Surging and sometimes won't start.

kl-sc

Registered User
Hi all I have a new problem, maybe two, that I'm trying to figure out. Just last week I pulled my '90 SC out of storage to drive this winter. Has only driven 2-3 times the last 18-20 month.

Well, it starts up fine. Then driving along at highway speed it starts pulse or surge engine RPM like stomping and releasing the throttle. At idle I see the tach jumping around between about 600 and 1200 RPM all by itself.

Then the other day, thinking I may have some old/bad fuel, I stop to get gas, fill up, and afterward it just spins and won't start. Something was weird here because normally after the blower builds some pressure the starter can barely turn it over and you have to wait a few seconds for the pressure to bleed off, but instead the starter just spins it like there are no spark plugs. I wait a few minutes, really trying to figure out what's wrong, open the hood and see nothing out of the ordinary. I slam the hood shut and try to start it up and after a few rev. the pressure from the blower builds up. Wait a few sec. and try again and she starts right up. However, I notice the tach. reads 0 RPM, but she runs OK. I drive her home and half way the tach. snaps to life and starts to read normal RPM.

Next morning I start it up in the driveway and let it warm up. Runs fine idle for 5 or so min. then starts surging again on its own.

I'm thinking there may be some problem here that only shows up once warmed up and EEC goes into closed loop mode, but that doesn't explain the tach at 0 RPM when running.

I'd appreciate ideas on what may be wrong or what I should look at.

Many thanks!

-Kurt
 
Thats a bummer and all I can think of is maybe the cam sensor or crank sensor, probably the cam.


Good luck
 
When the tach quits working, or works intermittently then the DIS module or one of its input sensors is bad. The input sensors being the crank position sensor or the cam identification sensor. Mostly likely the DIS module or crank sensor. This could cause the surging also, as might a bad IAC. If this car has been sitting a long time corrosion on the ground connections. Make sure the engine to frame ground straps are in good shape and that the DIS module is properly grounded as well. Make sure there is no corrosion on the DIS mounting screws.
 
Viola!!!

90coug said:
Thats a bummer and all I can think of is maybe the cam sensor or crank sensor, probably the cam.


Good luck


I agree....When these cars have starting problems and on the third try it starts, the cam sensor is to blame. The crank sensor tells the computer where the crank is in reference to rotation. The cam tells the computer where Number 1 cylinder is.

If this happens again, and it does not start, take notice at the upshift light on the tach side of the cluster (best to look when the cars off, little yellow up-arrow). If the upshift light stays on WHILE cranking, then bad crank sensor, if not on, cam sensor or DIS module. Try the Cam sensor for the $12 it costs for a new one. I would guarantee that's the problem.


Don
 
Thanks so far.

Thanks for the ideas so far. Cam or crank sensor seem like a probable cause given what I've read on other threads. As I understand with a zero RPM tach. the cam sensor is more likely as that's where it's driving signal comes from. Right?

I bought a EEC code reader thinking that problem code would probably point in the right direction. Will either a cam or crank sensor show up as problem codes. Note I don't get a check engine warning light at anytime this happening. Probably ought to check the bulb on that too though.

I've also read some horror posts about harmonic balancers cracking. How is that diagnosed?
 
About the balancer...

Check for the "WOBBLE" of the balancer and make sure that the pulley is not wobbling around. Tell-tale sign of balancer on its way out. I also suggest that checking to make sure the bolt is attached to the balancer. You can feel it with your fingers....


Don
 
Kurt - I'll try and recap all the good advice you've got so far. However, it's most likely the cam sensor and the last one I bought was about $30 (it's just the top or stator part that you need & is easily replaced with just 2 screws - you may also need to clean off some oxidation inside the stator housing that can effect the signal). On early SC's the wavy tach was a typical sign of a bad cam sensor and, on later models it's CEL code #214 - so if you have your code reader you can check to see if that is recorded in the memory. If it's the DIS then more likely you will get CEL codes (can't remember the numbers) that indicate coil circuit failures and the car will go thru phases of stumbling (actually missing on some cylinders). If it's the Crank sensor, you'll know by the "shift light" staying on during cranking and the car will be very hard to start. As for the balancer, I'd just observe it rotating when the engine is running and look for any vibration or missalignment of the outer pulley. Then check the 4 small bolts that hold the outer pulley set to the balancer itself and of course the big center bolt that holds the whole assembly onto the crank. I've had both these sets of bolts fail at different times.
Good luck.
 
Cam sensor part?

Thanks to all for all the help so far. The consensus seems that the cam position sensor is the first part to look at. Everyone says it's an inexpensive part in the $12 range. However, when I check local auto parts stores they all seem to quote $35 and a local Ford dealer wants $74 for a "cam shaft position sensor", a round part with 2 screws on top to hold it down and an electrical connector that inserts from the side. Do I have the right part? Motorcraft part no. DU-47.
 
One more piece of data...

Just went to check the upshift light during cranking. It's on when KOEO, but goes out during cranking. When cold it started right up. Ran until up to temp and turned off. Won't start again. Cranks freely, but doesn't start. Then every once in while while cranking the cranking bogs or slows just like it normally would if it didn't start right up when running fine. I assume that's because the blower has built up pressure that the starter is cranking against. But why does it crank freely most of the time. I counted more than 5 rev. when spinning freely as I've read the ECC will count 5 rev. before providing spark. Noticed on other thing that I never noticed before. While cranking freely the "Check Gauge" light is blinking in 1-2...1-2...1-2 pattern. What does that mean?
 
If it's the actual red "check gauge" light - it means exactly what it says - check the gauges. I don't have the full specs, but if you are low on fuel, oil pressure, coolant overheating, etc that gauge will light telling you to look at your main gauges. Is your tach responding when the car does start? - maybe that's what it's indicating. Did you also check the computer yet for any stored codes like "214" - that will definitely help point you in the right direction. $35 for the aftermarket cam sensor is about right. I'd definitely begin by replacing that.
 
Read trouble codes...

Jim,

Thanks for your help and suggestions. I did verify that the tach. was working when I observed the blinking "Check Gauge" light. I use the procedure at http://fordfuelinjection.com/files/self_test.pdf to read the trouble codes. I get a 11 - system pass for the KOEO test, but I'm reading a 19 and a 33 from the Continuous Memory codes. From their code list at http://fordfuelinjection.com/index.php?p=46 codes mean:

19 = Cylinder Identification CID circuit failure.
33 = EGR valve opening not detected.

Any idea what these mean is wrong or I should look to fix either separately or together. Seem to me like there might be 2 separate problems like I initially thought as CID should come from the stator (I think). and EGR is a totally separate circuit and actuator.
 
I'm not quite so familiar with the old 2 digit codes, but have you changed the plugs recently? Cylinder identification failure could still be the cam sensor, DIS or coil pack; but from my experience it's possibly a bad plug wire connection or even a cracked plug insulator - which is why I wondered if you've worked on the plugs recently. It's very easy to crack these plugs because of the difficult install. Assuming you have say a 5 speed with EGR It sounds like the EGR is stuck and they can foul up over the years. I'd do a search on this site because I have seen some instructions for checking and cleaning them.
 
The EGR code could also be due to the cam sensor. If the car is convinced it is running at an RPM other than what it is then the back pressure is not there to actuate the valve transducer. The car expects to see the valve open and sets the code. The cam sensors are returnable so I would go for changing that out and clearing the codes from it.

No doubt the car will returning to normal running and then see if it posts the EGR code again.

BTW, I can't imagine the car having to attempt to start twice due to boost pressure. Check the voltage drop on your battery after 15 seconds of cranking, of course again the bad cam sensor can make the car do this also, as it will randomly choose coils to fire on start-up with the lack of CID input.

Ray
 
the dragging of the starter is due to the DIS module attempting to guess which coil pack to fire when the cam sensor fails (CID signal). you can measure the signal at the dis module to see if it is working. that goes for the crankshaft sensor too.
 
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