VVT Shutoff Issue Data Gathering

Try zip tie-ing the cam sensor to the oil tube in the valve cover. Effectively holding the cam sensor down into the hole better than just the 1 little M6 bolt can.

I'm not sure I would want the wires pulled that tight. That's how broken conductors inside of the jacket or wire broken right at the end of the terminal happen. That M6 bolt is more than capable of holding a plastic sensor down against zero pressure. 

Not the wires, the sensor itself. Remember there is only 1 bolt hanging off 1 side of the sensor so a little stress in the sensor or a few mils of paint/powder coating on the valve cover may not allow the sensor to sit flat in the hole. If it sees a disruption or sync loss in the cam signal just one time(tooth), it causes a shutoff event.

All the shutoff issues I have had are due to a less-than-perfect cam signal. A zip tie holding the cam sensor into the hole solved my problem last weekend.

Not the wires, the sensor itself. Remember there is only 1 bolt hanging off 1 side of the sensor so a little stress in the sensor or a few mils of paint/powder coating on the valve cover may not allow the sensor to sit flat in the hole. If it sees a disruption or sync loss in the cam signal just one time(tooth), it causes a shutoff event.

All the shutoff issues I have had are due to a less-than-perfect cam signal. A zip tie holding the cam sensor into the hole solved my problem last weekend.

It’s not fixed until it goes at least three more weekends, and even then the word “tentatively” applies.

Tyler’s situation this past weekend was quite unique. Ran Thursday and Friday all day fine. Super cold Saturday morning and it would just spit and sputter in paddock. Pressed down on cam sensor connector and it ran fine. Left go it went to crap. I though “ohh the connector is failing” zip tied connector to sensor. Not fixed. Zip tied sensor to oil line and ran perfect. Super weird it acted up in the paddock. Most shut off events can not even be duplicated on dyno let alone idle

I have pondered a single cause and also everything that anybody has done to “fix” the issue. It is my opinion that ANY disruption to an ecu signal from ANY part on the car will cause the ecu to “refresh” aka 2-4 seconds of dead stick. I wish I had an answer. Fortunately I haven’t had to deal with many problem cars

No idea other than a car I watched with the problem only shut off after 190-195 degrees. Out front he was fine...got in draft...died. Odds are this goes back to the theory of the computer seeing things out of sync...and temp is one of the parameters. I'm sure its not issue but cheap shotgun! Will car run without it plugged in?

Car will run with it unplugged. But vvt system will not function properly.

I would think a situation like that the sensor might be cracked and flexing it make/break a connection.

Tyler’s situation this past weekend was quite unique. Ran Thursday and Friday all day fine. Super cold Saturday morning and it would just spit and sputter in paddock. Pressed down on cam sensor connector and it ran fine. Left go it went to crap. I though “ohh the connector is failing” zip tied connector to sensor. Not fixed. Zip tied sensor to oil line and ran perfect. Super weird it acted up in the paddock. Most shut off events can not even be duplicated on dyno let alone idle

Maybe my issue was unique, but what if it wasn't? Could 50% of the issues out there be fixed with a zip tie? 10%? I thought it was worth mentioning after we saw what we saw.

Dave, the same issue persisted with 2 different new Mazda sensors.

Every pro builder out there has their own paint or powder on the valve cover, causing the sensor to fit differently than designed. Not to mention slight differences in valve cover tolerance stackup. I'm not saying it's everyone's issue, but it shouldn't be overlooked. Every VVT I drive on track again will have a zip tie as a precaution and a matter of habit, just like we do on the throttle cable bracket.

It’s not fixed until it goes at least three more weekends, and even then the word “tentatively” applies.

True, I will follow up

Maybe we should be get some measurements of dept from mounting surface to cam reluctor. I guess anything is possible that the gap is too big on some engines. Although luckily I have never had to deal with this issue, my car and some I've built use Kessler and the powdercoat/hydrodip on his motors is pretty thick. The cars are all either 2001 or 02. 

Maybe my issue was unique, but what if it wasn't? Could 50% of the issues out there be fixed with a zip tie? 10%? I thought it was worth mentioning after we saw what we saw.

Dave, the same issue persisted with 2 different new Mazda sensors.

Every pro builder out there has their own paint or powder on the valve cover, causing the sensor to fit differently than designed. Not to mention slight differences in valve cover tolerance stackup. I'm not saying it's everyone's issue, but it shouldn't be overlooked. Every VVT I drive on track again will have a zip tie as a precaution and a matter of habit, just like we do on the throttle cable bracket.

It’s an excellent thought, other than fixing with a zip-tie beyond a brief workaround. The bolt is perfectly adequate, just restore the correct seating surface for the sensor so the gap is truly correct, which a zip tie in no way provides. It would be extraordinary if that fixed a lot of cars. I do know that one person suspected a thicker than stock valve cover gasket might be the cause but it wasn’t.

Maybe we should be get some measurements of dept from mounting surface to cam reluctor. I guess anything is possible that the gap is too big on some engines. Although luckily I have never had to deal with this issue, my car and some I've built use Kessler and the powdercoat/hydrodip on his motors is pretty thick. The cars are all either 2001 or 02. 

 

I have played with this as well and found the valve cover stands are quite consistent on the 2-3 covers I measured and keep the sensor at a consistent gap, it isnt easy to measure btw.  I fooled with this gap and tightened up thinking that may be the cause of teh failures. Unfortunately, it did not fix my issue, so I concluded that was not the root cause.  I thought perhaps our aftermargket valve cover gasket was holding the valve cover higher, but that height is determined by the stands on the bottom of the valve cover.. 

 

 

FWIW, We make sure NOT to paint/powder coat the the surface where cam sensor mounts to valve cover

Jim

The problem is, step one in diagnosing any drivability issue...............can the issue be replicated in a controlled manner,i.e. on a dyno with instrumentation (scope,scanner,etc...) to have a better chance of pinpointing the cause.

The problem is, step one in diagnosing any drivability issue...............can the issue be replicated in a controlled manner,i.e. on a dyno with instrumentation (scope,scanner,etc...) to have a better chance of pinpointing the cause.

So far, not that anyone has disclosed publicly. But most or all have roller dynos without load-bearing options so can’t simulate track conditions. That’s why I have offered use of my hub-type dyno many times but I’m just not well located. However, I’ve just been in touch with someone who does have access to such a dyno and a car with persistent problems so we may hear something before long.

The problem is, step one in diagnosing any drivability issue...............can the issue be replicated in a controlled manner,i.e. on a dyno with instrumentation (scope,scanner,etc...) to have a better chance of pinpointing the cause.

I have a dynojet... I have never been able to replicate the issue we are talking wboiut here. I have had cars that have other issues act up on dyno

Jim

I have had the same VVT for about 8 years now and I had never had experienced the shutoff issue. I did replace my motor this year and all went well with the break in I was on my third weekend and the motor has been doing great. I was leading the Saturday race at Mid-Ohio this weekend and experienced my first dreaded shutoff. Not great timing.

 

Jim gave me the list of too do's in an effort to minimize it, I just wondered if anything came of the attempt to gather data any conclusions drawn?

 

Is the TPS on the list suspects?

I have had the same VVT for about 8 years now and I had never had experienced the shutoff issue. I did replace my motor this year and all went well with the break in I was on my third weekend and the motor has been doing great. I was leading the Saturday race at Mid-Ohio this weekend and experienced my first dreaded shutoff. Not great timing.

 

Jim gave me the list of too do's in an effort to minimize it, I just wondered if anything came of the attempt to gather data any conclusions drawn?

 

Is the TPS on the list suspects?

 

Sorry to hear this Frank.  Hope you get it resolved without too much effort.  

I have had the same VVT for about 8 years now and I had never had experienced the shutoff issue. I did replace my motor this year and all went well with the break in I was on my third weekend and the motor has been doing great. I was leading the Saturday race at Mid-Ohio this weekend and experienced my first dreaded shutoff. Not great timing.

 

 

Can't speak to the TPS specifically, but last fall a friend's recently built VVT experienced a mis-fire condition with a crank position related fault code.  Tightened the crank position slightly and issue went away for remainder of event.  Happy problem went away but not confident we really addressed the real issue. 

Fast forward to start of 2023 season and sure enough the car began to cut out again.  This time it gave a Mass air flow sensor code.  Car would also shut off while performing sensor connecter wire wiggle test.  Tried snugging up the connector pins  and even replaced the Mass air flow sensor but problem persisted and car would shut down while doing wire connecter test on the Cam sensor connecter as well.  Made changes to that connecter as well.  Put the car on track hoping it would get through a session but it completely shut down and would not re-start which was a good thing.  

 

While looking the car over closely, it appeared that the Alternator stud was somewhat angled coming out of the housing, and when the wire and stud were tugged on it came right out of the case.  Replaced the Alternator and the problem went away.  The car has completed two race weekends with no further issues.  The actual problem was internal to the Alternator in that there is an internal bolt that secures the stud protruding from the Alternator.  Conclusion is that this is just one more item to question if you are having intermittent issues as there were signs of internal arching of the Alternator that had been occurring resulting in cut-out problems after the internal bolt loosened to the point where it could cause an internal short.

 

Rich Powers