'90 Vette "pinging" when hot

[Steven C.]

My friend has a '90, bone stock except for no catalytic converters. Low miles, excellent maintenance, premium gas (93 octane).

He mentioned that whenever the temp gauge shows above 220, typically when idling at a stop light or during a parade, if he accelerates there is a lot of "pinging". Not a problem any other times, and I gather that the car isn't overheating, my understanding is that the newer vettes typically operate above 220.

Is this a common problem; and/or is there a simple fix...adjusting/replacing a sensor or switch, changing cooling components, computer settings?

Thanks in advance,

Steve

[Clem Z.]

Re: '90 Vette "pinging" when hot

My friend has a '90, bone stock except for no catalytic converters. Low miles, excellent maintenance, premium gas (93 octane).

He mentioned that whenever the temp gauge shows above 220, typically when idling at a stop light or during a parade, if he accelerates there is a lot of "pinging". Not a problem any other times, and I gather that the car isn't overheating, my understanding is that the newer vettes typically operate above 220.

Is this a common problem; and/or is there a simple fix...adjusting/replacing a sensor or switch, changing cooling components, computer settings?

Thanks in advance,

Steve

he will need to have a "scan" run to check out to see if any sensors need replacing.

[Ken A.]

Re: '90 Vette "pinging" when hot

How does he get away with no cats? Probably missing o2 sensors or using defective sims. If he keeps driving it, he will soon have major engine damage. Read the owners manual & pull the DTC's.

[Steven C.]

Re: '90 Vette "pinging" when hot

How does he get away with no cats? Probably missing o2 sensors or using defective sims. If he keeps driving it, he will soon have major engine damage. Read the owners manual & pull the DTC's.

Florida, no inspections...

Steve

[Steven C.]

Thank you, Clem and Ken

Thanks for the input.

Steve

[Joe L.]

Re: '90 Vette "pinging" when hot

Florida, no inspections...

Steve

Steve----

I agree with Ken on the catalytic converter situation. Modern engines (and, 1990 is well within the period I define as "modern") are "integrated systems". You can't just remove the catalytic converters without causing other OPERATIONAL problems, short term or long term. I would not even consider removing catalytic converters from my cars even if I could do so with impunity.

In any event, in this case his problem may lie with the knock sensors. These are the the primary component responsible for adjusting engine timing to prevent knock under all conditions. Of course, it could also be something "upstream" of the knock sensors, but the knock sensors are a likely culprit. Also, the knock sensors are quite fragile and can easily be damaged.

The sensors for his 1990 application are GM #52493120, aka Delco #21-392. About 45 bucks, each. I believe 1990 uses 2.

[Clem Z.]

Re: '90 Vette "pinging" when hot

Steve----

I agree with Ken on the catalytic converter situation. Modern engines (and, 1990 is well within the period I define as "modern") are "integrated systems". You can't just remove the catalytic converters without causing other OPERATIONAL problems, short term or long term. I would not even consider removing catalytic converters from my cars even if I could do so with impunity.

In any event, in this case his problem may lie with the knock sensors. These are the the primary component responsible for adjusting engine timing to prevent knock under all conditions. Of course, it could also be something "upstream" of the knock sensors, but the knock sensors are a likely culprit. Also, the knock sensors are quite fragile and can easily be damaged.

The sensors for his 1990 application are GM #52493120, aka Delco #21-392. About 45 bucks, each. I believe 1990 uses 2.

i have been running my 88 silverado 2500 without a cat converter since new 150,000 miles ago with no problems. i removed when the truck was new beacause i was using leaded gasoline that was still available at that time.

[Joe L.]

Re: '90 Vette "pinging" when hot


Dave----


That's another VERY great possibility. An aftermarket PROM fits right in with the removed catalytic converters, too. I'd NEVER use an aftermarket PROM. NEVER.

[Jim T.]

Re: '90 Vette "pinging" when hot

Steven you mention parading function on your friends Corvette. If he is sitting in traffic a lot or parading and not using the air conditioning, the coolant fans will most likely come on untill the temp gets to 210-220. Leaving the air on will keep the fans pulling air through the radiator in parades.

[Clem Z.]

Re: '90 Vette "pinging" when hot

Steven you mention parading function on your friends Corvette. If he is sitting in traffic a lot or parading and not using the air conditioning, the coolant fans will most likely come on untill the temp gets to 210-220. Leaving the air on will keep the fans pulling air through the radiator in parades.

GM keep changing the parameters for the cooling fans as now they use variable speeds BUT my C-5s fans came on at 232 degrees unless i had the A/C on

[Steven C.]

Thanks Clem, Joe, Dave, Jim!

I'm pretty sure that it is stock PROM. I'll let you know what the result is. Thanks for the input.

Steve

[Clem Z.]

Re: '90 Vette "pinging" when hot

sometimes on older cars the coolant temp sensor get coated with some junk that prevents a true temp reading so that would also cause pinging if it read the coolant temp was lower than it really was and did not reteard the timing

[Stephen B.]

Re: '90 Vette "pinging" when hot

the knock sensor also needs to be torqued correctly if it is to tight it will not operate correctly and send a low or no knock signal steve

[Steven C.]

Knock Sensor fixed it! Thanks to all.

My friend changed his knock sensor, and it completely resolved the problem.

Thank you to everyone who helped diagnose this.

Regards,

Steve