Rough Rich Idle Help

[RBD 305]

I just recently rebuilt my 7m-gte and got about 750 miles down so far..

I've always had a small idle issue where the car has a lumpy idle from 750-900rpm sometimes.
But recently my engine has been experiencing intermittent rough rich idles..
It starts up fine then about a minute later my idle drops from 1100rpm (cold start) to 500rpm and my Air fuel ratio bounces from 10.0 - 10.5 and the engine struggles to hold an idle. Black smoke puffs out from the tailpipe and its wont rev over 1500rpms.

My first thought was my MAF Sensor. It was working fine previously but had a small hole on it and some oil got inside of it..so I swapped another used one in and it still has the same problem..only other problem a friend of mine and myself can think of is a bad ECU.

Im towing the car to my dads shop this weekend for further diagnoses..

Any tips or pointers with this issue will be appreciated...feel free to ask any questions and i'll respond in a timely matter. Thanks.

 

[RBD 305]

Ok so I checked my DTC's today and this is what I got.

DTC 24 - Intake Air Temp Sensor Signal

Diagnosis = Open or short circuit in intake air temp sensor signal (THA).

Trouble Area:

Intake air temp sensor circuit
Intake air temp sensor
ECU

DTC 34 - Turbocharger Pressure

Diagnosis = The turbocharger pressure is abnormal.

Trouble Area:

Turbocharger
Air flow meter
ECU
Intercooler system

DTC 52 - Knock Sensor Signal

Diagnosis = Open or short circuit in knock sensor signal.

Trouble Area:

Knock sensor circuit
Knock sensor
ECU


All these problems seem to point to the ECU..I'm still going to go check out the IAT Circuit and Knock Sensors to double check. As for the DTC 34 (Turbocharger pressure) I'm assuming its only throwing that code because of how the engine is idling?? This isn't a stock CT-26..its an old school T66 Turbonetics in good condition.

I also checked my oil level today and its smells like gas and its at the full mark still. I plan to change it..

 

[IndigoMKII]

Code 34 is fuel cut, doesn't matter what turbo you have, fuel cut is fuel cut. Code 52 is normally a rewire, I had a code 52 and the wire checked out okay from a ohms check but when plugged in the ks wasn't sending the mV ac signal like it should be. It turned out that when the plug wasn't plugged in the wire was still 'good' but when you 'bend' the wire to plug it in the wire had massive high resistance. For code 24 make sure the AFM is plugged in and reset all the codes to see if it reoccurs.

 

[RBD 305]

Code 34 is fuel cut, doesn't matter what turbo you have, fuel cut is fuel cut. Code 52 is normally a rewire, I had a code 52 and the wire checked out okay from a ohms check but when plugged in the ks wasn't sending the mV ac signal like it should be. It turned out that when the plug wasn't plugged in the wire was still 'good' but when you 'bend' the wire to plug it in the wire had massive high resistance. For code 24 make sure the AFM is plugged in and reset all the codes to see if it reoccurs.

Ah ok thanks for the clarifying..I'll check out those KS resistance values and get back with you..do you know how much ohms the wires should have?

 

[IndigoMKII]

If the wire is good, very few. I think mine was 0.5 ohms from one end to the other after I replaced the wires.

 

[RBD 305]

Yesterday I installed another used MAF, rewired 2nd knock sensor, cleaned my fuel fouled plugs and did a compression test for the hell of it and reset the codes.

Still have Code 24
Code 52 is gone
Code 34 is gone
Had 170-175psi across the board (769 miles on engine)

Now I have a new code 14, I start up the car ran great for a minute then start going really rich again..but I noticed a random clicking noise every 20 seconds or so..sounds like an actuator is stuck or something..so today im going to take out the ISCV test it and clean it.

 

[RBD 305]

Today I checked the ISCV and its no good..spec is 10-20ohms I got 38-42ohms...powered it manually and nothing happens..I even disconnected while the car was running and nothing changed.. car started up idling from 1100rpm to 2800rpm over and over. So now im in the market for a ISCV anyone have a spare one for sale?

 

[IndigoMKII]

Today I checked the ISCV and its no good..spec is 10-20ohms I got 38-42ohms...powered it manually and nothing happens..I even disconnected while the car was running and nothing changed.. car started up idling from 1100rpm to 2800rpm over and over. So now im in the market for a ISCV anyone have a spare one for sale?

Unplugging the ISCV causes nothing to happen. You simply removed the power source from it not allowing it to do anything. Think of it as a door that moves when told, if you take the signal away from it, it stays still. When you tried to manually power it, did you follow step 2? http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=FI&P=107