Recently I have had a problem with pinging on acceleration when the engine is a cool 150 degrees. I have not changed the timing in a long time and it never used to do this.

Also, as long as I drive moderately, the car runs smooth. If I get on it, it accelerates good at first and then will be really rough and choppy, even after slowing down and parking at idle.

My plans are to:

change the fuel filter, check the exhaust for holes.

the plugs are good

Anyone had this problem and what did you do to fix it?

Much Thanks.

 

sounds like common detonation with the pinging you have on acceleration. What grade of fuel do you use try high octane I use it all the time with my 88 iroc. Also your knock sensor maybe bad and the ecm cannot advance the timing appropriatley to keep the a/f ratio at a constant. The other item which happened to me was my electronic spark module was junk and the ecm in that case could not advance the spark timing and the car would fall flat on it's face. Hope this helps

 

Reply to thread posted I apologize I did not view your engine to be carbeurated itself though still sounds like detonation

 

I always use the highest octane fuel. It doesnt make sense for it to ping and then run ragged especially when it is cool.

 

it does sound similar to what happened to me when I drove home w/ spun bearings (not to scare you lol). But the knock sensor just goes wild when it senses knock, it will retard the timing for some time. This obviously makes the engine run like crap. And having it run that much retarded CANT be good for the engine lol.

 

If the additives in the fuel don't keep the valves and cylinder heads clean carbon builds up, and increases compression slightly, this can cause pinging at higher loads/head temperatures.

 

I replaced the fuel filter and plugs for the hell of it. Still pinging and bogging down on acceleration. Timing is good too. I hear a popping noise on the drivers side in the engine bay too when I really mash the pedal. Any ideas what the popping noise could be? Could the headers or exhaust be clogged up? I have dual exhaust with two mufflers, no cat.

 

why dont you take the valve covers off and give a looksy.

 

What type of thing would I look for?

 

I worked on it this weekend and messed with timing, boosted fuel pressure to be sure it wasn't lacking fuel and to be sure the fuel pressure regulator wasnt clogged.

It still runs like crap when I try to accel. It idles fine. But when I stomp on the gas, the car knocks, shakes like hell, doesnt go anywhere and feels like it's gonna fall apart. What the hell could it be???

Could it be the ignition box going out?

 

"But when I stomp on the gas, the car knocks, shakes like hell, doesnt go anywhere and feels like it's gonna fall apart."



As what sellmanb stated, my 301 acted the same way with a spun bearing. I thought it was an ignition/fuel problem as well, until a couple of days after the first symptoms showed. Complete engine seizure at 130kph on the highway. It was a quick stop.

Pulled the bottom apart, and two of the con-rod bearings (what was left of them) were like soda crackers, very crumbly (is that a word?)

 

Damn that sucks. You are probably right...mine's probably the same. The next car I buy is going to remain stock with upgraded parts. This engine swap to a totally different moter and fuel system is a crap shoot, and an expensive one.

I appreciate the replies.

 

That had to have been scary! That's one of my big fears with my new engine...


You should get a mechanical oil pressure gauge, and read it while you're driving, or attempting to atleast. Or even just revving it in park. Though it'll probably be worse when you drive it.

 

Never saw this mentioned.....


Did you look at the cap and rotor?

When was the last time they were replaced?

 

The cap and rotor were checked and cleaned about 2k miles ago. But I'll check it again. It cant hurt anything at this point.

thanks.

 

I checked all internal parts of the distributor. Everything is clean and intact.

I made sure that the heaviest springs were on for a slower advance. Also that the biggest bushing was on for lower total timing.

Here is how yesterday went after the above was done...

Decided to unhook the vac advance - almost no ping, but dead acceleration. This vac advance is not adjustable.

Advance the timing - better take off, lots of ping back.

After tweaking and messing with it a few hours, got it decent at low and medium rpms without vac advance.

Decided to try to advance it one more time - I hear a noise under the cap and feel a thumping inside. Motor starts running erratically and wont stabilize, the tach fluttering around. The fuel pressure at idle is steady at 7lbs. That's what it's always been, so it cant be a fuel delivery problem.

Now, no matter what I do to the timing, the engine runs ragged.

I looked under the hood in the dark with the engine running and saw no arcing.

My next move is to install a new GM distributor. If that doesnt work, I guess I'll be taking it apart. Any other ideas? BTW, the engine only has 12,000 miles on it. The distributor only has about 8,000. I have always had the 'almighty' Mobil 1 in it.

 

Is it possible that the vacuum advance mechanism is not retracting during WOT? At WOT the manifold vacuum drops to nothing and the "vacuum advance" is more like "no-vacuum retard". It does this to avoid pinging under a load (which sounds like your problem).
I hate throwing money at a problem, so I would suggest a junkyard distributor for diagnostic purposes. You got any friends that might have one lying around?
"I hear a popping noise on the drivers side in the engine bay too when I really mash the pedal. Any ideas what the popping noise could be?"
A burnt valve maybe?

 

a thumping under the distributor cap?

take the cap off and take the rotor off... it sounds like your rotor just blew up inside the cap.

 

Everything still looks in good shape under the cap. If another distributor doesnt work, I will just take it back and then begin disassembling the motor. If it comes to that and gets to be something serious, I'm going to buy a new motor and kiss this one goodbye because if it turns to junk after just a few thousand miles, I'm better off getting rid of it.

thanks for the suggestions.