[Poppy]

What would cause an ignition ping in a 1999 4.6L with COP ignition?

No codes.

I accellerated onto the highway that was on a long upgrade.
When I got to approx 60 mph I noticed a strange sound, and by time I got to 80 mph, I had rolled down my wiindows and realized that it sounded like the engine was pinging. I let off the gas so that it was not accellerating anymore and it instantly went away.

I jumped on the pedal a couple of more times and it did not reoccur.

Thoughts?

 

[Boghog]

Off the top of my head,it could be bad gas,EGR engine temp,defective knock sensor,a vac leak that leans the mixture down,ign timing.How's tha for a start.Were you towing anything?

 

[Poppy]

Let's see.. drove 130 miles this morning no issues. Filled her up at a station that I fill up at more often than not, and parked her for an hour.

Drove 20 miles, and parked for an hour. Drove a mile or two and got on the highway. Its about 60 F out, so I guess the engine was at about 80% operating temp. No I wasn't towing anything, and I was the lone passenger.

It has distributorless ignition system with COPs the ignition timing is controlled by the PCM. Am I missing something there? I know that my first thought went back to the old days... ignition timing.

 

[Boghog]

Stick a vac gauge on your egr and see if it's working under load.And could you have been in to high a gear going up that incline at too low an rpm?

 

[Poppy]

I don't unserstand how to check the EGR with a vacuum guage.

Here are two pictures of mine, please explain how I would do that.

 

[Boghog]

Connect a long hose to the EGR valve hose so that you can monitor it while driving.Splice in with a T fitting.This way you can see if the EGR is getting the right amount of vac while driving in the conditions you mentioned earlier.Also if you have a hand vac pump apply to the egr to see if it holds vac and doesn't leak.

 

[Poppy]

Well I didn't do quite what you suggested but this is what I did.

I started the car up and while it was still cold, I checked for vacuum at the EGR. There was none.

I then pulled vacuum on the EGR valve. It held vacuum, so that is good, and the engine idle dropped, and stumbled a little.

I seem to have a mental block regarding the EGR system and how it works.

I scanned some info on it yesterday, and noted that when it is dumping exhaust gases that the timing is retarded a little bit. (If I read that correctly)

One other thing that I failed to mention is that I do have a cel on for a Cat below effenciency, I forget which bank, not that it would matter. Does that play into a retarded timing, or anything to do with the EGR?

Sorry if this is confusing. I certainly am confused, or at least lack knowledge and understanding.

 

[Canuck623]

When you pull a vacuum on the EGR valve with the engine at idle the resulting vacuum leak would be large enough to stall the engine. If your idle just changed a little the passage on the intake side of the valve could be plugged. If the intake air does not have the right amount of exhaust gas in it that will cause a ping.

 

[Poppy]

Canuck623,
To my surprise, when I pulled the vacuum hose to the EGR, there was no vacuum. Could it be that there is a PCM controlled switch that controls the vacuum? OR should I be looking for a vacuum leak?

 

[Poppy]

So it seems that there is some EVR solinoid. I just don't know when to expect it to call for vacuum so I can test it.

 

[electro]

Rather poor illustration...
I'll keep looking.

 

[Poppy]

LOL... Thanks electro. I just read that and my eyes glazed over.
Oh boy... gotta get back to my real job Thank God for that!

 

[phantom]

I agree about the egr system may not be allowing enough egr gas to recirculate and cause ping. Also i was thinking about carbon build up on the pistons.Have you ever performed an induction service and injector flush ? There is also a way to limit spark advance when the pcm is reprogramed on some models.

 

[Poppy]

I don't know what an induction service is, but yeah I did have my injectors cleaned I'm guessing at 120,000 miles, I'm at about 165,000 now. I had them out and replaced the O rings last summer, about 10-12,000 miles ago.

I put on a new intake manifold at that time due to the nylon plastic cracking and leaking coolent.

 

[phantom]

An induction service is similar to the seafoam treatment but it is sprayed down the throttlebody while the vehicle is running then allowed to set and then driven to blow it out so to speak.

 

[Poppy]

OIC... I cleaned my throttle body, and IAC when I replaced the intake manifold. I guess that is similar. I don't recall, but if there were visible EGR ports, I cleaned them.

 

[mark v]

I know a bad carbon build up on the pistons and valves will cause this issue even if everything checks out in perfect working order.

 

[Boghog]

One thing to also consider is the engine my be running too lean due to the catalyst CEL.If the PCM senses the CAT isn't operating effeciently it will reduce injector pulse width to lean the mixture as to not overheat the Catalyst.

 

[Poppy]

I don't know if I will EVER fully understand the EGR system, and BogHog, I wondered if the poorly functioning CAT might contribute to the problem.

Here is another wrinkle, could it be that I have an underperforming coil?
I don't like to run the AM radio because I hear a ticking in it that increases in speed as the RPM increases. Would a poorly performing coil cause that? and if not, what would?

 

[NcFurnitureman]

My vote is for bad gas especially if it hasn't happened since. Does octane boost work? I have never used it.