Can "Intake Induction Service" damage the IAC unit?

Situation: A shop recently performed an intake induction service on my car. After picking up my car and driving a few miles, the engine began revving to 5000 rpm by itself in neutral (I have manual trans). I took it back to the shop the next morning and was told (mechanic just turned on the engine, but without any further inspection) that it is probably to due to the chemicals used to clean the system and it will go away after some miles on the highway. That evening, I put on 100 miles, but the problem persisted - the car will speed to 70 mph on the highway flat without pressure on the gas pedal.

After bringing the car back to the shop, I was told that the IAC unit was bad and needed to be replaced. I was also asked if anyone had worked on it before because it contained silicone - No one worked on the engine except for them.

Thereafter, I took it to a Ford dealer and the problem was diagnosed as a bad IAC valve and fixed for close to $600. At least the car works afterward. When asked, the dealer said that an improper induction service could damage the IAC, though they can’t say for sure.

I don’t believe the local shop intentionally damaged the car (shop has a good local reputation from the online sources and BBB that I checked), but I told them it was “hard to believe” that this problem was coincidental. They denied any blame.

Question: What is the probability that the IAC unit gets damaged by an improper induction service routine?

A) Background:

I have a 2004 Ford Focus with a 2.3L PZEV engine and 100k miles. I am the original owner and the car has never had any issue. The only engine related maintenance is periodic oil change.

As part of an oil change/annual inspection in NY, I recently took it to a local shop (one that I did not use before) to check out a weird clanking sound emanating from the engine compartment (sounded like a hole in the exhaust to me). The sound was particularly loud as I accelerate. I also mentioned that it idles a bit rough and seemed to hesitate on acceleration. However, engine does not cut at idle and runs fine.

B) List of things the shop recommended:

Must do:
Broken cross links which must be replaced to pass inspection

Suggested things to make the engine run better:
Change air filter
Change brake rotors and pads
Change the spark plugs
Intake Induction Service

I had everything suggested performed except for the rotors/pads (pads still good) and air filter (I said the 2.3L does not have a normal air filter - weird that the shop suggested this).

"I said the 2.3L does not have a normal air filter "

Well, all cars have air filters. What kind does it have?

And while I can’t see it from here, the combination of an unneeded service (intake induction) with a new problem tells me they probably caused it.

Parts of your story confuse me, but if the general question is “Could improper induction intake service damage the idle air control valve” the answer is “Duh.” Proving it would be another matter, and it depends on exactly what they did, of course.

Rockauto shows a “normal” air filter for the 2.3 Liter engine, so your comment confuses me.

If they recommended brake service, and you looked at the pads and saw plenty of usable thickness, that would have been a sign to inquire further about other items they recommended where you can’t see it. (But plugs at 100K is normal and a good idea.)

“Intake induction service” sounds like a scam to me. They probably recommend it to everyone with an old car or who complains of rough idle or hesitation. I doubt that they took off your throttle body or valve covers and actually observed significant deposits. One web site described “intake induction service” as spraying solvents into your intake manifold while they gun the engine. I hope they charged less than $20 for this service.

“Intake induction Service” has become one of the most prolific scams in the business. Unless you’re having an operating problem, it’s of no use whatsoever.

Yes, they can screw up your IAC while doing it. In your case they apparently did.

My “BS” detector goes off any time a shop says ‘drive it a while, it’ll get better’. Translated, that means “go away, and we hope you won’t come back!”


In the manual, it said it’s a “lifetime” filter for Duratec 2.3L PZEV. I just checked a few blogs online and the suggestion is replacement at 100k to 150k. So the shop may be right about this. However, at $400 or so that is mentioned in these blogs for the unit, I am going to hold off since I don’t seem to have any issue like poor mileage. I will do some additional research on this or it could be a new question if it’s possible as DIY.

After I agreed to the “induction service” for $130, I checked online and wished I did not agreed to this. I didn’t think this $130 lesson would turn into a $730 lesson. At this point, I just want to know the likely truth so I can post a review of the shop for other people after me. Beyond “non essential” maintenance most shops have, induction service seems to be a very risky thing to do, even if it’s free.

OK, this is the first car that I’ve heard of that has a ‘lifetime’, no maintenance air filter. Learn something every day! Which model focus is this?

Your owners manual says at 75K and 150K to “check air filter minder and replace air filter as required” so in this case, “lifetime” means, “until the warranty runs out and its not our problem any more.”

StrongDreamsWaitHere: “Rockauto shows a “normal” air filter for the 2.3 Liter engine, so your comment confuses me.”

Unfortunately, the information on Rockauto is wrong. I wished it was a normal cheap filter too. See the link below:

texases: "OK, this is the first car that I’ve heard of that has a ‘lifetime’, no maintenance air filter. Learn something every day! Which model focus is this? "

It’s a basic Ford Focus ZX5. I think in 2003-2004, a special 2.3L PZEV engine was available option in CA and NY only for some state emission thing at no additional charge vs the standard 2.0L engine. It had a bit more power than the 2.0L and has been a trouble free engine so far.

yeah, the PZEV Focus does indeed have “lifetime” air filter, you aren’t even supposed to open the filter housing unless the air flow gauge on the housing indicates there’s something wrong. The air filter assembly looks more like something you would see on a diesel truck than an economy car.

The problem going away after some miles are put on the car sounds like a brush off line to me.

As to whether this service caused an IAC problem is debateable. It’s not just the age and mileage on the car but I’m getting the feeling you have a car with a damaged engine due to very little engine oil.

Define this sound like a hole in the exhaust, particularly loud when accelerating clanking noise you refer to. At this time you also had an oil change.

Should I ask how much, if any, oil was in the engine at that point and when was the last time you raised the hood and checked the oil level.

Should I ask if the red oil pressure light has been flashing on or not and whether this clanking noise still persists, even at a much subdued level?

I don’t quite understand it either but the PZEV cars have emission warrantees of 100 or 150K. That was part of the deal with EPA I guess. So if it needs a filter, it should be covered by the warranty.

@0k4450, the weird sound that I thought was the exhaust turns out to be the vibration from the bad cross links. Once these were replace, I no longer had the noise issue. I checked the engine level frequently, and had this been an issue, I am sure the shop would have let me know during the oil change that they performed.

@Bing, I didn’t realize the “lifetime” filter was such a unique situation. Ironically, it makes me feel better about the mistake the shop did in pushing an air filter change among a list of other things “recommended.” Once I mentioned that this engine didn’t have a “normal” air filter, he was confused and told me he will call me back. Apparently it confused them too.



ok4450, “The problem going away after some miles are put on the car sounds like a brush off line to me.”

I want to clarify one thing. When I brought back the car the next morning, the front desk guy just turned on the engine and saw the exact problem that I was describing. He said that it was due to the solvents that need to work through the system from driving. It seemed to make sense at first, but didn’t go away after driving 100 miles on the highway.

When I brought it back again, my guess is that they tried to clean out the throttle body and then asked me if it had been worked on before since it contains silicone. I told them I had no engine related maintenance of this type (I don’t understand how silicone could get in the throttle or effect of it). While I said in the original post that the shop said the IAC was bad, I was pretty sure they said the throttle body was bad and needed to be replaced for $300. I was pretty upset at that moment so they may have said IAC unit (I was not certain, so did not want to add incompetency to issues). I really felt it was the shop’s fault so I told them I was picking up the car. After having trouble finding an immediate appointment at a dealer, I asked the shop to do the change they suggested. They told me they would call me back, but never did. (This last part I would not blame them for brushing me off. I think they did make an effort to correct this issue, but wanted me to pay for it… after I just spent over $500 in works already.)

As I mentioned before, I don’t think anything malicious was done simply to generate expensive work. The shop is convenient, easy to schedule appointment, and people seemed cordial and professional. I did check the limited online info available and did not see any thing bad mentioned. The “revenue enhancing stuffs” is unfortunate, but in hindsight, the only truly unnecessary item was the “intake induction service”. The really unfortunate thing is that in addition to the $130 for this service, I ended up with a bad IAC unit that needed to be replaced by a dealer for another $600.

It’s hard to believe, but I was thankful that I had to take it to the dealer since I am pretty sure the shop said the throttle body was bad (the dealer said the throttle body was fine and no silicone issue.) If my recollection is correct, then the shop would have performed another unnecessary change and I would still have to go to the dealer for a new IAC. So I was glad the shop ignored my call in the end.

Hindsight 20/20 required a $730 lesson of money I don’t have. I just think someone in the shop didn’t cover up the sensors and solvents damaged the IAC. I just wished the shop had own up to this reasonable conclusion as it wouldn’t have cost them that much to correct the issue, given that I just spent over $500, including the $130 of unnecessary intake induction service.