I have searched for this problem!!!!!


I have an 89 vert(125000 miles) with HKS exhaust RB header and bonez high flow cat. Bonex intake filter, Rotary perfomance underdrive pulleys, RP ignition and 10mm magnacor wires, new NGK plugs. It does smoke at high rpm between shifts only. Not at start up

I adjusted the TPS and checked my timing and idle speed. I was having an idle problem and adjusted the timing to 5 degrees advance( inbetween the second and thrid mark on the RP pulley) as it appeared to be 5 degrees retarded. The idle smoothed out and holds at 750rpm.

I am now getting an odd sound under full throttle only. It sounds like a playing card in the spokes of a bicycle wheel. It still pulls hard to the redline even when making the sound. As soon as I feather back the throttle just a little it stops. When it was 5 degrees retarded it would not pull to 8K rpm and it would make the same noise under full throttle as it is now but not NEARLY as much.

I have new NGK plugs, run redline SG1 fuel cleaner through it. Added Marvel mystery oil to the last oil change less than 1000 miles ago. The only thing that has not been changed in the fuel system is the filter. It has approximately 25K miles on it.

Is it pinging? or is something rattling under full throttle? ANY ideas?

Thanks,
David

 

The smoking at high rpms between shifts probably isn't good. I'm afraid I can't help you out with your main problem.

 

Let me restate that. If you can't find out anything from the forums, try looking at the problem from the point of view that neither the TPS or timing had any effect, and figure out what is causing the abnormal smoking at high rpms. It might be related.

 

The sound is kind of like a ticking, then? Mine did that for a little while, right before it blew.

 

It sounds like you are pinging, and I would bet that your messing with the timing has some thing to do with it. I wouldn't drive it hard until you can get that figured out, or you risk popping the motor.
Now I don't know much about timing, but I would wait until someone that knows about it posts the right info. You need to find another way to fix the idle besides screwing with timing.

 

smokes @ higher rpms= I think your oil seals are on the way out...

 

My idle was a little low, about 600rpm and a little rough even with my TPS adjusted to spec. I moved the idle up to 750 with the idle adjustment screw on top of the UIM but it was still a LITTLE rough. When I checked the timing with the idle at 750 it showed 5 degrees retarded. I moved the idle to 5 degrees advanced and the idle moved to 900 rpm. I then adjusted it back to 750 using the screw on top of the UIM and it is very smooth and steady now. The noise only happens at WOT and if you come off the throttle just a little it goes away.

 

You need to back off the timing, a little at a time, until the detonation stops.

(In the old days, that's how we used to tune all engines.)

The problem is - one good detonation can crack an apex seal before you get the timing set.

 

I am at a loss to explain the noise. If it is detonation, the amount of pinging I have heard should have already blown the motor, would it not? It sounds bad.

The timing marks on my underdrive pulley indicate it is at the factory 5 degrees advanced. Would that amount of timing cause it to detonate? Before it was at 5 degrees retarded and the sound was there as well just no where near as much. It was a lot more random, now it is a steady noise under high rpm and WOT.

Could it be a clogged fuel filter? The filter on it has not been changed in the last 25K miles. I am ordering one from Rotary Performance and changing that to see if it makes a difference. In the meantime I will set the timing back to 5 degrees retarded eventhough it runs sluggishly at that setting.

Thanks
David

 

are you sure its not just something loose and rattling?

Perhaps the fan is hitting the shroud when you stomp on it because the motor is twisting enough to allow that?

 

I think that is more likely, but nothing looks obvious.

Why would it seem to increase since I set the timing to the stock setting?

I guess it could just be coincidence.

I will continue looking for something mechanical.

 

If you just reset it to the stock timing, then I would say that its ok to leave it there. I wouldn't use full throttle until you can figure out what the noise is, though.

 

I agree with sideways7. After I rebuilt my engine I had the timing way too high because my timing light quit working. I set the timing where it idled best and it was about 30 degrees too high. I played with timing a little bit on the dyno and stock setting was about the best.

 

Sorry to resurrect a dead thread, but I have noticed the same thing. It almost sounds like a second car's exhaust note reving at the same speed from the exhaust. I play with the timing and can get it to go away, but then it comes back randomly. Also, when the noise happens I experience a small loss of power, ie. It will be accelerating fine under WOT, then the noise starts and it seems to choke out a little. When I back the timing off, I lose a lot of power, but the noise goes away. I've been fighting with timing and fuel maps to try to find a happy medium, because I can sometimes get it to go away by adding more fuel, but then I'm way too rich and lose power again. What's frustrating about it is that the car will run great and makes excellent power all the way to redline with no sound, but then it will start making the sound and losing power with no change in fuel or timing. I have noticed that the problem seems to be worse when it's hot. It does not happen when revving at a stop, only under load, and only at, or close to WOT. Also usually only in the higher RPM ranges, like above 4-5k. I'm thinking about going back to the stock ignition system, in case the MSD is somehow causing the problem. BTW I am running an 84 GS, N/A S5 13B streetport with a Holley Commander 950 Pro FI system, MSD 6a box firing one coil for each leading plug in a wasted spark setup (Not using the distributor cap to direct the spark) getting it's input from the mag pickup in the stock distributor, and stock trailing timing with an MSD Blaster 2 coil. I've tryd connecting/disconnecting the vaccuum advance, but it doesn't seem to change much. I know the fuel isn't 100% right, because I haven't gotten a WB O2 yet, so I just tuning with the butt dyno and a Narrow band O2.

 

unlikely you are pinging on a nonturbo. timing has to be WAY out to be pinging. I had my n/a advanced at least 6+ degrees and it never detonated. hell it put down 172 with ease

 

Anyone?