Hello all

Picked up my C4 on Monday fter buying it, and I notice the engine pinks quite a lot. I think Americans call it pinging?
I'm using premium fuel, but buying it from different outlets. The max octane rating I've seen so far for premium I've bought is 91, which seems low.
Are there specific gas stations that sell a higher octane premium fuel?
Is that likely my problem?

Thanks!
Fred

 

Welcome to the Corvette Forum, Fred. Do I understand that you're now in the USA to pick up your '90 Corvette, then do some touring before shipping the car to New Zeland? Sounds like a great adventure! Are you now too far from the dealer to have them check the ignition timing? That's the first thing to check for excessive "pinging" (pre-ignition). It's not good to drive the car with that problem. Where are you? There might be a Forum member right around the next corner that could probably help you!

 

Well there you go I didn’t know New Zealanders had a funny word for pre-ignition as well.
Are you in the US to pick up this Vette? If so remember that in the US fuel octane is expressed as an average of the Research Octane Number RON and the Motor Octane Number MON. So BP ultimate is marketed an Australia as 98 octane but that is RON. It has a MON value of 88 so in the US that fuel would be marketed as 93 Octane. I imagine NZ is the same as Australia and uses RON to market fuel.

 

HI Roy
Thanks for the quick reply. You are right, we've had the car serviced in LA and new tyres, and today are in Kingman, Az. The reason I think it's fuel is because when I picked the car up, it wasn't pinking. Now it is.
Also, I though the ignition timing would be spot on being electronic, and non adjustable?
If there's a member in Kingman who can help, fantastic! Althought we are off to the Grnad Canyon today.
I'd really like to get it sorted though, I hate to hear that sound...
Tomorrow we're on the road again, we're doing around 6,000 miles in the next 6 weeks in the car.

 

HI Greg
Thanks for the info. But I'm not sure if it helps me? Mainly I'm after names of gas stations in the USA that sell the highest octane of fuel, so I can gas up there (if that's the problem with the car).
Cheers
Fred

 

I think you might be running into a regional gasoline formula issue. I know California has specific blends by law they are different from other states. here in the southeast 91 octane is very rare. Pretty much every station from a mom and pop mini mart, to Chevron, BP and Shell all sell 93 vs 91.

That said, based on your travels, any old gas should be gone. And the car is designed to run on 91.

The owners manual states:

If you’re using fuel rated at 91 octane or
higher and you still hear heavy
knocking, your engine needs service.

The electronic distributor can adjust to an extent but can't compensate for a distributor that is turned. You didn't mention what service was done, but if a full tuneup was done and it ran normally for a while, I'd be concerned about a distributor that worked it's way loose.

 

Hello there Fred!

It sounds like you are at the beginning of a great adventure! The Grand Canyon is amazing isn't it? I drove cross country with my family in our RV a few years ago and I saw 100 octane lead free gasoline while driving across I-40 thru the center of this country. I wish I could get some of that gasoline in Virginia. Another piece of advice, there are gas apps for your phone to help find stations that do not use ethanol in their gasoline. Your Corvette would prefer that of course but don't use anything like the E85 fuels in your Corvette. How far east are you planning on going with your Corvette?

Here in Virginia we have Sunoco gas stations and they sell 93 octane fuel at the local stations. Just be careful buying gasoline from no-name places offering prices far below the rest. The old adage "You get what you pay for" is all too true.

If your car is pinging or detonating I would have someone check the timing to be sure it is accurate. I have a 1988 C4 and I run "regular" (87 octane) through it with zero issues. The chances are your car is detonating due to deposits in the combustion chamber like carbon that glows and will pre-ignite the incoming fuel. In a lot of cases you just need to drive it and occasionally "drive it like you stole it" as it can loosen up the carbon. My in-laws used to use inexpensive gas and drive gently like most elderly folks. Whenever I drove their car I would stomp on it and you would see clouds of carbon and other junk blowing out the exhaust. A little exercise is a good thing even for an engine. If it is something simple like the timing is off would make it ping. Whomever you bought it from did not drive it hard it sounds, that is a good thing.

You might want to verify that your knock sensor is working or damage may occur if the knocking is left alone. To verify the knock sensor you have the car idling with the hood open. You then take a ratchet handle or a wrench and rap it against the side of the engine block (Don't break anything) and the engine should drop in idle speed for a second and recover. My knock sensor went bad and my timing was retarded automatically. After replacing the knock sensor the performance was much better. The biggest improvement I got was when I replaced the Catalytic converter and installed a cat-back "Chambered Exhaust" on my C4 which gets rid of those bulky mufflers and some weight. The car gained close to 14 hp from the installation of a High Flow catalytic converter and the chambered exhaust. I have been able to break into the 30 mpg range with my automatic transmission and 3.07 rear gears. Some of the C4's get fairly good mileage and when you combine that with "Fun to drive" aspect of Corvettes they are great cars and we are so lucky to be able to enjoy them.

As you drive this car learn what parts you need and buy them here and ship them home inside your Corvette. You will save a bunch of money that way while you are visiting this great country of ours!

By the way Fred, When near that part of Arizona you are at altitudes which means lots of hills to get there. When it is hot and you are driving up the sides of the mountains it might do better to run the higher octane (like 93 octane). You should try a bottle of B&G 44K Fuel injection system cleaner when you fill it up one time. The B&G product will clean your fuel system to make it work at its best. It is about $25 a bottle for the B&G 44K but worth every penny in my humble opinion

Do you know how old the O2 sensor is on your "New to You" Corvette? These devices are frequently ignored and they can have some bad effects on your Corvette when they start to act up. Sometimes pinging (detonation) can be aggravated by a too lean situation. An older Oxygen sensor does not have the strength of signal of a new one but they also tend to lag behind and send data to late to the ecm. Going up in elevation and having a slower O2 sensor could be all it takes to make it detonate. Have somebody verify the signal or age of the O2 sensors. I would say your MAF system is okay as you have changed altitude without major problems. The oxygen sensor is CRITICAL to get the most out of your Corvette, I was taught to replace them every 2 years or 50,000 miles. When the O2 goes bad it can make a bunch of strange symptoms and they are hard to diagnose at times. This is why I replace O2's before they wear out. When travelling distances in my RV I keep spares for all four of them. They seem to last longer today but they are a wearable item and should be replaced to ensure the car's best performance and efficiency.

While you are in the United States you should find a good Corvette shop and have them do another once over to help you out. There are probably more Corvette shops here in the U.S. than in N.Z. so save yourself some time and money. They could also install any new parts so you don't have to pay import taxes on them in N.Z.. I would do as much to the car as you can and then ship it home all done so the Customs Inspectors will see used parts on your Used Corvette.

I hope that you have an awesome trip in your Corvette! I hope that my fellow country men are polite and kind to you as well. Enjoy Yourself!!

Best regards,
Chris

 

Wherever you buy gas make sure it has a "Top Tier" sticker on the pump and you should have no problems. Some of the stations are Shell, Exxon, BP, Sonoco, Mobil, Texaco, Costco, Sinclair, Chevron. You should be able to find one of those easily. Good luck and have a great trip. Wish I had to time to cross country in my 88.

 

As mentioned before, check the timing first before worrying about higher octane gas. These cars should be able to run on regular without pinging.

 

x2 timing, adjust the tps make sure its running at its peak first....then when it is blow the carbon out of that thing.

 

Fred bought this C4 in L.A. at sea level and drove it up to near 6800' altitude and that is a fair test of the engine with a steady climb.

It is also the prime time for detonation in any engine. If it had regular gas in it on a typical 90* day lumbering up those mountains I could see where it might be hot enough after climbing a difference in altitude.

Fred is probably fine with some good quality octane in the mountains and could get away with less octane without the hills. I just hope he has the trip of a lifetime as it sounds like fun!

Have a Blast!

Best regards,
Chris

 

Looks like you got the info on petrol brands and you know that 93 is equivalent to 98 so that’s the fuel taken care of.
You could pick up a timing light and set the timing yourself. You have to disconnect the EST plug it is a single wire weather proof connector with a brown and black striped wire. With it disconnected the ECM will not adjust the timing. At idle it should be set to 6 Deg. So then you can set it in the usual way (maybe pick up a distributor spanner when you get the timing light). Reconnect the plug stop and start the engine, your timing should now be right and your CEL should clear.
The knock sensor should retard the engine if it pings. You can replace it pretty easily from underneath the car. It screws into a water jacket but if the cooling system is sealed you can replace it without much water leaking out. Don’t do it up too tight it’s meant to be 15ft pounds only. Maybe check that the wire is connected.
my car is an 84 so some things might be different but on mine the knock sensor connects to a ESC module that is mounted on the back of the heater blower box. It is a flat square looking thing with a 8 way (I think) plug on it. Of course you only need to look at the knock sensor etc if if doesn’t test good.

Happy travels. I did that drive in a piece of **** Chrysler Charger hire car, if it could do it I think a horse and cart wouldn’t have any trouble. I wish I had of had a Vette but the family wouldn’t have fitted.

 

HI Chris and others
Chris, thanks so much for the detailed reply - very helpful! I hadn't thought of altitude affecting the car.
I bought the last tankful last night in Kingman AZ so not California gas as someone else had mentioned. I'm only buying 93 for the car, nothing else.
We're driving right across, at the moment we're at the Grand Canyon, then following Route 66 all the way to Chicago. From there we'll drop down to Kentucky- I want to go to the Blowing Green museum. After that we're heading to Richmond, VA to stay with a friend for a few nights, then up to Philly, on to New England, then down to New Jersey where the car is being shipped home from,
I'll buy a timing light online - we've got two days at least in Phoenix from this Wednesday, so that will give me time to check the timing etc. I'll also do the knock sensor test.
The car was going totally fine when I picked it up, and it was running really old petrol, which I why I don't think it's timing or a knock sensor, but who knows.
SOme questions, since you seem to be the man of knowledge;

• Roughly how much is a knock sensor (should I need one).
• Ditto O2 sensor - how many are there, and approximate price? Are these and knock sensors available off teh shelf? I've had issues buying things for the car, and only being availble for delivery.
• Is there any way of telling how old the O2 sensor is?
• I've got a small toolkit I've bought to keep with teh car for our trip - if I need to adjust the timing, what spanner is needed to do this? Is it some special one to get into a tricky spot?

I will buy some injectory cleaner, teh one you recommended, and try thrashing the car tomorrow and see what comes out the exhaust.
Thanks again - hugely appreciated.
Fred

 

HI Chris, and others who have supplied such helpful info. I did write a long reply and posted it, but I see today it didn't appear! So here's a truncated version.
We're driving the car 6,000 miles over 6 weeks. Tonight we're in Williams, AZ and tomorrow night. Then we're off to Phoenix AZ for at least a couple of nights. I've purchased a timing light online and it will be delivered while we're in Phoenix, all going to plan.
After Phoenix we're back on Route 66 to CHicago, down to Kentucky (must go to the museum), over to Virginia, then Philly, New England states, then down to New Jersey eventually, leaving the car there to get it shipped back home.
Chris, a few questions for you.

• How do I know how old the O2 sensors are?
• How much do they cost?
• Are they easy to replace?
• Is there more than one O2 sensor?
• Ditto the knock sensor - expensive, easy to replace? I'll try out the method you suggested.
• Do I need a special spanner to adjust the timing, or will a standard one do? I have a very small toolkit that's in the car.
• I have given teh car a thrashing a bit today, will do teh same tomorrow, but haven't noticed anything coming out the exhaust.
• i will grab some of that injector cleaner you suggested.

Thanks again - hugely appreciated advice.
Cheers
Fred

 

When will you be in Phoenix? I'm in the east valley, maybe I can help?

 

HI there
We're arriving Wednesday, aiming to leave Friday.
If you can give me a hand, that would be awesome! I'll have a severe lack of tools at my cousin's house, I have no idea what tools her husband has...he's not a car guy.
I've bought a double DIN head unit to install (and a reversing camera) and hoping to get it all done in Phoenix, as well as checking out the O2 sensor, timing (I've bought a timing light) and the knock sensor.
So what I'm saying is, any help greatly appreciated.

Chees
Fred

 

Buccaneer will have a distributor spanner (it’s awkward to get the the retaining bolt). And he is helpful knowledgeable.

 

Is the camera a "wired" or "wireless" type?

If wired, read this:

https://www.corvetteforum.com/forums...up-camera.html

Does the car have a "Bose" system in it currently?

 

Hello again Fred!

That is a very ambitious schedule you have there for seeing the United States. It sounds like fun! I would love to make the trip around the U.S. in a Corvette.

The knock sensor is less than $40 and are available at most big NAPA auto parts stores. When replacing the knock sensor you will loose some coolant so do it very quickly and you won't have to add much to make up for it.

The O2 sensors are less than $30 each and I am not sure just how many your 1990 has on it. Here is where we need a fellow 1990 owner or somebody who knows the right answer.... I would suggest that if you don't know how old the O2's are then replace them, at least the ones in front of the catalytic as they are the ones that influence the fuel mixture. You might have a gas station install the O2's for you as then you don't need to buy any more tools.

To install a O2 sensor they make a special socket which allows for the wiring harness and is very helpful when working on any O2 sensor. I would suggest a good auto parts place will have them on the shelf.

The fastener that holds the distributor down requires a special tool also. Again the tools are available in most Auto parts stores. I do it with a wobbly socket extension and a ratchet

The only parts that will likely need to be ordered are the special hoses that are molded properly to fit on the Corvette. Fortunately there are not too many of them. I would order them from someplace like ZIP Products. Since you will be in the Richmond, Virginia area you could visit their facility and pick up whatever you need from them and ship it home inside the car. Check out ZIP Products online and you will see who I am talking about. These guys are big into Corvettes and they are near Richmond, Virginia. I order from them because they ship very fast and their prices are not bad either. I strongly recommend them.

How are your tires on the Corvette? I have heard that they are much more expensive in N.Z. with the tariffs. Check out the Tire Rack while you are here in the U.S., they will ship them to a local installer so you can have them put on. You might be able to save some money while you are at it.

Once you put a bottle of the B&G 44K into your engine use about a half tank of the mixed gasoline and then really "Drive it like you Stole it". That is usually enough for most cars. The B&G company makes a variety of fuel system cleaning products, they offer a three can set where one is the 44 K and goes in the fuel tank, a second bottle is a spray can and has throttle body cleaner and the third can gets pulled by vacuum into the throttle body vacuum lines.

I had a good friend whose father was the Ambassador from New Zealand to the U.S. back in the mid 1970's. We had some serious parties at the Ambassador's residence. There are a lot of good memories from all the fun we had. The Ambassadors son went to the same High School I did.

If there is anything that you need to know or are concerned with please feel free to ask! This will be a good test of your "new to you" Corvette and after 6000 miles you should have all the bugs worked out.

I have shipped Cars to my Brother back when he was living in Germany. The most important thing is to deliver the car to the port with the least amount of gasoline possible. In Baltimore harbor there was a guy who would remove the gasoline but charged an arm and a leg, over $200 to drain out most of the gasoline. Beware...

Let me know if you need anything, I am here and very anxious to help! Having been in 44 countries I know having a friend in country always helps. Here on this forum, You have a lot of friends Fred!

And we all want you to have the time of your life on this trip of a lifetime!

Best regards,
Chris

 

I'm open Wed/Fri this week. I have ANY tool (including a dizzy "spanner") (grin ) that would be required to work on your vette. What I'm lacking specifically is on a 91 vette, never done that, but with a little insight from the newer C4 guys on the EST, I can figure it out. Where in Phoenix will you be, does your cousin actually live in Phoenix or another surrounding city...cross streets? If you had an 82/84, you would be in luck for sure.