kevinr1247

Hi Folks, This is my first time posting.....been a long time lurker. Anyway, I've gone and done it again.....'87 Coupe w/ 108k Diamond Blue Metallic/Burgandy. My first an '88 Coupe Silver/Burgundy.

It's amazing how similar these two cars are. All the creaks, clanks, pops, clicks.....the same. But on the '87 when the engine is pulling hard uphill at about 4500 rpm and beyond....the classic engine knock sound which gets more pronounced as RPM increases.

I'm wondering, could this be related to cat delete (which it has)? A performance chip that I don't know is installed? Non-ethanol fuel? It seems to do it only when I'm accelerating up a hill and at the stated RPM.

I wish I had all the records for this car, but I don't have any actually so there is a bit of mystery. I had the car checked out by the pros but that was very soon after I bought it, sort of a post purchase inspection (risky I know). Advice?

Steve Weiner-Rennsport Systems

Kevin,

Engine knock is NOT a good thing and needs to be addressed immediately to prevent serious (expensive) damage.

You didn't say what kind of fuel you use, and I'd strongly recommend looking to see if you have a performance chip inside the ECU before driving it any further. Some chips are good and some are terrible so you should check this out ASAP.

Assuming for the moment that you are using the highest octane premium fuel you have available, I would see if you have the stock chip or an aftermarket one as that may be the root of the problem, depending on what you find.

kevinr1247

Thanks Steve, Yes, I'll dig into it to see if there is a chip installed. My suspicion is that there is a chip but of course I'm not 100%.

Recently the Shell station down the road has been selling 91 non-ethanol fuel so I have been using that.....two tanks so far.

This gives me a place to start. I'll post what I find and I won't drive it until I find out for sure what is going on. If the chip is stock, what could be another possible culprit? Could the cat bypass be the issue? Is there a different mapping for cars w/o a cat?

Thanks again.

Kevin

Ed Hughes

Where are you-Calif?

As Steve suggested, the chip is the first place to look. There are a lot of them setup for 93. Someone such as Steve Wong will alter the map for exhaust mods, but it ain't enough to cause a knock, IMO. Let's hope it is fuel/chip related...

Amber Gramps

Kevin, if I'm reading this right you currently have two 911's. What about swapping out the DME one with the other? Put the DME from the '88 into the '87 and see if you still have the knock. It takes about 10 minutes and only requires a 10MM socket. If you have no knock after the swap, then it is time to take the cover off the '87 DME and look for an aftermarket chip. We can easily walk you through this.

rusnak

Someone could have played with the fuel quality/ advance **** as well.

kevinr1247

Well, It hasn't been chipped. So, I think I'll go ahead and order the Steve Wong chip while I have the DME out. Unfortunately, I sold the '88 so I can't compare and contrast as suggested. Sorry I wasn't clearer on that. I hate to talk about the loss.

What are the next steps? My thought was that the cat bypass might have something to do with it but that might not be the case based on the responses. I do live at 2700 feet, and typically drive the twisties at 3000 to 3500 feet. Maybe drum up some 93 octane somewhere?

kevinr1247

I thought about that too. I'll check that as well. I saw a diagram on that somewhere. I assume it will be obvious if it has been adjusted?

Amber Gramps

Well, that answers that.

kevinr1247

easy now amber lamps....this is serious business/detective work.....

the DME, as far as I can tell, hasn't been opened so I'll assume the setting hasn't been changed.

rusnak

911chips.com has a good description with pictures of the fuel setting ****. The best thing is to leave it in the stock setting, with the stock chip - ironic, isn't it?

kevinr1247

yeah, will do. In the meantime I'll wait for the performance chip to arrive which I just ordered. It occurs to me that driving between 3000 and 3500 feet might have something to do with it because the knock does seem to be intermittent. As I get to know the car better, I'll hopefully have a better idea. But it's not like I'm all that enthusiastic about encouraging the problem.

Amber Gramps

I'm inclined() to think altitude may be playing a part in this. What do the guys in Denver experience?

Sorry, couldn't help myself.

Ed Hughes

3000' ain't that high. Denver's fuel choices are 85, 87 and 89, or similar, so apparently high altitude allows use of lower octane. I think more description on the knock is needed.

kevinr1247

right on, I'll see what I can do in a couple of days as far as better pinpointing the noise. For now, the DME is open and serving as a coffee table centerpiece. Waiting for the chip to arrive then I'll reassemble.

I did read on the 911chips website about a sensor that detects an altitude of 3250' hence my suspicion because I'm right on the cusp. I do know that this car spent quite a bit of time in Denver actually.....and the Boise area, according to the Carfax.