Ka24e: cleaned MAF and Iacv/aac valve, now car doesn't run the same

[spray2020]

Order of events:

Problem: car was running ok, but at stoplights and stop and go the rpm's would "hunt" around, bounce up and down a lot. Started to annoy me to the point where I wanted to try and fix it.

First attempt:

I read up that normally the Maf or IACV is the reason for this. So I first tried cleaning the MAF, and little sensor inside the airbox using Pyroil Parts Cleaner. After putting it all back together the car ran exactly the same.

Second attempt:

I took the iacv off, took it all apart and cleaned everything using the same Pyroil Parts Cleaner and also Simple Green. The housing, springs etc. Then dried everything off and put it back on the car. The car idled, but then slowly went to running rough and idling weird. Sounding like it was misfiring. Note, I did notice that the inside of the intake manifold was just as dirty as the IACV before I cleaned it, could this be a reason for it running rough? Would cleaning the manifold out help anything?

Third Attempt:

Replaced old spark plugs and wires, as they were old. Car still ran the same, idling all over, bouncing idle and running rough- Drives smooth once moving but just the idle is bad.

Fourth Attempt:

Replaced the IACV with a brand new one, and again- the car still runs rough and idles weird, misfiring it sounds like to me.

When I start it when its cold it will idle fine, then I go drive it around the block a couple times and get to a idle again and it goes really rough and the idle drops super low and will stall if I let it go long enough.

Fifth attempt:

The car also sometimes feels like it has random cut outs of fuel when accelerating, so I replaced the fuel filter and fuel pump. Car runs a bit better but still the same idling issue and running rough/rough idle.

My end thoughts:

Could I narrow it down to be the MAF/ airbox sensor that is the problem?

[Kingtal0n]

O2 sensor? boost leak ?

[spray2020]

Originally Posted by Kingtal0n

O2 sensor? boost leak ?

boost leak? It's N/a! Doubt it is the o2, I haven't touched that.

[spooled240]

you're supposed to clean the maf with "air flow sensor cleaner" which is easier on the hot wire. I recently had an issues similar to what you described and it was because my mafs was super dirty. After spraying a generous amount of maf sensor cleaner the car runs perfect and no longer does the annoying idle "hunting".

I'd either clean it again with the proper stuff or swap out the maf for a working one.

[spray2020]

Originally Posted by spooled240

you're supposed to clean the maf with "air flow sensor cleaner" which is easier on the hot wire. I recently had an issues similar to what you described and it was because my mafs was super dirty. After spraying a generous amount of maf sensor cleaner the car runs perfect and no longer does the annoying idle "hunting".

I'd either clean it again with the proper stuff or swap out the maf for a working one.

Just tried using the CNC maf cleaner, car still runs the same

I guess I have option but to replace the maf and see if that helps

[Apex Eight]

Could possibly be your coolant temperature sensor (the one that goes to the ECU, not the gauge) or your O2 sensor.

[adversedroyd]

When this happened to my single cam I got some throttle body and air intake cleaner and Cleaned the throttle outside plate and also inside it on the intake waited for it to dry and it worked for that engine. Later on on my dual cam engine it did the same thing and the same fix didn't work for it. My friend ended up blocking of the maf with his hand only left about a quarter of it to get air it would idle fine. So we replaced the maf and it work fine after that. It can be several things I would check the small stuff first then the bigger stuff. Maybe vacuum lines as well?

[Kingtal0n]

You can still have an air leak somewhere. "Boost leak" still applies one way or the other -> if the atmospheric pressure is higher than the pressure in the tube post-maf, then "boost" from the atmosphere will leak into the engine's air path, screwing up your fuel duty%.

O2 sensor is more likely, because you are ignoring it and have not tested it.

[spray2020]

Originally Posted by Apex Eight

Could possibly be your coolant temperature sensor (the one that goes to the ECU, not the gauge) or your O2 sensor.

I will have to check both of those out. I do know that the wire connector that plugs into the 02 was cracked, I previously tried repairing it. The temp sensor seems affordable enough to just replace.

Originally Posted by adversedroyd

When this happened to my single cam I got some throttle body and air intake cleaner and Cleaned the throttle outside plate and also inside it on the intake waited for it to dry and it worked for that engine. Later on on my dual cam engine it did the same thing and the same fix didn't work for it. My friend ended up blocking of the maf with his hand only left about a quarter of it to get air it would idle fine. So we replaced the maf and it work fine after that. It can be several things I would check the small stuff first then the bigger stuff. Maybe vacuum lines as well?

Yeah Im thinking the intake mani/ throttle body is now so dirty and the IACV is not- maybe it needs a good cleaning to run smooth. ButI will say that all of this rough idle (sounds like a truck) started when I cleaned my old IACV and re-installed. Then with the new one it didn't change much. I will take a look at the vacuum lines also. I know there are a lot of those lol

Originally Posted by Kingtal0n

You can still have an air leak somewhere. "Boost leak" still applies one way or the other -> if the atmospheric pressure is higher than the pressure in the tube post-maf, then "boost" from the atmosphere will leak into the engine's air path, screwing up your fuel duty%.

O2 sensor is more likely, because you are ignoring it and have not tested it.

Thanks for the explanation of this, I will take both of these into account while I do my next attempt to fix this issue. I think it may be a leak somewhere for sure. As if I drive the car when it is cold it is ok, not until it warms up does the rough idle come back and then eventually starts to idle so rough that it will stall.

My o2 looks like it is brand new, but I think the wiring may be what is bad.

[Kingtal0n]

just unplug the O2 sensor and do a boost leak test / solution

[spray2020]

So, im still stumped why the car is running rough. Its had a cel since I bought it- and it never ran rough. But I checked it and its some code that references the egr system. So i pulled the intake manufold off, cleaned the inside of it, cleaned the throttle body.

I noticed some vacuum hoses that were cracked, so I replaced every single vaacum hose in the back/manifold area. Pressed on the egr and it moves fine, doesn't seem stuck. Car still runs rough. I hear a "hiss" noise near the throttle body are when the car is running, but I cant find any other leaks .

I unplugged the o2 and ran the car, it runs the same, I don't think it is the sensor.


Should I just replace the maf at this point? It's the only connector that still has that metal retaining ring on it- so I assume its pretty old lol.

[ultimateirving]

When the car is idling spray some carb cleaner around the throttle body if you yhink it's still leaking there. Vacuum leak still sounds appropriate.