KA24DE Surging issues

[AlexSR]

My S14 keeps surging/bucking whatever you wanna call it, when under load at idle at operating temperature...

There was no check engine light on at all, until I unplugged the MAF when it was running to inspect it (thinking that maybe it was a dirty MAF sensor causing the problem)

So I decided to scan the codes for the hell of it even though there was no check engine light on when the problem occured in the first place and I came up with 4 codes:

P0130: O2 Sensor Bank 1 circuit
P0325: Knock Sensor condition
P0100: MAP/BARO or MAF/VAF Sensor condition
P1605: A/T diagnotic communication line

Can anyone please help me solve my problem, Its my DD..and it's making my gas mileage poor

[BNASTYs13]

id guess its a mixture of all of them. resolve all of the issues and then go from there. a bad knock sensor will throw your car into a limp mode. bad 02 sensors cause poor MPG

[mxexux]

I don't get, under load or at idle. Never heard of under load at idle. Is it AT? Maybe its a swapped 5-speed which would cause the A/T comm line code if it is using the original ECU. You may have caused the rest of the codes when you pulled the MAF. Clear the codes and drive it around for a little while. If any come back, its worth looking into. My guess would lead to a dirty IAC from little info you left. Does it happen all the time or only when cold or hot. More info would be helpful.

[AlexSR]

Its an Automatic, So im saying in gear with foot on brake, such as at a redlight, stop sign etc..

And at hot, I stated at operating temperature..

And what do you mean by "limp mode" ?


There was no check engine light when the problem started occuring to begin with, only from unplugging the MAF sensor trying to diagnose it, that it came on

[mxexux]

Clean your IAC and also check the ground wire coming from it; it goes from the valve to the intake manifold and has a tendency to corrode.

[AlexSR]

Which IAC?

I'm looking at a diagram right now, and I see 4:

IACV-FICD solenoid valve - Ambient Temperature switch Diode
IACV-Air Regulator
IACV-AAC Valve
IACV-FICD Solenoid Valve


Also what's the connector all the way back behind Injector#4? 1 of the 2 wires on the connecter is corroded due to the insulator having a tear. I believe its the EGR and Canister Control Solenoid Valve? Not sure..but would that wire be the problem do you think, or no?

And how do I clean the IAC?

[AlexSR]

Nvm I was looking at connectors..

Anyhow, today I cleared the codes, and test drove it, and repeated 3 times. And I only got P0325 Knock Sensor with the MIL off, which was probably how it was to begin with..I checked knock sensor voltage and it's within specs.

So it looks like the original code is from the knock sensor, which seems to be good and all the other codes are from me unplugging the MAF..

Anywho...Help? lol

[mxexux]

The IACV-AAC valve. This is the valve that physically pulses open/closed to control your idle speed. This valve sometimes gets all clogged up with carbon and begins to stick causing the idle to surge. Its a bit of a pain, but you can remove it and clean it out really good to see if the surging goes away.

[AlexSR]

Okay, I'll try it..what else do I have to lose lol. What the easiest way to remove it? Looks like a bitch to get too with the whole intake plenum in the way.

Would I be able to run fuel system cleaner through the system to clean it instead of me removing it and cleaning it?

[mxexux]

Fuel system cleaner probably won't do anything to clean the IAC since the injectors are way down steam of it. Unfortunately, trying to spray it with carb cleaner through the throttle won't do much either. You can remove it without taking the intake mani apart; a little difficult but doable.