Hey all - I need to pick your brains. I have had this chatter/rattle type noise coming from my engine bay ever since I bought car. It is only under load and does not happen in neutral or at a stand still. It sounds almost like marbles vibrating really quickly kind of like pinging (aka detonation, spark knock) Gets less apparent the higher the rpms I reach and the higher the gear I reach - very apparent in 1st and 2nd gear anywhere from 1500 rpms to 3500. Only happens at or above about 50% throttle - not if I am very gentle starting off. At first I thought it was my t-belt slapping against the mount, but replaced it and the tensioner about 2 days ago. Cam timing is dead on, ignition timing - not so sure about.

The car: 1990 CRX HF with D16z6 swap (5mt) - as purchased

What I've done in the past year (still same problem) -
Swapped L3 tranny (original crapped out), new clutch, pressure plate, throwout, pilot bearing
Timing belt, tensioner, water pump, t-stat, all fluids
Rear and side tranny mounts
Header, 02 sensor, fuel filter, plugs, dizzy cap and rotor, came with ngk wires

Right now I'm running regular gas

I can't for the life of me figure out what it is. After going through everything I thought that could've been the culprit- exhaust, timing belt, tensioner, etc. I'm still stuck. My one idea is maybe the ignition timing, but I have tried retarding the dizzy all the way forward, still have the same issue. Cam timing is dead on. Car runs great otherwise. Noise is bothering me though. ANy ideas?

PS- It's not the aem intake, there;s already some rubber under to stop it from hitting the metal

 

I'm having the same noise on my '91 DX hatch, all stock. I'm starting to think it has to do with the crank pulley, or alternator pulley. Not sure yet.

 

just turn up the radio.

 

Yeah I'll turn the radio up till something happens to my internals and then i'll have lots of time to listen to it while parked.

Sorry, but if you don't have something intelligent to report, please don't bother replying. To the competent - thank you for your input.

PS I've tried seafoam and to no avail - still there.

 

i know you said exaust, but are you sure its not a heat shield loose and rattling?

 

Sometimes its the heat shield on the cat or around the manifold.

 

Sometimes gravel will get up there too. Definately check all of your heat shields. The one on my stock header would vibrate badly at certain rpm.

 

pull your plugs - take a look at them -

check heat shields just to be sure

might try something like the seafoam and changing your oil after - then also go ahead and change your plugs and wires...bet that clears it up
e: noticed you replaced those - did you gap the plugs right? check the gap and go ahead and try swapping them just to be sure

 

check your headlights, mine are rattleling like crazy and new motor mounts usually work

 

*All 3 mounts on the tranny are new, just haven't replaced the side engine mount. Headlights are aftermarket, but an oem replacement, they are quite loose and sh**ty, but I doubt they vibrate enough to make that loud of a noise.

*There are no heat shields on the car. Exhaust is as follows

(brand new 4-2-1 header) --> (welded test pipe) --> (resonator) --> (muffler)

New gaskets, and the exhaust is not hitting anything. No leaks, very solid

*The brand new spark plugs are gapped correctly, ngk wires can't be more than a couple years old. The old plugs were ngk's that appeared normal, but not gapped correctly.

*Tried seafoam, issue is still there

 

this is a hard one, n e way u can make a youtube video of the noise when it happens so we can get a better understanding or type of noise it is???

all the typical noise have been covered already in this forum.
so imo it'll be very helpful for us all @ HT to get a video of the noise.
right now its like finding a needle in a hay stack.

 

good idea ^

 

Ok guys, no video yet. I have some extra info that may or may not be of any value. I am really leaning towards detonation. I forgot to mention that I do have an aftermarket intake manifold - don't know if that affects fuel mixture. I also am running 5w-30 full synthetic oil changed about 500 miles ago. My bud is bringing in a timing light so I can check the ign timing tomorrow. The car is running very rich - a friend was driving behind me says I got some black smoke at some points and it also smells pretty rich which at idle. I am now running premium fuel, and the issue is still there. ECU is stock d16z6 p28. Thanks for all your help guys.

My question: if it is detonation, how can my car be running rich with the dizzy retarded or advanced and still pinging?

 

Have you hit it for sure with a timing gun?

Have you replaced the timing belt tensioner? Mine made a horrible noise.

 

I will be timing it today once my buddy brings in the light. And no it is not the tensioner - just replaced it a couple weeks ago.

 

So I timed the car today: It was a little advanced so I retarded it back to 16* BTDC. Noise is still there. Maybe a little better, but still very apparent under large load or wot. Again I went over everything in the bay to make sure nothing was hitting or rubbing.

Side note: Oil gauge is at 25 psi @ operating temp while idling. Max pressure is about 75 psi.

Although I believe it to be detonation, I pulled the plugs again and I still don't see any specks on them.

 

The fuel pressure regulator cold have gone bad. I had mine go bad and was dumping a lot of fuel into the cylinders making it run rich. Recommend putting a gauge on the fuel filter so you can always see what your pressure is at all times. Also had a valve lash broke making it make horrible noise.

 

Problem Solved: So after I timed the car I realized that it wasn't pinging, so I kept looking for aftermarket parts that were rubbing. And what did I find - well the junk2 IM was hitting the firewall. There was a little bolt for one of the sensors the was periodically hitting the firewall under load. I used a hammer and a flathead and was able to push the part of the wall back far enough to where it didn't touch.

I feel like a moron, but hey, atleast I got all the preventative maintenance out of the way in doing so. Thanks for all your suggestions. And as for it running rich, I'll check out the regulator.