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Old 07-30-2007, 10:23 PM   #1
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Default Need some help. Guys at M.net arent helpful at all

Sorta copied and pasted my post from m.net, but anyway.

Just the other day, I've had a noticeable loss of power to my NB 1999. There arent really any strange noises coming from the car anywhere, except one time when took a corner this morning to see what was going on. Sounded very high pitched, as if something was rubbing on something.

Anyway, I bought a compression tester, I will be doing that when i get the chance to figure out if my compression is still good. Im pretty sure its fine, but this loss of power is still bugging me. It accelerates fairly slow now, it doesn't have the kick it used to have. and this was just the other day!

It cannot be the catalytic converter, because I swapped for a 2001 header and i have less-than-month-old RS midpipe on there. No check engine lights are being thrown, so coil packs seem to be out of the question (unless? i dont know). It doesnt seem like I am running only 3 pistons or less or what not.

My plans were to turbo this car, but now this has arised, im going to have to fix this problem before i do the turbo.

I have this feeling that it might be the timing belt, could have skipped a tooth. what do you guys think? i need an better view or someone who has had a similar experience. the car has 118k miles, and i have no knowledge if the previous owner changed the timing belt for maintenance before the transfer of ownership to me.

What i have tried so far:

Check spark plugs, although they are only 2 months old.
Change spark plug wires, still runs the same.

pretty much thats the advice they gave me at M.net, and no one is willing to suggest something.
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Old 07-30-2007, 10:52 PM   #2
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Sounds like 2 different problems.
You've got a power problem, and a noise problem.

Does it rev fine in neutral... if yes, then probably a fuel issue. I'd get a new fuel filter to start with.

Noise problems can be harder to diagnose. If it only makes noise in a turn, check the condition of the motor mounts to start.

Tell us about the mods on the car... list them all.
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Old 07-30-2007, 11:02 PM   #3
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Check your compression first.. that is a biggy

also check you timing.

like sam said check your fuel.. it seem odd that it would be a major change but it does happen.


again like sam said,.... mod list please
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Old 07-30-2007, 11:30 PM   #4
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Thanks for the quick replys.

well, mods concerning engine include a lightened flywheel and exedy clutch. besides that, the engine is stock (for the time being).

im a little worried about doing a compression check, because ive read up somewhere that 1999 miatas coilpacks tend to crap out, and cranking it with power and no load can toast it. if everything else ive done doesnt work, then ill use it as a last resort... but i doubt its compression issues.

it does rev fine in neutral

i popped off the valve cover the other day, and it seems like the timing belt has been rubbing rubbing somewhere, could possibly mean it could crap out soon? the front of the belt looks like it has been "tapered" the belt looking at it from a side point of view originally looks like this, looking at it from the passenger side fender
___ __
[___] but now looks like this. [___\

anyone get this? haha

as for noise problems, there are no more, it was only at that time when i took a right curved turn at about 60-70. but when i try to reenact the situation, theres no sound like the one i heard. sounds normal as usual, besides the power loss.

im not burning any oil, no unusual colored smoke coming out of the exhaust.
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Old 07-30-2007, 11:33 PM   #5
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o2 sensor and acc belts
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Old 07-30-2007, 11:40 PM   #6
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could it really be the accessory belts?? i dont see how they would affect the power of the engine besides slipping making a loud squeal. the sound i heard is definately NOT a belt squeal.

as for O2 sensor... it looks fine, but maybe it could be going bad? ><
i would think the CEL would be going off.

also, just recently, i have switched to using 91 octane in preparation for the turbo, but could that also have a significant change in power?
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Old 07-31-2007, 12:13 AM   #7
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not for the power, no for the fuel

No the CEL wouldnt nec. go off.
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Old 07-31-2007, 01:06 AM   #8
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compressions is crap, do a leak down test I have seen motors give great compression readings but fail horrible in leak down test.

cats can have sudden failures

i would check for fuel issues like everyone said.
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Old 07-31-2007, 08:08 AM   #9
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Do you see any "wobble" in the crank pulley? Long nose crank problems can appear after a poorly done timing belt change. The timing belt rub is one of the indications.
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Old 07-31-2007, 01:35 PM   #10
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thrust bearing issues? just throwing that one out there
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Old 07-31-2007, 04:36 PM   #11
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i doubt its the thrust bearing, but i will check for wobbles in the crank pulley. thanks for the help guys. i havent changed the timing belt myself yet, but i hope it doesnt come to a serious engine problem

Update: no wobble on the crank pulley, no movement at all. its as steady as all the other pulleys. right now there are no unusual sounds, just as usual as is it should be. ill be doing hte timing belt change ASAP when the parts come in... my car is due for it anyway.

Last edited by Marc D; 07-31-2007 at 04:55 PM.
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Old 08-02-2007, 02:15 PM   #12
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Measure manifold vacuum at idle. Too low and your timing belt may have skipped a tooth, or your ignition timing is horribly retarded.
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Old 08-02-2007, 05:20 PM   #13
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well heres and update... and holy **** what a surprise.

i removed the valve cover earlier, and found out the belt was rubbing somewhere. I decided to have a shop take a look at it, and the timing belt was nearly about to snap.

im sure that this didnt really have anything to do with the power loss, but they further removed what was needed to take off the timing belt.

it comes t othe conclusion that on the back place behind the cam gears, one of the screws somehow unthreaded themselves. so in turn, the bolt whipped around, and got stuck inbetween the timing belt cover and the belt and started to eat away at it. in the middle of the timing belt somewhere, the timing belt looked like somsone had slashed it with a knife. not looking good. possibly the screw had caught on along with the belt and pulled it back a tooth, hence the strange noise. hopefully this will solve the problem. ill keep you guys updated.
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