I've got an 85 with the L98 iron head engine. I just did a little run from New Orleans to Brownsville (about 800 miles each way). The car ran fine but the temps were high. If I pushed the throttle a little too hard with the engine temps at 199, I would get that pinging noise. I'm running premium and it looks like everything is working fine with the engine. I just tried adding some Purple Ice to the coolant to see if this will ease the problem.
Any of you have similar problems? What was your fix?

 

199 is a OK Hwy temp if your knock sensor is working you should not get any pinging. I would check the timing to be sure its right. Adding things to coolant is not going to help your temps are fine.

 

Set your base timing to 6 degrees BTDC and check the connection on your knock sensor. Your temps are fine, and there is no reason you should have to run premium fuel in a stock L98 if everything is working correctly.

 

as stated

 

I had the same problem on my 86,replaced the knock sensor and connector all is well.

 

I've already done the timing, knock sensor and all that. This car has a replacement engine in it. I have no idea what engine they put in but it will not run on regular gas and will ping with any temps above about 190. I put in a 185 thermostat and when the weather is cool, it runs great. The cooling system in the car is built to maintaine about 200. With the outside temps at 100, there is just not enough cooling to get it down to 185.
The Purple Ice is a wetting agent that keeps small bubbles from forming around the cylinder walls and heads. Seams to help a lot. No pinging at temps up to 195.
The ping only happens under hard throttle. If you really nail it and the transmission kicks down, it will not ping. Under normal running (even with hills) it will not ping. If the temp is low enough, it will not ping. If I could still get 98 octane gas I that that would be fine too. If I had the aluminium heads I think that would be fine too.

 

check your oil level,,,,,might be a little low

 

Oil level checked good.

 

Why did you say that? I thought it was necessary to run premium? I know my fuel filler area has it etched in to run premium.

 

If the knock sensor was working correctly, it would retard the timing until knocking (pinging) was eliminated no matter what conditions it occured under. I still suspect you have an issue with either the sensor, connector, or associated wiring.

You say the engine was replaced, but you're unaware of what components they used....have you run a compression test? I'd be interested to see the readings. Maybe a cylinder or two with excessive carbon buildup?

Try this....hook up a timing light to the car....leave the ECM connected. Have an assistant run the car up to 2500 rpm. Smack the engine with a rubber mallet as close to the knock sensor as you can safely get....tell me what your timing does. Also, measure the resistance between the wiring on your knock sensor to the ECM.

I reiterate....there is absolutely no reason that your engine should be detonating even up to 230 degrees. I'm running 10 degrees of base timing on my high mile 84, live in an extremely hot climate where the car regularly sees a constant 215 degrees, use regular fuel, and have NO detonation under any condition. The heat above 195 may be causing a spike in electrical resistance on an already weak connection to your knock sensor, but it is otherwise unrelated.

Something is amiss on your car, and it isn't the cooling system (assuming your gauge is accurate).

 

The 1985 L98 has 9.5:1 compression. Why would that need premium?

 

Didn't it only have iron heads which makes it more prone to detonation?

 

I've done the hammer test and the system retards the ignition. I may have to change the ignition modual, it does not look like OEM. Any ideas here?

 

You may check the installation of the knock sensor. I read somewhere that you should install it in the block dry, without any thread sealant. You may also try screwing it into the block farther if possible. I am assuming that these procedures make it more sensitive to detonation.

 

Yes. A few actually. Run a compression test and post the results of all 8 lungs. I'm wondering if the replacement engine may be carboned up. Not likely, but easy enough to rule out.

Also, tell me how many inches of vacuum you have at idle....I'm specifically looking for a lean condition that the ECM isn't compensating for. I'd also like to know what your o2 sensor is doing....any chance you have access to a scan tool or WIN ALDL? I'm really curious to see if your engine is going excessively lean at a certain temp.

Also, take a look inside the distributor cap and see if you have any evidence of carbon that could be causing a misfire. And pull that module out and have it tested.

I strongly suspect an ignition issue....but again, the cooling system isn't at fault here.

I'll be out of town with little if any internet access until the weekend. You should have it fixed by then.

 

I've been driving the car around for the last three days and can not get it to ping. Engine temps have been running normal to warm (185~200). Seems like the Purple Ice did the trick.

 

Industrial strength pain killers will mask the "discomfort"of cancer but will not cure the disease.

 

probably got some crappy gas,,,,,,i got a batch a few weeks ago,,made my car run crappy till i added some octane boster,,,g#d damm corn juice blended tree hugging crap that costs 2.50 a gallon,,,,,,,,sorry all

 

I totaly agree. This 10% ethanol gas is pure crap. I get less mileage and less performance. It has also caused food prices to go up. We don't notice it here, but in countries here people live on $1.00 a day, they'er going hungy. I want my 100 octane gas back.

 

Man over here it's 3.15g for reg. 3.55g for prem. @ 91 octane. Can't get over 91.