[dorifuto.boi]

hey guys,

i have a 1mz-fe

im gonna make my trip up to school thursday and i want to get this problem taken care of. Im going to drop my car off at the dealership tomorrow morning to diag this problem but i just wanted to ask here first before i take it in to see if anyone have any ideas.

i hear random popping sounds from the intake. i don't have a check engine light. a mechanic at the dealership had a small handheld obd2 reader and he told me that it showed a random misfiring. (but there was no check engine light so i dunno wher he got that from)

i have new plugs and new plug wires.
i bought one new ignition coil and swapped it with all three ignition coils in the front bank but the problem never disappeared.

does anyone have any ideas/advice ?

thanks a lot,
d

 

[93celicaconv]

What year is your Camry? Does it have OBD-II or OBD-I?

If it has OBD-II, the ECU has capability to detect a single cylinder misfire and will trip the check engine light and a DTC code. If you have OBD-I, that ECU does not have this capability.

You said the tech had an OBD-II scanner. If so, it may be possible the misfire is so infrequent that the ECU tripped a pending code (which would not turn the check engine light on yet).

It is very unusual, almost impossible, to hear a popping noise coming from the intake manifold, because the intake manifold is not open to anything that would allow this noise to be heard from (unless you don't have the ductwork connected to the throttle body).

On old cars with carburetors (which technically is an opening to the intake manifold), popping sounds could be heard. Typically, on those old cars, a popping sound meant an intake valve was not always closing completely, so the piston was pushing compressed air/fuel vapor into the intake manifold - and if there was enough pressure in the cylinder to create an ignition, it would also ignite this air/fuel vapor into the intake manifold, creating a popping sound. Usually this meant an intake valve spring was broken, or the valve wasn't moving freely anymore. It rarely meant to valve was burned, because if it was, there would always be a misfire on the affected cylinder, rather an a random misfire.

Let us know what the service tech finds out as the cause of this issue.

 

[73sport]

What year is your Camry? Does it have OBD-II or OBD-I?

If it has OBD-II, the ECU has capability to detect a single cylinder misfire and will trip the check engine light and a DTC code. If you have OBD-I, that ECU does not have this capability.

You said the tech had an OBD-II scanner. If so, it may be possible the misfire is so infrequent that the ECU tripped a pending code (which would not turn the check engine light on yet).

It is very unusual, almost impossible, to hear a popping noise coming from the intake manifold, because the intake manifold is not open to anything that would allow this noise to be heard from (unless you don't have the ductwork connected to the throttle body).

On old cars with carburetors (which technically is an opening to the intake manifold), popping sounds could be heard. Typically, on those old cars, a popping sound meant an intake valve was not always closing completely, so the piston was pushing compressed air/fuel vapor into the intake manifold - and if there was enough pressure in the cylinder to create an ignition, it would also ignite this air/fuel vapor into the intake manifold, creating a popping sound. Usually this meant an intake valve spring was broken, or the valve wasn't moving freely anymore. It rarely meant to valve was burned, because if it was, there would always be a misfire on the affected cylinder, rather an a random misfire.

Let us know what the service tech finds out as the cause of this issue.

^^ We'll said!

Doubt its a burned valve as once its done, it can't be undone. So that leaves us with variables. . . Does your check engine light work?

Fuel trims during said issue could be of value, as well as ignition timing. I think the ECU is pretty sharp, but when mine went on the frits w/the bum coil, I swear I was hearing some form of detonation, but I think it was a misfire or a latent fire from a bad coil if such a thing is possible.

How'd you know which coil to switch and if it didn't fix it, well I'd move it to another hole and try again.

Need more info!

Edit; his is post 96 having OBDII and 3 coil packs MZ if I'm not mistaken.

 

[dorifuto.boi]

hey guys, thanks for the responses.

its a 99 1mz-fe with obd2

my check engine light works because it turns on when i almost stall lol. he did have a handheld obd2 scanner but i don't know what information he got from it. all he told me was that it was a random misfire and a specific cylinder wasn't pinpointed (does this mean that the computer can't tell which cylinder is misfiring or the computer senses misfires in every cylinder ?) (but the check engine light isn't on so he probably pulled the "pending" code like you said ?)

i can hear the popping noise (its not a strong popping. they are soft popping sounds) from my aftermarket intake/filter and it occurs randomly around 2-3s intervals.

if it happens to be a worn valve spring, i hope the tech will be able to detect that tomorrow and that its not too expensive to replace. also if i happen to not replace it, will it hurt anything if i drove across the US with that problem ?

i don't know the fuel trims because i don't have that software nor do i have an obd2 -> usb cable. (oh that brings up something. can you guys recommend a brand of software i could use with an obd2 -> usb cable where i can get all the readings from the ecu like the fuel trims and misfires, etc ?)

about the coils, i bought a new coil and just swapped it with all three one by one and listened to the intake after each swap to determine if the problem persists. the problem persisted lol

thanks a lot,
d

ps. also, in addition to the popping sound, if you open a door and put your hand on top of that opened door, you can feel the pulsing (in sync with the popping)

 

[93celicaconv]

I'll bet the tech got a P0300 (Random Cylinder Misfire) pending code. This means there were sufficient misfires detected, but no one cylinder was getting clearly more misfires than others. The OBD-II register will show how many misfires occured in each cylinder over a period of time. It would be interesting seeing that data, but you probably don't have access to it.

This also tells me the theory of a valve spring going bad is not the problem. A valve spring failure would cause an intermittent misfire on one cylinder only. From what I am interpretting from you, all your cylinders are occassionally misfiring.

As to what is causing the problem, I'm not sure. I don't know your engine at all. I was thinking that maybe your timing belt jumped a tooth or two, causing this problem. Not sure if you wouldn't get a check engine light though, because I think the ECU would detect a position problem between the crankshaft and camshaft. But if it doesn't check this, then a jump of the timing belt may be a cause. Not sure what else there might be.

Let us know when the dealership diagnosis is complete.

 

[73sport]

repeat valve spring would not be random! It would be FATAL when the valve drops into the cylinder killing the piston, valve, head and maybe the block and cylinders next to it. I SERIOUSLY doubt this is your issue so put your mind at rest K.

Burned valve shows up on compression test. Lost compression that doesn't come back. Not Random either.

That leaves - - - -

Sounds like you need better wires, plugs or coils. The random misfire means the ECM is being told the spark was not delivered to the plug because the energy discharged did not have the proper signal to LOOK like SPARK to a PLUG.

This could be lean condition also so run some techron through it ever other tank and change the fuel filter, run a tank of 92 oct too and see if it changes anything. K

 

[dorifuto.boi]

this problem persisted after i switched to new bosch spark plugs a month earlier. i will buy some ngk plugs soon cause apparently bosch sucks for toyotas.

i have new ngk wires put in a month ago.

maybe i had 2 bad coils and since i only purchased one new coil, theres still a bad one....

i've ran thru a tank of those bottle of cleaners you mix in in your gas when you refill about a month ago.

edit: maybe the wires leading to my coils are bad ??
also i don't know if i should take my car to the dealership cause they'll tell me to replace this and that and in the end none of them fixes the problem >.< ugh i hate it when that happens.

 

[73sport]

Just a thought - but its like 11 years of accumulation, I doubt 2 bottles of junk is gonna cure the average car. . .

Pull the plugs and take a good solid close up pictures, NO cell phone crap pictures! Be sure to number them so we know where they come from. This will help us help you. CLose ups K!

Sorry, hate to say this but even new parts can be bad. Was it a yoda part or something else?

 

[93celicaconv]

Sounds like a plan.

BTW, a broken valve spring will not drop a valve into the engine. There are still keepers in place to prevent that. But sometimes a valve spring breaks, like a coil spring on a suspension component, and the result is less spring pressure to close the valve.

But again, we know this can't be the problem, because the service tech said there is a random cylinder misfire, not on any one particular cyliner. So one has to look at causes that would generate a misfire on one cylinder one time, on a different one the next, etc. That is how I am interpretting the information presented so far. And since I don't know this engine very well, I should probably step aside.

But I would like to see cylinder compression pressure values, and would like to verify that the crankshaft to camshaft timing is spot on. Maybe more so the compression values, because I think a jumped timing belt would cause a rough running engine, not something that runs smooth and occassionally misfires on any given cylinder.

 

[dorifuto.boi]

hey guys, thanks for the help. i'll continue this thread later on. im gonna make my drive up to school now.

the tech told me that the 300 code he pulled was from the history. i used to have a misfire problem and apparently i fixed it with the new plugs/wires/coil. but for some reason im still hearing popping sounds from the intake and feeling pulses from the door. the people at the dealership told me that there is no misfire and that he doesn't hear the popping from the intake nor the pulsing from the door. maybe im imagining things.

anyways. i'll take a look at the plugs later when i have time
thanks again,
d