20valve LIMP HOME MODE (ecu experts please help me)

[dave_g]

I know that high base idleing has been discussed alot and I've read all the threads but haven't found any sloution to my problem, so I'm starting my own thread. I think my 20v might be running in limp home mode as it's idleing high and it has next to no power. When I clamp the air hose from the iscv the idle rpm drops straight down to a normal range between 800 - 1000 rpm, as it does when I put 12v on the iscv and earth one of the other wires. It was working fine but,.. my ecu isn't controlling the iscv at all. How do I get it out of limp home mode. I've tried reseting the computer by releasing all the residal power, which did not work. The problem is my ecu.


I am completely stumped and have nothing left to try. I need some help ASAP

["Z" UTE]

dave g, have you tried pulling the codes from the ECU?. Bridge T1 and E1 in the diagnostic plug., turn ignition on, and count the flashes of the engine check light. If you have reset the ECU, by removing battery power, then any new codes, should show your current fault.

Many,many so called faults in the ECU, are sensor related. The most common cause of erratic engine RPM behaviour, is the coolant sensors not actually reading, which is caused by LOW COOLANT LEVEL.
The cold start time switch sits in the coolant. If not in coolant it will consistently read cold, and maintain your cold start injector to the on position, resulting in a very fast idle.

I suggest you bleed all air out of the coolant system, by using a soft drink bottle with the arse cut out of it. Jamb the bottle in the radiator filler, and half fill with coolant/water, get your engine up to operating temp, and watch all the bubbles discharge from the radiator. Cycling the heater tap, will also assist in purging the air.

Let us know how it goes, cheers Chuck.

[dave_g]

Yes, sorry, I forgot to mention that. I have bridged TE1 and E1 and there no fault codes to display, even when I unplug various sensors. The light blinks ON and OFF at short intervals which tells me that nothing is wrong with the engine, when there clearly is.
Thanks Chuck. I'll let you know if I make any progress.

Dave

["Z" UTE]

dave g, yup, that confirms my suspicion about the sensors. In diagnostic mode, the ECU sends out various voltage outputs to the sensors, and interprets the return voltage. If all components are good, then you will get a OK return from the ECU.

I had major problems with a 4AGE, and it all came down to a leak in the coolant system, constantly leaving the cold start, and thermo swithces dangling in an air pocket, hence reading the lower air temp, and not the hotter coolant temp. Resulting in high idle, and oveheating, due to thermofan not being told to turn on !!!.
The additional fuel being pumped in by the cold start injector, resulted in an over rich mixture, and very pedestrian performance.

Cheers Chuck.

[JP]

pull the lid off the ECU and look for leaking capacitors, faulty caps in the early 90's import ecu's are starting to become more common. I've seen a couple of 20V's and a few 1J's with leaking caps now causing all sorts of strange problems.