97 5SFE, Getting P0300 and P0302... Need Opinions!

[Thomas-Hawk]

All,

Bought this car two months ago, 110,000 miles. After one week, a plug fouled, suspected plug #2, as it was a seized, and was a bit blacker that the others. Replaced all plugs with factory spec NGKs, and NGK wires. Seemed ok for a week or so, and since have been getting P0300 and P0302 codes. Engine idles rough, and CEL pops up usually when the engine is cold and put in gear, or under a load (A/C on and in gear). Have stumped two local shops, and now car is at a Toyota dealer for diagnosis. I would like to get some experienced opinions (Mike Gerber's, and others!) as to what the problem might be, so the dealership doesn't have as great of a chance of ripping me off.

Here's what has been done so far:

-checked coil resistance per Chilton's, check ok (performed by me)
-checked IAC valve per Chilton's, check ok (performed by me)
-cleaned throttle body & IAC (without removing) (performed by me)
-replaced EGR valve and EGR vacuum modulator valve (performed by me)
-replaced fuel injector for cyl #2 (performed by local shop)
-checked for vacuum leaks, none found (performed by local shop)
-checked compression, was ok (performed by local shop)
-wire for cyl. #2 swapped again, no help (performed by local shop)
-fuel filter replaced (performed by local shop)

Any ideas? Thank you in advance for your help!


-Tom

[93celicaconv]

What exactly were your cylinder compression pressure values?

Your ECU is detecting multiple cylinder misfires, but #2 cylinder has the highest frequency and is setting its own unique code. You may have a couple of issues coming together to cause these two codes and your rough idle when cold and/or when under load. But you have already addressed some of those potential issues through replacements, with no apparent improvement in results, except for the 1 week after your replaced your spark plugs.

You could also put a scanner on your engine and gather the number of individual cylinder misfires over a period of time. What I would wonder is if your #3 cylinder was very close to your #2 cylinder is number of misfires, but was not quite at the threshold to trigger a P0303 code. If so, you might have a weak ignition coil that feeds #2 & #3 cylinders.

[Thomas-Hawk]

93celicaconv,

First, thanks for the reply! Unfortunately, I don't know what the compression values were. The shop just told me they tested the compression, and it looked fine.

I do know one shop had the scanner hooked up to the car while the engine was running, and we could watch cyl. #2 misfire, about once every 3 to 5 seconds while under a load. No other cylinders were showing a misfire.

I am wondering if I might have a coil pack that is breaking down under a load? But, wouldn't I get a P0303 code as well, since cyls 2 and 3 share a coil?

[Mike Gerber]

It seems you and the shops you have taken the car to have checked everything that would normally cause those missfire codes. The only other thing I can think of is a blown head gasket. Has anybody checked for that? I know that's rare at your mileage, but you probably don't know how the car was maintained before you. It could have had a coolant leak and been severely overheated. That would be my next step. I know I'm grasping a bit here, but if there are no other codes and all those tests were performed properly, then there aren't too many other things that can cause missfires.

Mike

[Thomas-Hawk]

Mike,

Thanks for the reply, but wow... no offense, but I hope you're wrong! Fixing a blown head gasket could be around a $1500 repair... OUCH! But, you're right... I have no idea how well the car was maintained by the person before me. There were no service records kept.

What are the chances of it being a faulty PCM?

[Jason.MZW20]

1997 5SFEs, IIRC, use MLS head gaskets, so it'd have to be severely overheated to fail (warpage/weakening).

Remember, the coils are coils AND igniters. The ECU gets the ignition confirmation signal from the igniter portion of the coil. It's possible the coil resistance is reading in spec, but the igniter could be intermittently failing causing a misfire on cylinders 2 and 3. Test the spark on the affected coil/igniter for multiple ignition sequences. If it fails to fire even once, you need to replace that coil/igniter assembly.

You didn't check the camshaft position sensor or crankshaft position sensor. Those are equally important in the ECU's ability to keep the engine in time and to track engine misfires.

[93celicaconv]

No doubt #2 cylinder is the major misfiring cylinder. But you had a P0300 code in your ECU as well, which tells you there were enought misfires in at least one other cylinder to cause P0300 to be set. So #2 cylinder cannot be the only misfiring cylinder.

I would still be interested in actually seeing the compression values of the engine when it is warm.

You might also want to try cleaning the intake manifold with a product like SeaFoam, and make sure your PCV valve is working properly or replace it (and the grommet) before running again on a cleaned intake manifold.

[Thomas-Hawk]

All,

Thanks again for the replies. Just got a call from the dealer. They say a valve is hanging up, and that I need a complete valve job, to the tune of $2141.56!!!

Thoughts? I'd like to think this one over before I give them the green light to do it. Man, that's a lot of money.


-Tom

[Cranky-Condor]

wow.... I had an old 4 cylindar VW Dasheer where the valves used to hang up every 30,000 miles and I got good at taking the head off, removing the valves, cleaning them off, reseating them and putting on new valve guide seals on over a weekend... Saves big money if your up to it and have a few tools. I have 3 Toyotas with the 1MZ V6 and it would be more work but something that I would do if I had to.

[Mike Gerber]

Originally Posted by Thomas-Hawk

All,

Thanks again for the replies. Just got a call from the dealer. They say a valve is hanging up, and that I need a complete valve job, to the tune of $2141.56!!!

Thoughts? I'd like to think this one over before I give them the green light to do it. Man, that's a lot of money.


-Tom

Ouch! But I'm also a bit confused here. You said a shop did a compression check and they said it was OK. This is what confuses me here. Like 93celicaconv said, I too would be interested in seeing (well hearing actually) the exact compression results on each cylinder.

Also, if one valve is hanging up, why are you getting the P0300 code (in addition to the P0302 code)? The P0300 code means that multiple cylinders are misfiring. At lest that's the way I interpret that code. How can that happen from one valve hanging up? Maybe someone else can chime in here.

Mike

Interesting reading here. I guess it can be the computer, or one burned valve, or O2 sensors, or even the cat converter. I would check everything else listed here before pulling the head off the car. Maybe even switch the fuel injector from cylinder 2 with cylinder 4 and see if the misfire moves to cylinder 4. I keep thinking back to that OK compression check.

http://www.obd-codes.com/p0300

[93celicaconv]

Right, Mike Gerber. Unless the valve that is hanging is doing it intermittently, and there isn't anything physically wrong with the valve or the seat themselves. Like maybe some dirt got into the valve guide and/or lifter/spacer bore. Or maybe the valve spring broke and doesn't have nearly as much force to close the valve as it once did. A compression test may not pick this up because the engine turns so much slower, and if the misfire only happens once every 3-5 seconds on a running engine, it may not happen at all during a compression test.

I have a hard time believing some debris is in the valve bores preventing it from moving freely myself, unless the engine has a lot of sludge buildup under the valve cover. Otherwise, with the valve cover off, one could test valve spring tensions with a flat blade screwdriver to see if one pushes down a lot more. But with compressed air going into the sparkplug hole, valve springs, lifters and seals can all be worked on without taking the head off and doing a complete valve job.

If I were Thomas Hawk, I would ask exactly what test the service tech did to determine a valve in #2 cylinder is hanging up, to see if they analyzed it well, or just gave you a line and hoped that with $2k of money to spend, they will find and correct the problem. And ask them to explain why your ECU also through the P0300 code (multiple cylinder misfire) if only one valve in one cylinder has this problem.

[Thomas-Hawk]

Spoke with the service advisor again. I questioned him about why I was also getting a P0300, and he told me that ALL of the valve clearances were way off, especially on cylinder #2. He also said that overall everything looked like it was in decent shape... it just looked like someone had been messing around in the engine, perhaps someone who didn't have a clue what they were doing. He said there were no sludge problems, signs of abuse or neglect, etc.

If I have the valve job done, I should be able to get another 100,000 plus miles out it, which I really need, as I can't afford another car or a car payment right now. I dunno... what do you guys think? Is the dealer trying to stick it to me? Would you spend $2300 out the door to fix a '97 that only has 110,000 on it?

Thanks again for everyone's input. I do appreciate it.


-Tom

[fenixus]

so what's the problem per dealer ? sticking/hanging up valve in cylinder #2 or out of spec valve clearances on all cylinders (worn or wrong shims used by someone before you) ???
tool for valve clearance adjustment cost $20 on internet, shims are cheap even at dealer, it's all about labor (which with enough time and determination can be done by a DIY-er for free).

if it's about installing correct shims to keep valve clearances at max norm then it can be done by a local shop (specializing in engine repairs) for about $400 i think (if i remember correctly)... i wouldn't trust the dealers honestly, those bastards usually pull as much money as they can and do the least job they can to fix the root cause of problem quickly (they DO cut corners too sometimes)...

i wouldn't spend 2 grands to a dealer that most likely will simply replace all shims to specs (a few hours labor and almost zero parts cost to them).

sorry, but my local dealer cheated me on changing the differential fluid (which they didn't do) when i ordered a complete tranny flush AND differential drain&refill for $200 ... they lied to me 2 times about it (yes i mean you East Coast Toyota in Woodridge, NJ)... i don't trust dealers.

[Jason.MZW20]

Agh! Well thanks to that database error, my whole post was lost.

Basically, I said that the 5SFE uses wasted spark, so a P0300 can be set because of a faulty coil/igniter, as they control 2 cylinders each (1 and 4; 2 and 3). So, the ECU reported P0300 and P0302, but we don't know the timeframe between those codes. We do know the firing order of the 5SFE: 1-3-4-2; coil 1, coil 2, coil 1, coil 2. A failing coil can give you a P0300 if the engine is turning fast enough to trigger a multiple misfire code (it also means a random misfire too though).

A Toyota dealer with a TechStream tool can monitor the misfire frequency on each cylinder via the Toyota enhanced OBDII data. Did they do that? I'd be interested in seeing that data.

I'm skeptical on the whole valve clearance issue unless someone really did mess with the shims. It's extremely rare for ALL of the valves to be out of spec.

[93celicaconv]

So what does the service tech mean by "valve hanging up" then on #2 cylinder? Does he mean that the valve to camshaft clearance is all gone (now no clearance) and the valve cannot close all the way, so it is leaking? If so, then your cylinder compression pressure test would show this. The compression pressure test might not show a valve that is being held up in its spring-return travel back to close due to dirt in the guide, but if the service tech means the "only" problem is the valve clearance, then I would either get the cylinder pressure valves provided to you, or you do your own compression check.

Valves that can't close completely also can't dissipate absorbed heat from the combustion process, so they tend to distort and burn, and the only way to correct this is to remove the head to get the damaged valve out and put a new one in, and lap the valve to the seat. But again, if this is happening, your compression check would show that.

IIRC, valves in this engine tend to have the clearances shrink with wear, so they will get tighter. But having no clearance after only 110,000 miles? Wow, there are a lot of Toyota 5S-FE engines out there with a lot more miles than that which are still within the valve clearance tolerance range. Unless the previous owner didn't do oil changes hardly at all. But this engine would build up sludge if oil change intervals were not followed, and the service tech said there was no sludge problems. This all isn't making much sense.

If I were you, if you know a mechanic you can trust, or if you can do this on your own, I would bring it back and have another person check the compression pressures and the valve clearances. See if you really have a valve clearance problem on some valves, and if your compression pressures show evidence of lower pressures where the valve clearance is off most. If your compression pressures are all good, your valves are sealing good, so the head doesn't have to come off. If your valve clearances are way off, then you can determine if you or a mechanic should address that. I just woulnd't spend that kind of money at a Toyota dealership without verifying their diagnosis. I suppose you have to pay for what they have done already (removing the valve cover, and the testing they have already done). Maybe you should pay the service tech a visit so he can show you exactly what he is seeing.

PS: If you have too much valve clearance, you would have a noisy valve train, but this would not be the cause of your misfires.