Car is a 99 DX hatch with the D16Y7, 100,000 miles, I/H/E, EX tranny & intake manifold.

I hear detonation (pebbles in the can) when the car is under heavier loads. Usually 3rd gear getting up to speed on the highway or climbing a hill on the highway in 5th gear. I checked the timing, it's set at 16 deg. on the money.

From what I've read it's usually due to timing, excessive intake temps, or a lean mixture.

Like I said, timing is on. Primary O2 sensor is 2,000 miles old, (did this beforehand anyways).

Any ideas why this is? I usually run 87 octane in there, but I put in 91 this morning just to see if that helped and it did. But on this car I should be able to run 87 with no problems.

 

Any ideas?

 

Carbon build up?
Plugged exhaust?
Air filter gunked up?
Bad plug's?
Air temp sensor?

There's a starter list.
Is it a stock ECU?

 

Hasn't been too long since I ran some seafoam through it, maybe 10,000 miles, if that. Plugs were changed at the same time. Guess I could seafoam it again, but I would have to change the plugs again.

Air filter is pretty clean. Conical style filter, not very new but clean I think.

Air temp sensor should be good as far as I know. It's plugged into the intake pipe, and there are no CEL's. I suppose it's possible for the temp sensor to be bad and not show up as a CEL.

ECU is the stock P2E.

 

Don't forget to check your fuel pressure ...and when was the last time you changed your fuel filter??

Just a thought but like thesmogman noted it's just one more "easy" thing to check and if you haven't changed since you bought it , then it's a good 16 to 22 bucks well spent anyways. And that's for oem filters autozone ones can be had for cheaper.

 

Fuel filter was replaced 5,000-7,000 miles ago.

 

Well, Fuel is a good call. FPR?

Temp sensors as for most sensors can go bais one way or another without setting a cel.
And check for vacuum leaks too. Brake booster and all.

 

does the motor burn any oil?

 

Did this problem occured when u have your stock dx tranny?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Jeterkm02 &raquo;</TD></TR><TR><TD CLASS="quote">does the motor burn any oil? </TD></TR></TABLE>

1/2 quart at most over 3,000 miles.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dude_123 &raquo;</TD></TR><TR><TD CLASS="quote">Did this problem occured when u have your stock dx tranny?</TD></TR></TABLE>

Yes.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ****** &raquo;</TD></TR><TR><TD CLASS="quote">1/2 quart at most over 3,000 miles.</TD></TR></TABLE>

That doesnt sound like much at all but oil will greatly decrease the octane level of your fuel which will leave you more prone to pre-ignition/detonation.