Pinging or detonation under WOT

WhiteVert

Registered User
Mind you I am new to the SC world, but not to forced induction.

I just picked up a 1994 SC auto and it seems to run fine at idle and under a light load but when you punch it from a roll it wants to detonate to a serios note.

It was owned by a good friend of mine and it belong to his wife before they were married so I have no reason to not believe any thing is truely wrong with this car.

He stated that he paid a local shop to install new plugs and wires not that long ago (within the year), and I know it has sit in his garage for the past 6-8 months with little to no drive time on it. ( AKA poor gas)

What are some of the basics I should be looking at beside the normal tune up or a 100K mile service. Also had the headgasket recall performed on it by a Ford dealer.

Any thought of where to start?

Thank you

Butch
 
Bad Gas

Mind you I am new to the SC world, but not to forced induction.

I just picked up a 1994 SC auto and it seems to run fine at idle and under a light load but when you punch it from a roll it wants to detonate to a serios note.

It was owned by a good friend of mine and it belong to his wife before they were married so I have no reason to not believe any thing is truely wrong with this car.

He stated that he paid a local shop to install new plugs and wires not that long ago (within the year), and I know it has sit in his garage for the past 6-8 months with little to no drive time on it. ( AKA poor gas)

What are some of the basics I should be looking at beside the normal tune up or a 100K mile service. Also had the headgasket recall performed on it by a Ford dealer.

Any thought of where to start?

Thank you

Butch

As you know, these cars are highly fuel-sensistive. For a first step, try to get rid of the bad gas by topping off with 93 octane when it drops to 1/2 tank. That will improve the fuel mix without sucking the bottom of the tank, in case there's any moisture in the tank. Dump in a couple of bottles of Heet or equivalant every time you fill. After you top it off 3-4 times, run it all the way down, and fill with 93 octane. That should take care of the fuel question.

I did exactly this when driving my white car home from Michigan. It had sat for 4-5 years, and the fuel was pretty bad. After about 2-300 miles the pinging was gone, and it was back up on power.

At least after eliminating the fuel question, you'll have a basline if the problem still persists. I'd also change the fuel filter after doing the above.

Good Luck,

JD
 
Thank you

JD

Thank you for your response, I have yet to spend any time with the car beside the drive home accross town (maybe 3.5 miles at best). I normally do an all out piece of mind tune up on used cars that I buy and no I have not run any type of diagnostics. At this point with no CEL I did not see the point. I will be sure to top off the tank with the best fuel, 92 octane in this area along with some tolelyne (know to bump octane).

Are these car really that sensative to octane?

The other forced induction cars I have or have been around are GN's & TTA's and they are or do not seem to be that sensative but then again I think they have a much better IC ( IE bigger & some what more effecient per stock form) as far as cooling the intake charge. Dont get me wrong these are diffently two different beast and should be treated as such.

Butch
 
These things are fuel-sensitive. Maybe it's the way the fuel "sees" the supercharger vs. a turbocharger. There are some people on here who can answer this more completely.

Just noticed you're in Lawrence. We used to live in Wichita, and later, Cottonwood Falls before we relocated to S. TX. My wife's from Hays, and still has a lot of family in the area.

Sounds like your problem will be fixed with good gas. Just keep diluting it down, and use something to help absorb any moisture.

JD
 
I think the problem could be bad gas, but if that doesn't fix it, I would look at the ignition. Maybe a plug wire came loose. Or maybe there is moisture inside the coil pack boots or something.
 
S Mazza

I will look into the coil packs but, I do not think it is a loose spark plug wire because it idles fine and smooth. I do however think it idles on the LOW side. If that could play into the situation.

JD

Yep, been in or around Lawrence my whole life. Fun little town, the University sure keeps things moving. And I am thinking I have been on a beer binge or 2 in Hays with a buddy that lived in Hoisington. Wished I could remember, it's just to darn fuzzy of a memory. :)

I will get back with all of you when I get more to report...............

Butch
 
Another thing you might check is the heat range of the plug. I don't know SC's, but I know high performance engines. With high dynamic compression (either by static CR/cams or forced induction) you need a colder plug to resist pre-ignition. The 3.8 SC and the normal 3.8 SHOULD use different heat ranges. If the wrong plugs were put in you can have major pinging issues. With NGK plugs, the number designated the heat, and higher is colder (I raised my CR in my Lancia from 8:1 stock to 12:1 and had to go from a BPR6ES to a BPR9ES).

Also, oil passing by the rings will cause detonation to some degree. Racecars sometimes use the high velocity exhaust gasses to extract gasses from the crankcase, in place of a PCV setup. This attempts to keep the pressure in the crankcase lower than the combustion chamber at all times, and keeps the oil from entering the combustion chamber. It would be interesting to rig up a similar setup on an SC. It would go in place of the PCV system and keep oil from circulating through the supercharger and intercooler.

Other than that, bad gas for sure. Toluene is what F1 uses and is one of the 'T's in TNT. Great octane booster and is MANY MANY MANY times more potent than the crap octane boosters available legally in stores. Toluene is also known as Tolulol and is available in 1 gallon and 5 gallon containers from paint stores, I got mine from sherwin williams. It can be a little hard to get, it is not normally out on the sales floor as it is also used in the process to cook up meth. Just ask for it. I think I paid $15 for a gallon, which will raise 10 gallons of 92 up to 94.2. The octane boosters in stores are measured in "points", which a point is equal to .1 of an octane number.

Good luck, let us know what fixes it,
Jason
 
I had a loose plug wire once that made the car idle fine, but as soon as there was a high load on the ignition, it missed. That's why I mentioned it.
 
Greenwood

So you know about the toluene, I used to use it in my Grand National to up the octane until I started using a isopropyl injection. It was a much easier set up and most of all much cheaper. The best I could get was a 5 gal. can for around $25.00 and I think it was Sherwin Williams also. Did you get to sign the DEA form also?

Boy, I really hate the idea of digging into it to see if the plugs were of the right nature, ( have no clue to the brand of plug installed) and I will if I have to. For now I think I will let the 1.5 of ice and 4 inches of snow go away before I take it out. Got plan, just need to execute it......


Butch
 
The other thing that may do it is dirty injectors. A dirty injector will have a poor spray pattern with larger fuel droplets. Larger droplets don't atomize well, leaving you effectively lean. A lean mixture will burn hotter, quicker and will ignite more easily. All bad if you are fighting detonation.

I would start with octane booster to make the car driveable, but that is only a band-aid.

Jason
 
If you have a loose wire at the spark plug you should be able hear it arcing against the spark plug.

I have experienced a plugged catalytic converter that caused pinging on harder then normal acceleration. Anything that effects normal operation of how easily air enters the motor and exits will cause pinging. In your case this probably isn't the problem unless the air filter is severly dirty.

chris
 
Time on my hands

I had time to spend with the SC the other day. I bottle of HEAT a top off of 92 octane fuel has just done wonders for the ole girl. The spark knock is all but gone, I think that another couple of tanks worth and she will be as good as a bone stock SC can be. As soon I as can get some more time I will swap out fuel filter and upgrade the sparkplug wires to something larger than the 7mm. I still plan on a complete tune up. I want the car to be as good as it can be mechanically before I start any modifications performance of visual.

Now on to the next problem that has surfaced, I will post it in another thread.

thanks to all

Butch
 
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