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I'm experiencing a weird metallic noise at idle on my freshly rebuilt (1200km ago) full stock 93 FD.
It only happens when the car is hot, at the lowest rpm. If I slighty touch the accelerator pedal the noise disappear above 1000rpm, and I definitely can't hear it when I'm driving.
It's some kind of clicking metal sound, not regular, not very loud. But I can hear it easily when I'm in my garage. I'm struggling to find the source of that noise, but I would say it's coming from the rear of the engine. Under the UIM I'd say, but really not sure.
Besides this problem, the car operates pretty normally, idles well at 750rpm, starts cold and hot instantly, boosts fine.
I replaced my spark plugs along with their wires (all oem), but this did not help. I checked in the engine bay and fixed some shaggy metallic parts (I removed some AC pipes and the condenser just before I noticed this sound), but no luck again. At some point I thought that noise was coming from the heat shield around the downpipe, so I tried to push it against a wrench today, but the noise was still here, so it's probably something else.
I've read/seen some comments about the Air pump making a similar noise. Or gearbox ? the engine ?? What do you think ?
I would really appreciate any tips, help or feedback, I own the car since 2 months and this little thing is going to make me crazy
Get a long screw driver and put one side on the part you think is making the noise and the other side to your ear. Move the screw driver around until you find the source.
I really do appreciate the trick !
I don't have a very long screwdriver, but I'll try with a long and thin metal pipe, should work the same I guess.
Thnak you !
Only the catback is not oem.
Should I check right after the downpipe ? (Mid pipe/catalytic convertor) Any trick to check if there's something in without removing it first? (My garage is so tiny that it will be a real pain removing the exhaust...)
It's still on stock ECU. (Actually I've got a Pfc but I am waiting to complete the engine break-in before installing it)
Indeed the idle isn't pretty steady in the video. Since then, i've changed the spark plugs and wires. Still need to check if it changed something, otherwise i've already prepared a list for other things to check (tps, vacuum leaks, ics, etc...)
Your cat may contain some debris. You could try tapping it with something to see if you can hear anything inside, but it's really not that difficult to remove. Do you have a pre-cat like USDM models? That could be a source of crap as well.
As for the idle, i would start by checking for vacuum leaks
Yes, I may have a pre-cat because it's a USDM model. (R2), eventhough, I bought it pretty recently and never checked it before. Noy sure if I can see it on this photo or not... ?
Anyway, I'll try to reach the exchaust pipes and tap on them first.
For the idle, I've checked the hoses today, they looked fine, visually. So I'll check for vacuum leaks with a carburetor spray tomorrow.
I'll keep my researches updated here for sure
That's the pre-cat. Supposedly they puke their insides due to the extreme heat from the turbos. That then clogs the main cat. I recomend pulling both. The pre-cat is somehat of a pain though. If you can get your main cat off (comparitively easy), you should be able to see if it's got chunks in it. If it does, you probably should replace your pre-cat, preferably with a catless downpipe. Depending on how much is in your main, you may be able to suffice by simply banging the debris out.
If the cat is getting clogged and you don't address it, it could continue to get more clogged until it starts affecting your engine performance due to the restriction in the exhaust.
Thanks TomU, I really appreciate your help !
So, I took the car this morning and tried to figure out where that metal clicking sound comes from.
It's definitely not from the catalysator converter, nor the pre-cat pipe, but really from the engine bay.
I could hear the noise really loud and clear when touching this cylindrical part : (wastegate?)
Don't know if it's coming from the wastegate itself or not, but it's probably very close to it.
I didn't see it when I took the photo, but now I can see a little black metal shield just above the wastegate, or the 2 other shields on the photo, that may cause this sound, I guess... So I'll take care of that next time.
Ok, well, the more I'm looking for fixes, the more I'm thinking about misfires. I'm not experienced with this, but to me it can explain why the engine has this lumpy idle, pops, eventually vibrates more than it should, and on some 'bigger' misfires that metallic clicking happens.
can someone tell me if in this video the 'pops' we hear can caused by misfires ?
I still need to check my TPS and ISC voltage/ohms first, but do you think those misfires (if they really are misfires) can be caused by a bad ignition coil ?
Also, since all of this happened after my radiator exploded on the highway and the engine got warmed up, maybe one ignition coil has taken damages ? or ignitor or something else causing those misfiring ?
Some quick updates
I've been able to check the TPS and the ISC
To me, they seems ok.
The ISC has 11,8 ohms, which is between the expected vcalues recommanded by Mazda. (I cleaned it, though)
The TPS has regular values, but I'm astonished that the narrow range 'grows' immediatly tu full voltage. From 1,2V (close throttle) to 4,9V immediately as soon as throttle opens. (And remains at 4,9 until WOT)
Also, I friend of mine told me, after I explained all this happened after the radiator exploded, that my problem could come from the CAS plugs that could have been possibly altered by the coolant leakage. So I'll check and clean them asap.
My friend came by and for the first time someone checked the symptoms. He found out quite easily that my exhaust was leaking. At least inbetween the cat/DP connection (photo below) and most probably from the other side at the Turbo connection, because we noticed some smoke when opening the hood.
Can such a leak cause misfire / idle problems like I have ? Or is it just another problem ? (That I will fix asap anyway)
Otherwise, the ACS plugs look not easy to access, so I'll try this after the DP change.
09-16-18, 02:59 PM
