engine coolant temperature sensor and loose/damage coil packs. I assumed you replace all your coil packs. You could have a dirty/clogged fuel filter.

Lexmex

Again, I wish I were there. Sometimes I have seen things on vehicles that when someone described it to me (usually when I was at the track back in Mexico) on the phone or in an email, I see it in person and then I see what's wrong.

Blkongray

Hey Guys,

Thanks so much for all the input. When I changed out the plugs and rotated the coil packs, I checked the contacts on each and they looked clean. In fact, everything looked good.

Thanks also for the list of possibilities on the cause. I had found many of these possiblities for the P0300 and related specific misfire codes through TSB's and other trouble shooting guides (www.obd-codes.com), but for me being pretty much a 'weekend mechanic' I just don't have the time or equipment to really go through and narrow the possibilites... so, it goes into my trusted shop Tuesday morning.

As to when the hesitation happens, it misfires sometimes when it's cold, and sometimes when the engine is warmed up... it's pretty sporadic. The most notable oddity is that the misfiring is much, much less (almost non-existent) when the outside air temperature gets up in the upper 80's or 90's. We had a hot stretch for a couple days here in Portland where it was nearly 100, and in the hot afternoons, the RX ran beautifully. I can't think of what would be temperature dependant on a misfire.

The only other thing I can think to note is that the 'misfires' actually feel like little 'cut-outs'. For example, I could be on the interstate and have the cruise control on and when the studdering would kick in, it would be like the vehicle was first running smooth, then cut out for a fraction of a second, then back to running smooth, then give a series of little tiny sequential 'cut-outs' and then run smooth again. They are like little repeated power drops... not the rough misfires that accompany a bad coil pack. Also, I can feel the power drops/studders at times and the CEL wouldn't come on. It would finally come on and flash after the cut-outs happened for a while and came on a little stronger. Because the CEL doesn't quickly come on when the studdering starts, I'm thinking the problem is mechanical.

I wish I had more time to diagnose this problem and fix it myself (I hate having to finally break down and take my vehicle(s) to the shop), but I've got my inlaws coming up from Cuernavaca, Mexico in a couple weeks and we need both cars to show them around. So, it's going into the shop on Tuesday and I'll give them a detailed list of what the problem is and what I've changed/replaced. The guys at this shop are sharp, and I'm sure they'll find the problem quickly. I'll give a detailed report of the findings.

Thank you to everyone who posted... I really appreciate it! Even though I couldn't figure it out, it's nice to see it's not something that is readily identifiable.

Pocket Tre

Taking it to your trusted mech is probably the best you can do. I ended up like you on a different vehicle.

I had the same problem once and it ended up being the ECM. This was on a different vehicle of course.

Hope you get it taken care of.

If it is in fact an ecm problem you can get one programmed to your vin number online for pretty cheap. That is what I ended up doing and solved the problem for $350.

OH did I mention with a money back guarantee too.

I thought that was pretty cheap for an ecm.

Blkongray

thanks for the input, Pocket Tre... I may follow up with you on where you got your ECM. I don't think I'm there yet, but I may be heading there.

I brought the vehicle to my trusted mechanic/shop. Driving it in that morning it drove smooth as silk until about mile 18, then it started to sputter a little and throw a code/CEL. I checked the code when I got to the shop, and it was the repeated P0300 and P0303. I had written an overview of the symptoms, what had been done on the vehicle (replaced spark plugs, replaced #3 coil pack, cleaned MAF, replaced OCV, etc.) to give the tech a head start.

They had the vehicle about two days and finally called and said it was ready to pick up. The owner wanted to talk with me, but I missed his call, so he left a voice mail. He sounded a bit frustrated and said they couldn't pinpoint the problem. They took it out for a drive and after about 20 minutes they got the CEL again (I had cleared the code before I dropped off the keys with them). Again, the P0300 and P0303. The owner said the P0300 is so generic there isn't much info that can be taken from that, so they looked more to the P0303. They first went right for the coil pack and exchanged it with the #2 pack. From there, they drove it randomly throughout the day for about an hour total and couldn't get any codes or any sputtering... so they handed it back to me.

I picked it up the next day and it drove nicely nearly to work, but then started to give the little studders with a flashing CEL as I got close to work. I checked the code when I stopped, and it was a lone P0303 code. The owner of my shop said he knew there was something going on, but it wasn't revealing itself enough for them to find it. He suggested in may be a fuel injector issue.

Anyhow, I drove the vehicle home in the evening, and it drove very well... a little bit of studdering at about half way home, but then went away and drove smooth. The strange thing is that the problem seems to be getting progressively less and less. I tried filling up with plus grade fuel to see if it had any effect. We drove it down to the Salem area this afternoon and it ran beautifully for about 50 miles, but then had some notable studdering in the last 10 miles. I checked the code when we arrived, and it was again the P0300 and P0303.

The info I did get from the shop wasn't too enlightening. Here's the report from the analysis:

STFT: both banks normal
LTFT: bank 1% lean, bank 2 6% rich (the owner said this isn't ideal, but not way off either)
MAF readings low: 4.2 gps @ idle
cylinder balance, 50 rpm deviation

I had cleaned the MAF, but the readings are still a bit low... yet the STFT (short term fuel trim) readings are normal... but the LTFT (long term fuel trim) readings are off, although a 5% deviation is considered normal. I'm wondering how much impact can a wacko MAF have on performance.

I've been following the performance issues and as the issue falls into a sporadic random pattern, the sensation of the fault is as if a 'choke' is being kicking sporadically and really quickly while I'm driving, but then it suddenly drives smooth again. It's never really an on/off effect, but rather like little tiny quick repeated spurts of a choke coming on... what I'm getting at is that it feels like it's being "controlled"... like it's a sensor going wacky and freakin' out for a bit, then going back to controlling properly, not like an issue of a dirty injector or clogged fuel filter or other physical component failure. Who knows, maybe I'm the wacky one at this point... but with that sensation, I've ordered a new MAF.

Now that the shop can't find it, I don't feel so dumb, but I'm also at the point of starting to just replace parts and see what fixes it. I think it's a gremlin, which usually stems from electronics. I'm thinking the MAF... maybe something sporadically shorting out somewhere, maybe the ECM. But then again I don't know exactly all the symptoms a faulty fuel injector would cause. Why would the code repeatly be on the #3 cylinder? I've changed the coil pack, changed the spark plug... the only thing left is the fuel injector. The old plug I pulled out looked good... not fouled, not scored... just looked like a nicely worn plug.

(heavy sigh) So, I'll report in later next week after I change my MAF and let everyone know what the result is. Hopefully when I find the culprit it may help someone else diagnose a problem like this. The $100 at the shop to run a diagnostic didn't tell much, but at least it's more than I knew before.

Do any of the readings on rich/lean and/or the MAF trigger any red flags for anyone regarding diagnosis?

As always, thanks again for the input/help!

One last thing, I came across this website: http://www.aa1car.com/library/2003/ic30336.htm and here's the symptoms they give for dirty injectors:

"The fuel feedback control system will compensate for the leaning effect once it is in closed loop, but it can't correct the underlying condition that is causing the problem. The injectors need to be cleaned, if an engine is experiencing any of the classic symptoms of dirty injectors, such as lean misfire, rough idle, hesitation and stumbling on light acceleration, a loss of power, and higher hydrocarbon (HC) and carbon monoxide (CO) emissions. Lean misfire may also trigger a misfire code and turn on the Check Engine light on 1996 and newer vehicles with OBD II systems. The code often will be a P0300 random misfire code, or you may find one or more misfire codes for individual cylinders, depending on which injectors are most affected."

Sounds like the problems I'm having... if the MAF doesn't do the trick, new injectors are going in.

Blkongray

Here's another quick update... maybe all this will help someone else in the future who has this kind of a problem...

I keep on thinking this problem might be bad gas, but I've been watching it and it's so sporadic... enough so that I keep driving the vehcile to try and toubleshoot it. I've gone througha about 5 tanks of gas now, and one I ran all the way down to nearly empty. I then ran a full tank of premium (coworkers said fuel manufactures are starting to run higher percentages of ethanol in the low grades of fuel, so it should run cleaner with premium). I also ran one tank with fuel injector cleaner in it. All resulted in the same freakin' thing happening.

We got back last night from the Salem area and the CEL was flashing at me nearly the whole trip home. When we got home, I popped out the MAF and cleaned it again. Upon starting it up again, it ran better... hmm. Then, this morning on the drive in I started to get the flashing CEL again, but right towards the last part of the commute the light went off and the vehicle drove smoothly. There was one point while sitting at a light that I could feel slight little surges and stumbles of the engine... very slight, but they were noticable... but not enough to trip the CEL. Then, while sitting in Drive at a light, as if someone flipped a switch, the engine went whisper smooth, RPMS dropped a little, and it drove great for the last few miles.

When I pulled the codes as I got to work, I had a handfull of them: P0300, P0302, P0305, P0171, P0100, P0110. The last codes refer to the MAF, and this is the first time I've ever got a code for the MAF.

What I know now is that what ever is causing the problem is sporadic, and when it acts up, it sometimes trips the CEL and sometimes not. That tells me what ever is the culprit is 'working' within the limits for the most part, but just not working correctly... then it drifts out of the limits, trips the CEL, but then drifts back into the limits and CEL shuts off... but all the time it's still crappin' out. It seems like what ever is failing is triggering other related codes, but not the primary code for the component that's failing. Since I've changed coil packs and all the plugs, and I've replaced the OCV, it now down to either the MAF or the injectors.... my money is on the MAF, but I'm still not sure why it has been giving a consistent P0300 and P0303. Perhaps the P0303 (#3 cylinder misfire) is the most affected by a spasmatic MAF.

I read somewhere that if you are having symptoms like these, a way to check and see if it's the MAF is to have the engine running and idling and to disconnect the MAF and see if it runs a little better. If so, then it's probably the MAF. Now, I have no idea how influencing the MAF is on the system and whether or not it directly controls the primary functions of combustion or if it's more of a 'trim' and refinement sensor. Well, after getting home yesterday I had the engine idling and it was a touch rough, so I pulled the plug from the MAF and the whole engine totally died instantly. I'd say the MAF has quite a bit more effect on engine performance than just a trim or refinement feature... seems it's a pretty primary component to get it to run at all. If that's the case, then a freaky MAF could be the culprit. I've got a new one on the way and will let everyone know as soon as it gets installed.

Pocket Tre

You may be getting to something there with the MAF connector.

May I suggest to every time you disconnect any of your electrical plugs you spray some electrical connector cleaner and lubricant. Better yet, also ensure the lengh of the poins is correct and also ensure that on the plug side the receiver is to the proper lengh as well.

All DC electrical connections have to be perfect. It is not like AC where just barely contacting gets you there. DC needs to be true to the connection.

Also if you see any buildup just get a hair BOBBY PIN and scrape it a little with the NEG disconnected of course.

I hope you get it fixed soon.

Sounds like a real pain cause it probably is not broken. That is just my opinion having read your posts. Bad connection somewhere.

You know just for giggles you could treat every single accesible conector while you are at it. You never know, you may hit the one and correct the problem.

Juan

Blkongray

So, ya’ll want to know what the culprit was? Here it is (see picture)… somehow, and I have no idea how this could have happened, the electrical snap-fit housing on my #3 injector was broken. I’m guessing it’s been like that for years, but just recently either it started to vibrate loose, or just the movement/exposure was causing a poor connection. Either way, I couldn’t see this failure for the injector is buried under the intake plenum. I had initially thought it might be the MAF, but I replaced it the other day and it had the same symptoms… no change. I knew the injectors could stand being replaced, so I pulled the trigger and replaced them all. I went through Motor Man and got all newly reconditioned injectors for $230 delivered over-night (I was torn between Motor Man http://www.fuelinjector.citymaker.co...injectors.html and Injector Whse http://www.injectorwhse.com/servlet/StoreFront …Injector Whse had free shipping on all orders over $99, but I had read many good review for Motor Man, and they would ship them out over night for just $18, so I went with them).

I spent Saturday replacing the injectors, and the front rail is cake… so easy. But the back rail makes up for that. I couldn’t get anything under that plenum, so off came the plenum. To do that meant removing nearly my entire intake system. I had to pull the intake air hoses, the butterfly assembly, and then I could access the plenum. What I struggled with is that there are three support mounts behind the plenum and butterfly assembly that one can’t see (see other picture), and they are a serious buggar to get to (two go to metal support posts, and one is a tie in on the pressurized A/C refrigerant line. It’s a job that makes replacing spark plugs or coil packs look easy.

Anyhow, I’m back on the road, no codes, and running fairly well. It’s been a little ‘hiccupy’ for the first few instances of WOT with the new injectors, but after a nice hour long road trip, the computer seems to be readjusting to the new flow of the injectors. The drive in to work today was nice and smooth and uneventful… that was definitely the root of the problem. I don’t know how the injector got broken, or stayed connected that long… in fact, I don’t even know if the connection was the problem (even though the housing was broken) or if the injector was just going bad. Either way, this seems to have done the trick.

I took a lot of pictures of the repair job, so I think I’ll write a DIY for replacing injectors for the RX300. I’ll see if I can get some down-time and write up a tutorial (since I couldn’t find a single thing online of how to replace injectors on our vehicles… I couldn’t even find a picture of the engine with the plenum removed (or any other component for that matter).

Thanks again for everyone’s input and brainpower on this issue… seems to be a weird failure that just wasn’t diagnosable from the symptoms… one had to get their hands dirty to find the root of it.

Blkongray

Here's the other picture of one of the attachment points behind the plenum.