gr4v3r

I noticed my car doing something very strange recently that I have never noticed before. Under normal driving everything is fine, oil pressure is at about 60 and the car is quiet. When i go WOT it goes to around 80 but as I approach 5.5k rpms the oil gauge tack starts jumping for 30-60 really fast and the car starts making a chattering noise. There is no loss of power but something doesnt seem right. Has anyone ever experienced something like this and can point me in the right direction? I keep reading it may be a bad ground, but there seems to be a noise connected to the issue as well.

I have a 94 so it is a real oil pressure gauge which is what scares me.

SchmoozerJoe

iTrader: (2)

Any chance the noise you hear is detonation?

I've read (here, I think) that the OPG can act as a sort of knock sensor under heavy detonation.

Perhaps you could pull your spark plugs and see if there are any signs?


(Quick example of a plug with detonation going on... notice the little bits of crap on the center section and electrode...)

gr4v3r

Thats a good start, I will take a look. Thanks! Should i pull every plug or will they all show the same signs?

gr4v3r

Looking into it, it sounds like it is definitely detonation. Is this something I can see in a data log? I and fairly clueless with tuning but can pull a data log and follow instructions :P

nitrodann

Its detonation.

SchmoozerJoe

iTrader: (2)

Data logs won't show much... you should really fix your tune.
In general terms... that probably means less timing and/or more fuel.

You say this just started occurring.... any chance you put a lower octane fuel in your car?
Are you running boost?

gr4v3r

Strictly 93 and 14psi. I will be going to a tuner in 2 weeks so hopefully he can help. It was tuned originally in the winter, could it be he was able to run more timing in the cold weather? AFR is reading 11-12 on the wideband at WOT. I also ordered some NGK (4644) BKR7E spark plugs, maybe that will help.

SchmoozerJoe

iTrader: (2)

Check all four plugs. See if one particular cylinder shows signs of detonation over the others.
If it's just one plug, I'd look into that particular injector. Clean it, replace it, etc, since you could have a clogged injector.
That could cause a particular cylinder to lean out and detonate and would explain the recent issue with detonation.

But if you're at 11 or 12 to 1 on the AFR and this detonation is a recent thing... it's most likely a clogged/bad injector on a particular cylinder.

At least, that's where I'd put my money if I were to wager.

mlev

iTrader: (5)

Definitely knock.

Are you intercooled? At 14psi you darned well better be.

I'm guessing the cooler intake temps combined with colder air moving over the intercooler and radiator kept things cooler in winter, avoiding pre detonation.

Also, the fuel may have had a higher ethanol mix keeping things cooler, too.

Pull a couple degrees for now, until you can get a tune.

---

Also +1 to everything in the post before me.

gr4v3r

The injectors were cleaned and flow tested about 4 months ago so i don't think it would be that. Also I put in new plugs at the time of tuning, so like 4 months. Cooling system seems fine, I see no signs of overheating. I did a coolant reroute last month but I don't THINK there is any issue there.

gr4v3r

ya im intercooled. Sounds good, I think thats a solid plan for now until I can find out a bit more. Thanks for all the help everyone and I will try and follow up