Fixed Idle Problem, But Now Stalling At Abrupt Stops?

Micheal Nadeau · Sep 29, 2014

A thought.....
The first place air is measured is the Mass Air. I have had Mass Air sensors trigger both lean conditions and rich conditions. Just the other day, a Mercedes S430 gave me a rich bank 1 and rich bank 2. If anyone has the specs for the Mass Air, I would ohm out the Mass Air. If its telling the computer its getting more air than it really is, it will lean out the mixture to compensate.

dz01 · Sep 29, 2014

Gearbanger 101 said:
So you have a vacuum gauge? That should give you a good indication if you've got valvetrain issues. This would be an ideal time to pick yourself up a gauge. They're not expensive and can be worth their weight in gold when chasing issues down.

Advancing the timing will generally help to some degree if you've got low idle vacuum symptoms because of a hot camshaft. A little ignition advance can help you pick up a couple of inches of vacuum.

Regarding the lean O2 codes....when was the last time you did a tune up? Dirty fuel filter, dirty injectors, etc could have you starving for fuel at idle. When you pull the vacuum line off the regulator, is there any raw fuel in it?

Dumb question, how do I go about checking vacuum to see if I have valve train issues?

Micheal Nadeau · Sep 29, 2014

With a vacuum gauge attached, you will see the needle fluctuate excessively. This will tell you that you aren't maintaining steady engine vacuum due to a valve sticking or not seating properly.

Gearbanger 101 · Sep 29, 2014

This is by far the best reference material on how to read a vacuum gauge I could find....

http://sbftech.com/index.php/topic,3020.msg29429.html#msg29429

jrichker · Sep 30, 2014

Watch for what codes you get when you dump them...

No codes, then some sensor is on the marginal edge of being bad, or there is a bad connection or bad wiring.

dz01 · Sep 30, 2014

Micheal Nadeau said:
With a vacuum gauge attached, you will see the needle fluctuate excessively. This will tell you that you aren't maintaining steady engine vacuum due to a valve sticking or not seating properly.

Dumb question #2, where would I connect the gauge? I ordered a gauge last night so I'll have it in two days.

dz01 · Sep 30, 2014

Gearbanger 101 said:
This is by far the best reference material on how to read a vacuum gauge I could find....

http://sbftech.com/index.php/topic,3020.msg29429.html#msg29429

Great, thanks!!

Micheal Nadeau · Sep 30, 2014

Pull the brake booster line.

dz01 · Sep 30, 2014

I think my next steps will be:

- Pull O2 ground (orange wire on back of head) to ensure good contact. Clean and reinstall
- Swap out MAF with bone yard MAF to see if there's a change- may also put in new performance MAF which is much larger (4")
- Check timing to see where set
- Check engine vacuum for potential valve train issues

Thanks for all the help so far guys. I'll report back soon.

Gearbanger 101 · Sep 30, 2014

dz01 said:
Dumb question #2, where would I connect the gauge? I ordered a gauge last night so I'll have it in two days.

I plug mine into the spare branch of the vacuum junction on the firewall.

dz01 · Sep 30, 2014

Gearbanger 101 said:
I plug mine into the spare branch of the vacuum junction on the firewall.

Thanks!!

jrichker · Sep 30, 2014

Do your changes 1 thing at a time. That way if a change introduces a new problem, it will be easier to find and fix the problem.

dz01 · Oct 1, 2014

Good feedback!

I pull the O2 sensor ground bolt last night and cleaned the two connections (orange O2 ground wire and the metal wire that connects to the firewall). I don't know if I mentioned before, but about 2 months ago I found this bolt threaded in only half way. Both wires were spinning freely. Based on the resistance tightening the bolt, I would guess the bolt has been like this for a while.

I cleaned the threads, both grounds and wire brushed the back of the head (looked like it was a little rusty (surface). Everything looked good until I dropped the stupid bolt down the back of the bell housing. After searching high and low for over an hour I hung it up for the night. I cannot possibly imagine where this bolt landed. I searched from the top and bottom, around the tranny, frame, front suspension- nothing! I supposed it won't cause any problems if I can't find it, although now I need another bolt!

Strikes me as strange when the bolt likely slid down the angle of the bell housing, then should have hit the floor. I don't think it's possible for it to have landed on top of the tranny, but I'm out of ideas.

Think the dealer has this bolt on the shelf?

jrichker · Oct 1, 2014

Home Depot, Lowes or Ace Hardware should have the bolt. All the bolts on the engine are standard US thread bolts, no metric or odd bolts on the engine itself.

dz01 · Oct 1, 2014

Thanks. I'll pick one up at Ace.

Any reason I should hunt for this bolt? Can't think of anything detrimental that would occur.

dz01 · Oct 1, 2014

I did notice this last night on the ground next to my battery. I'm assuming the broken/missing wire is not factory and I should just pull it off?

dz01 · Oct 1, 2014

O2 ground all set. That was fun.

Checked vacuum too and pulling about 17. Sounds like anything between 15-22 is normal op. Needle did fluctuate slightly from 17-18, but pretty consistent. Ran car for 10 minutes.

I'll pull battery cable to reset computer and go for a test drive when it stops raining later this week.

dz01 · Oct 3, 2014

Still pulling codes 41 and 91. O2 ground wasn't problem. Sun is finally out today so I'll be putting some miles on the car. Not sure when I'll report back since baby #2 is on the way any day now...

Gearbanger 101 · Oct 3, 2014

You are pulling the battery cable after each attempt at fixing your codes, right? The ECU can store codes in memory and still have them show up on your scanner....even after they're fixed. You need to clear the ECU each time.

dz01 · Oct 3, 2014

Gearbanger 101 said:
You are pulling the battery cable after each attempt at fixing your codes, right? The ECU can store codes in memory and still have them show up on your scanner....even after they're fixed. You need to clear the ECU each time.

Yes, typically I pull the negative cable for 30 mins then reinstall. This past time it was off for probably 2 hours.

Fixed Idle Problem, But Now Stalling At Abrupt Stops?

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