Question about 1988 Ford Bronco

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1986 Ford Bronco, 302 EFI. Surges in idle. Speeds up then slows down.

Engine in park, speeds up , slows down. Runs but will act like it's starving for gas.

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Look for a vacuum leak. Most of the 302's of this vintage we get in the shop are suffering from a vacuum leak causing poor idle or surging. To do this, start the engine and allow it to warm to normal temp. Then, take a can of "Brake Cleaner" and with the straw attached to the spary top, direct the mist along all the vacuum hoses and the gaskets around the intake manifold, and alont the fuel rails. If there is a vacuum leak, the rpm's will pick up noticably and you will be able to pin point your vacuum leak.

Posted on Mar 08, 2015

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Probably a loose or missing vacuum hose. Check the vacuum diagram under the hood and look for loose or cracked hoses.

Posted on Apr 22, 2014

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emissionwiz
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SOURCE: engine runs rough at certain speeds 3.0 v6 flex-fuel 1999 ranger

Check and see if the EGR valve is leaking, to check this spray water on it at idle, if the water steams off the valve is leaking and is the source of your problem, also are you sure you hooked the new DPFE sensor up right? re-check it..

Posted on Nov 23, 2008

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SOURCE: 97 Ford Expedition with shkaing at idle and low speed

Most auto parts stores will scan the engine codes free or allow you to use theirs on site. Scan the code and post it back here for additional help.

Posted on Jun 24, 2009

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SOURCE: 1987 F150 302. No trouble codes but engine idles too fast

The IAC (idle air control) may be stuck from dirt or malfunctioning.It's located in the intake near the throttle body.Remove it clean with carb cleaner and reinstall

Posted on Nov 23, 2009

Testimonial: "Thank you for response. Actually had IAC off and was clean inside. Resistance within range 9 ohms but voltage signal at 12.5 V rather than 10.5 V"

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SOURCE: FORD WINDSTAR 3.8 V6 ENGINE IDLE ROUGH UP AND DOWN WHEN STANDING

Idle air control valve is the problem. "idle motor" tap it with a hammer it should temporarily solve your problem. it is right on top by the throttle body.

Posted on Dec 19, 2009

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SOURCE: Engine runs rough at idle and slow speeds.

clean the idle air control with brake cleaner or carb cleaner

Posted on Jun 19, 2010

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97 toyota surges at an idle


(which engine. ?????)_
as always check all fuses. and scan the ECU for DTCs. first.
there is no need to fix OBD2 cars like 1980 cars (hard rows to hoe)
it can be 2 problems this......
lets fix the easy one first. idle. (and hope for moving issues to fix for free) it idle car is parked, so is 100% safe tests. (not moving)

so it surges at idle.
questions.?
1: hot or cold or both.?
2: low extreme RPM and high at idle.

400 to 800 RPM? surge.
1000 to 2000. what? numbers tell the tale.

first off, idle is the last thing to work right on any engine.

there are many ways to find what is wrong.
fix idle surge way.
i make sure that the engine holds closed LOOP status.
hot idle, if not , i fix that first.
keep in mind if not in closes loop and lean
all lean engine surge and guess what the ISC will add to the surge
because idle is way too slow, so the ECU open the ISC wider
and wider and its still too slow, so the ECU resets the ISC
this cause a worst hunt (surge)
the ECU adjust spark time and the ISC to get 800 rpm. (spec. look up yours)
so say , i see closed loop failed, OBD2 scan page 1
i look at the O2 sensor an its stuck lean.
if stuck lean and it really is (o2 bad?) then its lean and it will surge
.
examples.
1: i find 02 sensor bad, (only effects idle and light steady cruise)
2: i find fuel pressure at 15PSI , hopeless low .
3: i find all injectors clogged. and lean.
4: with MAF EFI, ( i find maf reading too low, (dirty) causing lean.
5: if MAP car, i find the MAP stuck hard high vacuum causing lean.
not knowing what engine you have or the idle hot surge range,
i can not go farther.

the driving bog tells me,
1: scan the ecu ,get DTCs; do that first.
2: clean MAF if car has one, ask how..
3: check fuel pressure.


my guess is engine is lean. and starving for fuel all the time.
cept WOT.

MAF cars starve for fuel if there are any vacuum leaks.
MAP cars do opposite, they race fast with 100% full power.
MAF is air density EFI
MAP is speed density EFI.
apples and oranges diffr. so what engine.


Jan 07, 2014 | 1997 Toyota Tacoma

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2006 Suzuki forenza. sometimes it takes a long time turning engine over to start. when it does start, the tach revs up to 4 and won't slow down. when you shift the car into gear, it shuts off. when it is...


bad idle, and surges.
gets better, does that mean it idles at the correct regulated RPM
HOT? 800.?
and does the engine coolant hit 180 to 200 F and hold there.?
Sounds like the ISC valve is stuck open, clean it.
ISC means, idle speed controls.
also air leaks, vacuum leaks can do this on speed density, EFI.
Im not sure which EFI you have, too lazy to look that up.

which engine do you have, and what country, ?
as a mech, i open hood and look, on the net , i cant do that.
so.... no real help

Sep 11, 2013 | 2006 Suzuki Forenza

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Low idle 1986 ford bronco 302


This problem is commonly caused by a dirty automatic idle speed control valve and throttle valve but always run a OBD2 fault code as well as the cleaning procedure. Buy a can of throttle valve cleaner (do not use carburetor spray cleaner!) from NAPA or Carquest (made by CRC chemicals) and spray it into the air intake while the engine is running, use up about 1/2 the can, engine will try to stall hold the speed up, shut it down and let it soak for 30 minutes, restart and blow out the remaining fluid, shut it down and disconnect the negative battery cable for 5 Min's to reset the base idle control


Oct 11, 2012 | Cars & Trucks

1 Answer

I have a 1989 ford bronco with a 302 that ideals up and down and dies out when park in red light


A number of things could be the problem here:
  1. Bad plugs - fouled plugs would cause erratic idling
  2. Bad wires - also would cause erratic idling
  3. Bad or worn distributor cap
  4. Bad MAF (Mass Air Flow) sensor
  5. Bad TPS (Throttle Position Sensor - this controls the idling speed under all conditions. A bad TPS would idle fine under certain conditions ie engine cold, engine warm with AC on etc but could be bad when truck is warm and at a stop.

Oct 10, 2011 | 1989 Ford Bronco

2 Answers

1992 Ford F150 Auto trans 302 engine. Stalls when you put it in reverse


replace you intake air control (iac) valve right next to the throttle cable end two bolts hold it on and has two wire plug its about three inches long and round. hope this helps you.

Feb 13, 2010 | 1992 Ford F150 SuperCab

1 Answer

I have a 89 bronco with a 302 in it. I went mudding and it doesnt want to go now. Runs great at idle but if I push the gas pedal it stalls. Even if I press it fast or slow it stall. Any ideas it seems to...


Might sound simple, but did you check to make sure the airfilter isn't clogged? run the car up the street without it, see what happens, another thing to try, replace your fuel filter, it may be dirty and starving the engine. Remember we are here to help as best we can, Good luck

Dec 17, 2009 | 1989 Ford Bronco

1 Answer

1981 ford bronco failed emissions twice


Look behind the motor, next to the firewall. There's a vacuum check valve that keeps the air gulp pump from pressurizing the crankcase. Mine was shot; had the same symtoms. Also, make sure that the EGR valve is closing at low idle.

You don't need an engine light to check the codes. First, do a KOEO (key on, engine off), but, let me tell you, when this happened to me (1986 Full size with 302 EFI, multiport injection) NOTHING showed up. No one, not Ford, not emission specialists, nada, knew the vacuum check valve existed.

By the way; are you getting motor oil in the air filter housing?

Jun 03, 2009 | 1981 Ford Bronco

1 Answer

1986 Ford Bronco dies once it is put into gear


Sounds like a fuel mixture/vacuum problem. Vacuum advance line on the distributor could be loose/leaking/collapsed.

Feb 09, 2009 | 1986 Ford Bronco

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