New Issues After Installing FSZE Intake Manifold. Hopefully Simple?

Luken10

Member
If any of you found my other thread you will know that I recently had a FSZE engine put in my car. To get the most out of it I installed the FSZE intake manifold as well. This is when things started going wrong...

Whenever I am driving and I put the car in neutral and let the revs drop completely, they drop too far. They will go to the 200 - 600 rpm range and then jump back up to a normal steady idle. It does this without fail now. My normal idle is perfectly fine. It's only when the revs drop.

The only time my idle does go crazy is when I completely fill my gas tank. The first time I start the engine it immediately wants to die. It will not stay alive without feeding it some gas. Once I drive it for a couple of minutes everything is fine again.

I'm really not sure if the two problems are caused by the same issue. The second problems seems like more of an EVAP issue.

As stated above I have the FSZE intake manifold installed. Brand new gasket was used. I also have a throttle body spacer, properly sealed with two new gaskets. I used the throttle body off my old manifold, so I know it worked fine previously. I did THOROUGHLY clean it with throttle body cleaner. I also installed new spark plugs. I forget the model number, but they are the "long reach" plugs compared to factory. I also only use premium 91 octane fuel. Sadly the car will not throw a code for any of this. I have driven over 700 miles with the issues, but nothing has triggered.
 
Fuel trims?

Spray some brake cleaner around the injectors and see if they're leaking vacuum. They did when I changed them.
 
How would I go about inspecting/changing fuel trims? To be honest I really don't even know what that implies.

Good idea about the injectors. I'm 95% sure I installed them correctly, but I thought it was a little strange that thay weren't super snug in fitment.

Also, just to add. I do not have a fuel pulsation damper any more. It isn't built into the FSZE fuel rail. I couldn't really find any consequences online for not having one.
 
Fuel trims are a measurement of addition or subtraction to the amount of fuel injected. Negative numbers mean the PCM is pulling fuel, positive means it is adding. You need a scan tool to view them.

The injectors are only sealed by little donuts and downward pressure from the rail. If they get hard and brittle or have debris under them, they will leak intake vacuum. They gave me trouble after my swap

https://www.mazdas247.com/forum/showthread.php?123847126-DIY-Injector-Seal-Replacement&highlight=
 
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I'll get the jelly filled kind to really make it seal!

Tried spraying some throttle body cleaner in the injector seats. I didn't notice any sort of idle change. Was really hoping it would be this simple fix. Sprayed it around the intake area as well with the same results.

I reset the ecu again just to see what would happen. The problem probably won't manifest itself again till I drive it a bit more. The weird thing is that there is a large noticeable increase in power whenever I reset the ECU. This is the second time now I have reset it due to this issue, and it pulls alot harder. Once the problem comes back and the ECU adjusts I always seem to be a little low on power again.
 
What do you guys think about a the neutral safety switch being bad? Before the engine swap I had the P0705 code intermittently. It would go away on it's own and never caused any problems as far as I could tell. I haven't gotten this code at all after the engine swap, but it makes me curious.

I'm thinking the ECU doesn't know when the car needs to idle. So when I push the clutch in and the revs drop to far, the ECU has an "oh s***" moment and intervenes in order to stop the car from dying.

I don't think it's the IAC because it idles perfectly after it recovers from the stumble. Unless using the USD IAC on the JDM manifold is the issue. As far as I can tell they are the same.


Also, regarding the fueling issue. When I swapped the manifold I forgot to plug in the charcoal canister vacuum line. I drove like that for a couple of days and it eventually threw a code. Would this damage the charcoal canister?
 
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What do you guys think about a the neutral safety switch being bad? Before the engine swap I had the P0705 code intermittently.

That makes sense to me... The ECU needs to receive 10 bad signals (maybe in a row) to register a fault...

If you have an intermittent fault it might keep resetting after a good signal.

It may also be the wiring for the switch shorting or breaking to open.


 
I actually got the idea from a Miata thread I had found where the NSS was the culprit. What's interesting is I can for sure make the car do the idle drop more than 10 times during a drive cycle. I would have thought it would have flipped a code by now. I've driven over a thousand miles with this condition.

pcb I found the thread where you kept recommending to replace the entire length of the wire and the guy just wouldn't do it, ha! I felt your frustration. I've unplugged the NSS for now to see what happens. I read some other threads where the problem goes away when you do this. Obviously I would not keep it long term, only for diagnosing. I tried testing the ohms for the switch. To be honest I don't have a great understanding of how to do that. However, I got a value of 1 when it was in gear and a different value when I put it in neutral. I am assuming this tells me the switch is working.

As for the rough idle after filling the gas tank, I went ahead and checked to purge control solenoid again. I know it is working because I hooked it up directly to the battery. However, I was able to suck a small amount of air through the port the charcoal canister plugs into when the valve is closed. I don't think that should be a problem though, because that would be going in the wrong direction. Back to the canister and not flooding my engine.

The circled port is the one I was able to suck air out of. I wasn't able to blow air though either port and I couldn't suck anything from the manifold port. When plugged into the battery, it is completely open. I don't understand how my engine could be flooded, if worst case scenario, the PCS is stuck closed because it isn't being activated. Everything I have researched online points to the PCS, but that just isn't making sense to me after doing my diagnosing.
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Gonna fill my gas tank tonight and see what happens.
 
Just filled my tank and had absolutely no stumbling or idling issues. Not sure if I did something to fix it, or it just worked it out on its own. For now i'm just going to consider that taken care of.

I'm pretty sure the other issue is not a neutral switch. When the car detects it is not moving, but does not detect that it is in neutral it automatically jumps the revs by about 500. I've never had that happen previously, so I am ruling that out.

Is it possible it's the lightweight flywheel? Are the revs dropping too fast for the ECU to compensate? I thought this issue only came about after I swapped the manifold, but maybe I just didn't notice it after the engine swap. I had the mazdaspeed familia lightweight flywheel in before the engine swap and never had a problem. I have a fidanza in it now, which is 6 or so pounds lighter than that.

Here's a quick video of the issue.
 
Is it possible it's the lightweight flywheel? Are the revs dropping too fast for the ECU to compensate? I thought this issue only came about after I swapped the manifold, but maybe I just didn't notice it after the engine swap. I had the mazdaspeed familia lightweight flywheel in before the engine swap and never had a problem. I have a fidanza in it now, which is 6 or so pounds lighter than that.

Here's a quick video of the issue.

And here we get to the issue. It is likely that the light Fidanza is part of the problem. I had similar issues when I had big cams getting more air through the engine.

Your manifold will be getting more air into the engine and your ecu will be close to the limit of keeping your idle high enough. The Fidanza tips it over the edge and that is why the revs drop so far.
 
I did a good bit of research about using the fidanza in the Protege and no one mentioned any problems. It makes sense, but why doesn't this happen to everyone? It's fairly noticeable.

I have another IACV that I am going to try out. The black plastic that covers the electronics is slightly broken, but it may be worth a shot. If that doesn't change anything I guess i'll just drive it the way it is. It doesn't throw any codes, but it's kind of annoying.
 
I actually got the idea from a Miata thread I had found where the NSS was the culprit. What's interesting is I can for sure make the car do the idle drop more than 10 times during a drive cycle. I would have thought it would have flipped a code by now. I've driven over a thousand miles with this condition.

However, I got a value of 1 when it was in gear and a different value when I put it in neutral. I am assuming this tells me the switch is working.

I'm still suspicious of the NSS...
You could have a sticky switch that isn't continuously failing.

It may need ten bad signals in a row with one good one to reset the count?? And you have thrown the P0705 code before....

If you feel like throwing a few bucks at your car, I'd throw some there...
 
The ECU was able to clear the fault on it's own. Leading me to think it's okay. Still, as you mentioned, the code did show up before.

Let's just assume it is the switch. Why would the RPM drop every single time if the switch is intermittent?

I'm not putting any more money into this car. After the engine swap and a few upgrades I'm at my limit for a 13 year old econobox, haha. (Even though I love it!)
 
... I've unplugged the NSS for now to see what happens. I read some other threads where the problem goes away when you do this...
.

So did you throw the P0705 code when you did that ??

You could also have a problem with your clutch switch.

Either switch should tell the ECU to hand over idle control to the IAC.... And your IAC idles the car fine at idle...
I think your car isn't getting the signal although I have no idea why you aren't throwing a code ???
(P0704 is for a faulty clutch switch)

Anyway... Here's the list in case you missed something.




Maybe just ignore the problem like you said... If it doesn't irritate the hell out of you.
 
...I'm not putting any more money into this car. After the engine swap and a few upgrades I'm at my limit for a 13 year old econobox, haha. (Even though I love it!)

I hear that...
Ya don't wanna put a ten dollar saddle on a two dollar horse....

 
So did you throw the P0705 code when you did that ??

You could also have a problem with your clutch switch.

Either switch should tell the ECU to hand over idle control to the IAC.... And your IAC idles the car fine at idle...
I think your car isn't getting the signal although I have no idea why you aren't throwing a code ???
(P0704 is for a faulty clutch switch)

Maybe just ignore the problem like you said... If it doesn't irritate the hell out of you.
It does bother me... I want to know that my car is running properly. I actually didn't check the code when I unplugged the NSS. I just assumed it was P0705. I don't think it's the clutch pedal switch because the RPMs would directly respond to me pushing the clutch in. Clutch out, the RPMs would be about 500 too high, acting as some sort of safety mechanism compensating for the NSS being unplugged. Clutch in, and the idle would instantly drop back to normal. Did it every time without fail.

I'm sure it's possible I have a vacuum leak. I did just replace the entire manifold... I have a suspicion my gas mileage is also being adversely effected. Granted I've been doing a lot of idling and some WOT for testing purposes. Leading me to beleive something else is wrong, like a vauum leak. I want to go to a vape shop and pay some guy ten bucks to blow in my engine bay. Thanks for posting that section of the service manual. You've been a huge help pcb!

For now, when I get the time, i'll just try switching the IACV. If that doesn't work then I'm probably going to assume it's the flywheel. I found a few other forum posts for different cars that exhibit the same symptoms.


I hear that...
Ya don't wanna put a ten dollar saddle on a two dollar horse....
Tell me about it. I have for sure paid more for upgrades and maintenance than I did for the entire car. Although, I think mine looks close to new compared to yours. Rust is a sad, sad thing.
 
.... I don't think it's the clutch pedal switch because the RPMs would directly respond to me pushing the clutch in. Clutch out, the RPMs would be about 500 too high, acting as some sort of safety mechanism compensating for the NSS being unplugged. Clutch in, and the idle would instantly drop back to normal. Did it every time without fail.

That suggests to me that both switches are working properly.

So that means you have some sort of air leak or you need to install a heavier flywheel. ???

A new or better IAC valve may respond better and may be able to keep up with our dumbly ECU.
(pretty sure we're running Windows 95)
 
Well I'm definitely not opening up the transmission any time soon! If I would have known I already had the lighter Mazdaspeed flywheel I would have just kept that. I loved the way my car drove and responded with the previous FSDE setup. (Mid Range Torque)

The other IACV I have has some damage, so I don't have high hopes. It's crazy how they stack the engines when they come over in the shipping containers. Lots of smaller plastic bit's were broke. Definitely worth a shot, though. Fingers crossed I don't strip one of the phillips head screws!
 
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