Hi, I've been trying to track an intermittent stalling issue on my '99 GC for 3 years.

- it only stalls when slowing down i.e. approaching a stop or turn
- it only happens in winter and only on very cold days <-10C
- it is always restricted to very short timeframe i.e. it may stall 1-4 times in a 5 minute interval and then be fine for the rest of the day
- it will never happen once the engine is fully warmed up. Obviously this varies with ambient temp but it's safe to say that it will never stall after it's been running for 15 minutes.
- it needs to sit unused >10 hrs (or overnight) before it will stall again
- it has only happened once for me but many times for my wife - there may be a driving style connection but I've not figured out what this is yet
- after stalling it restarts fine but may be a bit rough for up to 15 seconds or so

I've done the usual checks and routine tuneup stuff (plugs, leads, filters, new battery etc). I have also checked/cleaned the throttle body, IAC, TPS, vacuum connections, error codes etc.

My scanner has shown no codes until now but I did have a possible clue a couple of weeks age week - an EGR code P0401 which cleared itself. My FSM indicates that feedback for the EGR test is the O2 sensor so I'm guessing that this could also cause this code. Also, since the EGR is tested only once any intermittent failure would have to coincide with this test.

Can the EGR or O2 sensor cause this sort of stalling without seeing any persistent error codes? Is there an easy way to temporarily keep the EGR closed without blocking it in order to rule it out e.g. is disconnecting the electrical connector sufficient.

Could it be vulnerable at the point when the ECM transitions from defaults to closed loop control?

Any other ideas what may cause this sort of stalling behaviour?

 

You bet an EGR can do this

Read this post

http://www.ricksfreeautorepairadvice...-3-3l-and-3-8l

 

Thanks for the link. Like the more detailed procedure in the FSM these test instructions are good for a totally broken EGR but I don't think they will help find one that is intermittent - occasionally sticks (possibly partially) open and at a certain temperature which would account for the symptoms I see.

Short of a plate over the EGR tube what is the best way to temporarily disable it in the closed position? I would like to see if it still stalls when there is no possibility of recirculation.

I don't intend to start throwing parts at this because there are just too many possibilities.

 

How about getting yourself a factory service manual. If you want to eliminate the EGR valve, just disconnect the vacuum line and leave it off for a while. You will set a code but then you can eliminate it as being the cause. Additionally The EGR valve can be tested buy drawing a vacuum on the valve's port. It must open and hold a vacuum. with the engine running, pull a vacuum and the engine will stumble, or even stall. However this is only ONE small possible problem, You could have a bad IAC, PCM, a vacuum leak, and I'm sure a lot more.

 

Yes, I do have the factory service manual but as I already pointed out it describes how test a clearly broken EGR and not one that, for example, is intermittent or a bit sluggish to close over a certain temperature range. I have disconnected the vacuum from the transducer and will wait to see if it will stall again. My assumption here is that if the engine idles OK then the valve is fully closed and will remain in this position.

If it continues to stall I will know that there is another cause and start to look elsewhere.

I realise there are many possible causes which is why I'm not randomly throwing parts at it. For now I'm just looking suggestions of things to try that will identify the issue at a system level. Once I can ascertain what is causing the problem at the system level I can then look at the individual components in the control loop.

 

I know this is an old thread, but my 99 Caravan is doing exactly the same thing.
No codes coming up, only running rough when temps are below 20 degrees F.
Local mechanics can not figure it out, getting expensive.
I was hoping that dirtmover would read this, and let me know if he found the problem.
Thanks for any help
avery

 

Send them a pm.

 

I would suspect/ replace the air intake temp sensor and the upstream O2 sensor.

This sounds like a fuel mix issue.
And only at very cold temps?
Sounds like the PCM is getting bad input from a sensor.


My thought,
EZ1

 

I will send him a PM.
Thank you
avery

 

So, with the EGR disconnected (unplugged the vacuum line and plugged the nipple on the intake) it ran stall free for 8 weeks. This was enough for me to conclude that the EGR was the problem. I've changed the EGR and it has not stalled since.