Missing and Shaking going on

rickbtbird

Registered User
I got a 90SC automatic with 84,500. I was running normally on the hi-way this morning about 65mph not under boost. After a slow down due to traffic, I slightly stepped on the gas and all of a sudden the car started missing and shaking like it was only running on 4 cylinders and continued to run bad until I got to work. I don't see any evidence of any smoke or steam. The temperature and oil pressure gage look normal. No lights on the dash board. There’s not too much I can check right now as the car is to warm.

Any suggestions?
 
rickbtbird said:
I got a 90SC automatic with 84,500. I was running normally on the hi-way this morning about 65mph not under boost. After a slow down due to traffic, I slightly stepped on the gas and all of a sudden the car started missing and shaking like it was only running on 4 cylinders and continued to run bad until I got to work. I don't see any evidence of any smoke or steam. The temperature and oil pressure gage look normal. No lights on the dash board. There’s not too much I can check right now as the car is to warm.

Any suggestions?

Maybe a bad crank sensor or cam sensor. Possibly a balancer going bad, but I doubt it as it doesn't sound catastrophic enough for that. I have a good used crank sensor off my '93 SC AOD for sale.
 
Last edited:
Knock, shake and rough when AC is on

It’s 10:30 now and it's been parked for about 2.5 hours. I check the oil and coolant and they are full. I started it up and it's doing the same thing. When stepping on the accelerator and when idling there's an occasional knock and a shake. The blower tension pulley occasionally hops. Again, no lights on the dashboard, the oil, blower, and temperature gages all look fine. I turned on the AC and it got really rough.
 
rickbtbird said:
It’s 10:30 now and it's been parked for about 2.5 hours. I check the oil and coolant and they are full. I started it up and it's doing the same thing. When stepping on the accelerator and when idling there's an occasional knock and a shake. The blower tension pulley occasionally hops. Again, no lights on the dashboard, the oil, blower, and temperature gages all look fine. I turned on the AC and it got really rough.


My guess is that it got more rough when the AC was turned on simply b/c it is taxing an already poorly running motor.
 
pablon2 said:
My guess is that it got more rough when the AC was turned on simply b/c it is taxing an already poorly running motor.
Agreed, I'm looking for troubleshooting steps to determine root cause but I'm not sure where to start on this one.
 
rickbtbird said:
Agreed, I'm looking for troubleshooting steps to determine root cause but I'm not sure where to start on this one.


I've already mentioned the two sensors, one of which I believe is the cause. Perhaps one of the more seasoned veterans can chime in?
 
My 89 started the same thing awhile back and the balancer was going bad. I went to check it and the bolt came off in my hand. I would check and see if the bolt is there. I also would chack the wire harness that comes up from the crank sensor and see if it has been cut by something. FL SC owner just found the same thing on his poor running SC.
 
Last edited:
My bet would be the DIS module is failing. You could try cleaning the mounting surfaces and recoat the heatsink grease to see if it helps. But, I think once it fails it's a lost cause. John
 
Thanks for the suggestions. I have to get it home tonight so I can do additional troubleshooting. Right now it's 12 miles away were I work.
 
Another thing to check is the IC tube seals. Start it and spray some carb cleaner in the 4 IC tube connections. If it get sucked in, then replace your IC tube seals. I had a similiar symptom and that was it. Good luck and take care.
 
Well I got her home and it was the worst ride of my SC life. I'm going to let her cool and try to troubleshoot tomorrow but I might end up taking it off to the dealer.

I did read a post where this sounds like it could be fuel related and another post where no root cause was ever posted that matches exactly http://www.sccoa.com/forums/showthread.php?t=51617. Last year I had Ford install a new fuel pump, seal, and pigtail in the gas tank. Fuel filter was replaced last year as well. Maybe I should have went with the after market pump.

I'm not quite sure where the cam and crank sensors are located yet but I got a few books. Sucks for me I don't have any spare parts to try.

Once I get to the bottom of the problem I keep you all updated.
Later...
 
rickbtbird said:
Well I got her home and it was the worst ride of my SC life. I'm going to let her cool and try to troubleshoot tomorrow but I might end up taking it off to the dealer.

I did read a post where this sounds like it could be fuel related and another post where no root cause was ever posted that matches exactly http://www.sccoa.com/forums/showthread.php?t=51617. Last year I had Ford install a new fuel pump, seal, and pigtail in the gas tank. Fuel filter was replaced last year as well. Maybe I should have went with the after market pump.

I'm not quite sure where the cam and crank sensors are located yet but I got a few books. Sucks for me I don't have any spare parts to try.

Once I get to the bottom of the problem I keep you all updated.
Later...

Sure sounds like the balancer. With the engine running look to see if the crank pulley is wobbling. If you can't tell turn the motor off and reach down with both hands and pull on it up and down to see if you can feel any movement. While your down there reach inside the crank pulley and feel for the large bolt in the center that holds the pulley and balancer onto the crankshaft.

It there is any movement or the head of the bolt is missing the balancer will need to be replaced. The crank sensor is located behind the balancer and if the balancer gets loose the trigger wheel hits the sensor (hall effect vane type) or gives it a bad signal.

If that's not it, it could be a bad DIS module, Cam Sensor or a vacuum leak. Check the balancer first and report back.

David
 
It was my car in the FL group whos car was acting like a mad 2 year old. I found the harness for the crank sensor had come loose and hit the serp belt and was running like crap. Stalling, mis-firing, bucking ect,. I knew it was not the balancer because I have a BJH so I looked at cam sensor, dis and crank sensor and wella, found the wire had been cut. Took me about 2 hrs to fix it right and wella, car is running awsome! :)
 
David Neibert said:
Sure sounds like the balancer. With the engine running look to see if the crank pulley is wobbling. If you can't tell turn the motor off and reach down with both hands and pull on it up and down to see if you can feel any movement. While your down there reach inside the crank pulley and feel for the large bolt in the center that holds the pulley and balancer onto the crankshaft.

It there is any movement or the head of the bolt is missing the balancer will need to be replaced. The crank sensor is located behind the balancer and if the balancer gets loose the trigger wheel hits the sensor (hall effect vane type) or gives it a bad signal.

If that's not it, it could be a bad DIS module, Cam Sensor or a vacuum leak. Check the balancer first and report back.

David

Dave,
I removed all the belts, check the balancer bolts, it's there. I pulled on the crank pulley and it's solid as a rock. I also ran the engine for a moment and the pulley is spinning like a top. I also went and traced the wire that looks like it might go down to that area and it doesn't appear broken, although it's wrapped. I'll have to put it up on stands tomorrow to trace it further.
What’s next?
 
Last edited:
rickbtbird said:
Dave,
I removed all the belts, check the balancer bolts, it's there. I pulled on the crank pulley and it's solid as a rock. I also ran the engine for a moment and the pulley is spinning like a top. I also went and traced the wire that looks like it might go down to that area and it doesn't appear broken, although it's wrapped. I'll have to put it up on stands tomorrow to trace it further.
What’s next?

Spray all the IC tubes and plenum area vacuum hoses with carb cleaner (engine running). If you hit the area with a leak the engine will rev up. Sometimes the leaks can be fixed just by tightening stuff up, other times it has to be taken apart and resealed. Tbird88 (Wynn) sells some nice teflon gaskets, but I prefer to use copper RTV to seal just about everything on the motor.

David
 
Fuel???

Just a guess but maybe a stuck or clogged injector??

How is your exhaust? Does it smell gassy? A lot of vapor?
 
Mline said:
Just a guess but maybe a stuck or clogged injector??

How is your exhaust? Does it smell gassy? A lot of vapor?

The exhaust is a bit gassy so maybe it's time to clean them. I've never messed with them or the fuel rail ever so that will be a learning experience. I understand that a burst of air is what's used to blow them out.

Since I ordered new aluminum pulley sets and I want to get a better look at the balancer, I decided to tear into it and start removing the ones I'll be replacing. I got the water pump pulley off but the crank pulley turns when I try to turn the pulley bolts so I guess I have to put the water pump pulley back on and install the belt to keep it from turning?

Also, I'm at a step here where I can pull of the cam sensor but the book say I need to get cylinder #1 to 26 degrees ATC of the compression stroke. I'm use to a distributor so what's the best way to determine where #1 is in the cycle when I'm at 26 degrees ATC?
 
i would try some stp in the gas if that dont help pull the plugs to see which ones arent fireing , just take the 2 screws out of the cam sensor you dont have to adjust timing
 
Also, I'm at a step here where I can pull of the cam sensor but the book say I need to get cylinder #1 to 26 degrees ATC of the compression stroke. I'm use to a distributor so what's the best way to determine where #1 is in the cycle when I'm at 26 degrees ATC?

Positioning the motor as you describe is only necessary if your removing and reinstalling the entire cam sensor stalk/scyronizer. For changing only the sensor, you just remove the two screws and install the replacement in the same position. No adjustments are needed.

David
 
Check your coil pak!

My 94 started running bad when I left work a while back. It would miss, had no acceleration and would occasionaly die when I stoped. It would also die if I tried to accel hard. My coil cracked on the bottom and started puking white stuff.

Ed Springer

90 Black XR7 5-speed: 70mm TB, Fresh Air Intake, '94 Supercharger, 5% SC Pulley, Raised SC Top, I/C Fan, UD Pulleys, 190 l/h Fuel Pump, 36 lbs Injectors, Headers, Magnaflow Muffler (no cats) with stock resonators, 3:27 Gears, Ripper Shifter, 73mm CL MAF (Blue Tube), Magnacore Wires, NGK Iridium Plugs, Royal Purple Lubricants and Rear Spring Air Bags.

94 Red SC Auto: 70mm TB, Fresh Air Intake, Stock 90 SC Pulley, Raised SC Top, I/C Fan, 190 l/h Fuel Pump, Headers, Raven Muffler (no cats) with stock resonators, 3:73 Gears, Accel 36# injectors, 76mm CL MAF (Gold Tube), Magnacore Wires, NGK Iridium Plugs, Royal Purple Lubricants, TRANSGO Shift Kit, Pro-Torque 2500 Stall TC, Haydon Auxiliary Transmission Cooler, Tokico Struts & Shocks, American Racing 17” Sniper Wheels, Michelin Pilot Sport A/S Tires and 235 RWHP with 315 LB-FT Torque.
 
Back
Top