Tach Needle Dies then Comes back to Life

[Marccus]

My tach needle intermittently drops to 0 and the car runs really badly - chugging, bucking, etc. Then after a period of time which varies anywhere from 1 to 5 minutes it comes back to life and the car runs like a charm.

It happened a few days ago and then once today, where the tach stayed at zero and the engine ran like shit and the tach didn't come back to life. I had to pull into a parking lot and turned the engine off. It was very hard to start; I had to keep the throttle wide open to get it to start. Once started, the tach was OK and it ran fine.

From what I understand, when the CPS goes, the tach goes, and then the car won't run at all.

But when my tach dies, I can still drive it.

The CPS is only about a year old and I replaced the water pump at the same time even though it didn't need to be replaced.

I've checked the CPS before for something else and it was fine. I used thread locker on the screws so the CPS wouldn't loosen, slide towards the vanes and be worn down.

So I'm sure the CPS is OK. But then the wiring for the CPS may not be.

What else can cause the tach to die besides the CPS malfunctioning?

Where should I start to troubleshoot this problem?

 

[SHOspazz92]

As with anything on the SHO, run the codes first! However here is what I think about it.

This would be your CID (Cam Sensor) causing your issues. I've had two SHO's that have done this, both were fixed by replacing the cam sensor.

Here's the cam sensor.



It's located on the passenger side of the car, towards the firewall.

-Sam

 

[sperold]

The tach needle on my 89 drops to 0 like yours, but mine runs A-OK when this happens.
My code is 18 and is likely a connector or wiring issue.
My bet is yours is code 19, which is a cam sensor issue.

 

[LJRuddy]

Tach issues are 97% always the effect of a bad cam sensor.

 

[Redneck1465]

It's either the cam position sensor or the crank. If you know the crank is still good then my bet would be the cam position sensor.

 

[SHOstuff]

The tach needle on my 89 drops to 0 like yours, but mine runs A-OK when this happens.
My code is 18 and is likely a connector or wiring issue.
My bet is yours is code 19, which is a cam sensor issue.

Are you going to fix yours Sperold?

 

[Marccus]

Well, the cam sensor is even "newer" than the crank sensor. I just replaced that about six months ago.

But, I'll run the codes (duh - I forgot that!) and see what I get. If I can't find a solution, I'll replace the cam sensor anyway and see where that gets me.

I just haven't run codes for such a long time (lucky me) that it didn't occur to me. I should have done that before submitting this question. Sorry.

 

[LJRuddy]

It's either the cam position sensor or the crank. If you know the crank is still good then my bet would be the cam position sensor.

Crank sensor has nothing to do with an erratic tach. So we can bet money that it is not that sensor. A bad/failing crank sensor will cause no starts or stalling. A failing cam sensor will cause erratic starts and a poorly/non operating tach.

 

[sperold]

Are you going to fix yours Sperold?

I keep hoping it is going to fix itself, but I guess that doesn't happen very often. Every time the tachometer reads correctly, I think great..... it is OK now!
I am not going to replace the cam position sensor, but I am going to unhook the electrical connection at the sensor, and I think there is another one in the intake maze.
The problem now is the weather is non stop rain or nasty overcast, with lots of wind, and it is not going to happen till that has improved.

 

[Marccus]

Crank sensor has nothing to do with an erratic tach. So we can bet money that it is not that sensor. A bad/failing crank sensor will cause no starts or stalling. A failing cam sensor will cause erratic starts and a poorly/non operating tach.

I'm getting a continuous memory code 19, co it's the cid. I'll change it out.

 

[sperold]

What cam sensor did you buy 6 months ago (which make or from who).
It doesn't look like a snap to change, so I would like some info on what to buy if it comes to that. New parts make me more nervous than old parts, so I would like to have the odds on my side, if I can.

 

[itwonder]

What cam sensor did you buy 6 months ago (which make or from who).
It doesn't look like a snap to change,

CID, aka CAM sensor, is really easy to change if you take the crossover off of the intake; the part the DIS bolts to. Only takes minutes to do and really opens up access.

 

[Marccus]

Replaced the CID and the problem remains. :banghd:

I still get the same memory code 19. :cuss:

So now what should I do? Trace the circuit?

Does anyone have the wiring diagrams for the CID circuit and any suggestions on how to trouble shoot it?

Thanks.

 

[sperold]

If you cancel the code, does it reappear?

 

[Marccus]

Only if the tach needle dies again. During the interval while running the engine that the tach is OK, the code does not appear. If the tach dies during a ruh, when I next check the codes, fault code 19 reappears.

 

[Marccus]

What cam sensor did you buy 6 months ago (which make or from who).
It doesn't look like a snap to change, so I would like some info on what to buy if it comes to that. New parts make me more nervous than old parts, so I would like to have the odds on my side, if I can.

It's the only one I've ever found; made by Standard Motor Products.

 

[tool88]

when you replaced the cid was there fresh oil it might be time for some cam seals.

 

[sperold]

I am out of ideas.
What I will comment on is Standard Motor Products have their main products, and then they have a T-series product.
The regular series cam position sensor is LX228 and is priced at $37.00.
The T-Series cps is LX228T and is priced at $24.00.
The Motorcraft cps is DU47 and is priced at $46.00.
Even if you paid a lot of money, chances are you got the T-series cps.

I would use the T-Series unit myself, but I would be wary if I started having problems. There is a small chance that you are getting a bad run of CPSs.
I would take your latest one out and return it.... you have the code data to back up the story.

Look on Rockauto for an easy to read list of parts for your car. Other great sources are Shosource and RCMautomotive as well as others like Advance etc.

 

[rubydist]

its possible that the new cam sensor is bad, but relatively unlikely.

tracing the wiring is pretty easy, since there are only 4 wires. one goes to the pcm via one of the 8 position connectors that lay behind the rear valve cover. the other 3 go to the dis module.

 

[Marccus]

when you replaced the cid was there fresh oil it might be time for some cam seals.

It was bone dry. I've dealt with the oil problem before and have changed the seals in the past, but this time there was no oil.