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Discussion Starter · #1 ·
Hey everyone, first post!

Quick intro, I just bought a ‘95 camry from a co-worker to give as a gift for my little sister who’s going off to college. The car was “supposedly” an extra car that they didn’t need anymore, blah blah. Actually drove it twice before and it seemed fine, granted I didn’t have any experience with the 1MZ, but it didn’t have a knock, noisy valvetrain, etc. and the only issue I could immediately see was leaking valve covers…not that big of a deal so I bought it

Fast forward to a week later, I’ve driven it maybe a total of 30 miles at this point, so I go to get it smogged. Everything checks out (no CEL) so it passes, but while I’m driving home, as luck would have it, the check engine light comes on. Damn.

Get home and pull the codes, and it shows p300, p301, p303, p305. So basically misfiring from the rear/right bank. It looks to have invidual coil packs over each plug, so chances that all 3 coils, wires, or plugs went out simultaneously are low (I think).

What could be causing all three to misfire at the same time?

Quick thoughts-
Intake manifold leak? Wouldn’t that then throw a code for low manifold pressure? Fuel issue? Is there a separate fuel regulator for each bank?
I mentioned they have coil-over-plugs, so unless I’m missing a separate ignition module unit, it can’t be a spark issue right?

I’m dreading even thinking that it could be the headgasket, but I had a v6 firebird that had a similar issue and sure enough, the HG was bad. So Murphy’s Law would have me think that I just picked up a $1600 problem.

I’m gonna check for audible leaks, check wires, etc, but can anyone steer me into the right direction before I start tearing into it too far?

Thanks!
 

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Did you get a print out when you got the smog? Any emissions numbers high but not so much where it would fail smog?
Doubt it's the HG because you'd have more symptoms such as overheating or performance issues.
Also as you mentioned all those 300 codes hitting at once has a low probability of all those components failing at the same time.
The vacuum leak is the most likely culprit. Pass a propane source over the engine and near the intake, if there's a leak the rpm and sound will reflect it when the propane is close to the problem area. Also rent/make or barrow a smoke machine if you hear a change but can't locate it.
 

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Discussion Starter · #3 ·
Forgot to add, oil doesn’t look like it’s gotten coolant in it, and flushed the coolant to see if it’s dirty and it looked good.

I did the coolant block test where you try to suck up vapors to detect exhaust gasses in the coolant. Ran it 4 times total (2 from the coolant cap on top of the timing cover area, 2 off the hose leading into the overflow tank) and all tests came back negative. Although I take this test with a grain of salt since I know they’re not the most accurate.
 

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Discussion Starter · #4 ·
Did you get a print out when you got the smog? Any emissions numbers high but not so much where it would fail smog?
Doubt it's the HG because you'd have more symptoms such as overheating or performance issues.
Also as you mentioned all those 300 codes hitting at once has a low probability of all those components failing at the same time.
The vacuum leak is the most likely culprit. Pass a propane source over the engine and near the intake, if there's a leak the rpm and sound will reflect it when the propane is close to the problem area. Also rent/make or barrow a smoke machine if you hear a change but can't locate it.
I checked the smog sheet they gave me, seems like they have it as a pass/fail so I don’t know if it even found coolant or other vapors in the exhaust. I don’t know if it matters or not, but I know Nevada’s smog checks are pretty lax. I think if your CEL is off, you’ll pretty much pass lol.

I’ll try to do that propane check, maybe pull the rear plugs too to see their condition. Thanks man
 

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Hey everyone, first post!

Quick intro, I just bought a ‘95 camry from a co-worker to give as a gift for my little sister who’s going off to college. The car was “supposedly” an extra car that they didn’t need anymore, blah blah. Actually drove it twice before and it seemed fine, granted I didn’t have any experience with the 1MZ, but it didn’t have a knock, noisy valvetrain, etc. and the only issue I could immediately see was leaking valve covers…not that big of a deal so I bought it

Fast forward to a week later, I’ve driven it maybe a total of 30 miles at this point, so I go to get it smogged. Everything checks out (no CEL) so it passes, but while I’m driving home, as luck would have it, the check engine light comes on. Damn.

Get home and pull the codes, and it shows p300, p301, p303, p305. So basically misfiring from the rear/right bank. It looks to have invidual coil packs over each plug, so chances that all 3 coils, wires, or plugs went out simultaneously are low (I think).

What could be causing all three to misfire at the same time?

Quick thoughts-
Intake manifold leak? Wouldn’t that then throw a code for low manifold pressure? Fuel issue? Is there a separate fuel regulator for each bank?
I mentioned they have coil-over-plugs, so unless I’m missing a separate ignition module unit, it can’t be a spark issue right?

I’m dreading even thinking that it could be the headgasket, but I had a v6 firebird that had a similar issue and sure enough, the HG was bad. So Murphy’s Law would have me think that I just picked up a $1600 problem.

I’m gonna check for audible leaks, check wires, etc, but can anyone steer me into the right direction before I start tearing into it too far?

Thanks!
Re: The coils

You can test the coils with a DVM (or even a VOM)

Resistance should be .54 - .84 ohms on a Cold (< 122F) coil and .68 - .98 ohms @ > 122degree F
 

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What are the fuel trims for bank 1 and 2. Try a bottle of Techron Injector Cleaner. That it is only one bank could just mean that the other bank isn't bad enough to detect or that bank is a little hotter so more varnish. A high long term trim LTFTR would indicate a lean condition given age and mileage, look at injectors. They are all going to be varnished just some more so. Coils would give you a P0350 series depending on witch coil (P0353 for example)
 

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Discussion Starter · #10 · (Edited)
I swapped out all 6 plugs with new ones, codes came back on after maybe 30 minutes total of driving (disconnected battery, didn’t manually clear codes). Judging with how bad the plugs were I hoped that was the issue, but it’s doing the same thing it was prior to swapping them.

The only symptom (aside from the codes) would be stumbling and surging at 1200-1800 rpms ONLY. It idles completely fine, and while I’m driving the car, it accelerates fine under load. I’ve had it parked and rev’d it to 2000/2500 rpms and it holds fine without stumbling

I don’t think it’s the headgasket anymore (thank God), did a cooling system pressure test, did the balloon/glove test over the full neck, both tests seemingly showing the headgasket is good. Plus I drove it around for 10 mins (seems fine driving around) and parked it in the driveway while idling in 110 degree Las Vegas weather, and it didn’t overheat and spew coolant
 

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Discussion Starter · #11 ·
The vacuum leak is the most likely culprit. Pass a propane source over the engine and near the intake, if there's a leak the rpm and sound will reflect it when the propane is close to the problem area. Also rent/make or barrow a smoke machine if you hear a change but can't locate it.
Try water from a spray bottle.
Tried both tests around the rear bank gaskets, didn’t notice any change. I’ll probably end up tearing it down to the intake manifold gasket anyway, just for peace of mind.

Re: The coils

You can test the coils with a DVM (or even a VOM)

Resistance should be .54 - .84 ohms on a Cold (< 122F) coil and .68 - .98 ohms @ > 122degree F
Thanks for the tip, the coils all checked with little resistance
What are the fuel trims for bank 1 and 2. Try a bottle of Techron Injector Cleaner. That it is only one bank could just mean that the other bank isn't bad enough to detect or that bank is a little hotter so more varnish. A high long term trim LTFTR would indicate a lean condition given age and mileage, look at injectors. They are all going to be varnished just some more so. Coils would give you a P0350 series depending on witch coil (P0353 for example)
I just ordered a ODB live scanner so I’ll post fuel trims when I pull them. Anything else I should be looking for?
 

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Your plugs look all the same and lean but admittedly old. Before you create new problems try the Techron. It has a proprietary ingrediant the the others do not. Most other brands are just variations of mineral spirits that doen't really work on the varnish burned onto the injectors by the heat. If you wait and check fuel trims before you will see the improvement in the LTFTR before and after as proof. Like carb cleaner vs. WD40.
 

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Discussion Starter · #13 ·
Re: The coils

You can test the coils with a DVM (or even a VOM)

Resistance should be .54 - .84 ohms on a Cold (< 122F) coil and .68 - .98 ohms @ > 122degree F
I read another thread that mentioned how he tested resistance, and now I’m second guessing my numbers. What’s the correct procedure to get an accurate resistance reading on these coils?
 

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Discussion Starter · #14 ·
My OBD scanner just came in tonight, so I’ll try to log some fuel trim numbers and put them up, then try Wheat’s suggestion with Techron (probably do the fuel filter too) then post after numbers.

Swung by the pic a part on the way home from work and got three oem ign coils and an oem TPS ($10 total) just in case that’s what was wrong. Put in the TPS and no change, granted the sensor could be bad too.

I also found a vacuum hose completely deteriorated under the EGR vacuum solenoid. Replaced that and no change.
 

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For fuel trim you want car warmed up, drive around the block, in park at idle. You should see fluctuations but overall both LT and STFTR should vary from -10 to +10. It is telling you the injector duration variation from base time. I predict you'll find LTFTR somewhere north of +20. TPS and coil voltages are monitored by the ECU and so would throw a code. Fuel pressure is not monitored and the fuel pressure regulator is controled by manifold vacuum. Low vacuum, wide open throttle, is full pressure so failure of the FPR would cause a rich running, ie. LTFTR would be less than -10. The goal of the ECU is to regulate the fuel mixture at 14.7:1 ratio. Both banks O2 sensor 1 should be close to each other and cycling. O2 sensor 2 are there only to monitor catalytic converter efficiency and do not effect the engine. normal is around 0.7 volts at temp and will set a code P0420 if out of range.
 

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Vacuum on the EGR is there to stop pinging and reduce NOx by cooling the cylinder walls so not likely to cause a drivablily issue, though the ping might cause the timing to retard. With the brake applied it is disabled.
 

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I read another thread that mentioned how he tested resistance, and now I’m second guessing my numbers. What’s the correct procedure to get an accurate resistance reading on these coils?
Sorry for the late reply. I've not been logged in for awhile.
One probe from the DVM goes to the spark cable that connects to top of plug. The other probe to the metal part of the coil (where coil pack gets screwed onto valve cover)
 
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