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Engine Noise Near Throttle Body

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freethnker

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Discussion starter · #1 ·
First, I want to say this forum community is great and has provided answers for maintaining my focus for a long time. Thanks to all the contributors.

I have a 2000 ZX3 with a DOHC Zetec engine (130k miles). My focus recently started idling very high after starting the engine. My mechanic replaced the throttle control valve. As soon as I started the car, there was a throbbing engine noise coming from near the intake and throttle body. I searched around the forum quite a bit and decided to replace the throttle body along with the TPS sensor. I bought a used working condition TB (Ford told me new TB is little over $300), cleaned it well, and installed today. I also disconnected the battery while changing the TB to reset the ECU once repair is done. Idling is normal but the noise is still there. It sounds as if the intake is sucking in much more air but the noise is coming from deep down the throttle body area. The noise stops while accelerating heavily at around 30-45mph. Anyone have any ideas what's causing this noise?
 
Discussion starter · #2 ·
Just to clarify a bit more. The vacuum lines have been inspected and one hose replaced. This noise originally came on after replacing the Idle Air Control Valve. I tried removing the new valve again and inspected it, but everything seems and fits fine. Took off the air intake and started the car but the noise was still there. It seems as if it is below the throttle body. I saw a similar post about noise in the intake manifold. The owner replaced the manifold and the noise was gone. Could this be the resolution to my issue?
 
#3 ·
Being you don't mention any loud sucking sound, as most describe it, I'm going to go with this being normal during the re-learning process for the new IACM.

Lets say the old IACM was clogged/worn/bad, but the car still ran and idled/tried to idle. The ECU would learn those settings and correct itself for them. Now with the new IACM those same learned settings are present but they are wrong and the car is taking in too much air at idle. It will try to re-correct itself in a short time but during that process it may feel/sound funny.
Though maybe this isn't the case. But I'd say drive it a day and see what happens. It should drive normal.

The other thought I have is maybe something with the PCV. I know it can make somewhat of a pulsing sound. Check both those vacuum lines (one form behind ex manifold other from valve cover). It's common for the PCV Elbow to become soft and collapse, search should turn up a replacement part # for it.
 
Discussion starter · #4 ·
Thanks for the reply. The noise is very loud; medium-pitched, consistent, definitely coming from the intake manifold area. I've been driving with the new IACM for 3 days now and it has not corrected itself. The engine runs fine and gears shift like they did before. My mechanic replaced one PCV hose and the second looks fine. Any other suggestions?
 
Discussion starter · #6 ·
When you say IACM, do you mean the Idle Air Control Valve that I mentioned was changed? Or is there some other Idle Air Control Motor? The valve is in tough spot and can only be reached from under the car. I removed it this morning to see if perhaps some debris was there from the last one but nothing. Put it back and it did not resolve the issue. I'm getting frustrated with this noise.
 
#7 ·
Did you replace the IACV gasket?
Other intake manifold (IM) ports in that area: Brake booster, PCV hose, individual vacuum lines for EVAP valve, fuel pressure sensor and EGR valve actuator (further up the IM) and the EVAP canister purge line.
The intake runners also have sealing gaskets where the ports meet the cylinder head.
Also the metal EGR tube can sometimes come adrift from the IM; it should be bonded in.
Sound like you have a very small air leak somewhere, not enough to affect performance, but just enough to make a noise.
 
Discussion starter · #8 ·
Spent the last two days checking all hoses, tubes, and sensors. I cannot find any air leaks. The car now often dies upon starting the engine. Got a check engine light for the mass air flow sensor. Got one from a junkyard, replaced, and the engine noise is still there. There are some sounds of backfiring in the intake now when I rev up the engine. Spoke with another car enthusiast who suggested that the timing belt might have skipped some gears causing uneven distribution between air and gas coming to the engine. I'm gonna have another mechanic check the timing belt tomorrow. I replaced the last one about half a year ago. Will post results.
 
#9 ·
sucking noise

i have a 2001 ford focus 2.0 dohc that is also doing the same thing it was dying and making a loud sucking noise coming from air box when un hooked from TB it would still make noise i am trying to figure out the problem because it is very annoying can you please let me know freethnker what you did to fix the problem
 
Discussion starter · #10 ·
After spending the entire summer going from one mechanic to another in an effort to resolve this problem on my '00 Focus, I finally purchased and replaced the idle control valve. Make sure you get the original one manufactured by Ford or motorcraft. I tried putting in used ones to try and save money, but it did not work properly. Ford dealers charge alot for this part, but you can find it cheaper online. The part number might be upgraded, though. Let me know if you need a link.

You can replace this part by yourself, but it is not an easy job. You have to get under the engine and position your arm to reach to a tight place with a wrench under the throttle body and manifold. Let me know if this works for you or you need more information.
 
#11 · (Edited)
CHEAP fix for composite manifold leak at vacuum line connections.
Did you check the vacuum lines connection, set of three near throttle body, for leaks? Easy fix is to stick a bicycle inner tube patch with smaller diameter holes matching vacuum ports layout. Apply some adhesive such as a miracle leak repair (Leak Fix by Rustoleum) on patch and position patch in place making sure the inner tube rubber stretches tightly around vacuum ports. I have done this months ago and it is still leak proof. The inner tube can flex as required while being leak proof.
 
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claude27459
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