2007 Kia Spectra Surging Idle

[cptbarkey]

I put a new engine in this 2007 Kia Spectra, it was from a 2010 Hyundai Elantra from LKQ. I swapped the original intake onto the new block. It sounds great but I have a problem after it warms up the idle starts surging up and down. I've tried several things listed below:

PO507 Idle too High

1. Cleaned throttle body
2. Cleaned IAC valve, and swapped another
3. Cleaned MAF sensor, and swapped another
4. New Intake Gasket (with extra RTV)
5. Replaced Valve Cover Gasket (with RTV where specified)
6. New Spark Plugs
7. Swapped Spark Plug Wires (not new but ok condition)
8. no tears in intake hose
9. pinched Solenoid Purge valve did not make any difference
10. visual inspect of brake booster vacuum line looks OK.
10. knocking on IAC valve made no difference
11. sprayed water everywhere, no changes in idle
12. in short, best i can tell no vacuum leaks
13. TPS sensor testing using a voltmeter seems to pass OK.
14. throttle cables are slightly loose and not tight.
15. PCV valve is ok, rattles when i shake it.

Engine surges up and down between 1200-1600
Short term Fuel pulses from 0 to +20% evenly
O2 Voltage pulses from .0 to .1 volts

Stuff I havent done yet:
smoke test to find vacuum leak
use a vacuum gauge? to see if it holds vacuum?

Obviously the fuel trim is off, and I believe the upstream O2 sensor voltage is too low, but I do not get an engine code. Also I *think* i'm getting no voltage from the rear O2 sensor but I need to re verify that, i tried several things at once and didnt do it methodically like i should have. What do ya'll think?

 

[Silverado12]

From my experience, a surging idle has been dirty injectors. The car may struggle to idle and sometimes there is a hesitation when accelerating. Does it bog down or surge during hard acceleration? May be low fuel pressure.

 

[cptbarkey]

I havent tried driving it with this surging problem but i'll give it a shot, thanks. also wanted to mention that the cooling system is properly bled, and the coolant temperature sensor seems to be reporting correctly.

 

[Doog]

Originally Posted By: Silverado12
From my experience, a surging idle has been dirty injectors. The car may struggle to idle and sometimes there is a hesitation when accelerating. Does it bog down or surge during hard acceleration? May be low fuel pressure.


+1 The first thing I would try just for elimination is a double dose of techron and freeway ride to check for dirty injectors.

 

[cptbarkey]

thanks, also going to build my own boost leak gauge, found some how to's and looks pretty simple.

 

[cptbarkey]

this is a nice challenge. all air is sealed up good, built a boost leak gauge and it holds, i did find two spark plug tubes leaking, the IAC was leaking, and that is now sealed. Fuel trims still reporting +20% at idle. the idle is going up and down in time with the fuel trim which bounces from 0% to +20%.

When i put it into drive or reverse, the idle surging stops and the car drives normal. No bogging or hesitation at all.

I have not yet tried cleaning the fuel injectors, but could the O2 sensors be suspect?

 

[Doog]

Originally Posted By: cptbarkey

I have not yet tried cleaning the fuel injectors, but could the O2 sensors be suspect?


yes, possible. I had one get lazy on the wife's old Lexus at 175000 miles and cause uneven idle.

 

[cptbarkey]

going to retest the TPS again, perhaps i didnt test it right, and pick one up at the pull a part, i'm finding through searching hyundai/kia TPS's are not reliable.