Idling and Starting Problems

[94stangfan]

This item in the checklist stands out...

14.) VSS sensor defective or wiring damaged. The MAF and Speed Density cruse control equipped cars will have a vehicle speed sensor on the speedo cable pickup. The purpose of the VSS is to increase the idle speed as the car slows to a stop. If the sensor is defective, you can experience stalling as you slow to a stop.

The reason it stands out is that My cruise control is not working right now. That was an item on my list to fix, but wasn't very high.

Can anyone provide more info about this?

Thanks,

Keith

 

[jrichker]

This item in the checklist stands out...

14.) VSS sensor defective or wiring damaged. The MAF and Speed Density cruse control equipped cars will have a vehicle speed sensor on the speedo cable pickup. The purpose of the VSS is to increase the idle speed as the car slows to a stop. If the sensor is defective, you can experience stalling as you slow to a stop.

The reason it stands out is that My cruise control is not working right now. That was an item on my list to fix, but wasn't very high.

Can anyone provide more info about this?

Thanks,

Keith

I'm the guy who created the Surging Idle Checklist. It says what it says. The VSS speed is supposed to speed up the engine idle when you come to a stop. This helps prevent the engine from stalling.

A defective VSS will usually set code 27 or 29. If the cruse control doesn't work, make sure the fuse hasn't blown and all the vacuum plumbing for it is connected up. The cruse control does not have to work for the VSS to prevent the slow down to idle stall problem.

 

[Mustang5L5]

Was your '86 converted to MA? If not, the VSS on speed density cars is only used for cruise control.

Do you have a VSS code?

 

[94stangfan]

This thing is about as stock as you can get minus the smog pump and cats... No conversion done. I am going to check some vacuum lines this weekend.

 

[94stangfan]

I think my problem is fixed

Ok,

After cleaning the EGR valve and replacing the ignition control module I have determined that was the main cause of my surging idle.

The after effects of changing the ICM is that I didn't put a timing light on. Once I did that I realized that my engine was out of time and I adjusted it accordingly.

This made the engine run much much better. I took it for a test run and I didn't experience any surging idle, but I did get one stall coming into a stop light.

I decided to do the routine maintenance on it and changed the oil and changed the fuel filter since that was mentioned on this list of items to check for. Added to that, I don't know when the last time it was replaced.

Once I did all of that I took it for a test run, no surging idle, no stalls.

The only thing I did experience is that when I came up to a couple stop lights, the idle would drop to about 250 and then speed up and level out around 650. It didn't stall or continue to surge. I am thinking this is normal, but please feel free to chime in if you don't agree.

So I think to sum it all up the culprit in my case was 3 fold...

1. Plugged EGR - got a code 33
2. Bad ICM - got a code 18
3. Fuel Filter

Thanks everyone for your help. I am no longer afraid to take the mustang out for a drive. It stranded me once.

Bonus: I found out my starter was on its way out, so I changed that and the solenoid. It will still crank a little slower than I would like when it is warm, but I think a bigger battery would fix that.

Thanks again,

Keith

 

[BlackGT89]

If the starter is turning over slowly when the engine is hot, there is a good chance you have a bad ground. The resistance in the wiring increases with heat. Check all of your grounds, especially the one going to the driver's side front of the engine. A galvanic corrosion sets up there because of the two metals types being in contact. When I first got my car sometimes the wires would actually smoke until I figured out what was going on. Even if the connection looks good you might want to take it apart and clean it down to shinny metal. I have to do this usually every 4 or 5 years.

 

[94stangfan]

Return of the Surging idle... I thought i had it fixed, but it returned yeseterday. I went back to the checklist and noticed I had not cleaned the throttlebody, so I did that. Now it idles faster. Before I was idling aroudn 550-600 RPM (guessing) but now it is at 750. When I push in the clutch now, the idle will go down to 1000 and then slowly down to 750. I assume this is normal.

Is this idle to high? The reason I ask is that my exaust smells pretty rich. It wasn't like this before. What should my next step be? Should I just leave it as is? For the most part the surge seems to be gone. It will go up to about 1000 and then slowly back down to 750, but doesn't do the quick surge up and then back down up and then back down.

 

[olbob]

The "surging Idle " check list is one of the nicest things on the Web.. Long may it Wave....
OLBOB

 

[jrichker]

Return of the Surging idle... I thought i had it fixed, but it returned yeseterday. I went back to the checklist and noticed I had not cleaned the throttlebody, so I did that. Now it idles faster. Before I was idling aroudn 550-600 RPM (guessing) but now it is at 750. When I push in the clutch now, the idle will go down to 1000 and then slowly down to 750. I assume this is normal.

Is this idle to high? The reason I ask is that my exaust smells pretty rich. It wasn't like this before. What should my next step be? Should I just leave it as is? For the most part the surge seems to be gone. It will go up to about 1000 and then slowly back down to 750, but doesn't do the quick surge up and then back down up and then back down.

Two things:
1.) Did you get any codes?
2.) Did you do the set the base idle procedure?

 

[94stangfan]

Two things:
1.) Did you get any codes?
2.) Did you do the set the base idle procedure?

1- I only get a 94 and 44 which I am expecting since the cats and polution pump are gone.

2- I have not done the procedure to set the base idle yet. My time is limited until this weekend. I had not set the base idle after any other step and it seemed ok. I will give that a shot this weekend.

Should the idle be around 600-650?

I am going to double check the timing on it this weekend making sure my mark is correct and that it is hitting the right spot.

Thanks,

Keith

 

[jrichker]

1- I only get a 94 and 44 which I am expecting since the cats and polution pump are gone.

2- I have not done the procedure to set the base idle yet. My time is limited until this weekend. I had not set the base idle after any other step and it seemed ok. I will give that a shot this weekend.

Should the idle be around 600-650?

I am going to double check the timing on it this weekend making sure my mark is correct and that it is hitting the right spot.

Thanks,

Keith

Base mechanical ide with no IAC/IAB and SPOUT out should be 575-625 RPM. The IAC/IAB and SPOUT added spark advance will bring it up to 650-725 RPM

See http://www.stangnet.com/mustang-forums/698148-help-me-create-surging-idle-checklist.html#post6855020 for the best way to set the mechanical base idle and cleaning procedure for the IAC/IAB.