Idling problem

Hey everyone I'm new to this forum and figured i would try to get some input on a problem i have. I've had this problem with my 92 SC auto for the past month or so, its been an intermittent thing...

Sometimes the engine will idle between 1500-2000rpm when in park or neutral and then when I put it in drive or reverse the engine will drop down to where it should be (700-800rpm). It doesnt matter if the engine is hot or cold when it occurs. MOre recently now, even when the car is in drive or reverse, the engine speed without pressing the gas pedal is between 1000-1500 rpm. Ocassionaly I have had the amber service engine light come on but does not remain on after turning the car off and back on again. When the car is idling at these higher rpms, it does so at a constant speed and does not fluctuate. My car is basically stock, only mods in the engine are a K&N and wiring my rad fan with a switch.

Has anyone else ever encountered anything like this or know what might be the problem?

Thanks

Yes we have.. Sounds like your Idle Air Control Valve (IAC as its commonly called). This is the black cylinder looking thing on the side of the throttle body. Try unplugging it and starting the car. If it has a ruptured diaphragm, the engine will idle fast even with it unplugged. Otherwise, it should start, go up briefly and then die.

If you decide to replace it, you need to know most of the aftermarket brands will not work on the SC, even if they are listed for it. This is because some Einstein designed the replacements such that they have to be installed 180 degrees out to work. Due to the placement of the oil filler tube on the SC, this isn't possible, so if you use one of these and install it normal... the engine will race.

Now, there are some which will work, but the only way to know is to look inside it and see if 1) the valve seat is closed at rest and 2) it has an accordion looking diaphragm like the original.
Best bet is to get the motorcraft one from Ford.. They're about $90... all in all, not a bad price for Ford stuff. Retail price at the chain stores is about $70 anyway.

Hey thanks a lot, I'll try that

Ok I unplugged the IAC and the engine hesitated a bit and then idled at a normal rpm smoothly. I shifted into R, N and D and it idled normal too. Is it ok to drive the car with it unplugged like that until I get the replacement IAC? Or should I just put up with the high idling?

It won't hurt anything to leave it unplugged.

You haven't recently done anything to the throttle plate set screw, have you? or worked on anything which deals with any vaccuum hoses?

Enough air is bypassing the throttle plate to idle the engine. Now, that is either because the plate is open just ever so slightly, or the IAC has a tiny hole in it. If you haven't touched any adjustment stuff, and when the IAC is plugged in the idle zooms up consistently, then we can be fairly confident that its the IAC thats the problem.
But I have to mention that its also possible that a vaccuum leak past the throttle body can cause the problem too. You can test for those with a propane torch (unlit of course) or some people use starter fluid, by spraying it around the TB with the engine idling. Do that in a well ventilated area. What will happen is the gas will get sucked into any holes in the intake and the engine will speed up.

Hi everyone,
I am new to this forum too. I do have a similar problem with my car. Hence I thought, I would post it hear, rather than starting a new thread. Hope no one minds.
My car is a 89 SC manual. When I am driving on a freeway or in the city, all of a sudden the Idle is abrupt, and the car starts jerking, and when I press the clutch the rpm goes from arount 600 to 1200, but the engine doesn't stop and when I keep giving gas in couple of minutes it starts running smoothly, and it keeps on happening randomly, once in a week or so or less.
When I took it to the dealer, he said he cannot do anything, unless it keep happening.
Input appreciated.

Hello Pirulo, welcome to SCCOA.

Replace your cam sensor and your problems should go away. $30 part from Oriellys, takes about 15 minutes to install.

Thanks a lot TbirdSCFan for your prompt reply.
May be I should give the whole story of my car.

As I mentioned, above the problem occured and I thought it could be, because it needs tune up and I got the tuneup done (6 platinum 2 sparkplugs, wires, air filter, fuel filter and PCV valve). But the problem didn't go away.
Couple of weeks back, my alternator went and the mechanic replaced and the car's idleing was off and the computer through all sorts of codes.
Then I drove it to the dealer (if it doesn't get more gas it will stop, it drove to the dealer fine). In his report he said he had codes 98,66,41,91,72,73,25 and 74, timing was off etc. He found out bad vacuum leakes, both end of the supercharger tube loose. He corrected it by tighting it and cleared the codes and there was no idleing problems and in his report he said very small vacuum leaks at intake manifold (I didn't know why he didn't correct it). Anyway I drove the car and everything was fine and I took it to my mechanic and he checked again and there were no codes. In couple of days the original problem came back.
So do you still think, I should change the cam.
I bought this car from my friend, who is a mechanic (he is in the East coast and I moved to west coast). He suggested me to let you know the whole deal and then take your advice.
You suggested to buy from Oriellys, do they have a web site or is it something like NAAP auto parts.

I have another problem, when I press the brakes little the Brake light comes up and then the ABS light come up and will go away. But the brakes work fine, do I have to replace any sensors.

thanks a lot.

Bad Accumulator

Hey Pirulo, The warning indicators you are getting points to a bad ABS accumulator. The accumulator is a black metal ball on the ABS hydraulic pump unit that maintains system pressure. If you continue to drive the car with this problem you will eventually kill the hydraulic pump. Contact Prior Remanufacturing (www.priorreman.com) or 1-800 444 4821. Ask for Rick Fletcher, and tell him you need an accumulator for the Teves Mark II ABS. It will cost you around $100.00 (US). If you decide to fix the problem (and I suggest you do) contact me and I will give you the step-by-step on replacing the accumulator (it can be dangerous if you don't do it the right way----I believe it is normally pressurized to around 2300PSI).
It is an easy fix, you just have to follow the steps......

Thanks LJGriggs
for your reply.
It is realy weired. When I put my feet on the brake and slowly apply pressure on the brakes, not lights comeup. If you tap the brakes the light comes up. But when I press the brake pedal slowly or otherwise, I hear twice clicking noise on the passenger side.
Do you still thing it is the accumilator.

Hey I have that same problem on my car too. If I dont care about whether my ABS works or not, is that something I can not worry about or is that hydraulic pump for the whole brake system?

I've learned so much about my car from only reading this forum for a few days, its great!!

The ABS hydraulic pump is the brake system. You can drive with a bad accumulator for a while, but eventually the pump will die due to overheating. The accumulator stores brake fluid under extreme pressue so that the pump doesn't have to cycle every time you use the brakes. With a bad accumulator, the pump has to work constantly to maintain fluid pressure. If you have a "panic stop" you may notice that the brake pedal fades then recovers (in a split second) as the pump catches up.

The accumulator will cost you about $100.00 from Prior (around $200.00 from Ford) or if you wait too long, the complete system will cost around $400.00 from Prior (or $1800.00 from Ford).


The accumulator is much easier to replace than the entire system, but both can be done "in the driveway".......

This info only applies to the '89 thru '92 SC's. '93 and beyond have the Teves Mark IV which has no accumulator and uses manifold vacuum to maintain system pressure (I think)

If I dont care about whether my ABS works or not, is that something I can not worry about or is that hydraulic pump for the whole brake system?

Click to expand...

Well actually due to the way the Teves Mark II system is constructed, the accumulator is a critical part of the HCU (Hydraulic Control Unit). It provides very high pressure brake fluid (Larry's correct with the 2300PSI spec) for 2 purposes. The 1st is the extra force for the power brakes, the 2nd is the force needed to cycle the solenoid valves when the ABS is kicked in.
So the accumulator is a crucial part of the system because without it you wouldn't have ABS (which may not be a big deal to you), but you also would have weak braking which means your leg power would have to stop the car and folks say it takes a LOT of leg power to do so. The other catch is you have no rear brakes when that happens.

The Brake+AntiLock lights cycling on/off while driving around are a dead giveaway for a worn accumulator. I could go into details about why that is, but this response is long enough already

Oh, and as for guys like Larry and me,.. we learned everything here too. In fact, wanna guess what my very first question on the forum was? It was something like "does anyone know why my anti-lock and brake lights come on and go off?"

On the cam sensor suggestion.

Pirulo,

You may be able to get a cam sensor from any of the chain stores such as Pepboys, Orielly's, Carquest. Autozone didn't stock them when I last checked. They run about $30 and from what you've told me regarding the history of the work done, it may or may not fix your problem. If the problem you have seems to happen out of nowhere and the car is jerking real bad, and then all of a sudden for no reason it just clears up and runs fine, then I'd say chances are 99% that its the Camshaft Position Sensor. This has happened to most of us at one time or another.

But, you need to check for vaccuum leaks at 5 significant places due to the work you say was done on the car. Even better, if I were you, I'd pull the joints apart and reseal them myself just to be sure it was done right. But parts of that job require some special tools.

The places you need to check are:
1. The base where the supercharger top bolts to the supercharger body
2. The great big collar nut which connects to the upper intercooler (IC) tube.
3. The joint where the upper IC tube goes into the IC.
4. The joint where the bottom IC tube comes out of the IC.
5. The joint where the lower IC tube goes into the intake manifold.
You can check these with the engine idling (pulling a vaccuum) using propane from a handheld cylinder such as an unlit propane torch.

Given that you had the alternator replaced (something I've become expert at and have it down to around 1 hour now), the mechanics would have had to remove the upper IC tube. This means they had to disturb items 3, and 2 (or 1 if they were clever.. but I doubt it). Since they didn't know how to reseal 3, they probably didn't reseal 2 correctly either. The other thing is to check very closely all the wiring around the coil pack to be sure it wasn't damaged.

Thanks a lot guys,
I will try to get the accumulator work done.
But TbirdSCFan,
Is the cam sensor and camshaft Position sensor the same.
Does this car has a crankshaft sensor (my mechanic friend told me to ask), he thinks that might cause the problem too.

Like you suggested I will check for vaccum leak. From the dealers work report, he sees a small leak at the intake manifold and everything is fine.

guys this sure is a great forum.

Long Live the internet and the information age.

Re: Bad Accumulator

Ask for Rick Fletcher, and tell him you need an accumulator for the Teves Mark II ABS. It will cost you around $100.00 (US). If you decide to fix the problem (and I suggest you do) contact me and I will give you the step-by-step on replacing the accumulator (it can be dangerous if you don't do it the right way----I believe it is normally pressurized to around 2300PSI).
steps......


Hey thanks for the tip, I just talked to Rick and got the part ordered, just over $100 with shipping and all, should be here in a few days. If I could get those step-by-step instructions that would great. Thanks

Here ya go....

The first thing to do is de-pressurize the system. With the Key OFF, pump the brake pedal until it is rock hard (around 25 to 30 times). When the pedal is really hard to push, the system should be clear.
Next, remove the plastic windshield cowling to get better access to the accumulator. Unscrew the accumulator from the fitting on the side of the pump. There is a "hex nut" on top of the accumulator where you insert an allen wrench to unscrew the accumulator.
You will need to work your way through the hoses, wires, etc. around the accumulator to get it out, but with some patience it will come free. This is the hardest part of the job. Once you have the old accumulator out, you will want to put it in an old coffee can to drain (you would be amazed at how long this thing will drip brake fluid).
Use a new O-Ring on the nipple of the new accumulator (it is already installed on the units from Prior) and lube the threads with clean brake fluid. Screw the new accumulator into the fitting. The Accumulators from Prior do not have the hex-nut but that doesn't matter. You only need to get it "hand tight" like you would an oil filter. I think the torque specs call for around 12 ft/lbs which isn't very much. Just don't overtighten or the fitting could snap off the pump (that would be bad).
Once the new accumulator is in, turn the key to ON and listen for the pump as it pressurizes the system. This should take from 10 to 45 seconds. Check the fluid level in the reservoir and add if needed. replace the windshield cowling. No need to bleed the system after this repair because you haven't introduced any air into the system.
The ABS/Brake indicators should no longer flash when you use the brakes, and you have added years to the life of the pump.

Torque spec is 30-34 lbs. Don't ask me how they came up with 34 lbs.. but that's what I recall from the Ford unit's papers.

Also, the Hex fitting is 12mm. DO NOT be tempted to use a 7/16" because its close.. its just loose enough to strip the hole out and mess with your blood pressure. It usually takes a hex socket, not one of the spindly flimsey Allen wrenches.

Good luck.

OK thanks a lot guys, I have a metric set so I'm alright. I'll let you know how things work out!

My dad is a 2nd generation transmission man who took over the family business when my grandfather passed. Even though he told me the same thing about my ABS and Brake light, it didn't seem to make sense until I read it on this forum. I passed on the family business and went to college, so this could be the reason he gets so frustrated when I ask questions about my car.

Thanks for helping me see eye to eye with him.

I have already contacted Rick Fletcher about the accumulator.

I also need new spark plugs and wires. What is the easiest way to get to them?