Bringing a 1990 back to life, revving problem

[Nicole]

I've acquired my dad's bronco, but it's been sitting untouched for nearly 10 years. I started out with some basic tune-ups (spark plugs, ignition wires, air filter, fuel filter, oil change, fuel change + injection cleaner) and while there's plenty more to be done before it's road worthy, I am a female and know more about laundry soap than I do vehicles - do not make fun of me, lol 0  - This is my project, this is the vehicle I grew up in and I want to learn all about it. with the help of a few friends and my dad, and after some basic fixes we've run into an excessive revving problem. We will start it and it will want to stall, so I continue to give it gas, let it warm up, and it typically will stop stalling afterward and run fine, idling where it should. Out of nowhere (and when you put it in park) it will rev itself up to 1500-2000 RPM and stay there. I'll turn it off, go to start it back up and it won't start again for an hour or more. It will normally start only after it's sat a while but not right after you turn it off. We changed the spark plugs (which helped), then the ignition wires (which also helped) and also the air filter because it was completely black. Most of what we've been able to think of has not fixed the excessive and random revving. Our other theories involved a new distributor, fuel pump gauge test, and/or something to do with the throttle--but what? what could be going on with the throttle or anything else that affects the revving? And, what other aspects of this Bronco need attention after having sat so long? I could be over looking very basic things. 

 

[68Mercury250Ranger]

since it has been sitting,  take the little plastic cover off the top of the intake (where the throttle cable and possible cruise cable hook up) and make sure the throttle shaft is not sticking.  steel shaft, inside aluminum housing can get seized after sitting for a long time!   

you don't need it running for this check, you can even unclamp the intake hoses from the upper plenum/intake.   move the lever with your hand (rotate the flaps)  if it is sticky, **** it with penetrating fluid until it becomes free and returns with the spring on its own.  

MAKE sure your key is shut off when doing this.  the idle air motor might be sticking too , that will play with your idle too.   you should probably pick yourself up a Chiltons manual for that vintage pickup or bronco.  

I hope my daughters shows some interest in my old broncos when she gets older , they are only 9 and 11 now but my 5yr old son is right into it.

 good luck Nicole.  

 

[miesk5]

yo Nicole,

WELCOME!

As 68 Merc advised, and;

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

http://broncozone.com/topic/14269-co...&mode=threaded

A helper is good to assist in reading Codes; best is to take a cell fone vid and replay it.

Some basics;

Visual Check

Battery is fully charged & connectors and grounds are clean

Inspect the air cleaner and inlet ducting.

Check all engine AND HVAC (under hood & in /under dash) Vacuum hoses for damage, leaks, cracks, blockage, proper routing, etc.

Check headlights

Check EEC system wiring harness for proper connections, bent or broken pins, corrosion, loose wires, proper routing, etc.

Check the Powertrain Control Module (PCM), sensors and actuators for physical damage; can use these two diagrams to locate ACT, TPS, EVP above EGR),

Ignition Control Module (ICM) on distributor mounted years (Ford re-located the ICM from Distr side to driver side hood hinge area on inner fender liner in 92-96);

http://www.diesel-dave.com/vehic/manual/stj/images/v4795g.gif

1 — ECT Sensor Location

(Part of 9424)

2 9F593 Fuel Injector

3 9C968 Fuel Pressure Regulator

4 9D280 Fuel Injection Supply Manifold

5 9D930 Fuel Charging Wiring

6 — Fuel Return Tube

(Part of 9F792 Assembly)

7 — IAT Sensor Location

(5.8L, 49 States Only)

(Part of 9424)

8 — Water Temperature Sender Location (Part of 9424)

9 — Pressure Relief Valve

(Part of 9F792)

Sensor Locations Diagram ECT, IAT and Water Temperature Gauge Sender; Sensor Locations Diagram ECT & Temp Gauge sender, PCV

http://www.supermotors.net/getfile/265237/original/GT-40%20lower%20intake.JPG

by Gacknar

Check the engine coolant for proper level and mixture.

Check the transmission fluid level and quality.

Make all necessary repairs before continuing

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.

Turn off all accessories; radio, lights, A/C, heater, blower, fans, etc. (close driver's door)

Then turn off engine and wait 10 seconds.

Do KOEO test First

Post Code(s) here according to:

KOEO

&

KOER

--

as 68 Merc wrote, Look 2 the (idle Air Control) Solenoid IAC (aka actuator);

IAC Location pic (Driver side of intake manifold under throttle body plastic cover)

http://www.supermotors.net/getfile/853886/fullsize/idle-air-controller-(iac).jpg

Source: by SeattleFSB

Ford vehicles with an Idle Air Control Motor (called IAC) that have idle problems and sometimes noise concerns

can be diagnosed in the following manner. For high idle problems, try unplugging the IAC motor. 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. Diagnosing an IAC motor and its circuit is fairly easy.

READ MORE @ http://web.archive.org/web/20030411092204/www.carquest.com/techbulletins/engine_controls/tt3q00.CQ.pdf

----------

IAC Gasket Mod by NELBUR http://broncozone.com/topic/22150-fast-idle-problem/?&pid=115710

---------

IAC (aka Idle Air Bypass (IAB)) Overview & Troubleshooting by Ryan M @ http://web.archive.org/web/20131025143319/http://oldfuelinjection.com/index.php?p=39

Read about sensors and actuators by Ryan M @

SENSOSRS http://web.archive.org/web/20130912130642/http://www.oldfuelinjection.com/?p=10

ACTUATORS http://web.archive.org/web/20130912151456/http://www.oldfuelinjection.com/?p=11

===

Try a Vacuum leak test Acronyms & gauge pic at http://broncozone.com/topic/23994-90-58l-getting-continuous-code-33-and-running-code-44/

see my post #11

==

 

[Rons beast]

Hey Nicole,

It's great to see a female taking interest in her fathers ride. You got good advice from M5 and 68 Merc. above. You did the right stuff changing the basic tune-up parts. Now don't get excited and start throwing parts and money at the truck. The problem is most likely in the Idle Air Control, (IAC), and /or the throttle shaft/ plates. These get pretty gummed up and coated with carbon. It's likely the system can use an intake cleaning, and a check of all the vacuum hoses for leaks. Often the throttle body gets clogged with carbon. It can be unbolted and cleaned at home.

This is one of the times patience pays off. Do the checks, and cleaning, and I bet you will like the results.

Good luck and enjoy the experience.