Pop at low rpm?
 

Once in a while i get a pop that sounds like its coming from the intake. I can hear it when i'm looking for parking at college and just keeping it in the low rpms. Its not a loud POP, its just a little pop here and there but its loud enough to notice with the radio in low volume or off. I hear it a bit more when i'm backing out from a parking spot and i'm just keeping it at about 1500 rpm. I can also hear something that sounds like a pop when i have the hood open and i open up the throttle just a bit to rev it (2k rpm max) when i let it go i hear few pops as the engine is decelerating but i dont know if its the same thing. It is not a continuous pop pop pop pop.

What do you guys think? bad valve? something with the egr? bad timing?

could be tons of shit... details on your setup?

all stock sir, I removed the little L pipe horn that comes out of the stock air box to increase response. Now its a bit louder under acceleration and obviously response is much better. Step on the gas it revs right away, before it felt more like drive by wire.
(the horn that comes out of the air box on the right of the pic is what i'm talking about)
thats a pic of my car. Anybody know that alarm on the left? Let me know if i purchased your car off the dealer :D.
Attachment 203405

On a side note, what do i do with the washer fluid when i install the turbo? Where do i relocate it? Yes i have abs on the other end.

where's the turbo? Seriously, are people driving these cars around without turbos?

The turbo is in my living room along with a xede system, i am waiting for few more parts but first things first i want to make sure there is no problems and if there are any, they are all taken care of and then the turbo will go on.

When i first bought the car, i got 6 months warranty and then apperently mazda didnt want to accept it since it was a '99 with out charging 400 application fee if i want the 6 months warranty. The dealership called me and they said because we made the deal, they will pay the fee for mazda to take it but only for a 3 months warranty (200 bucks). I told the guy i will think about it. I'm currently at the point where i can cancel the warranty and get my 350 bucks back or i can have another month and a half of drive train warranty.

It's probably the overrun fuel cut. Basically over a certain RPM and no load (accelorator not pressed, engine braking) the ECU will cut fuel completely.

At a certain RPM it will start injecting fuel again. Depending on when that happens you might get a small backfire through the intake. I don't think it's anything to worry about.

could it be backfire into the exhaust and into the egr?

I know i heard it a lot of backfire on my bike but never at low rpm like its on the miata.

its probly a dirty 02 sensor letting you laod up in criuse and backfire becouse of unburnt gas in the exhaust either that or, you car has hella bad carbon build up and is detonating this would be very bad. So i would
Check the compression
Check or change the 02 sensore seriusly its like 13 bucks
And depending on your results from these 2 you will have a pathway to a solution gl/

+1

alright well i toyed around with it on my way out, i'm very sure it only happens after i let off the gas (aka decelerating).

On to looking for tools for compression test.

yep this further confirms my to rich sentiments it is a good sign. :D

where do you guys disco the spark and the fuel when doing a compression test?

dont worry about the fuel part just disconnect the coils.

where do you do that? at the coils or is there a fuse? (never done compression test, sorry for my newbness)

ggrr bloody search shows everything BUT a compression test writeup

also where do you find O2 sensor for 13 bucks?

For compression check,
Step 1 – Drive car a bit to get it warmed up and top off the battery charge.
Step 2 – Let it cool down and then pull All 4 spark plugs out
Step 3 – Disconnect CAS to eliminate spark and fuel injection (OR FUEL INJECTION RELAY)
Step 4 – Screw compression tester into cylinder 1 nearest to radiator
Step 5 – With foot down all the way on the gas (WOT), turn the key to start and hold until the engine has turned 8-10 times and pressure no longer climbs on the gauge.
Step 6 – Record pressure on gauge and release air to zero and remove gauge from spark plug hole
.
Step 7 – repeat steps 4-6 for each cylinder moving from front to back of engine.
Step 8 – Check pressures and make sure no readings are more than 10-15% different

You should get yourself a manual...

if you dont have a long flexible foot you can also just prop the throttle body open with something on the outside.
As for the 02 sensor just go to the auto parts store and get a generic 02 sensor. At the most it is 4 wires. Do you know how to deal with joining wires in any way shape or form? Have you ever done any other automotive maintenance to anything?

i'm pretty handy with stuff however i'm nervous when i try new things that i've never done before such as messing with the coils... thats my main problem. As for wires, i can do wires quite well :), so its not an actual plug though, you have to cut and slash? The main reason why i ask is because i looked around for a o2 sensor and they are about 70-80 bucks on the web.

After figuring out your issue, do your turbo install now. You don't need the drivetrain warranty. These engines are very strong and that's why we turbocharge them. As for the transmission, unless you drive your car like a mortard it will be more than strong enough to be raced with stock power- spec miata proves that. The turbo is not really that difficult of a project; it is the beginning that will encourage and motivate you to work on your car more. I am probably one of the least mechanically and automotive service stuff knowledgeable people on the site but in a few weeks I'm pulling my engine to replace it and do a bunch of other work. The internet is my friend and your friend for "how-tos". I waited two years to turbocharge and that was a waste of time when I could have dramatically shortened the duration of my drives :).

i'm not too shabby about installing the turbo, i've read up on the stuff and i feel pretty confident about the hardware, I've never messed around with the xede that i bought to play around for the fuel but Stephanie is helping me out with that so i should be good.

The only thing i'm a little nervous about when doing the turbo is ripping out bolts since i have a lot of experience in that being in the rust belt :D. I've ripped out upwards of 9/16" diameter bolts when i was doing my control arms on my jeep 2 years ago :D Undoing the tiny 3/8" nuts on the exhaust makes me very damn nervous, other than that i feel confident that i can install the turbo with no problems.

I just want to confirm the motor is running in top shape possible. If something needs to be fixed, i'll take the warranty, get it fixed and install the turbo :)

Kroil kills rust!

KanoLabs.com

and thats something you've used and something you recommend sir?

yes, i bought it directly from kano.

back to the compression test,

From the looks of it i have to undo the 3 12mm bolts that hold the coils to be able to unclip the power?

even if you leave everything plugged in and just undo the plug wires to the plugs you will be fine for the 5-10 mins it takes at the most to do a compression test. I cant remember off hand but the connector isnt rocket sceince to get to. Plus not every bolt you touch on a miata is gonna distegrate like on a rusty off raod domestic vehicle, so use alil feel and get that car the way you want it man.

No. You should be able to reach around the coils to access the plugs. If you think that's difficult, try getting to that third mounting bolt (bottom middle) on the coil pack bracket and report back with your findings. ;)

ok i finally see the 2 plugs in the back :laugh:

fyi, daylight is good when working on your car.:bowrofl:

aaahh dammit, tool i got from vatozone if fuked up, the joint between the rubber boot and the part that screws in the spark plug hole is trashed so it falls apart when i put pressure on it, i'll see if i can glue it together, if not i'll have to go exchange it :( dammit.

btw "fuel inj" fuse shuts off the injectors right?

off to get another one, i was able to get 1 reading before the glue gave out but i dont know how good that reading is.. 182 on cyl 1

Finally found a good tool after 4 autozones, i got back.. engine is too cold and i'm getting reading for #1 at 145 and reading for #2 at 135.. i guess i'll have to tear it all apart after my short drive from work tomorrow and try again. :(

lol for a cold motor that isnt bad. Make sure the throttle is full open while cranking and try that sucker warmed up the first cylinder is a very good baseline of what the others should be. If you other numbers are as low as 150s then you have a problem.

if your engine has high mileage, doing a compression test is near meaningless. Rather, do a leakdown test.

baby steps man this is his first compresion test ever probly let him get that done before he trys something harder.

the odometer has 58k miles on it even though its a '99.

I had the throttle fully open and the clutch pressed in.. the gauge would not move any more.

well guys i gave it another shot, came home after a half an hr drive waited 5 minutes then started undoing spark plugs, and the coils and took off the fuel inj relay/fuse, screwed in the tester, floored the clutch and the gas, crank crank crank 7-8 times.. run out to check... 146 wtf!!!!

then i tried the 2nd cylinder.. 90 :(

so i tossed in some oil into cylinder 1 (only cylinder 1) and also some oil on the threads that screw into the spark plug area. Screwed it back in.. cranked and oil steam went flying out of the spark plug hole :( i dont know what to do now :(

back to the popping. When i've parked the car with the engine idling, i turn the wheel a tiny bit.. maybe 1/8 of a turn and i hear it pop, i turn it the other way, i hear it pop again.. turn it back... pop.. rev up the engine to 1500 rpm turn the wheel.. pop.. wtf? it sounds like its coming from the air filter area..

i tried to check it and its definitely coming from the air filter. Since i have a cone filter now i can hear it pretty clearly.

I press the gas a tiny bit to rev the engine just a bit to around 1300rpm, let go of the gas, as soon as it goes down to idle i turn the wheel.. pop

any ideas? :(

just forget about it man it is obviusly not hurting anything.

alright then :) i'll go with the turbo install lol

hopefully this weekend i'll be able to toss it on there :D