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miss and knocking noise when it is reved up in neutral
1988 Mazda RX7 1.3L Rotary MFI 080 CID
If some one knows the next step I would very much appreciate it. I am bleeding $$$. Here is the breakdown
5/8 - took car in for squish brakes and radiator leak This is what was done - New Manual trans driveshaft, new radiator, new exhause Y pipe, midpipe, gaskets, new brake caliper front pass side (had other side fixed a few months before)
As I was driving it home started to make a loud knocking noise - turned around and took it back - Ran a engine compression test and was above min standards - healthy engine
6/3 - A new clutch kit was put in, clutch slave cylinder
Car is still making noise
June 20 - rechecked engine - good shape, checked fuel injectors and swap out ignition coils, checked crank angle sensor, air flow meter, belts and pulleys, pressure senor, throttle position senor, fuel pressure and ecu. All good.
Still making noise. PLEASE TELL ME SOMEONE KNOWS WHAT IS WRONG! I was told I could pick it up or leave it there longer and they will try to look into some more.
Help! Renee
I think you should re-evaluate your process of “fixing” the problem.
sure I get it, you bring your car to the shop for brakes and a leaky radiator. They find more issues, you agree to them fixing the other issues. You start driving home, notice a problem that was not there before. You bring it back to them, but instead of ensuring the problem either was caused by them or a byproduct of showcasing something else broken, you agree to more random fixes which did not fix the problem.
Then money is thrown at other random maintenance things. I get it, they should be replaced. But are they targeted at fixing the issue?
Make a video for people here to see. Problem should be explained “sound starts at xx mph, only when accel or decel, I can feel vibration coming from rear of car”.
When it comes to fixing cars (and everything really) there are two types of people, people who throw parts (money) at a problem with the magic net of hope of fixing the problem, or those who take time to diagnose, research eliminate variables. Guess which one is cheaper and less labor intensive.
I’d also recommend evaluating whoever is doing the work. Are they even familiar with these cars? Do they have a real thorough understanding of cars? Are they just agreeing to taking your money? Are they even good mechanics?
but welcome to the board. If you work with the people helping you, you have a much higher chance of solving the issue and saving money.
I’d also recommend evaluating whoever is doing the work. Are they even familiar with these cars? Do they have a real thorough understanding of cars? Are they just agreeing to taking your money? Are they even good mechanics?
quoted for agreement and emphasis ....
i thought of voicing a similar opinion, but figured i'd start trying to get more info on your problem instead.
I has been a while since I heard it. But if I remember right kind of like a clangy ticking of a big clock. The noise seems to be coming from the front of the car. It mainly happens when accelerating at a low rpm. Not sure if my descriptions have helped. Thanks Renee
I have to be honest I am not sure how to respond to posts on here. I feel stupid.
The noise happens with you accelerate at a low RPM. It seems to be coming from the front of the car because that is where he first started looking when I bought it immediately back. Now this part will be described in total girl fashion…because I don’t know the proper verbiage. The noise even happened when he manually revved up the car manually with the pull thing when he was under the hood.
However, I have not seen the car in 4 weeks it is hard to remember what the noise sounded like. This repair shop came highly recommended by another RX-7 owner in the car club I am a member of. Plus I called around St Louis he is the only place that will work on a 88’ rx-7. The next closest place is 4 hours away I could find.
This guy almost exclusively works on RX-7 & 8. People have their cars towed in from other states for him to fix theirs or modify them. I had him fix many things and this is the first time for something like this. The car sat in a garage for years, so it needed work when I first bought it.
Coming on the forum was my last ditch effort. I don’t want to sell the car, but at what point do I say enough is enough. The bigger bummer is that a huge portion of the cars inners have been replaced and are new. If I found someone to buy it, once they heard that noise I know I would not get my $$ I put in it.
Did you or the mechanic try removing the belts then starting and/or driving the car right away to make sure the noise isn’t anything being run by the belts? A bad bearing can make a ticking noise.
In the mechanics opinion, is the noise low or high risk?
Has the clutch fan been looked at? Is any tape or anything slapping the fan blades? Are all blades intact? Fan blades need to be intact to remain balanced.
If the cars at the shop, can the mechanics or you take a video of the noise and a walk around of the engine? You can post the video to YouTube and allow only those who have the link to view it if, or googledrive, there are other online video hosting solutions as well.
We can guess all day, but a video or at least audio is the best path forward.
Before this gets too far outta hand..I'm the one working on the car, I've been working on rotaries since the late 90's. I frequent these forums often so this post popped up and I figured I knew the poster..Absolutley NO money has been spent yet on this particular issue, just at least 3-4 hours of unbillable time from me. The noise and miss from the engine started AFTER the above mentioned work was performed(minus the clutch). Which if you read have nothing to do with the work performed. The car originally came in for brakes, we fixed those. Then it came in and had a fuel leak, which could have burned the car down(FPD), which we fixed along with a brand new fuel injectors since we were there and they were flooding the engine while sitting..Then the radiator was leaking so we fixed that with a new one. Then they came in because the exhaust was loud(was rusted with holes) we fixed the exhaust with a nice OE replacement I had around for pennys on the dollar, also they wanted the u-joints replaced which if you know FC's you have to replace the driveshaft with new. Finally it came in because the clutch went bad, now thats fixed..This car sat very long without much if any maintenance performed, then it became a daily driver and now all these wear items are cropping up at once, it happens..At first I suspected a spun bearing, because thats almost what it sounds like, but right now I think loose exhaust sleeve. Because typically spun bearings make the noise all the time, and they are down compression which this engine is not..AS for the engine miss I'm totally at a blank, it's got good spark, new fuel injectors and evrything else has been checked (AFM,ECU,IGN coils, Spark plugs, Vac leaks etc etc.) nothing..Maybe water thermosensor? We'll see, I've worked on at least 50-100 FC's in my life and this particular noise and miss I've never ran across. They could be related or not, the noise is definitley coming from the engine area. Oh and we checked evrything mentioned above already. I'll get it fixed I always do .
My first thought was a scorched rotor bearing. However, it has been stated that this happens only at low RPM. This lessens the chance of a bad rotor bearing in my opinion. Plus, rotor bearing failure is very uncommon on the FC. Its more prominent on the Renesis. A loose exhaust sleeve would make a rattling noise. Wouldn't hurt (other than time) to pull the manifold and check it. Would be great to post a video of the issue so we can help determine a potential point of failure.
Hello I wanted to update you on the noise. We picked up the car yesterday with the intention of selling. We just could not be down a car any longer with school starting and my son getting a job. My neighbor is a retired Mazda mechanic and apparently was known as one of the top Rx-7 guy 20-30 yrs ago. We have tried not to bother him because of health problems he was going through. But I figured before I put it up for sale I would ask him just to listen and give advise. He actually drove it around the block and heard the noise. Popped the hood looked around and switched the wires that ran to the spark plugs. He did explain to me about front rotors and back rotors and how they have different spark plugs.... it's all too complex for me. He said they were hooked up backwards. My son says the car drives better than it did when we bought it, so it probably has been like that all along. I am still think we are going to sell it and get him a more reliable daily driver. However, I will let him enjoy it the last few weeks of summer.
ALSO, I must give a big thanks to Ernie our mechanic. He has helped us with many other problems with the car and kept it running. He knows what he is doing, this was just so weird. I have been told by many that Rx-7 are money pits and have constant problems.
Ok I'm gonna debunk this..
The spark plug wires were definitley not the cause of the miss or knocking, it's a convienent thing to say if you didn't fix anything though..If you have a stock igniton FC I want you to go out and swap the wires, it will make zero difference on a wasted spark set-up like the stock FC's. They do not care front or rear rotor which spark plug wire is on. You can even swap the leading and trailing and the engine will run just fine, although now the timing will be a bit retarded on the leading yes, but it will NOT knock and miss-fire as this FC was doing in neutral and at idle. I've even verified this with another FC here just to make sure hehe. I've had a few days now to ponder it, I'm thinking the wrong fuel was put into the car(e85 possibly) or maybe just really bad batch of gas from a low volume location. But I am glad that it worked itself out and the engine is running better now!
07-10-23, 05:55 PM
miss and knocking noise when it is reved up in neutral
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