timing issues and high idle

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i have a 1990 ford bronco with a rebuilt 351w EFI Automatic.  the timing is set around 12 BTDC with the spout connected.  i try to set the timing around 7 with the spout out. but when i put the spout back in the timing went up to around 14 when i check after i put it back it.  also my idle in park is around 1000 to 1200 RPM. My main question is should the timing change that much with the spout connected and with it disconnected. and is there any way to adjust my idle to lower. i put a 62mm BBK throttle body on.

 

Seabronc

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Yes,  once the computer is connected, it controls the timing.  Setting it manually with the spout disconnected is only for rough timing in an EFI engine.  The computer uses other inputs to0 determine the exact timing for any given condition.  You should set it with the spout connector disconnected as outlined on the vacuum diagram.  

:)>-

 

miesk5

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Yo,

NOTE: COMPUTED TIMING IS EQUAL TO BASE TIMING PLUS 20° BTDC ± 3°. Set timing with SPOUT OUT to 10 degrees. Re- do the timing adjustment

READ MORE

Source: by Ryan M (Fireguy50) READ MORE

at http://web.archive.org/web/20120815125016/http://oldfuelinjection.com/?p=71

High idle;

Vacuum leaks... see my leak diagnosis @ http://broncozone.com/topic/23994-90-58l-getting-continuous-code-33-and-running-code-44/?p=125535

In Post #20

..

Check throttle plate and linkage for binding, etc.

Sticking throttle linkages or PLATE

Speed Control chain is binding, if equipped

Air intake tube is damaged

 
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I adjust the timing back to 8BTDC and runs much better. The idle is still around 1k RPMs. Found no vacuum leaks but there is no smog on but everything is buttoned up.

 

miesk5

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Yo,

OK, good on the timing!

Borrow a vacuum gauge at local mom and pop parts store.

Post readings here and look in my Vacuum leak test for gauge interpretation.

Without seeing the vacuum operated devices, including the HVAC inside cab and engine bay I can't even guess.

Try a Self Test for Diagnostic Trouble Codes (DTC)s by my pal, BroncoJoe19

@ http://broncozone.com/topic/14269-code-reader/?pid=74587&mode=threaded

Some basics;

The engine temperature must be greater than 50° F for the Key On Engine Off (KOEO) Self-Test and greater than 180° F for the Key On Engine Running (KOER) Self-Test.

Run it around to heat the engine up and shift thru all gears including Reverse.

Make sure A/C is off and transmission is in Park (automatic); or in Neutral for a Manual & release clutch.

Then turn off engine, all accessories/lights (close driver's door) , etc.

Do KOEO test First

Post Code(s) here according to:

KOEO

&

KOER

...

Idle or Noise Problems & Troubleshooting; including HIGH IDLE Conditions; "...For high idle problems, try unplugging the IAC valve. If the idle drops, its usually due to an input signal to the computer which results in the computer raising the idle speed. If this is the case, look at all of the computer inputs to make sure everything is up to par. If the engine RPM does not drop when the IAC motor is disconnected, then either the IAC motor is not functioning properly, or, there is a vacuum leak in the engine. *** Stop the engine, remove the IAC motor and block off the passages. Restart the engine to see if there is any change in engine RPM. An idle speed higher than base idle specs indicates a vacuum leak. If the engine RPM is at base idle specs, then the IAC motor is bad. Resistance specs are 7-13 ohms. A good resistance reading does not necessarily mean that the IAC motor is good. Occasionally, an IAC motor will become weak, and will actually bypass too much air, causing a high idle condition *** even though everything else is operating properly..." Source: by Mike N

On the 62mm BBK throttle body, was the idle stop ***** touched?

"...It sets a bottom low speed base idle.

Lower than the computer would want it to ever drop. Think of it as a "Limp Home" mode for the idle in case something goes wrong.

I always set mine slightly higher than spec for a better buffer, but still low enough for the EEC to control idle via the IAC.

This is how I set mine.

1. Start engine

2. Warm engine to operating temp.

3. Remove the plug on the IAC.

4. Turn the throttle stop ***** until you reach 600rpm.

5. Turn off engine but place key back in on position.

6. Test the TPS. It should read .90, if not adjust it till it does.

7. Restart engine, is idle still at 600? If yes then continue to step 8. If not repeat 1-7 until you have 600rpm idle with a .90 reading on the TPS.

8. Reconnect IAC.

9. Idle should rise to around 640rpm..." by Gacknar

IAC Overview & Testing; "First let me say this little thing has many names. But they all talk about the same item under the hood. Here all the names I've had the torture of learning throughout the years: Idle Air Bypass ***Idle Air Control*** Idle Speed Control Throttle Bypass Air Idle Bypass Inlet Air Controller Inlet Air Bypass Intake Air Bypass Intake Air Control...This is really easy to test. First as with all problems you should gather the trouble-codes from the computer. Follow the codes for testing and repair. If you get a code that points to a problem with the IAC start the vehicle and bring the engine up to operating temperature. Allow the engine to idle without any driver input to the throttle or pedal. Go under the hood, and disconnect the electrical connector to the IAC. If the engine begins to stubble or stalls the IAC is functional and does not need to be repaired. If the engine idle does not change you should remove the IAC for inspection.

The IAC can pass and still need repair, or it can fail and not need replacing. The plunger and internal spring can get clogged with dirt and oil. This will slow down the air flow and not allow the IAC to function properly. Remove the IAC and clean it. There are 2 halves to the IAC, and you can not buy just one half, but you can take it apart to clean it. But if the internal solenoid is faulty the IAC needs to be replaced..."

Source: by Ryan M (Fireguy50) @ http://www.fuelinjectedford.com/page39.html

..

http://www.thedieselstop.com/faq/9497faq/maint/stj/images/a20799b.gif

IAC Location

...

"..The curb idle and fast idle RPM are controlled by the EEC-IV processor and the idle RPM control device (miesk5 note IAC) and cannot be adjusted". Ford cautions to only enter the Idle Setting Procedure after you have eliminated the possible idle problem causes listed below. In other words, an OEM idle requiring adjustment should only be when you have significantly modified your engine or mis-adjusted your Idle Set *****:

- Contamination within the throttle bore..IGGIE CAUSE IT'S A NEW TB

- Contamination within the IAC

- Contaminated or defected O2 sensor

- Throttle sticking or binding

- Engine not reaching operating temperature

- Ignition timing out of specification

- Vacuum air leaks (air intake manifold, vacuum hoses, vacuum reservoirs, power brake booster where applicable, etc.)

In other words, the EEC will command a certain airflow for a specific rpm that it is trying to achieve. It then monitors the rpm to see if it's correct. If not, the EEC will adjust airflow up or down to hone in on the target idle rpm. If the IAC Airflow Function and Throttle Body Airflow Scalar values are not what the engine requires, the EEC can start hunting the idle up and down in an attempt to get the idle speed to the target value.

On another note, turning the idle stop ***** in a "counter-clockwise" direction closes the throttle plate and each small estimated adjustment must be done with the engine off in order to reset the zero "Ratch" setting of the TPS. Ratch is the output of a ratchet algorithm which continuously seeks the minimum throttle angle corresponding to a CLOSED THROTTLE position.

Zero ratch works right up until about 1.1v, which is the maximum of what the computer would ever see as idle. So if you have to modify your stop ***** to increase minimum airflow due to an engine modification, you might have to modify the TPS to get it back down below 1.1v. But on a stock engine, you normally shouldn't have to touch it.

The engine should just barely be able to breathe with the IAC disconnected. When you unplug the IAC, it closes completely so the engine would now breathe just through the closed throttle plate air gap. Most of the time, the minimum airflow ***** should be set to where the car just barely runs when you unplug the IAC.

From that point, the IAC adds air (15-30%) to control idle up to normal idle speed. Then it adds another 15% or so to compensate for the A/C being turned on. Then it adds even more percentage of airflow to increase engine idle when cold. As you can see, the extra airflow required by the IAC adds up to more and more duty cycle. The job of the minimum airflow ***** is to add the minimum amount of air the engine will need to run, and then IAC picks it up from there and brings it to the desired idle speed.

Again, you should never have to adjust the minimum airflow *****. But if you have a modified motor, or it has been misadjusted already, then unplug the IAC and set the engine RPM so the engine barely runs. Then plug in the IAC , check the TPS voltage to make sure it is just less that 1v and delete the computer memory..." by Seattle FSB

 

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