Rough Idle and Bad MPG
 

Hi all,

Every rotary is built different, your first engine could have been capable of 18 city but the new one may only be 15. (fwiw my 8 get 15 city 20 highway)

as for the AC and rough idle, the AC and lights have a rather large steal from the engine but if the vibration is extremely bad check the engine mounts if those are good i'd say its normal


the hot start issue could be the dwell time with the bhr ignition a tune would fix this

[QUOTE=sonicsdaman;4630366]Every rotary is built different, your first engine could have been capable of 18 city but the new one may only be 15. (fwiw my 8 get 15 city 20 highway)

Get your alternator tested. A few of your symptoms are in line with an alternator problem resulting in voltage/output fluctuation, which in turn can cause spark and fueling problems as well.

In case that isn't it, disconnect and thoroughly clean all your major grounding points, since grounding point corrosion can also cause voltage fluctuation.

You would have kept the same alternator from your old engine to the new, it is just transfered over.

Also check to be sure that all pulleys are spinning freely. You will have to remove the belts to test this by hand. If any of them have resistance or grinding or lumpy motion, that could contribute to your problems.

I suspect that all your normal mileage related parts are fine, because of the highway mileage. When everything is stable and the fans aren't needed, your mileage is predictable. It's city mileage that is the problem, which means something is soaking engine power more than you normally expect. I'm going to assume this isn't a change in driving habits, even from external sources like thicker average traffic or an extra light, or a change in light timing that means you sit at lights more. The fact that you have symptoms that point to a voltage or current control problem tells me that there is a real issue there, even excluding outside factors.

City driving will have much more fan activations and a wider range of RPM usage, both of which challenge the alternator more. Even a slight problem there could easily have a noticeable impact in gas mileage.

Remans will have lower starting compression, it takes time and mileage to wear in the engine back to where it should be for a 'new' engine.

If it is the car that shakes at idle, but the needle is stable, then yes, it's likely a motor mount problem. If the needle is what isn't stable, regardless of whether or not the car is physically shaking, then there is another problem that has nothing to do with motor mounts. If you fix that and the car still shakes physically at idle, then yes, motor mounts too.





(Remember to get your coolant system flushed between 3,000 and 5,000 miles after the reman change, to ensure you don't have a cooling system failure from the excess sealant Mazda uses on the reman builds)

Listen to riwwp he's better at this then me :lol:

Thanks!!

Can I test the alternator with a multimeter at home? Just monitor battery voltage while I start the car and rev it some? Or is it better to have it tested professionally somewhere?

The idle shaking corresponds to the RPM needle dipping, it's not just shaking with stable idle. That suggests it's not (or not only) the motor mounts?

You're all better at it than me! :lol2: These forums have been a life saver many many times.

Test it professionally. Most auto parts stores can do it for you, though some aren't willing to test it on the car, some can't test it off the car. I'd expect most privately owned shops can do it too. It's more than just the output voltage.

However, that being said, if you test the output voltage with a multimeter while it's idling, and it ISN'T stable, or is outside the ideal range (~13.2 - 14.9v), then you have confirmed the core issue. The next steps would be to fine out if it's because of an alternator failure or because of a poor electrical connection somewhere. Both will still be possible without a professional test of the alternator.

Yes, if the needle is dipping with the shake, it's not the motor mounts that is doing that. Put another way, the motor mounts can't possibly make the idle speed change :)

So the output voltage was stable at 14.3 when idling. I went around and loosened/tightened all of the ground contacts which might have improved idle smoothness; I'll keep an eye on it when I drive more later.

Now that I was looking more closely at the alternator, the belt on there looks to be in pretty bad shape (frayed edges). Do they not replace belts when they switch out an engine? The belt felt tight enough, just didn't look great:

Alternator Belt - Imgur

Time to order one of those and replace it? I can check pulleys then too.

Yeah, replace them. Whatever your local auto parts store has works fine. OEM ones from a dealer are around $60 i believe, including markup.

Interestingly, that could also contribute to your problem. It's rare, but possible. When I had my 99 Miata, I apparently clipped one of the belts when installing the 2nd engine (it went through more engines than my 8 did), and frayed. The frayed bit has metal in it, and it was hitting the crankshaft sensor (same function as the e-shaft sensor), and disrupting the magnetic signature periodically when it would hit at exactly the wrong time and crank position. Took me a bit to figure that one out.

Ouch, that sounds like a tough one, that intermittent stuff is frustrating. My Subaru started having it's AC clutch stick open every once in a while depending on how large a bump I drove over. That, combined with some funny wiring, was a real chore to narrow down.

Okay going to try and pick up some belts and throw them on tonight. We'll see how late the auto parts place is open.

Changed out my belts this morning and had everything running. Went to tighten down the last bolt on the AC belt, the wrench slipped off, and totally destroyed my VFAD solenoid. Arghhh.

Anyone know a good place to pick up a VFAD solenoid?

Oh, and all the pulleys spin freely.

Ouch, sucks :(

On to testing the alternator and disconnecting/cleaning grounding points.

One of the partout threads over in classifieds is probably going to be the cheapest replacement solenoid, otherwise, contact Mazmart.

i think i have one in my garage

That's not attached to your car? :lol2:

If you want to get it out of your garage I'd be happy to buy it from you, but it looks like Arlington and Ebay could get it to me too:

Arlington

Ebay

Oh, and here's mine:

Very Sad

yep almost positive i have one. ill check when i get home

Short term, just disconnect the line towards the VAFD actuator, disconnect the wire, and plug the vacuum line. I think the default is open for the actuator and the vacuum closes it.

Great, thanks. That should make it drive-able until I get the solenoid?

I've got another vehicle to use for now, but just in case it would be good to have the option.

I actually have that line capped off, the wire connected to the dummy port on the air box, and the VAFD in a box in the garage.

Reduced intake temps a rather large amount (like 15F) when I pulled it out.

The silent portion is a tube that runs across the top of the radiator, it makes a great air charge heater.

Interesting. Are you running a lot of other aftermarket parts? Are there any drawbacks to doing this on an otherwise stock engine? I'd imagine they put it in there for a reason, right?

my vfad is in the garage too. i do have a bunch of mods but it doesnt matter. its there to keep noise down at low rpm iirc. you can cap it under the throttle body

Great, thanks for the info. I'm not opposed to forcing some more rotary noise on the people around me.

Okay I pulled the alternator this afternoon and took it to get checked. The guy at the auto parts store ran the test three times, and it checked out just fine. I had some 4awg wire sitting around at work, so I made a grounding kit as long as I had everything pulled out. I followed this guide:

DIY Grounding Kit

I didn't have enough wire to make the link across the back of the engine bay (through the cowling) or the wire from the battery negative terminal down to the bolt under the airbox (there's already a wire there). While doing that, I used a dremel with a wire brush to clean up all of the ground contacts.

If anything the throttle seems more responsive and power feels more immediate, but it's hard to tell if that's just placebo effect because I've been wrenching on her all day! Idle still has it's small quirks where RPMs will drop and the car will shake slightly. Maybe the ECU is still trimming in? I'll keep an eye on it and see how gas mileage does.

Beer time. :beer:

Sounds like you did well.

I have started to believe that the ground are a big issue (did you notice that you were cleaning paint of the grounding surface) and a kit, or at least star washers, really help. All of my lines terminate at the bolt under the air box, and then one line runs up to the battery. That makes things look cleaner.

I think I have the intake manifold area bolt attached to the one in front of the oil filter (PITA) then to either the Coil bracket. Coil bracket is close to the compressor, so that is good. Coils are a good source of noise. Just make sure you have a big wire running to the battery.

And, likely things are improved. On mine, the idle when smoother almost immediately. You have not reduced a ton of noise from the sensor lines and that is how the ECU runs the engine. There is a different DIY in the Congrats thread below, but it is much the same as you did.

You might want to look at the rest of the $100 items as well. Those are things that made my life easier.

I've now run through 1.5 tanks of gas with the change (additional grounding wire). The first tank I left the vfad off but had the grounding kit installed. For that tank I traveled 173 miles on 13.1 gallons of fuel (all city driving). That gives me 13.21 mpg, which is right in line with previous tanks. For the most recent tank I installed a replacement vfad solenoid (just to rule that out as impacting anything), and I've gotten around 80 mi through half a tank...so it doesn't look like additional grounding has helped gas mileage much.

The idle seems to be the same if not a little more rough. When the AC is turned on I get a big dip in RPMs, and just a standard idle with everything off feels like it's got a little more rumble than normal. That's with a 4 awg ground line running from the battery's negative terminal to the bolt on the AC compressor.

Any ideas? Is there a way for me to check for grounding issues under the hood with a multimeter? Or is there something besides grounding that could be causing issues?

Thanks for the help, everyone. I'm kinda stumped on this one.

I'm now 7/8 of the way through this tank, and I've got just under 160 mi on it. Definitely not an improvement, and possibly a step in the other direction. I have noticed a high-pitched whirring sound linked to RPMs right when I start the car up. It goes away after a minute or two, but there's consistently a noise similar to pump cavitation or bad bearings coming from behind the glove compartment. It sounds similar to the "marbles in a blender" issue that I had in the past, but this is more consistent (and I have the orifice installed in the heater hose, which previously had fixed that issue for me).

I'm not sure if that's related, but my idle is definitely as rough as ever. It's getting colder here, so that may start to have some effect too.

Hm,

So, to review the bidding...

New Engine, Cleaned MAF, Cleaned ESS, Good Grounds, Good Alternator, Good Battery, Good Fuel, Good Ignition,

If it were me, I would hit it with a can of fuel injector cleaner for giggles and grins, then start looking at fuel pump. I suggest a way to gather some data as well. I like the ultra gauge. You can watch fuel trims and see if they wander a great deal (fuel pump indicator). It will also give you an idea of instantaneous mileage, which you can use to see if something you are doing is causing an issue.

How old is the CAT? If plugged, or with media rattling around, it could be causing issues, and it is below the glove compartment. Is the floor warm, or the shifter warm?

I've got the TorquePro app and a bluetooth ODBII reader...is that enough, or is the ultra gauge a better option? I'm pretty sure I can see fuel trims with Torque.

The CAT is original, so has roughly 70,000 mi on it. The dealership said it was "good inside and out" when I asked them to open it up and look, and that was 2000 mi or so ago (assuming they were telling the truth and actually visually inspected it). I haven't noticed any more warmth in the center console (or shifter) than usual. It's always been a little warm inside the cupholders, but that's dated back to when I got the car.

I'll see if I can pinpoint the source of that noise a little more closely next time it's cold and I start it up. In the meantime I'll set up Torque to record fuel trims for me. Anything else I should be logging?

Okay the high pitch whirring noise is definitely the air pump. Still can't tell about the other bearing/cavitation noise.

Also, it looks like some squirrels decided to take up residence under my hood and chewed up a whole section of the cloth liner...bunch of jerks.

Here's a picture of rodent damage:

https://i.imgur.com/2pszDpj.jpg

They should be paying rent.

I also uploaded a video that I took under the hood. Check from the ~20-25s mark on to hear what I think might be the sound I'm hearing when accelerating. Almost sounds like something vibrating? I do not remember hearing this sound before (although it's possible it was there), so it could be something I did while installing the grounding kit.


And one more watching the idle. It's hard to get the extent that the car is shaking from the video, but a good set of headphones tells some of it through the bass. I flip the compressor on/off a few times and then the lights after that.


I'm close to the end of this tank (169 mi so far), so I'll throw some fuel injector cleaner in tomorrow morning right before I fill up.

Threw in a bottle of fuel injector cleaner yesterday and filled the tank up. I plugged my OBDII reader in and logged a handful of things with Torque for a trip to work and then back home at the end of the day. These are pretty typical drives for me and should be making up the bulk of my driving. I made a bunch of charts comparing each value to engine RPM:

Trip to Work

Trip Home

I'm not sure what the normal values are for a lot of these things, so I couldn't really pull much out of it.

This may not be an extreme enough variance, but I don't think I've seen anyone referring to alignment or tire pressure. Have you had an alignment done since the issues have risen, and is your tire pressure at or above 32psi all around?

What about air filter? Has that been checked and replaced? Simple stuff, but I find it's easy to look for more hidden problems even while the common ones stare us in the face.

I definitely hear you there; I'm looking at anything and everything at this point.

Tires are one thing I forgot to mention - they were replaced around 6 months ago. At that point they should have been aligned, and I keep them around 34 psi normally. I haven't noticed any abnormal wear or change in gas mileage from the old set to the new one.

Air filter was replaced at the end of last year, and I swapped it out for a K&N reusable filter just a month or two ago.

And thanks again to everyone for reading through and helping, it is much appreciated.

You know... I've never had it before, but that rattle kind of sounds like the whole "marbles in a can/miac" issue with the SSV.. Anyone wanna corrrect me?

I had a similar revving issue that ended up being ignition related... Have you tried with some working good OEM coils and healthy plugs by chance? Also what type of new wires did you get to pair with your BHR ignition?

So I had the marbles-in-a-can sound before, but after installing an orifice in the heater hose it seemed to go away. This sound is similar from inside the cabin, but seems to be coming from further behind the glove compartment (and maybe more centered) than that noise. When I hear the sound with my head under the hood it's a little closer to a baseball card in bike spokes. Very strange. I'm going to use a piece of tubing and see if I can narrow down the source of it.

I got my replacement wires from Charles at BHR, so they're the same ones that come with the kit originally. I haven't tried with stock ignition coils since before the engine was replaced, but my ignition performance was pretty consistent when I switched to BHR originally. Plus I was on my second set of OEM coils/wires at that point. It's possible I've screwed something up with the ignition system, but it's seemed to be pretty consistent across multiple installations (with the exception of one stock coil that was bad out of the box).

I hate to necro-post (no, really. I do), but I feel like posting here in order to provide some historical information to the group. Here goes:

I bought this guy's car. Of course he didn't mention the idle or noise issue (to be honest, any idle fluctuations are almost entirely unnoticeable to me so maybe he thought he fixed it), but I believe I've found the root of the ticking issue.

One of the spark plug wires (whichever is from the rear most coil) has been rubbing against the dip stick tube, and appears to be intermittently arcing to ground. I'll add pictures as soon as my replacement wires and retainers arrive and I can get in there with a camera.

The wire routing seems like it was designed deliberately to interfere with the dipstick.. it's weird. I'll update with pictures so you all can see what I mean.

OK, so I went under the hood today before my drive to work and adjusted the spark plug routing and used some tape to keep the wire from rubbing on that bastard dipstick tube. Ticking or "baseball cards in bicycle spokes" (also known as the sound a spark plug wire makes when arcing) sound is gone, and the idle is perfect. I mean, really perfect.

I took a short video after pulling into the parking lot at work:



Now on to BHR to get some new wires, since it appears that OEM fitment wires won't work with these fancy coils. Anyone have any information on where to get wires for BHR coils? Are they stock fitment for some other vehicle, or totally custom?

Speaking of coils, I noticed the coils have little heat sinks on them. Neat. :wiggle: