idle surging

[derekhollister]

Ok I'm trying to help my buddy out his 89 240 sr20det swap randomly started having a idle surge we have chnage mafs twice cleaned iacv chage coolant temp sensor also changed fuel pump. Then I checked the ground for the maf that was good. But the constant power wire had no power and the switch power read 46.7 dc. Can you guys please help me help him.

[derekhollister]

Also has a code 11 and 12

[derekhollister]

bump need help.

[blkvrtswp]

Idle surge = idle going up and down and never coming to rest at a constant rpm?

Try removing the BOV and blocking off the hole on the piping to see if that helps.

Also verify that the intercooler piping has no leaks - you need to check all the couplings carefully for tears or popped off clamps.

[derekhollister]

I've checked that all. Ecu is now stuck in limp mode and throwing code 55

[blkvrtswp]

Check the MAF wires all the way back to the ECU. +12v power, ground and signal wire. Sounds like there could be a short somewhere since you not getting correct voltages on 2 wires. Limp mode is almost always due to MAFS / MAFS wiring.

[derekhollister]

i checked them all. the ground and signal have continuity while key is off. the ground checks good but the 12v const does have any power when the key is off. when the key is on the signal power has like 37 or so vdc and the constant has like 10vdc. but the car isnt throwing a code and is in limp. this is the second maf new coolant temp sensor clean iacv. the idle still bounces around. at start up is jumps to 2k then after a little it bounces from 1500 to 2k to 25k ish

[blkvrtswp]

If you have 10 volts on a wire that is supposed to be 12v start there. That ain't right. Dig into your MAF wiring, unless your whole car is running at 10v then check your alt/battery wiring.

[derekhollister]

The battery is 12v idk how it's not getting 12v idk what to look for the wires are good

[blkvrtswp]

There has to be a short somewhere. You are going to have to unwrap the MAF wire all the way back to where it enters the main harness and goes thru the firewall. Then you will need to test the wires individually for continuity using a multimeter to see where the short is.

There is no way a MAF is going to work properly with 10v input. Also MAF signal to ECU is like 0-6 volts - if you have 12v on there you also need to check your ECU for burnt smell / burnt MAF signal trace.

Good luck!

[derekhollister]

Both of those have continuity. I don't smell anything burnt.

[blkvrtswp]

Continuity from the ECU pin to the MAF plug? Plus zero continuity with ground. 'Cause that is what you need to see on the signal wire.

[derekhollister]

I got continuity from the constant wire from plug tk ecu the ground is the same

[blkvrtswp]

12v constant should not have continuity with ground. Not sure if that is what you are saying you have. If not, sorry man - I'm out of ideas.

[derekhollister]

No they didn't have continuity with each other they both had it with the ecu. But he took his ecu to a local scl chassis place and he told him his ecu was bad