95 Lexus SC300 cranks but will not start
12-24-19, 12:42 PM
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95 Lexus SC300 cranks but will not start
I have taken my SC to a diagnostic shop to see why it wont start. All they did was remove the timing cover, said the timing was off, but also said the intake and exhaust valves stay open at the same time, and that could be caused by a bent rod or piston ring, and I just need a new engine. How would these "mechanics" know that both valves are open if all they looked at was the cam timing? Also this thing was running completely fine one day (besides my MAFS being broken), so I replaced that, tried starting it and it hasn't started since that day. How could the rods or anything else be bent/damaged just from replacing that piece? They also said I was getting low compression on cylinder one, but I have spark, I have fuel up to the rails (have not tested but i can hear it being sprayed up front). They basically said they couldn't give me a straight answer as to why it wouldn't start, besides that it needs a new motor. Can anyone think of anything it could possibly be? I also had to do the 12v mod for the fuel pump to kick on now
Thank you all and Merry Christmas,
Zach
Thank you all and Merry Christmas,
Zach
12-27-19, 07:31 AM
#2
I'm assuming this is a stock 2JZ GE?
How did they go straight to the timing belt as part of their diagnosis?
They must have done other, more likely steps that lead them to it...like, fuel, air, spark...once those are checked and confirmed, it's not out of the norm to check compression. If low compression is found, one of the next steps would be to check timing. If that proves faulty, it's very possible you have bent valves. 2JZs are interference motors, meaning if the engine is spun while the entire assembly is out of alignment (timing belt) a piston can/will make contact with a valve and bend it.
Aside from that, and wether, or not, their diagnosis is correct, is anyone's guess. You mentioned a few other problems and it's a little difficult to get a clear picture of what all went down and in what order.
How many miles on the motor? When was the timing belt last replaced, if ever? It's possible that either the belt broke, or a tensioner went while you were diagnosing/fixing other issues and assumed something else was the problem for the car not starting.
How did they go straight to the timing belt as part of their diagnosis?
They must have done other, more likely steps that lead them to it...like, fuel, air, spark...once those are checked and confirmed, it's not out of the norm to check compression. If low compression is found, one of the next steps would be to check timing. If that proves faulty, it's very possible you have bent valves. 2JZs are interference motors, meaning if the engine is spun while the entire assembly is out of alignment (timing belt) a piston can/will make contact with a valve and bend it.
Aside from that, and wether, or not, their diagnosis is correct, is anyone's guess. You mentioned a few other problems and it's a little difficult to get a clear picture of what all went down and in what order.
How many miles on the motor? When was the timing belt last replaced, if ever? It's possible that either the belt broke, or a tensioner went while you were diagnosing/fixing other issues and assumed something else was the problem for the car not starting.
Last edited by emLEX; 12-27-19 at 07:36 AM.
01-20-20, 02:31 PM
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Yes its a stock 2jzge. They checked the timing belt first because all they figured out was the timing was off. There's about 145,000 on the motor. I'm not sure if the timing belt has been replaced or not, the motor is not the original one that came in the car, but i'm assuming when they replaced the motor they got a new belt along with it. The belt doesn't feel loose (at least to me), and it looks fairly new, and after they corrected the timing issue there was still no luck. I'm not sure what else to check, but i'm going to take it to a shop in a couple weeks.
Thanks for the reply by the way
Thanks for the reply by the way
01-21-20, 09:29 AM
#4
Where does everyone come from with bad information, 2jz's are not interference motors normally speaking.
You did not bend any valves or anything most likely, and it could be something electronic instead.
I do not think your timing belt just jumped randomly, it would have come apart and ripped up the covers in front and the belt and possibly the fan shroud if that really happened.
That makes me wonder what they mean by adjusted it or put it back.
If they did a compression test and one cylinder is low, that is not great and you could have a headgasket issue or engine issue, but it should still start and run with just one cylinder down on compression.
Unless they just checked the one cylinder because it is in the front and easiest to access.
This makes me wonder what good a compression test does if they think the timing was out, cause it would be a meaningless test if the timing is not set right.
Honestly first thing I would do is veify the timing myself now, it takes just a few minutes.
Do steps 2a and 2b in this picture (Ignore 1 and 3), line crank up at zero and verify cam timing marks. you just have to take off the top cam cover its like 4-6 allen bolts super easy (DO NOT DROP THE BOLTS INTO THE BELT AREA OR YOU WILL HAVE HOURS OF WORK).
If it all lines up you are good.
if you have fuel then you probably don't need to do the 12v mod, you can jump b+ and FP (fuel pump) in the diagnostic connector and you should hear the fuel flow through the rail, if you do you are good.
I am going to guess that it is your ecu or your maf, since you have a 95 and under do not clean the maf with maf cleaner, it can ruin the maf as they are an older karman vortex style maf, not a hotwire that you can clean.
if you did shoot maf cleaner in there, take a hot dryer to it for a while and let it completely dry up on the inside, completely evaporate, stick it in some rice, whatever you got to do to get the moisture out, then try is again the next day.
you can also try unplugging the maf completely, then trying to start it and see what happens. sometimes it will run better without the maf when it is messed up.
sometimes its just the ecu going bad, and throwing a maf code randomly. if you can get your hands on a spare ecu to try I would suggest doing that and ruling that out.
mechanically speaking, these 2jzge's are pretty bullet proof, if it was running before chances are it would run again even if it isn't starting right now unless something major happened.
It could be something electronic, or if you had a engine or headgaske issue maybe it got worse.
I would verify timing, try another maf and ecu if possible like I said above, and if nothing is going do a full compression test on the motor, all cylinders and possibly even a leak down test.
that stuff is alot harder than the electronic stuff, so start there first. it could even be a 12v fuel pump mod situation but doesn't sound like it from what you are saying.
You did not bend any valves or anything most likely, and it could be something electronic instead.
I do not think your timing belt just jumped randomly, it would have come apart and ripped up the covers in front and the belt and possibly the fan shroud if that really happened.
That makes me wonder what they mean by adjusted it or put it back.
If they did a compression test and one cylinder is low, that is not great and you could have a headgasket issue or engine issue, but it should still start and run with just one cylinder down on compression.
Unless they just checked the one cylinder because it is in the front and easiest to access.
This makes me wonder what good a compression test does if they think the timing was out, cause it would be a meaningless test if the timing is not set right.
Honestly first thing I would do is veify the timing myself now, it takes just a few minutes.
Do steps 2a and 2b in this picture (Ignore 1 and 3), line crank up at zero and verify cam timing marks. you just have to take off the top cam cover its like 4-6 allen bolts super easy (DO NOT DROP THE BOLTS INTO THE BELT AREA OR YOU WILL HAVE HOURS OF WORK).
If it all lines up you are good.
if you have fuel then you probably don't need to do the 12v mod, you can jump b+ and FP (fuel pump) in the diagnostic connector and you should hear the fuel flow through the rail, if you do you are good.
I am going to guess that it is your ecu or your maf, since you have a 95 and under do not clean the maf with maf cleaner, it can ruin the maf as they are an older karman vortex style maf, not a hotwire that you can clean.
if you did shoot maf cleaner in there, take a hot dryer to it for a while and let it completely dry up on the inside, completely evaporate, stick it in some rice, whatever you got to do to get the moisture out, then try is again the next day.
you can also try unplugging the maf completely, then trying to start it and see what happens. sometimes it will run better without the maf when it is messed up.
sometimes its just the ecu going bad, and throwing a maf code randomly. if you can get your hands on a spare ecu to try I would suggest doing that and ruling that out.
mechanically speaking, these 2jzge's are pretty bullet proof, if it was running before chances are it would run again even if it isn't starting right now unless something major happened.
It could be something electronic, or if you had a engine or headgaske issue maybe it got worse.
I would verify timing, try another maf and ecu if possible like I said above, and if nothing is going do a full compression test on the motor, all cylinders and possibly even a leak down test.
that stuff is alot harder than the electronic stuff, so start there first. it could even be a 12v fuel pump mod situation but doesn't sound like it from what you are saying.
Last edited by Ali SC3; 01-21-20 at 09:48 AM.
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01-24-20, 03:22 PM
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@Ali SC3 Everything is right in time, I tried starting with and without MAF and with the 12v mod and none of it did the trick. Its not even throwing any codes. The check engine light blinks repeatedly when turned to ON postion but thats it, so I would assume my ecu just went bad maybe? I'm completely stooped on it
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