DVerdeyen

iTrader: (1)

Okay guys I need some help. I'm not sure what an engine on its last leg sounds like ect, never had one. Starts fine, runs just as powerful as the day I got it, yeah some hot starts aren't so great.. But now I have this issue.

Issue #1: Once engine is warm and I come to a stop, not always, but every now and then the rpms will dip well under idle and the car revs itself to keep it alive. This will happen every few stops, or if it's warm and I sit idle for a few minutes, like in the video it dips and hops.

Issue #2: it sounds as if it's got a slight knocking. I'm changing the oil today, so hopefully that helps slightly. But it's now noticeable.
The video is hopefully good enough to hear the slight knock and the engine drop rpms.

The exhaust is where you will hear the drop and hop much more clearly with the changes of rpms.


Thanks for any info!!



The link bellow is to the video.

nycgps

iTrader: (1)

clean ur throttle body

N0P1st0ns

BUMP. I have the exact same knocking noise.

Harlan

iTrader: (3)

Take a look at this:
https://www.rx8club.com/rx-8-discuss...icking-213634/

DVerdeyen

iTrader: (1)

I'll check and see if there is any oil in the intake.

@Harlan I've been thinking about going ahead and cleaning it all out. Just never have the time since I've never done it and I'm sure it will take me forever.

DVerdeyen

iTrader: (1)

Okay guys so I've gone through and cleaned everything. Throttle body, Ssv, MAF.. Idle did improve slightly, but is back. So I ran a fuel system cleaner. No luck. But I did notice something..

I drained my coolant, more like the bucket leaked and went all over my garage, so I added all new coolant. Checked it after a drive, it was low. So I added distilled water until full. Now I used to have the coolant light come on at a cold start, roughly 32 degrees cold, and after a few seconds it would disappear. After completely filling the system, it's starting to happen again. Even if I top it off again. Just takes about a week and the light starts up again.

So. From this my hypothesis is that I possibly have a bad, or slightly leaking coolant seal. My next idea is just to get all new seals and replace all the internal seals with new ones. Since the car still runs well and the power is still perfect, would this be a solution to this problem?? I would assume at this point since coolant may be running into the engine that this may also cause some hard idling at lights since it doesn't combust like gasoline??

Anyone want to comment on this theory? Thanks!

200.mph

iTrader: (9)

replacing the coolant seals=rebuild your motor

9krpmrx8

iTrader: (46)

You should leave the theories to someone else IF you want to know what the problem is, properly troubleshoot the issues. Pressure testing your cooling system will tell if you have a cooling system leak or not. Or spend $20.00 and send off an oil sample to if coolant is present in your oil.

M A Z D A

DVerdeyen

iTrader: (1)

I understand it's a rebuild, but if it would just be a seal, since the motor is still running strong, could I just replace the seals?

And who do I go to for oil samples??

9krpmrx8

iTrader: (46)

No, you can't really just change the coolant seals and slap it back together. Well you shouldn't anyway. And for oil sample test, Blackstone Labs.

DVerdeyen

iTrader: (1)

Thanks for the link, and okay maybe that's not the best idea.

So let's say it is a seal. Would that cause idle issues since it's not combusting? How long can I go before this really becomes a problem considering I continue to add more distilled water. Otherwise I'll look for other possible causes

9krpmrx8

iTrader: (46)

It can definitely cause issues with how it runs, I had a failed coolant seal at 30k on a reman and caught in a oil sample. But when it was happening I was getting random misfires at high RPM and a weird sound in the engine at idle (likely burning off the coolant in the combustion chamber) If I didn't have BHR coils it probably would not have started at all.

But, catching it early and taking it off the road can save you from ruining parts that may be salvageable now. IF it is a coolant seal failure, you want to stop driving it ASAP. BUT DON'T GET AHEAD OF YOURSELF, GUESSING WHAT THE PROBLEM IS WON'T HELP YOU.

This is a video of mine, it was driving me nuts. I tested everything and the car wasn't overheating so I just waited for the oil sample results and it told me what I needed to know before I had a chance to do the coolant system pressure test.

200.mph

iTrader: (9)

you really need to figure out whats causing your issues first. yes an internal coolant seal leak can cause weird idle on a cold engine and smooth out when its warmed up but you have to troubleshoot this issue the proper way. nobody can tell how long the engine has even if we did know what the problem was. everyone on this site can guess from 1-1,000,000 miles. wait let me check my crystal ball and call ms. cleo

DVerdeyen

iTrader: (1)

@9k After watching your video, mine does act like that. Cold starts have been no different for over a year. Hot starts.. well they're getting rougher over time. However when the engine is hot, that's the only time I will get the jittery idle. When I stop at lights, the car revs down to 1k. Drops to 850ish, then.. 900.. 700.. sometimes even a bit lower but it will kick itself back up to idling rpms.

I'll send an oil sample in ASAP to get results. I also understand guessing isn't helping the car any. But I have gone through the common remedies people see with rough idles and so far nothing has worked. That is why when I noticed the coolant light back on at start up today and saw that the coolant was lower than it was a week ago when I topped it off, I thought that was suspicious.

@200 I wouldn't be posting on the forums if I knew what was causing the issues. That is why I am here asking the more knowledgeable trying to find a solution to something they may have come across. However, the idle issue is not at cold idle, it is once the car is warm. I'm not asking for a number between 1-1,000,000. This is my only daily and if a coolant seal is a RIP in a week problem I would do my best to garage it. But if I have time until it does permanent damage I'll wait until the oil results arrive.

9krpmrx8

iTrader: (46)

Yeah it is hard to say man, it could be so many things. Personally based on what you have said I don't think it has anything to do with a coolant seal.

The coolant level sensor light can be problematic and can't really be trusted in a lot of cases so personally I would check the level visually. If you are losing coolant and it is not on the garage floor or steaming off off the engine somewhere then an internal coolant leak would make sense but I'm not sure based on what you have described.

DVerdeyen

iTrader: (1)

I have my cat replaced and have always had a CEL for it. I did buy a Cobb a while back and flashed the car. Then went back to the stock tune. Sold the Cobb. I guess that's approximately around the time this started. It should still be the oem tune it went back to but could it have changed?? Maybe too lean or rich at idle? It's so hard because once I'm driving everything is perfect.

I do have one more idea about it, and that's with the air box. I removed the everything after the air box. Vflad and so on that was oem and left the whole open to the Racing Beat air duct. Also the plug on back left of the airbox (left of the accordion tune) got chewed up in the belt a while back. I was told that wasn't too important and could be left alone.

Would either of those cause air flow issues and be what's effecting my idle? O2? I don't have a device to test those, but I can always get one.

9krpmrx8

iTrader: (46)

Did you cap the port behind the throttle body on the underside of the upper intake manifold? the plug should be for the VFAD vacuum actuator and it is fine without it so long as the wires are taped off and not hanging bare.

DVerdeyen

iTrader: (1)

Here's what I'm running with. VLAD and all the red line is removed. That nozzle is capped.

9krpmrx8

iTrader: (46)

That should be fine.

DVerdeyen

iTrader: (1)

Ugh this issue is annoying.

9krpmrx8

iTrader: (46)

I think you are over thinking it, you need to be methodical. The knocking sound you hear at idle is nothing more that the arm on the SSV actuator (search SSV on youtube) it starts to knock like that over time and if you put your finger on it, it will go away.

The hard starts could be a few things, from a damaged wearing battery (or a shitty new one, it happens) to a worn out starter. The dips in the idle speed could be a few things as well, you could have a slight vacuum leak and not even know it. A proper smoke test would find small vacuum leaks, and they can originate in quite a few places. Remember these cars are getting old, stuff wears out with age. That said, you idle sounds fine to me

As for the coolant, you need to determine if you are losing coolant and then if you are, figure out from where. It is pretty simple really.

DVerdeyen

iTrader: (1)

I'm really not too worried about the knocking as I did get that fixed. The starting, cold is fine, hot can be pretty rough at time, especially after filling up. It's the idling that is driving me crazy. It's not all the time. Just when its hot and I stop at a light, the whole hood and mirrors shake and it's completely noticeable at times.

Imagine pulling up to a light.. Idle goes to normal. And your obnoxious 2 12's in the trunk shake your entire car for a second and then turn off. Few seconds later.. Same thing. But when you're driving this never happens. Next light same thing. Every 50 lights your car may even idle so hard it dies..

Like what the hell.. Haha

GK1707

iTrader: (10)

Have you checked the condition of your motor mounts? Excessive vibration is also a common sign of worn or damaged motor mounts.

DVerdeyen

iTrader: (1)

I have not due to the fact that it only happens when hot and idling. I figured that wouldn't lead to a bad engine mount.

DVerdeyen

iTrader: (1)

Took another look at the codes for the engine light. I've had P0139 due to a test pipe, but I now have engine code P2096. Could 2096 be the cause for the rough idle?? Vacuum leak, and any idea where that code would be sent from such as intake or exhaust?