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What the Hell is With the Pinging?!

3038 Views 10 Replies 5 Participants Last post by  guidematic
Been driving the Seville to work lately while the Brougham was in the shop (again). HT4100 engine, the puniest engine Cadillac ever produced, runs 87 octane unleaded gasoline. The thing doesn't ping at all during my commute. It's quiet and reliable.

My Brougham is a different story.

I have to run the GOOD stuff in it and it STILL pings. EVERYTHING checks out on it. Every danged mechanic says the thing is practically brand-new. Everything is to spec or better.

So, what the hell is with the pinging? Is it really pinging? What else can SOUND like pinging under light to moderate acceleration on light to moderate inclines?

What could be easily missed on inspection? I don't recall having a pinging issue before, even running 87 octane.

I'll tell you what I think it is: EVERY time gas prices go up, quality goes down. EVERY danged time. My dad pointed this out to me and while I'm not one to believe in every conspiracy theory out there, I think he may be on to something.

I don't mind buying premium gas; it's not that much more expensive, really. But I do mind HAVING to buy it to avoid a problem I shouldn't be having in the first place. It's just a waste of money, really.

Sorry for the rant but I'm hoping someone will say, "Okay, go have a beer and relax. This is what might be causing your engine to ping, despite "sophisticated" technology to compensate for it." OR "Okay, go have a beer and relax. The sound you hear may also be..."

This site has been so helpful and I don't know that I've offered much in return except more problems. At least I give people something to talk about, even if it's behind my back. LOL

Disgusted with Myself & My Car =P
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My '93 went from silent to sounding like someone was shaking a coffee can of marbles everytime I got on the gas. Also would get the check engine light at the same time, on the highway typically.

A simple diagnosis turned out to show that the EGR valve was pretty much blocked/clogged, so they replaced that and the solenoid and all has been back to silent ever since.

I'm assuming they would have already checked that on your car, since you said EVERYTHING has been gone over multiple times, but still just thought I'd post what my issue turned out to be.
you ever check the egr crossover in the intake manifold.make sure it is not plugged. you will see the passages when you remove the carb. also make sure the egr valve is operating properly, mechanicly and electonicly. just a thought
Yup, EGR is a big cause of pinging.

1. Engine temp, bad t-stat? cooling fan not working?
2. EGR pluged, valve failed, hose broken?
3. Timing set wrong?
4. Clean chamber with X66P or X66A from your GM Dealer. Follow directions, this is very effective on chamber deposits.

307 Olds were much more sensitive to pinging than any other engine I have ever seen. To fix mine I had to remove the carb and run a drill bit down the EGR tubes. The carbon was in there hard. My long term fix was installing Brass plugs with 3/8" holes drilled in them to replace the EGR tubes. No more plugging. And a bonus of a little more HP.
N0DIH, you off ALL members should know that my entire EGR system was inspected and found "clean as a whistle." All three mechanics were STUNNED at how spotless everything is.

The timing was set to 20 degrees, factory spec. If it's changed at all it wasn't because of anything anyone has done.

One thing nobody mentioned: a bad knock sensor. I don't know if the ECM is "smart" enough to detect this. I've been told that it's probably not; just to be safe, I had all the sensors checked and everything was within factory specs.

Now, given my peculiar electrical issue, it's possible that some monkey business is at hand that ordinarily would not be. If the ECM is sensitive to this issue, it may throw some things out of whack. Likewise with any system. It's difficult to know (unless you're the electrical engineer who designed this specific system) what seemingly random effects can occur because of an electrical problem. I'm going to hope that this is the case.

I'm going to post this in my other thread but I'll mention it here: my CE light came on again tonight while on the highway. Code 53: EGR/Factory Alarm/Alternator Spike

As mentioned, the EGR is as good as it can get, at least without some kind of mod. I have no factory alarm. The alternator has been checked 4 times by 3 different people and works like a charm. It's a wiring issue.

Will the fun ever START?! =P
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I don't believe it would be a bad knock sensor. The system is not designed to live in knock. The sensor is to fix things when there is a temp problem with fuel or something. As we have learned before that when the knock sensor ckt will pull out 50% or so more timing needed to kill the knock than what timing created the knock. i.e. If the timing is at 22 degrees and it starts to ping, it might take 17 to make it stop.

ok. Lets dig into pinging. The ECM program is pretty agressive for timing. Nearly 50 degrees timing can be seen at idle (not in set mode) at times. I always had an issue with pinging around 35 mph, light load, typically under gentle acceleration.

Try this, (I am from Missouri), take a vacuum hose that has vacuum (or get a hand held vacuum pump, that is best, I have one, one of my favorite tools), and rev the engine up to around 2000 rpm. Then apply vacuum to the EGR valve. You should note that engine rpm decreases some. If the EGR isn't working, that won't happen.

Now, if it DOES work, get a vacuum gauge and put it on the EGR valve line. Rev it up, it should gain vacuum. If not, trace back to the little black box on the driver's side valve cover. There is 6 lines, 3 in, 3 out. And an electrical connector. This is nothing more than a vacuum switch. On or off. The bottom 2 are fed from manifold vacuum, the top is fed from the line that goes to the front of the carb, as you are looking at the fuel inlet, just to the right of it in between the fuel line and the accelerator pump. This is the ported vacuum port formerly used for vacuum adv, now used for EGR. Make sure it is hooked up right.

If it doesn't do you have a low restriction exhaust? That will mess up the EGR valve operation. I would recommend if you keep the exhaust low restriction, then get a PORTED EGR valve from a 76 Olds 350. I think that is the one that fits. Starting 1977, GM went to a negative backpressure EGR till 1979, then changed to the Positive backpressure type through 1990 (On Olds V8 gas engines). Make sure it is a PORTED not a BACKPRESSURE type.

If you do not have a low restriction exhaust, and you have a problem still, it sounds like the valve may be damaged or the backpressure port is not working. Remove and diagnose.

Let me know what you find.
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Another quick test. Unbolt the EGR valve, start the engine and let it idle. Remove the EGR valve and the engine should stall. If it does not, the EGR passges and/or the tubes under the carb are plugged.

I used a 17/64" drill to drill out the tubes in my '86. It pinged before, but now does not ping at all.

What about a bad smog pump? I notice it's rattling lately. Coud it cause a code 53 (EGR)?

That stupid CE light comes on during my morning commute (sometimes), when I'm at low-RPM cruising. It's like, instead of releasing the TCC or downshifting, the light comes on, forcing the TCC off.

The TCC solenoid is fine but the actual clutch itself..? Probably explains that awful bump when I come to a stop...
The AIR system is independant of the EGR and problems with either will not affect the other.

TCC solenoids are a problem on all 200 4R transmissions. They are easy to replace and relatively inexpensive. It sounds to me like you are experienceing early problems with it.

guidematic said:
The AIR system is independant of the EGR and problems with either will not affect the other.

TCC solenoids are a problem on all 200 4R transmissions. They are easy to replace and relatively inexpensive. It sounds to me like you are experienceing early problems with it.

But what you don't know (because this was posted elsewhere) is that the TCC solenoid was replaced twice, recently.
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