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Doug
Doug, ASE Certified Technician
Category: Mitsubishi
Satisfied Customers: 8538
Experience:  Mitsubishi employed and Factory trained ASE certified technician
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I changed my camshaft position sensor but my car still won't

Customer Question

I changed my camshaft position sensor but my car still won't start. What's else is wrong?
Submitted: 1 year ago.
Category: Mitsubishi
Expert:  Doug replied 1 year ago.
Hi,
What year/model is this?
Customer: replied 1 year ago.
2002 MONTERO 4WD 3.5L
Expert:  Doug replied 1 year ago.
Thanks.
Was there a trouble code indicating a cam sensor issue that caused you to replace it, or was it just a guess?
If it was just a guess, do you know if you have spark while cranking?
Customer: replied 1 year ago.
My car stopped running in the middle of driving. I ran the codes with the reader and it gave me P0340. I changed the sensor erase the code, but it came back on and the car doesn't start.
Expert:  Doug replied 1 year ago.
Thanks, ***** ***** a lot.
If this is a full size Montero (not a Sport), you should have an oil cap that attaches right to the passenger valve cover (rather than on an extension hose). Please take the oil cap off and have a helper crank the engine while you look down the oil fill hole. Can you see movement inside the cylinder head (rocker arms moving up/down) as the engine is cranked?
Customer: replied 1 year ago.
I couldn't check now but could run either scenario with rocker arms moving and rocking arms not moving. I mean, the car cranks but it won't start.
Customer: replied 1 year ago.
I meant to say: Could you run either scenario?
Expert:  Doug replied 1 year ago.
No problem. I'll give some back ground too to help explain why we are looking there too.
When you have a P0340 of course the sensor is suspect, but overall the message is just the computer saying it sees a problem with upper end movement. It monitor the crank shaft and the driver side cam shaft to make sure they always stay synchronized. If there is any difference in the signals (be it due to sensor failure or other means), it sets the cam sensor fault. If it sees specifically both signals but they just aren't matched, it will eventually set a P0335 as well (crank sensor fault).
Seeing only the P0340 and no P0335, provided it has been cranked substantially trying to start and still P0335 did not set, is indicating either a sensor failure or the cam shafts not turning (belt failure).
Looking through the oil cap is a very easy way to see if things are turning up top. If there is no movement from the top end of the engine, then you know without a doubt that the timing belt has either stripped or broken.
This is very bad news if this is the case... this is an interference engine and if the cams stop turning the pistons pretty much just beat the valves to death. At that point your only options are to pull the heads for repair or put a used engine in. Clearly we don't want this to be the case. If you are unsure if you see movement, I would suggest unbolting the drivers upper timing cover and carefully pulling it forward (it won't easily remove like this as there is stuff in the way, so just pulling it out of the way a little is preferred). While holding it forward so you can see the cam gear/belt, again have a helper crank and see if it spins.
If you DO see movement up top you only have two areas of consideration. Either a sensor related issue (be it sensor itself or wiring to it etc) or the belt has slipped and it just has not set a P0335 yet.
At this point you can inspect the belt timing, but this is a long process to get to the timing belt marks (and if you are paying a shop, a few hundred dollars just to "look")... Given that you would not have seen P0335 yet though, I would be leaning more toward a bad cam sensor (I know you replaced it already). From here I would unplug the sensor and make sure you have 12V/5V/ground on the harness to verify the wiring is OK. Obviously if it is not, more investigation would be in order for the wiring. If the wiring tests OK then I would consider another sensor ---if the one you installed is not a genuine Mitsubishi sensor---. It is very important to note that Mitsubishi computers do NOT get along with aftermarket hall effect (cam, crank) sensors. The aftermarket cam sensors simply do not work on these. I know that sounds crazy, but it is the way it is... they don't work, you have to use a genuine Mitsubishi cam sensor on this engine or it won't run.
Hopefully we just have a sensor that failed and the replacement was no good like usually is the case... but before doing -anything- else, check for upper end movement. If the top of that engine is not spinning, nothing external is going to fix it so you need to verify if that belt failed or not before putting any more effort or money into external fixes. I do hope sensor is the issue, but you have to check that belt operation first to be sure.
Customer: replied 1 year ago.
Thank you, ***** ***** check it first thing tomorrow morning and pray that there is movement when I look inside the oil fill hole. I will keep you posted once I finish doing what you asked me.
Expert:  Doug replied 1 year ago.
I'll have my fingers crossed as well. If you need more help just reply back here; I wont be in until late morning but will check for messages as soon as I arrive.
Customer: replied 1 year ago.
Hi Doug,
No, no movement inside the oil fill hole. Broken timing belt it is then unless you have any other suggestions. Thank you in advance.
Expert:  Doug replied 1 year ago.
I'm sorry to hear that, that is definitely worst case scenario. You can do the double check from behind the timing cover like I mentioned, but if there is nothing going on in that fill hole that is pretty definitive anyway.
At least you know now though, and can proceed with proper repair course rather than pushing forward with other external tries that obviously aren't going to make a difference with the engine not spinning up top.
As for repair.... start making some phone calls as you will definitely want several estimates on this as it is an expensive repair. I would be pricing out the following options:
a) Used engine
b) Pull cylinder heads and replace damaged valves/guides (and of course new timing belt and associated parts)
c) Install remanufactured cylinder heads (will already have new valves etc... and of course then new timing belt and associated parts etc)
You may find that you can get your hands on a used engine and have it installed for less than the cost of refurbishing of the heads etc, or the cost may be only slightly more but have added benefit making it worthwhile. For example if you can locate an engine with lets say 60k miles for a reasonable price, it may have considerably less wear than the engine you are replacing, which would then make sense to spend a little extra on it and not have to worry about putting a lot of money into an already worn out engine etc (speculating on the age/condition of yours of course).
Customer: replied 1 year ago.
Hi Doug,
So I changed the timing belt and crankshaft sensor. I have no codes whatsoever, but the car still doesn't start. It cranks and I see through the oil fill hole that there is a slight movement of the cams. It also sounds like it is about to start while is cranking but thats about it. What did I miss? Did I install the timing belt too loose, the tension had a bit of play (about 1/2") but no more than that. If it is not with the right tension, will this cause the problem? I aligned the timing marks, but if I did it wrong, would that cause the problem of almost starting? Thanks in advance.Frank
Expert:  Doug replied 1 year ago.
Hi,
If there is movement in the upper engine then that would certainly change things considerably.
With regard to the sensors.... be aware that if you put aftermarket sensors on there, you likely created another problem. This vehicle (this era Mitsubishi in general) does -not- get along with aftermarket cam/crank sensors at all.
At this point you need to do a compression test to make sure the belt did not have any issues on install. If the compression is good then continue with normal diagnostics (not part replacement), checking for spark, fuel pulse, fuel pressure etc.
Before anything else though, I would be on the compression test since you had a recent timing belt install.

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