Hi
I just finished my vacuum hose job on the FD, and had the first test fire today. Unfortunatley its not running clean at all anymore.

What i did:
- All vacuum hoses in rats nest.
- Installed Efini y-pipe
- Installed HKS downpipe
- Changed air filter and belts.
- Dismantled and painted UIAM.

Symptoms, high and rough idle. Engine is vibrating. Sounds like a portjob at the exhaust but the engine is 100% stock and had very nice compression numbers before i started on vacuum.
It is also running _very_ hot. only after idling for a few minutes, the exhaust and cat was ticking from the heat, and the exhaust tips where warm to the touch.

Here is a video:

 

First thing to check is plug wires. If you have plug wires on wrong, the car will backfire, run weird, and have REALLY high EGT's.

High idle can be a vacuum leak, that can be ANY leak between the throttle body and the engine.

Dale

 

I did not touch the plugs and wire, but i may have a bad connection to the coil since the coilpack was moved out of the way for the vacuum job. Would a bad connected coil/plug wire give the same symptoms as plugs put on wrong?

 

Upon the disassembly of my engine I cracked the nipple on the vacuum or pressure chamber (the one behind the alternator) as I was trying to remove the vacuum line.

 

I would also make sure the MAP sensor vacuum line is hooked up properly. I've seen cases of people putting check valves in that line (there isn't one, stock there is a filter) or hooking the vacuum line up to a threaded stud or something on the back of the intake manifold thinking it's a vacuum port.

It's possible the coil pack harness was damaged or something. But, I would take a beat and triple check the plug wires - you may have quickly unplugged one and plugged it back in during the process and forgot about it. Or, it may have pulled loose with moving it and it's not making a good connection.

Dale

 

The problem was, as you guessed, the lack of pressure to the MAP sensor, combined with a to tight throttle cable. I guess thats what i can expect when putting together the intake after 10h of wrenching.



So now the car starts and runs nice, the idle is stable where it should be, but i got a new disturbing sound emerging now:

It comes when i nudge the throttle cable. If i take it very slow and steady i am able to get the RPMs very high without it making a noise. At idle i hear nothing. I suspect it is a clamp or something that hits something else at some rpms, but i really dont know since i can make it rev high without noise if i take it slow.

 

I noticed in the last picture the hose that connects to the plastic elbow wasn't connected. I didn't read anything about you putting that hose back on.

 

All such problems are 100% user errors. You must recheck 100% of everything!

 

I did

Yeah, i am aware of that Its all my fault, but maybe someone else did the same mistakes and can guyde me to a solution

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After some searching i found a video with a similar sound, and that was a broken air pump. So i tried to unhook the air pump, and then the sound went away. So it is somehow related to the air pump. And i can think of two things that might be the cause:

1 - The OEM 100degree hose bend between the pump and the pipes broke when i removed it, so i have temporarily replaced it with a regular coolant hose. Problem is that it dont bend well so it may restirct the flow somewhat.

2 - I managed to spill some water on my working table that ended up on the floor where the pump was sitting, and i may ahjve gotten some of it inside it. Would that be enough to ruin it?

 

Yep, that's the air pump moo. Air pump air goes into the air control valve and extra air is vented (stock) back to the air box where it is silenced.

Search on air pump moo, it's been covered a lot, and I have an anti-moo device that's easy and cheap to make.

Dale

 

Thanks for the tip! Ill look into it, tho i would prefer to have everything working as it did. I am one of those guys who want everything looking like it came form mazda What is causing the sound? With the exception of the hose, and mentioned water, nothing in the intake has changed, and it was dead silence before i redid the vacuum?

 

On my FC it was really more pronounced...Funny as hell though...on my car anyways.
I read something about a table leg stopper.You know,the bottom rubber thing that prevents the leg from scratchin the floor thing-a-ma-jig.
But I took out all that stuff eventually.

I also think there is an Airpump delete pulley you can get of you decide to eliminate the air pump.Like an Idler pulley I believe.

*Dale..how do you milk an Airpump?

 

Do you have the air pump return line hooked up? It's something in that return line. It comes from the air control valve, back towards the firewall, then around to a metal tube running along the upper intake manifold. From there it goes to the stock air box.

Did you unbolt the air control valve from the lower intake manifold? There's a valve in there (I call it the wagon wheel because that's what it looks like) that has to sit flush in its recess in the LIM. If it's cocked it can cause noise. Also, if you have a bad gasket (the new gasket is metal) you could get noise as well.

Dale

 

Thanks again Dale! Really helpfull answers! I had that apart yeah, and i reused the gaskets and the wheel, will try to open it and check, and also order replacements for them. Now that i know whats causing the noise i am positive it can be fixed