Sideways7

iTrader: (7)

I just drove my car this morning and it ran great. When I got home, I pulled of my K&N air filer, and cleaned it then re-oiled it according to the directions. Once it was dried and ready to go, I took it for a drive.

Once it was warmed up and I gave it some gas, it bogged at around 3800 (it has never had a 3800 rpm hesitation) then kept on hesitating/bogging until I let off the gas. I tried it in several different gears and with varying throttle input, and it still did it. It would even hesitate some when revving in neutral. It is still perfectly smooth and powerful below 3800 rpm, though.

I then took off the filter and it did the same thing. Next, I disconnected the TPS and it still behaved the same. The aux ports are opening normally as well.

What I can't figure out is why it suddenly did this when all I did was re-oil the filter?

misterstyx69

iTrader: (142)

check the connection to your AFM,as it is the closest thing that I can think of to the Filter that May be the problem.

Sideways7

iTrader: (7)

Oh, I already checked the AFM connection, its still on tight. I also checked the connections to the secondaries, and they are both on tight.

lax-rotor

iTrader: (1)

old hat but: What's the pressure/atmospheric sensor doing?

Sideways7

iTrader: (7)

I assume its plugged in, but I didn't check it. Next time I get out there I'll take a look at it.

Sideways7

iTrader: (7)

Also, I forgot to say this in the original post, but its important:
When it stumbles/bogs/whatever, it goes VERY lean on my AFM.
It is a narrowband gauge (Autometer) attached to the O2 sensor in the stock location. It has about 5-10k miles on it.

lax-rotor

iTrader: (1)

When was the last time you had your secondary injectors cleaned or your fuel filter replaced?

Sideways7

iTrader: (7)

About 10k miles ago. I doubt they would suddenly go from running great all the way to 8k to bogging at 4k in a matter of an afternoon. It seems to me like its a something that got unplugged or bumped, or something, but I can't figure out what.

lax-rotor

iTrader: (1)

It definatly sounds like it's a problem with the secondary injectors though--whether that means it's because of the pressure sensor ground crapping out on you, or because you got silt in the injectors again--I couldn't tell you. But the pressure sensor is in the general vacinity of the AFM so maybe you knocked it?

Sideways7

iTrader: (7)

Yeah, I definitely agree that it sounds like the secondaries aren't coming on. Would the pressure sensor not working cause this?

lax-rotor

iTrader: (1)

I think it does, let me see if I can dig up the article.

lax-rotor

iTrader: (1)

sorry this took me so long to find, had to turn on some computer services that I had turned off to connect to a vpn because my internet sucks:
http://www.aaroncake.net/RX-7/grounding.htm

Sideways7

iTrader: (7)

Yeah, I'll have to check that out when I get home. I just hope its something simple.....

ilike2eatricers

it shouldnt be related to the secondary injectors if he said the symptoms are the same while revving in neutral since the 2ndaries need load to operate above 3800rpm.

why dont you just pull the codes? might save you some time.

MmSadda

iTrader: (2)

While this would not explain distinctly '3800-rpm hesitation' symptoms, I see this as a possibility: You've likely over-oiled the K&N filter.

My logic is this: I have a K&N for my FC, and the first time I ever cleaned it, I significantly over-oiled it. I saw a drop of probably near 25-30% in the fuel economy, and a significant decrease in performance. It felt like the car wasn't breathing. I dropped in a paper filter, and everything was back to normal.

I'd suggest: re-clean your filter, and oil it lightly.

Sideways7

iTrader: (7)

I am almost certain that the secondaries open above 3800 regardless of load.
Also, I don't think the s4's have very many codes. Are there any that could relate to this?

Also, it still bogs even with NO FILTER, so it can't be because it's over-oiled.

lax-rotor

iTrader: (1)

No, he's right. I didn't read that you didn't have it tested under load. Secondaries only kick on under load unless you connect a specific jumper. I'd say still double check the Pressure sensor as it not only sends signals for the secondaries but also to the primaries. It's at least worth looking over before dropping any money on to the problem.

S4's have a few codes that you could pull and compare to. Mostly tell you if you have a specific problem with a sensor or the harness to a sensor. Beyond that, it'll tell you if you're in closed loop or not. It's a dandy deal on the S4's for being a stock feature. I may at some future point hook up the LED lights into the cabin so I know when I'm closed loop for sure.

What currently are your symptoms?

Are you able to rev it past 3.8k at all? Even lightly depressing the throttle may show that you can get past the bog.

Are there any other symptoms that you could make us aware of?

How's compression?

We need a little more info to figure out at least what might be at fault.

ilike2eatricers

have you thought ofthe possibility that perhaps over oiling the filter could have gummed up the AFM. Take off the filter and feel in the inside of the AFM and inlet duct to see if it's coated with oil.

Smoken'

iTrader: (1)

I agree with the above. You probably got oil in the afm causing it to read funny. See if you can clean it out and try it again.

Sideways7

iTrader: (7)

You know, thats actually a pretty good possibility. I'll have to check that out. Is there any specific way to clean out the AFM?

As for the bogging, it isn't just right at 3800 rpm. It continues way past that. If I keep going it will slowly rev up, I've gone as high was 5500 before I let off for fear of detonation.

Right now, I think over-oiling is the most likely cause, as it makes the most sense. I'll go check it out. Also, its a freshly rebuild (1300 miles) engine with pretty good, and very even, compression.

Sideways7

iTrader: (7)

Ok, it appears that my AFM might be bad.

I took it out for another spin when I got home, and sometimes it would run smoothly to 7k, sometimes it would hesitate slightly above 4k, and sometimes it would bog horribly starting at 4k or so. As far as I can tell, it is load and throttle independent, and happens completely at random.

When I got back, I pulled off the filter and the AFM didn't feel oily at all inside. Next, I pulled it off to spec it out according to the FSM. Everything checked out except the actual movement of the vane. The resistance was about right at wide open, but nowhere else. It was about 300-400 ohms at full closed and when you opened it slightly it went to about 500. From there, it would vary all over the place from 500 to 200 until you got to full open when it suddenly went to about 50, where it is supposed to be there. When I move it slowly, the needle on the multimeter literally moves back and forth between 500 and 200 4 or 5 times between full open and full closed.

This can't be normal, so does this mean my AFM is screwed?

Druken

Why dont you try to use the AFM cleaner that they sell. I think it takes like 5 minutes to clean.

Sideways7

iTrader: (7)

AFM Cleaner? I assume they sell this at parts places? I'll have to check it out, then. Could I just take it apart and clean it with electrical cleaner, or is it a bad idea to disassemble it?

This is unrelated, but I just discovered that my variable resistor for my idle mixture is broken (won't adjust resistance) which would explain my my idle is bad and the variable resistor doesn't make any difference.