Cam Sensor and timing help

[MummifiedCircuitry]

Story time, I'll try to keep this as short as possible.

97 Montero SR with SOHC died randomly in a parking lot a few seconds after starting it, this was after driving it for about half an hour at 55mph. Crank but no start, I was checking fuel pump and spark, ended up finding a fusible link in the engine bay that had popped (in a weird spot that wasn't immediately obvious). Put a new fusible link in and it started up, seemed fine, drove it for a couple days.

Then it died on my again under similar circumstances. Only this time I was getting a P0340 (cam position sensor) code from my ultragauge, and it would sporadically start and drive, but giving it gas would sputter and die, and it would repeatedly blow that fusible link in the engine bay. I tried to limp it home and blew/replaced about 8 of those fuses, something kept frying them, seemed like faulty Cam position sensor. I bought a new cam position sensor and installed it, started up fine again and code was gone.

A couple days later ultragauge started throwing a code for idle air control valve and it stalled a couple times, I pulled the IACV and it tested bad one one circuit, bought a new one, installed it and that code went away. (I think this issue may be unrelated and just a coincidence)

Now I wasn't getting any codes and it was driving alright, then yesterday I suddenly felt it stutter and I got a P0340 (cam position sensor) code pop up again and it died in the middle of traffic, wouldn't restart. I checked that fusible link that was blowing and it's fine, when I crank it over it also sounds a bit strange, almost wheezing sometimes and slowing then cranking normal speed again sort of line eyeinthesky's video here:


I lined up my cam gears today and took pictures of each one and the crank (as clearly as I could). Does the crank look lined up alright or possible slipped a tooth?

 

[Salonika]

Timing alignment looks as good as I’m used to seeing.
I hate to say it, but I’d start by cleaning all the grounds you can. Clean your sensor connectors with electronics cleaner and compressed air. Electrical gremlins show up when circuits get dirty…….and they are intermittent, and often lead you astray.

can you be more precise? Which fusible link was blowing? What circuit? Amps? Can you I.D. it in your manual / FSM?

 

[MummifiedCircuitry]

Timing alignment looks as good as I’m used to seeing.
I hate to say it, but I’d start by cleaning all the grounds you can. Clean your sensor connectors with electronics cleaner and compressed air. Electrical gremlins show up when circuits get dirty…….and they are intermittent, and often lead you astray.

Thanks for the reply, I had considered cutting the female/male plug off the cam position sensor and hardwiring it just to rule out a faulty pigtail. Could it be a ECU going bad, or do you know of any other reason a P0340 trips besides the actual CPS?

 

[Salonika]

Your fusible link blowing is bad juju esp. if it happened repeatedly……I’d focus on that first. Something that big popping could explain many other things.

 

[MummifiedCircuitry]

Your fusible link blowing is bad juju esp. if it happened repeatedly……I’d focus on that first. Something that big popping could explain many other things.

It hasn't blown since I replaced the CPS. The old sensor I removed had small cracks in the wire sheathing that looked like it was allowing wires to short on each other. I searched when I was having the issue and Eclipse owners were having the same issue with the fuse blowing when CPS was shorting. I might even tape up those areas on the old sensor and clean it, then install it and see if it starts. It's possible the new CPS I got from the parts store is faulty.

 

[Salonika]

As far as I know, the power for the CPS comes directly from the ECU and is not fused. It is very low voltage (like 6v maybe, and tiny amperage) I can’t see that blowing a bigger fuse.

 

[MummifiedCircuitry]

I had a little time to fiddle around with it today, checked wiring and plugs around the CPS and didn't see anything obviously bad. I pulled the front spark plug on the passenger side cause it's the easiest, cranked it and I'm not getting any spark, double checked the fusible links in the engine bay and they look good, swapped out the igniter module with a good one from my other montero, still no spark. I'm starting to think it is a faulty CPS that's cutting spark, otherwise I might think immobilizer or something except I got that P0340 before it died. I'm going to clean and swap my old CPS in and see if I can get spark. Possibly pull the CPS out of my other montero and swap it in.

 

[MummifiedCircuitry]

I cleaned and taped my old CPS sensor and put it back in, still no spark. Swapped fusible links with others I had just in case one was bad, but not obivous, and also did the reset procedure with the orange dash button in the off chance that was it, still nothing. I also checked my grounds, wiggled harnesses, and checked for frayed/damaged wiring, but found nothing. What else could be cutting spark to this thing? Any of these fuses on the under dash box capable of it?

 

[Salonika]

I know for a fact a faulty cam position sensor can cause a no spark condition. I would probably try a third new CPS before I did anything else. Has the 340 code come up again?
Also, how are you checking for spark? One old fashioned diagnostic trick is to spray starter fluid while cranking and see if it sputters. If it does, you got spark. Wait I just re-read an earlier post, you are doing a visual on it.

 

[MummifiedCircuitry]

I know for a fact a faulty cam position sensor can cause a no spark condition. I would probably try a third new CPS before I did anything else. Has the 340 code come up again?
Also, how are you checking for spark? One old fashioned diagnostic trick is to spray starter fluid while cranking and see if it sputters. If it does, you got spark. Wait I just re-read an earlier post, you are doing a visual on it.

I'll try to find a third CPS just to rule it out. I'm going to swap coils off my running montero and see if that works also. I'm not getting a P0340 code now, but it won't start so that's sort of expected. If it started and then had a fault I would expect to see a code. Could a bad ignition switch be possible? The past couple weeks, my key has been tight in the barrel and sometimes doesn't turn over past lock position unless I wiggle the key a bit. Does anyone know if these engines have an ignition failure sensor or is it build into the ignition control module?

 

[RyanY]

I would check to see if the ignition transistor unit is getting power when it's supposed to. IIRC it's supposed to see 12V at one of it's terminals, and if that's not there for some reason it'll give you a place to start searching. You do have the wiring diagrams for the ignition system, right?

 

[MummifiedCircuitry]

I would check to see if the ignition transistor unit is getting power when it's supposed to. IIRC it's supposed to see 12V at one of it's terminals, and if that's not there for some reason it'll give you a place to start searching. You do have the wiring diagrams for the ignition system, right?

I don't, do you know which terminal I should be checking for 12V or just all of them? I believe theres a VB for battery, TACHO for tach reading, GND for Ground, then 6 IB/OC coil pins.

 

[Salonika]

You need the FSM……

 

[MummifiedCircuitry]

I got a 3rd cam position sensor yesterday, tried it today and there's no change. I swapped coils with my other good running montero, still not getting spark. I unplugged the igniter module and connected my multimeter on the power and ground on the harness first on the good montero and got 11.4V when cranking, then checked the problem montero and also got 11.4V out of the harness also. So it looks like power is getting TO the igniter, tried two good igniters, but still no spark. Does the fact that I'm getting power to the igniter rule out a key/ignition/immobilizer issue?

 

[Salonika]

Do you know how to bypass / disconnect the alarm harness, so you can eliminate that as a cause? I’m not sure if the alarm system disables only the ignition system, or if it prevents the starter from cranking too.