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Discussion Starter #1
I've posted quite a few times the last month about a persistent problem that seems to be worsening. I feel bad because I feel like I always have a question/problem, but due to limited experience, have very little to offer in terms of solutions. So, it is with a great deal of appreciation that I post yet again about the continuation of this problem.

Engine has been stumbling off and on for a month. It's completely random. It may do today then wait three days and do it again. Each time, no check engine light.

I cleaned the throttle body and also did a seafoam intake manifold treatment.

Well finally, last Monday it tripped the light. It stored a 0303 and 0305...cylinder misfires in 3 and 5. I took it to a well known shop, not the dealer, and they concluded it was the coil packs on cylinders 3 & 5. He changed them and put new plugs on all 8.... Autolite Double Platinum. YUCK YUCK YUCK I Know. Those plugs lasted all of about 18 miles in my truck before the engine started stumbling again and sending check engine lights. I replaced them with the standard Toyota Denso plugs.

I installed the Densos but had some confusion about the gap. The dealer said they were pre gapped and had little protective caps on the electrodes. Well, the Denso site said to gap at .035. The Haynes manual said to gap at .031. The dealer said they were pre gapped. I checked them. They were gapped at .030. So I left them alone and installed them.

I also happened to check the Autolites that were in there. They were gapped at .045! So I figured that was these platinum plugs and huge gap that had the engine acting up and stumbling after getting it back from the shop.

I cranked it up and she ran great. No stumbling no hesitation. A completely different scene then from an hour ago. Well, since my original problem was intermittent, I held off on celebrating.

Good thing, we're right back to square one. Engine stumbles so badly it won't stay running. I was letting it idle and went back outside to check on it to find it dead. It wouldn't start. It cranked but didn't start.

SO I broke down and bought a OBDII reader. I just pulled similar codes as the original. This time it's 0300, 0301, 0303, 0304, 0305, and 0308.

After a few tries it finally started but still idles like hell. Giving it a little gas revs the engine, but poorly, and there is a noticeable rattle under truck...at about mid-way of the length of the truck.

Wonder if it's a cat issue. Please let me know what you think.
 

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all those codes are misfirre codes but have no idea what would cause it to wig out like it has? I would suggest taking to dealer and getting it done by a tech that i am sure has seen this problem, just get them to look at it and give you a fix price! could be something simple and cheap but probably not! sorry not much help but Good luck once again!
most spark plug manufaturers will tell you to gape them per manufaturer specs!
http://www.toyotaownersonline.com/pub-share/pdf/appchart_sparkplugs06.pdf
 

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Discussion Starter #3
Yeah I'm leaning towards DEFINITELY NOT! LOL... My cheapest repair bill at the dealer was $865. LOL. Sorry....dimentia is setting in....this truck is driving me C R A Z Y.

"In the news today, a troubled man attempted to drive his truck through the plate glass show room of his local Toyota dealership but was stopped when the truck stumbled and lacked the power to make it through the glass store front. (pause) Back to you Chip."
 

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was looking at wiring diagnostics and it was leaning toward oxygen sensors? could be wrong but DIY with out test equipment and swap tronics could be expensive also!
 

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Discussion Starter #5
Wiring diagnostics? You found a site with that or have it in a manual? I had three of those replaced about 2 years ago...yes...expensive. Everything on this truck is expensive. I am seriously debating getting rid of it. It's just been too much of a headache over the years. The sad part is, I've babied it the whole time. I've had so many problems since year 1 that it has me second guessing Toyota all together.

So anyway, I ran several more scans. The very first produced multiple cylinders misfiring.....#1, 3, 4, 5 & 8. I cleared the codes, waited 20 minutes or so, cranked the engine and let it do its thing. I re-scanned after it stubmled and I got similar codes again....cylinder misfire 1, 3, 4, & 5. I cleared these codes and cranked it over again....this time I scanned it and only got cylinder misfire in #5. SO, I cleared it and started it again...and it idled fine for 10 minutes or so. Then I took it for a drive and all was fine. I jammed on the gas for a second and the truck lept with acceleration. Then I immediately let off the gas...it stumbled for second....recovered and never did throw a code. I drove with the scanner connected looking for codes and freeze frame events. Nothing.

So, I know this is probably the wrong way to look at it, but the only common trait in every scan ever performed since last week is misfire in #5. Now, is a misfire in one cylinder enough to trip the timing for 5 out of 8 cylinders? I don't know. But that alone wouldn't explain the reason why it wouldn't even start at one point. I would think even a bad O2 sensor would still allow it to at least start...if only momentarily. When I had 3 of 4 fail it would still start. It just couldn't maintain idle or a steady RPM. When I had a MAF sensor fail, it too started, barely, but it did start.

Sooooooooooooooo I'm thinking it has to be something "global" that is triping up every so often...something like a throttle position sensor maybe or perhaps even a fuel pressure regulator or hell....even the fuel pump I guess....or maybe it's just those damn gremlins we were warned about in the 80s.
 

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Talk to your buds or your buds buds and find a good tech that will cost you money but not be more than your truck is worth. There are good independent shops, the secret is finding one.
 

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Discussion Starter #7
LOL....I just got it back from a shop that several people at work have used and loved. ANd as far as the dealer....HA....it just got bought by a husband and wife business partnership that owns 4 other dealerships and their reputation is as well known as a dirty politician. I'm talking so bad that she was caught trying to collect a red cross debit card that was intended to go to evacuees of hurricanes Katrina and Rita. If she's willing to defraud a charity, what's their business plan like?
 

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I have a 2002 Tundra and there was a recall on 2 oxygen sensors on each exhaust manifold. Mine went out after 50K miles and had to be replaced. I don't remember the codes but I replaced them myself before Toyota decided to recall them. This could be your problem. However my truck ran fine, just kept kicking codes.
 

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It wouldn't hurt to get a can of Electrical Contact Cleaner and hit every socket and plug under the hood. Take them apart and clean each side of the connection and plug them back together.

Then take a look at the ECM, it has 5 or 6 plugs, and could be the root of your problem. A little harder to do is to unplug each of those connectors and clean with electronic cleaner and replug. Oh, it's behind the glove box. Don't forget to disconnect the battery first, don't want to fry that ECM. Good [email protected]
BJ
 

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Have the timing belt, pulleys, tensioner, etc. been replaced?
 

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Discussion Starter #13
Have the timing belt, pulleys, tensioner, etc. been replaced?
No, the timing belt nor it's pulleys have been replaced. I thought I read in the Haynes manual about it being a 90k replacement item. It was on my list of "things to do in the coming year."
 

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it could be a seperated catalytic convertor causing 02 sensors to have inaccurate readings to the ecm and therefore the ecm tells the injectors to either have a shorter duty cycle(run lean) or have a longer duty cycle(run rich) and that could cause multiple missfires. but also as sandinmytires had asked "possible timing belt may have jumped a tooth" with a mallet tap on the catalytic convertor with engine off and listen for rattle....
 

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With gremlins like this, I would change the ECM out and see what happens. It worked on a Camaro that had multiple misfire codes that nobody could diagnose the problem. A local shop owner had seen this before and put a new ECU (ECM) in the car and it worked perfectly. If I were as frustrated as you, that's what I would try. Good luck!
 

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No, the timing belt nor it's pulleys have been replaced. I thought I read in the Haynes manual about it being a 90k replacement item. It was on my list of "things to do in the coming year."
Toyota Parts and Service
90K but there is also a time requierment of 72 months but that i seriously doubt could be causing your issue!
My dealer has several Master Techs that are really good and can be trusted and that's saying a lot for ME!:blabla:
 

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Discussion Starter #17
Well, here's the latest...

I took out every plug...one at a time of course, and regapped to the Denso specs of .035. I took it for a neighborhood drive and it performed better than with the .030 gap. The only time the engine would stumble was when I stepped on the gas, got the rpms to about 3,000, and then braked hard . It stumbled but no way as severely as with the previous gap. Even thought it stumbled my scanner found no mature codes, no pending codes, and no freeze frame data.

So, then I did vacuum test. I used a vacuum port on the top of the manifold, about 2/3rds back and closer to the passenger side.

At idle it holds steady at 22inHg.

It also did fine on a "leak down test"...let idle, pop the throttle to 2500+ and release.... vacuum dropped down below 5inHg, then immediately shot up to about 25inHg and then quickly settled back at 22inHg.

I tried to a do a fuel pressure test but like I told the guy at the autoparts store...the pressure kit didn't fit the Tundra. SO until I find one that fits our fuel rail, my only visual indication of fuel pressure is from the little screw that sits on top of the fuel regulator at the back of the fuel rail. It popped up on cue and after shutting down the engine, it held pressure for a several minutes.

While I was at it, I went ahead and changed the PCV valve. The old one still had movement but instead of a clean rattle sound, it was sort of muted rattle from oil inside it.

So, after all of this, I took it for a drive in the neighborhood. Couldn't get it to stumble and had zero mature or pending codes. I accelerated hard and braked about 6-8 times and it never tripped. BUT due to this problem being so intermittent from the start WHO THE HECK KNOWS IF SHE'S FIXED.

I can see the bad coils being the problem...then followed by the notoriously problem plugs (autolight double platinums). I can also see the gap issue with what Toyota says and Denso says about the proper gap. But I can't see the PVC valve causing engine misfires.

I'm done for today. Perhaps tomorrow will yield some more codes.

Ye-hah get to roll into work with a ride from my wife. How demoralizing. "Hi guys...yeah that's my wife...with a Civic...yeah she keeps my balls in the glove compartment."
 

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Discussion Starter #18
Well, if anyone is still following this, the events since Sunday are as follows....

Monday...drove it for about 15 minutes when I got home. It was raining and the ambient temp was lower than previous days. No problems to report. Ran like a champ.

Tuesday (7/15/08) drove it to work.....six miles away. Temps in the upper 70s. Ran fine. Made it to work without a single stumble. When I got there, I checked for pending codes...none. I also ran an "inspection/maintenace " (I/M) scan....those of you with an Actron CP 9175 Autoscanner may be familiar with this....anyway all of the emission sensors reported "OK", misfire monitors reported "OK", fuel delivery reported "OK"...etc etc. All were good.

Tuesday Afternoon- drive home- Ambient temp in the 90s with 100% humidity...engine stumbled lightly 4-5 times during the 6 mile drive home. No check engine light. No pending codes. No mature codes. Performed same I/M scan and all systems reported "OK". The stumbles all happened either at idle in traffic or nearly at idle during the last second or two of deceleration.

I checked again with Toyota dealer...they insist the Denso plugs are pre-gapped. The Tundra owners manual calls for .031. Haynes calls for .031. Denso call for .035. I ran the truck with them at the "pre-gapped" setting that was actually about.029. It ran rough and still stumbled. At the Denso setting it ran better.
 

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Believe it or not, there are still a lot of us following this thread. We'd all like for you to FINALLY figure it out just so we can file away the answer for our own future.
Good luck and keep us informed.
 

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Discussion Starter #20
Single,
I didn't mean for it sound negative in any way. I was just saying "hey I know I've been going on and on about this ...." Yeah I am about ready to give it up. I keep reading about the '02 transmission problems and with still trying to figure out my issue I am wondering if I should just trade it in on something. The last thing I or anyone wants is to put money into fixing a truck just to have the transmission fail like so many '02s are having happen.

As far as this issue goes, I found some article that said that sometimes the MAF sensor doesn't send an error code. I guess that could be true for any "intermittent" failing sensor. But the idea that it's fine in the morning on days that it's not so hot and then stumbles on days that are blistering, has me wondering about air density and whether or not the MAF is contaminated or in the early stages of failure. When I say it was hot today it was a sticky kind of hot that makes you want to stay inside. At 8pm, by just standing there I was soaking wet and combined with the 100% humidity it was still a heat index of over 100°.

I looked at the MAF sensor itself today. It looked clean. I mean, there were no obvious signs of dirt or anything. I hear that sometimes the cleaning feature of the MAF sensor can leave behind a residue that can sometimes affect sensor performance. I have some MAF cleaner but have never tried it. Scared to honestly.
 
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