Spastic, spontaneous heavy pinging...

[King_V]

Alright, this has me puzzled. My box is 100% stock.

Last Thursday, I was driving home from work. Spent about 20 minutes or so doing around 70-75 MPH . . took an off ramp from the freeway, and thus slowed down to about 35 or 40 or so. Then lightly stepped on the gas, barely feathering it, to maintain speed.

I was greeted by some serious rattling - it lasted maybe a half second, and stopped abruptly before I even had time to react and let off the gas. It didn't taper off and stop, it was quite literally like someone flipped a switch.

Saturday, something similar happened - not as fast in terms of the speeds I was driving, but was going steadily at a highway speed, then slowed down, and again, while still rolling, gave it a touch of gas, and the same major rattling/diesel-noise, that stopped very abruptly.

Later Saturday, I had the same symptom occur, but this time, I was at a traffic light, and when it turned green, I pulled away gently. Same thing - about a half second of VERY noticeable rattling, then it abruptly stopped without any change in throttle position on my part.

Hasn't happened since - and this was on two separate tanks of gas (re-filled Saturday morning).

What's going on? If this were a vacuum/weight operated distributor, I might suspect that it was getting stuck briefly with the timing too far advanced.

Didn't happen at all Sunday, which surprised me because it was quite warm outside, and I figured that would make it more likely to happen.

Thoughts?

[Southern_Pride]

EGR sticking it sounds like,

[gadget73]

yeah that could be, or the fuel vapor thing. Sounds like its going lean briefly either way.

[Pesty351]

Check your starter see if its loose. I've had that happen in a f-150 before couldn't figure it out to save my life. I just happened to grab the starter when I was under the truck and the thing was loose as hell. I didn't ever have a problem starting either.

[King_V]

Uh, is the EGR valve that thing on the front of the upper manifold (ie: opposite of where the IAC motor is)?

And, what's the fuel-vapor thing?

A bit more information . . .

As of today, it's more consistently happening.

It seems that if I:
Feather-touch the throttle: No problems
Push more than about 10-15% open: No problems

Something more than feather-touch but less than about 15% throttle opening: Lots of pinging

Today it was doing it fairly regularly following that rule, then later on it almost stopped doing it completely.


There have been other symptoms that started a few days before the pinging, but I have no idea if it's related or not.

I've noticed that when I start the car, cold, it briefly idles at higher speed, which is normal, then I guess about 15 or so seconds into it, settles down to normal idle. But in the past few days, when settling to normal idle, it acts like it's about to stall, then surges like the system is trying to prevent stalling, starts to settle down and is about to stall again, etc., Lather, rinse, repeat.

Finally, up until recently, while sitting in the car with the car idling, in gear or in park/neutral, felt absolutely rock-steady. In the past week or so, however, I've noticed a slight bit of trembling under the same circumstances. Maybe every few seconds, but somewhat irregularly.


I have no idea if those other symptoms are related, help point in a specific direction, or are a total red-herring.

Does this help narrow things down?

Thanks again for any pointers.

[P72Ford]

Mine started that last summer. I have been running 93 since, and it doesn't ping anymore.

[gadget73]

yes, EGR is the flying saucer opposite the IAC. If they get carboned up, the valve will stick. Could also be the vacuum modulator is not modulating, and dumping you to full open. I had that problem too, though it had different symptoms on my car. Maybe try unplugging the green vacuum line to see if anything changes.

Fuel vapor thing is a round canister looking device hanging somewhere between the passenger fender near the battery and the engine. Probably should be right near the fender, but sometimes its just sitting there in free space under the AC compressor. Unplug it and see if it makes any difference. I'm betting it won't, but its quick and easy to eliminate as a possible problem area.

[King_V]

Hmm, I'm guessing that if it IS the EGR, then it's likely stuck closed or not opening enough... since the more exhaust gas that goes in, the lower the combustion temperatures will be.... which is why when EGR was put on cars, ignition timing could be much more aggressive.

At least, that's what I understand the theory to be, at any rate.

[King_V]

Ack . . can't even test things now. The problem has simply gone away.

I almost HATE when that happens. But if it's an EGR issue, there should be stored codes, shouldn't there?

(I've just gotten an Actron that does OBD-I, OBD-II, etc., and has various adapters for Ford, GM, and Chrysler. I should probably actually finally put a battery in it and USE the darn thing!)

[Lincolnmania]

check the voltage on the coolant temp sensor next time it acts up