'90 SC being a pain

fordman90

Registered User
I hope Im in the right catagory.I bought a white '90 SC in February for $1,500. It runs but theres a miss or misfire.I bought new plug wires, coil pack,cleaned the inside of the throttle body, the misfire is still there.I bought new set of plugs,(AWSF34PP), those arent installed yet.When I first start it up, the tach needle will fluctuate,I'll hear a knock for a few seconds.If I dont keep my foot on the gas, it wants to die.After I restart it, the tach will stay steady.This is my first SC, I never saw so many senors on a car.At least the Check Engine Light isnt coming on.Ive owned Fords since 1973, from a 1938 Coupe to a '57 and up. but this is most complex car I ever owned.Any replies pertaining to my car problem is appreciated.
 
When the idle smooths out(I have to give it some gas to keep it from stalling), the vacuum guage will be above 20, right on the I in In-Hg.My neighbor mentioned it could be a vacuum line off somewhere, Last week I went to turn around in a neighbors driveway, I stepped down on it hard, it died.That was a little embarrassing.It cant be too drastic of a problem, it's just going to take somebody smarter to me to figure it out.If it was an old 292 Y block or a 390 , Id had it fixed a long time ago.
 
The pain

Good evening

Check for vacuum leaks. Smoke machine, carb and or brake cleaner spray for intercooler connections.

Do a Key On Engine Off (KOEO) and Key On Engine Running (KOER) tests for codes.

Check the harmonic balancer for missing/broken bolts. Remove the balancer cover if installed and check for wobbling while running.

Check fuel pressure. Key On Engine Off (KOEO) and Key On Engine Running (KOER).


Good luck.
 
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Ok, I'll do that as soon as my neighbor brings his code reader home with him.All I have is a Haynes Repair Manual to go by.It has the codes listed.I was looking at the SCP website, I noticed the Idle Control Valve that fastens on the side of the throttle body. How can I tell if that needs replaced ?
 
Kinda sounds like a bad cam sensor.....

Unplug it and try to start the engine.....

It might take a few tries.....
 
Get a Shop Manual, and an Electrical Diagnostics manual for your year, off eBay. You can pick up a set in good condition, probably for less than 50 bucks. The Haynes and similar manuals are better than nothing... but only just, IMHO.

Examine all the things suggested, so far...

When I got my 89, I went round-and-round with 'missing', weird tach behavior, non-starting (then 'magically' it would start).

Replaced: Plug wires; coil-pack; plugs; Cam sensor; Crank sensor; Ignition Control Module, ICM (FoMoCo part), Idle Air Control (IAC) module.

Plugs/wires/coil-pack corrected miss-under-load.

Crank sensor corrected unreliable starts (finally, it failed and the car wouldn't start at all).

ICM got ride of a weird 'miss' that came irregularly, e.g., I'd be cruising down the road and it would either miss once, or twice, or if I tried to give it gas during these 'episodes', it might 'buck' for a while before it would smooth out again (subsequently running like a champ...until the next episode in anywhere from 10 to 100 miles). I originally replaced the ICM with a third-party unit. It ran good...for 500 miles, when the problem returned. My mechanic located/installed a genuine FoMoCo ICM...and no problems since (in several thousand miles).

IAC and Cam-sensor were for 'good measure'.

My car is an '89, and had been essentially undriven for up to two years before I got it (death, probate...new owner--who sold it to me).

Thus, my experience is all these things deteriorate and overlap one another somewhat as to symptoms. You can certainly save money, and do a 'surgical' diagnostic on each item. But--in my case at least--if I had just gone out and replaced all the stuff I mentioned, from the git, I'd have saved time (and perhaps money). If these items aren't 'bad' right now, and haven't been recently replaced (in the last year or two)...odds are good they will go 'bad' in the not too distant future. From my perspective, you'd be better off to start with a clean-slate...then do specific trouble-shooting in the future, on individual issues. As I said, many of the symptoms overlap. Just my experience, and opinion. There are better ways to do things, provided you have plenty of time, but wish to conserve funds.

Good luck. Now that I've sorted through all my issues, the car runs reliably with nary a miss, cough, or hiccup. There for a while, I had my doubts. But if you keep after it, eventually you get these things sorted out.

Alan
 
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It will start with the cam sensor unplugged, let it run awhile, shut it off then try to restart it, it will start hard.I have a new cam sensor,the black plastic part, just havent gotten around to install it yet.The idle control valve is next on the list.Then I start it up cold, the tach will flucuate, after 15 secs or so it starts reading steady,but I have to give it a little gas., like its cold blooded.Put it reverse, it will die.I got it turned around, put it in Drive, tromped the gas, it died.I'll get it squared away eventually.Once the car is moving, no problem. Would replacing the black cap on the cam sensor make any difference.Oh, one more thing, when it first starts after sitting a few days, I'll hear a knock, but it disappears when the tach stops flucuating. I appreciate all the replies Ive recieved so far.
 
The choking sounds like the ever typical vacuum leak. If it wheezes when you turn the key off or if you watch the boost gauge go to zero real quick.. you have a vacc leak. The places to look are anything that was touched when you last worked on the car. A leak at the intercooler tubes is very common.
 
It will start with the cam sensor unplugged, let it run awhile, shut it off then try to restart it, it will start hard.I have a new cam sensor,the black plastic part, just havent gotten around to install it yet.The idle control valve is next on the list.Then I start it up cold, the tach will flucuate, after 15 secs or so it starts reading steady,but I have to give it a little gas., like its cold blooded.Put it reverse, it will die.I got it turned around, put it in Drive, tromped the gas, it died.I'll get it squared away eventually.Once the car is moving, no problem. Would replacing the black cap on the cam sensor make any difference.Oh, one more thing, when it first starts after sitting a few days, I'll hear a knock, but it disappears when the tach stops flucuating. I appreciate all the replies Ive recieved so far.

How does it run with the cam sensor unplugged? Is there any change in the symptoms? Ignore the hard starting - you cause that by unplugging the cam sensor. We are concerned with the "wanting to die".
 
The pain

I replaced the Idle Control Valve with a Motorcraft part, tach still fluctuates for maybe 45 sec or so. Next thing on the list is to replace the PCV valve.. How many of those PCV valves on the SC motor? I found one on drivers side, front of valve cover behind the coil pack. Now, whats the thing in the passengers side valve cover, at the rear, next to the firewall , under the throttle cables?. The car is for sale, Im too old for one of those SC's anyway.The only concern I have is the erratic idle on startup.
 
The one on the driver side is a vent. It connects via a plastic tube that threads under the blower across the engine to the airfilter /intake hose. The one on the passenger side is the actual pcv valve. The valve connects to a large downward pointing vacuum port on the intake plenum. .. (the one with the throttle that bolts up to the blower)
 
ignition question

First let me say "Thank you ALL for all the information you are sharing." I inherited a beat-up, twice-wrecked, no syncho, no heat, 87 turbo coupe and enjoyed it so much I traded it for a super clean 60K 92 SC (+ some cash)... Now I'm working the kinks out and this forum is a huge help.

Background: When I bought it, it had a hard start issue requiring multiple cranks. There was no tach and check engine light was always on. I replaced plug wires and plugs (+ unrelated stuff - belts, pulleys, window motors, speakers, stereo, thermostat). Then replaced cam sensor. The tach then worked and the check engine light went out. A few days later, the tach randomly goes out and the check engine light comes on simultaneously. Without diagnostics, I'm happy to throw parts at it, but am wondering the best order: ICM? Crank sensor? or Coil pack? Which affects the tach?

Again, THANKS! Love driving this car.



Get a Shop Manual, and an Electrical Diagnostics manual for your year, off eBay. You can pick up a set in good condition, probably for less than 50 bucks. The Haynes and similar manuals are better than nothing... but only just, IMHO.

Examine all the things suggested, so far...

When I got my 89, I went round-and-round with 'missing', weird tach behavior, non-starting (then 'magically' it would start).

Replaced: Plug wires; coil-pack; plugs; Cam sensor; Crank sensor; Ignition Control Module, ICM (FoMoCo part), Idle Air Control (IAC) module.

Plugs/wires/coil-pack corrected miss-under-load.

Crank sensor corrected unreliable starts (finally, it failed and the car wouldn't start at all).

ICM got ride of a weird 'miss' that came irregularly, e.g., I'd be cruising down the road and it would either miss once, or twice, or if I tried to give it gas during these 'episodes', it might 'buck' for a while before it would smooth out again (subsequently running like a champ...until the next episode in anywhere from 10 to 100 miles). I originally replaced the ICM with a third-party unit. It ran good...for 500 miles, when the problem returned. My mechanic located/installed a genuine FoMoCo ICM...and no problems since (in several thousand miles).

IAC and Cam-sensor were for 'good measure'.

My car is an '89, and had been essentially undriven for up to two years before I got it (death, probate...new owner--who sold it to me).

Thus, my experience is all these things deteriorate and overlap one another somewhat as to symptoms. You can certainly save money, and do a 'surgical' diagnostic on each item. But--in my case at least--if I had just gone out and replaced all the stuff I mentioned, from the git, I'd have saved time (and perhaps money). If these items aren't 'bad' right now, and haven't been recently replaced (in the last year or two)...odds are good they will go 'bad' in the not too distant future. From my perspective, you'd be better off to start with a clean-slate...then do specific trouble-shooting in the future, on individual issues. As I said, many of the symptoms overlap. Just my experience, and opinion. There are better ways to do things, provided you have plenty of time, but wish to conserve funds.

Good luck. Now that I've sorted through all my issues, the car runs reliably with nary a miss, cough, or hiccup. There for a while, I had my doubts. But if you keep after it, eventually you get these things sorted out.

Alan
 
Which affects the tach?

Start with the grounds - these cars depend on healthy connections, so be sure nothing is old/corroded, starting with the strap/cable from the pass. side motor mount over to the body. Corrosion can hide under sheathing, and new is cheap enough, so...

Then check the health of the upper/front harness that connects to the cam sensor, crank sensor, DIS, coil and main harness - see if it has been damaged/abused/repaired, etc. Also, inspect the ignition switch down on the side of the steering column (not the lock cylinder) - these are chronic offenders when aged.

Be sure the running volts are up - check battery volts off and running.

Next run codes. If you don't know how, visit a nearby auto parts store that will check for free, or search/ask here for details.

Good luck in any case :)
 
KMT,

I just checked and battery voltage *is* low and the battery appears undersized and the hydrometer says it is near death despite being a few months old! It's running 12.1 volts after engine is off for an hour or two. System is charging, as running the voltage is 14.3. I didn't know they were voltage sensitive, but this possibility makes sense because after sitting, it has the problem, then after driving for a few minutes, the tach starts working and the check engine light goes out.

The car has no corrosion that I can see, in fact is the cleanest car I have ever seen in that respect, but I will check all grounds. All wiring looks to be original and I have all records from birth, so there is no sign of any problems previously on DIS, cam sensor, or coil pack and they are original.

Thanks for the tips -- I'm starting a folder!

Ted
 
My '90 had a stall w/tach drop when I got it.

The bolt and connector at the arrow in the attached photo on mine was all greened up w/corrosion, when I got the car. Upper harness was taped up/oiled up.

I think the cam sensor needed replacement, but not sure about the one for the crank. Did them both regardless. Replaced the grounds and the harness and it finally all cleared up.

You'll get it...eventually :)
 

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