90 302 High Idle Issue

[kschirman]

I have a 1990 Bronco with a 5.0 EFI & automatic transmission. After starting the engine idle shoots up to about 2000 rpm while in park or neutral. If you shift into drive or reverse, the idle drops to about 1200-1500 rpm. Items checked so far:

- Replaced IAC valve (dirty, so replaced)

- MAP Sensor (tested MAP sensor bad)

- checked for vacuum leaks, none found

- checked wiring, ok

- checked plugs, wires, coil, cap, rotor, ok

The engine doesn't stall or die, just runs at a high idle and wont pass emission's to renew tabs. Read Bronco Joe's outline on how to pull codes, will check tomorrow.

Any ideas would be great. Thanks,

 

[kschirman]

I was able to to get the KOEO codes and came up with the following:

23, 23, 122 (could have been a 1 followed by a 22), 31, 22, 31

The 23's where in the active memory and the 31, 22, 31 was in the "history"

I wasnt able to follow Bronco Joe's directions to check the KOER codes as i dont have an OD on/off switch (mines manual). Is there another way to get the KOER codes?

Thanks again for any help.

Bronco Joe's Directions:

Next we'll do the KeyOnEngineRunning KOER self test.

You preheat the engine and turn her off.

Shut off all electrical accessories or disconnect them (radio, CB's, lighting, etc.).

set your jumper wire and start her up.

After you get four flashes, or sweeps (three flashes or sweeps for a 6 cyl).

you depress and release the brake pedal, turn the steering wheel 1/2 turn, push the OD on off switch, THEN after a single flash... snap the throttle (push it all the way to the floor once)

 

[kschirman]

I forgot to mention that the engine has never died or stalled on me, just the very high idle.

thanks,

 

[2percent]

22 MAP (vacuum) or BARO signal out of range.

23 Throttle sensor out of range or throttle set too high.

31 EVP signal is/was out of range.

suspects

22- Bad MAP sensor, vacuum leak, bad hose to MAP sensor

23- Bad TPS, throttle body base idle mis-set, dirty/sticking TB, no dynamic response

31- Bad EVP/PFE sensor, no exhaust back pressure or inoperative EGR

 

[kschirman]

Thanks 2percent.

I've replaced the MAP sensor and cant find any vacuum leaks, so hopefully that is fixed. I removed and cleaned the throttle body, but my next guess is the TPS sensor. I haven't really looked at the EGR valve yet, but when you remove the vacuum line or electrical plug, nothing changes, so i looked onto other areas.

* i also replaced the coolant control sensor because when i unplugged it, the idle came down, but when i installed the new one, it didn't change anything and the high idle remained.

I'll try the tps sensor and see where that gets me.

thanks again

 

[kschirman]

Okay, so i got home from work and planned on changing out the TPS sensor, but my Bronco was acting funny. Upon starting, the idle shot up, but then came down to normal, which was great, until i pressed down on the accelerator & the engine almost stalled out. After letting the engine warm up, this same behavior continued. then as i went to remove the tester plugs, the idle shot back up and no longer stalled when the accelerator was pressed down. So who knows, it was just playing with my emtions...

So i re-ran the test's to pull the DTC's and this is what i got:

KOEO -

Active: 23 (TPS), 23 (TPS)

History: 11 (pass), 11 (pass)

KOER -

12, 23, 45, 13, 73, 12, 23, 45, 13, 73

Any idea's? I'm going to replace the TPS tonight either way as its still coming up on both tests.

Thanks again.

 

[2percent]

code 45 Electronic Ignition. coil primary circuit failure. AIR not Diverting (AIRD).

code 13 Idle Speed Control motor or Air Bypass not controlling idle properly (generally idle too high)

code 73 No Throttle Position Sensor (TPS) change in "goose" test. Must get at least 25% throttle rotation.

 

[kschirman]

Thanks 2 Percent.

So with a code 45, ia there a way to test the coil or is it just bad and has to be replaced? I have a tps to replace the current one as it didnt pass the voltage tests.

Thanks again,

 

[2percent]

Yeh you take a voltmeter and put positive on the input and the negative on the output. If you have a Haynes handy itll help a lot as I do not remember the exact result but its really easy.

 

[kschirman]

So i replaced the TPS sensor and everything runs great! I got DTC-11 on both the KOEO & KOER tests & its running better then i can remember in the last 5 years or so!

Thanks again for everyone's help! Now i just have to fix everything else... Good times ahead.

 

[2percent]

good deal glad you got her fixed

 

[kschirman]

Great News, it passed emissions this morning! Thanks for your guys help.