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Discussion Starter #1 (Edited)
I think i've researched just about every thread on here but thought i should still post. Here's what i got:
p0303-misfire, #3 cylander.
p0300-random misire.
98 tac. 2.7 4x4, all stock.
265,000 miles, but runs like a champ. Doesnt burn a drop of oil
Maintained religously.
Trucks been perfect but about a month ago i noticed it kind of started idleing just a tad rough. Passengers never noticed it but i did. Than all of a sudden it throws the codes mentioned above. Just had the battery changed because a guy at walmart said i needed a battery because the truck took about 1.5 seconds to start after turning the ignition. Changed, started exactly the same. So i started working on the check engine light. This is what i have so far.
Changed the oil, spark plugs, wires and thought the coil might be throwing the code, changed it, not it.
Every fluid has always been changed. Radiator, perfectly clear green. Gas filter changed 1.5 years ago.
No visible smoke coming out of the exhaust, but the pipe does have carbon build up.
Spark plugs have a light kind of a brownish tint on parts of them now, changed about two weeks ago. Thats normal right? NGK plugs that are recommended in the hanes manuel. Gapped according to hanes manual. THe ones prior were sorry bosh's that the truck ate up pretty good. I installed them last summer but i do commute. Probably put about 25,000 miles on them.
After all this, cleared the code again, and it came back next day.
On the bad side:
I decided to check the air filter, dusty as hell. Am going to buy one tomorrow. I cleared most of the dust off and put it back in and cleared the code. Just curious, drove it, light came on after about 10 min.s. I've never ran a cleaner through it or taken it into toyota or anybody for any type of services. I do them myself. The motor has never been opened up and always ran perfect. The only things that have been changed that havent been mentioned are the starter. This week i am going to run sea foam through it,gas,pvc tube and booster cable hose. After this, i just dont know what else to do? Any insights before i move onto the fuel injectors and motor????????????
 

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Discussion Starter #2
And i did check all the vacuum lines, looked fine. Cleaned out the throttle body with a cleaner spray. Half assed it but did idle a tad better.
 

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did you get some electrical parts cleaner and clean the MAF?
I get those codes for all my cylinders when I idle the truck too long but I attribute that to the cams I put in. They make my truck idle at 620 rpm.
 

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Discussion Starter #5
I did clean the air mass sensor with electrical cleaner about two years ago. I forgot i changed the o2 sensor about 2 years ago and catalytic converter last spring. I'll clean the AMS, when i cleaned up the Throttle body some, the AMS looked fine though.....Thanks guys.
 

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You changed the battery because it took 1.5 seconds to start:lol:



Before you go wasting anymore time and money. Do a compression check. You could keep throwing money at it but never fix it if its got a burnt valve.
 

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Did you try resetting the code?
Unplug the battery for a few hours or buy an OBD II scanner and press reset.
I don't know if you did this, if not, sorry.
Chipsndukes

***edit*** forget the above, once again not paying attention before answering.

Anyhow:

Does anyone know what criteria the engine computer uses to set this code? Have insight into the ECU?
I assume it is looking primarily at the electric side, nothing with fuel can be monitored because the O2 sensor is a path with all cylinders, couldn't check specific cylinders.

Therefore assume it's pulling an electrical fault in the ignition, or like jaime is saying maybe an electrical with the injector.

Jaime, try swapping injectors back and forth. I believe this is possible without removing any part of the intake, you just have to loosen the two fuel rail retaining bolts and pull the assembly up, be careful where the injector tips end up sticking into. (I BELIEVE this is possible, maybe you have to take off the TB).

you may want to bleed fuel pressure first, you can do this with the banjo bolt on the rail and a rag (my method) or run the engine and unplug the fuel pump relay (buried under dash) the elegant method.

Maybe this will do something. If you have plenty of time and don't mind smelling like fuel for a while you might try this.

Chipsndukes

PS, I assume you know just CAREFULLY pull the injector out from the bottom, maybe number 'em, push it back in in another cylinder and see if you still get that fault.

Did you try rerouting the spark plug wires or isolating them from any ground source? (I know they're brand new, but this would really eliminate them as a possibility, is the most obvious cause from the outset.
 

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Discussion Starter #8
Im on it. I'll get back to you guys as soon as i get to the next stage. I just ran seafoam. We'll see tomorrow. Oh, and by the way, the reason i changed the battery was because it was atleast 8 years old. Figured, hey what the heck, im going deer hunting in the fall, cant risk getting stuck up there. I just thought i would mention it to rule it out..................................:funnyup:
 

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DTC P0303 Cylinder No. 3 Misfire Detected

CIRCUIT DESCRIPTION
Misfire: The ECM uses the crankshaft position sensor and camshaft position sensor to monitor changes in the crankshaft rotation for each cylinder The ECM counts the number of times the engine speed change rate indicates that misfire has occurred. And when the misfire rate equals or exceeds the count indicating that the engine condition has deteriorated, the MIL lights up.
If the misfire rate is high enough and the driving conditions will cause catalyst overheating, the MIL blinks when misfiring occurs.



DETECTING CONDITION
When the 2 or more codes for a misfiring cylinder are recorded repeatedly but no random misfire code is recorded, it indicates that the misfires were detected and recorded at different times.












 

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DTC P0303 Cylinder No. 3 Misfire Detected

CIRCUIT DESCRIPTION
Misfire: The ECM uses the crankshaft position sensor and camshaft position sensor to monitor changes in the crankshaft rotation for each cylinder The ECM counts the number of times the engine speed change rate indicates that misfire has occurred. And when the misfire rate equals or exceeds the count indicating that the engine condition has deteriorated, the MIL lights up.
If the misfire rate is high enough and the driving conditions will cause catalyst overheating, the MIL blinks when misfiring occurs.



DETECTING CONDITION
When the 2 or more codes for a misfiring cylinder are recorded repeatedly but no random misfire code is recorded, it indicates that the misfires were detected and recorded at different times.












OK, so it could be anything causing the misfire, as long as it's a misfire.
So that leaves spark, fuel, valves...

Hmmm...truck is smarter than I thought?

Peace, good luck jaime.
Chipsndukes
 

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Discussion Starter #12
Cant believe it after all the work i have done. I cleaned out the fuel system and combustion with seafoam straight through the vacuum lines. Turned off the light and the CEI has not came back.....Its been seven days and no light. It still idles rough but the light is gone!!!!:clapping:
 

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A lot of times at the dealer a lot of cars come in with crappy gas in the tank and it just totally makes the car go crazy. What kind of gas do you use? Most of the time i get cars at the dealer like that we pull the plugs, check prior services, and 90% of the time cylinder misfires come from bad gas gunk in the system, or diesel fuel. We usually empty the gas tank, give it a thorough E.F.I. cleaning, new plugs, fuel filter, and put in some fresh gas and problem resolved. I recommend pumping gas at a Shell, BP, or Chevron, not some Mickey Mouse named gas station that god knows where they get their gas. I always pump my gas at one of those places and I've never had a problem. But who am I, just some tech who works at a dealer, what do I know?:looney:
 

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Discussion Starter #14
My code came back!!!!!!!! I've now gone through 3 tanks of lucas fuel injector cleaner and continue to get the codes. I even figured that maybe it was the injector cleaner. So i waited to run out the treated fuel and pumped regular octaine. Still get codes. Its weird, i wont get them for a weak and than all of a sudden like 2-3 in one day. Same codes, #3 cyl. and random misfire. I am going to fill up next week with 92 octane chevron and see what happens. I have been using mostley arco and valero gas. I guess i'll take the last respondents advice and run better gas. I'll keep u guys posted. Thanks for the replys.
 

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Best thing to do is drive the truck with a scanner, watch the misfire data.
But you can just clear codes and wait for the code to set.....takes more time.
Like chipsndukes said...
swap #3 injector for #1

Normally faulty injectors end up with a "dead hole" not an intermittent miss.
You can listen to the injectors with a mechanics stethoscope, faulty injectors make a "thud" sound not the metallic "click"

Sounds like ignition, Did you inspect/replace the cap and rotor?
 

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i dont know if this is relevant, but maybe you need to change the timing chain. just thought i'd throw it out there. basically, idk what im talking about but just wanted to help.
 

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Discussion Starter #17
I actually did think about the timing chain. But i figured i would try the higher octaine gas thing first. Mine is a 98, so it only has two coils. No cap and rotor. I probably do need to change the timing chain anyway, after all, it does have 265000 miles:waytogo: All the tune up stuff is brand new, including the coil with the number 3 cylander. I run 10X30 oil. I guess i could change grade but what would i go to?
 

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with 265k i would think thats the lowest i would go in oil. maybe 10x40? with all that wear and tear it might help lubricate your motor better. are you using synthetic or normal oil? iv'e been running 5w-30 mobile 1 since i got the truck brand new and changing every 1500. iv'e never seen my oil black yet. once in a while ill give my motor some yummy royal purps. but my point is at 265k you should try to use or upgrade to higher quality products to keep it running longer.
 

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Discussion Starter #19
I'll jump to 10x40 here on out. I use regular oil, what ever is on sale!!! Is it ok to just all of a sudden use a different type of oil(synthetic)? If yes, im going to start doing that. I want my truck to hit 400,000 miles so i can write to toyota and be in a commercial........
 

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when you switch to syn do a good flush with a quart or two, then fill it up. then you probably want to do the next syn oil change soon after, (like 1500) the flush won't get all your old reg. oil out. then from there just do reg oil changes with the syn. oh, and good luck with the commercial...
 
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