Sounds like it's dieseling

ThunderDave

Registered User
I'll see if I can describe what sound the car is making. While cruising and at partial throttle, there is a noise coming from under the hood that almost sounds like a diesel. If I left off the gas or give it more gas, it stops making the noise.

It doesn't sound like a rod or bearing knocking. The only thing I can think of that would be close, is I read that someone said their blower sounded like it had marbles in it, when the bearings in it went bad. Would it make that sound all the time?

The car still seems to run fine with no noticeable loss in performance since I noticed this noise. Would a bad knock sensor cause this problem? It's my daily driver, so I'd like to get it figured out and fixed before it could become worse.

Thanks!
 
I lost three superchargers on my 93SC, Two of them made the marble noise at certain RPM's and it did sound kind of like a diesel clattering. One of them just locked up alltogether at random, and with gatorback belts, that makes a horrible noise. Mine however would all get worse with more throttle. Sounds kind of like spark knock that you are describing. I used to get that with crappy gas from cheap stations. BP or Exxon had the only gas that my SC wouldnt knock on. weird huh?
 
Cheap gas or knock sensor......

Did you notice this just after a fill-up?

With all the problems with gas shortages, you might have gotten some bad gas......

You might want to try some octane booster for this tank....
 
It only makes the sounds at a certain throttle point and it's been over several tanks of gas from different stations. :( :confused:
 
I think my SC makes the same noise as yours. It's a light ticking noise. It sort of reminds me of the kiddie gemstone tumblers they used to sell "As Seen on TV".

My car does not make the noise during acceleration or coast-down, only during light throttle cruise (maybe between 10 and 0 inches of vacuum). I *think* that it is cause by wear in my blower nose drive coupling. I think that what happens is that the blower drive is basically free-wheeling at that load point, so the play in the coupling is revealed. At coast-down, the engine is decelerating the SC, and on acceleration, the engine is accelerating it, so the play is taken up either way. Hence, no noise at those two extremes.

When I bought the car, the blower was basically empty of oil due to a leaky snout seal. Since then, I have kept it filled until I can swap the seal (that stubborn pulley is stymying me).

I would like to get a blower rebuild at some point, but I haven't yet.
 
S_Mazza said:
I think my SC makes the same noise as yours. It's a light ticking noise. It sort of reminds me of the kiddie gemstone tumblers they used to sell "As Seen on TV".

My car does not make the noise during acceleration or coast-down, only during light throttle cruise (maybe between 10 and 0 inches of vacuum). I *think* that it is cause by wear in my blower nose drive coupling. I think that what happens is that the blower drive is basically free-wheeling at that load point, so the play in the coupling is revealed. At coast-down, the engine is decelerating the SC, and on acceleration, the engine is accelerating it, so the play is taken up either way. Hence, no noise at those two extremes.

When I bought the car, the blower was basically empty of oil due to a leaky snout seal. Since then, I have kept it filled until I can swap the seal (that stubborn pulley is stymying me).

I would like to get a blower rebuild at some point, but I haven't yet.

Yeah, that's what it's sounds like. It's kind of in between giving it gas and letting off all the way. I have kept mine full of oil too. It did have a leaking seal when I got it, which I replaced, but maybe the damage was already done. Thanks for the tip.
 
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I replaced the blower with a ported one a few weeks back and still have the same noise as before. I'm wondering if it is a valve or lifter.:confused: I'm thinking about having a mechanic ride in the car with me to listen to it to see what he thinks.

I don't want to start tearing it down without knowing what I'm looking for.
 
How many miles you have on your Bird? Could be, but unlikely a floppy timing chain. Have you checked all your pulley bolts, may have one or two loose. Another guess would be a dry bearing on an idler pulley. These are only guesses, more than likely if you have eliminated the blower and all the other bolt on's, then I'll lean towards valve or timing issues.
 
It almost sounds like a spark knock. There aren't any other issues with how it runs. Since the arms length list of mods I've done over the last few weeks (it was a short arm:D ), the sound hasn't changed any, no better and no worse. I'm gonna try some more plugs and see if that helps. If not, then maybe I'll be going to Charlotte to get wings.:eek: ;)
 
David,

Is the ported blower you put on there used or new? Maybe it just happend to have the same problem that your old stock on had. Now that may not be the case and if you do deside to get plugs I strongly suggest getting a set of Iridiums (sp). I run the NGK Iridiums on my 35th and have not had one single problem.

Hope this helps!

Shane
 
Not real sure if this will fix it, but i reckon its worth a try. Pull the octane plug and see if it stops. If it does, you know is a spark knock issue.......

Derek
 
Yes, it did it with the old blower too, that's why I don't think it's the blower. I run 92-93 octane all the time. Unless there is a problem with the knock sensor, I'm just stumped on this one.
 
quick35th said:
You could always turn it into a race car, I am sure that could solve your problems as well :p :D

Shane

It was just a matter of time before you suggested that.:D

I'm gonna get the NGKs and see if that helps.
 
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