Pinging Problem, Tracing it's cause

Hi,

With my '98 Windstar 3.8 moderately bad pinging has been going on for a while. I had the wires and plugs changed a few weeks ago, with no improvement. The old plugs didn't look bad to me, nothing strange going on. There's no CEL. Today I started doing some testing.

I've checked that the EGR valve holds a steady vacuum, and with the vehicle runnning, applying vacuum makes the engine run rough. The EVR valve I believe is out of spec- resistance is under 10 ohms, and there is mild vacuum to the EGR even with the engine cold. I just started testing the DPFE, it's receiving 4.5 volts with the KOEO, but I haven't been able to backprobe the running voltages yet.

I'm wondering if the EVR might be stuck partially open but not all the way, causing the pinging. I don't know how to check for too hot coolant, but my temperature gauge remains steady and the fan doesn't kick in much, or at all that I've noticed. As far as checking for vacuum leaks, is it necessary to pull off the wipers and cowling to get at the back of engine hoses? And am I correct in assuming that the EGR valve is ok? Any suggestions would be appreciated.

Thanks,
Michael

The EGR valve is quite reliable on the Windstar.
There is normally some SLIGHT vaccum to the EGR valve at idle, but not enough to open it.

A likely cause of pinging is a slight vaccum leak, lots of possibilities there.
Can you direct the air inside the vehicle to the dash vents and to the floor?,....if not, there is a likely vaccum leak preventing the vaccum to get to the diverters to direct the airflow.
No vaccum will have all the air going to the defrost vents regardless of your selection.

Check the PCV vaccum line, after all these years it is possible that oil has broken down the hose material.

I am guessing that you don't have the Check Engine Light (CEL) on, which would indicate code(s) being stored which would help lead you to the source of the problem.

I would also change the fuel filter (under the vehicle just ahead of the rear, driver's side tire).
Also run some fuel system cleaner in the next 1 or 2 tanks of gasoline.
I found that, out of MANY brands I tried, Berryman's B-12 Chemtool (in the metal can) seemed to clean up my fuel injectors the best.
Dirty fuel injectors can cause a lack of fuel to one or more cylinders.

Another possible cause is carbon build up inside the cylinders, which has the end result of increasing the compression on each stroke.
The best solution for that would be to use a Mid Grade or Premium Grade of gasoline.
Which makes me think of something else......try another brand of regular gasoline to see if that makes a difference.
I have found that different brands of gasoline can make a difference.

Another thing, along the lines of the EGR system.
Clogged EGR ports.
The normal pattern for them to clog is that they clog the worst on the driver's side of the motor first.....closest to the EGR valve....and then the 2 cylinders on the passenger side have the least amount of clogging......up to the point (over time) that these 2 cylinders are the only ones with working EGR ports.
What this means is that at that point, ALL the EGR flow is going to 2 cylinders, causing the misfire that leads you through a troublshooting process that ends up with the upper intake manifold being removed and the EGR ports being cleaned.
I can (in my mind) see where before this clogging reaches that point.......your cylinders are getting different amounts of EGR flow......which causes things to be out of ballance, which could (maybe) cause other symptoms, like pinging.

The EGR port thing made me think of a little saying for my Windstar.....A upper intake lifted is 6 EGR ports cleaned.

wiswind,

Thanks for the reply and information, I now have a list. There's no CEL, and the fuel filter was just changed along with the plugs and wires.

I checked the heater blower and got air circulation up top and at my feet, although the foot blower air was only on the passenger side. And I went and bought the pcv valve and line from Ford to put in tomorrow or Wednesday. I have been noticing that when I restart the vehicle after I was on the road awhile, that it runs rough for a minute or two. The last time I had this symptom it was a leak in the pcv line, so if I'm lucky it's the same thing.

If vacuum leaks aren't the cause, I guess the next thing might be pulling the EGR and checking for carbon build up. I'll post as things progress.

Michael