IDLE PROBLEM

1992 FORD BRONCO
202,000 MILES • V8 • 4WD • AUTOMATIC
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CFBRONCO19
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i have a 1992 ford bronco 302 5.0l v8 with 202000 miles, i was having a problem with the engine that it would lope at idle or idle erratically. when i would start the engine up in the morning it would warm up fast idle at 1400rpms for about 10 seconds then it would come down to about 700rpms, it would then start loping on idle from 800rpms to 500rpms then back up to 1100rpms then back down to 500rpms. after about two minutes the loping would go away and idle fine after the engine would warm up. i decided since the engine had alot of miles and the valves were burned i did a top end overhaul, sent the heads out to the machine shop to have them replace the valves and re-deck the heads. i also replaced all the gaskets, vacuum lines, egr valve & sensor, coolant temp. sensor, o2 sensor, fuel pump, and full tune-up. unfortunately after everything i did, it still idles erratically. i do notice that the engine is running really rich when it does the loping on idle, small puffs of black smoke would come out of the exhaust. the only thing i haven't replaced yet that i think may be causing this problem would be a bad m.a.p. sensor or fuel pump regulator. i did check compression and its perfect, also checked vacuum and its vacuuming at 17hg in lbs which is perfect according to vacuum specs on the owners manual. can you suggest something that might be bad that is causing this problem? if so let me know. thanks
chris
Feb 14, 2008 at 7:10 PM
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RASMATAZ
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Check the fuel pressure/test the engine coolant sensor/idle speed control motor/valve.
Feb 15, 2008 at 12:09 AM
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CFBRONCO19
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I FIXED THE PROBLEM, IT WAS THE M.A.P. SENSOR THAT WAS BAD. THE TRUCK IS RUNNING LIKE BRAND NEW. I ALSO CHANGED THE 02 SENSOR SINCE IT EXCEEDED THE 60000 MILES.
Feb 15, 2008 at 7:47 PM
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PONYBOY88
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im looking at buying a 1993 Ford Bronco, relativley stock, about 140,000 miles, and it starts fine, idles fine for anywhere from 3 minuets to 10 minutes and then it just shuts off dies, it doesnt sputter
Jun 18, 2020 at 3:06 PM (Merged)
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BLACKOP555
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start right back up or do you have to wait a while?
Jun 18, 2020 at 3:06 PM (Merged)
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PONYBOY88
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starts right back up
Jun 18, 2020 at 3:06 PM (Merged)
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LEE PULSIFER
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I have circled the two components in the attached image. One is blowing and the other is sucking. There flexible but hard aluminum hose coming off the one which looks like it should attached to the other but the hose and the attachment point are two different sizes. Maybe a piece is missing?

What is this and how to maintenance it? Would it account for surging idle?
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Jun 18, 2020 at 3:06 PM (Merged)
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KASEKENNY
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This is the purge system. Basically it takes the fuel vapor from the tank and puts it into the engine so that the engine will run more efficiently and prevent the vapor from going into the atmosphere.

Yes, this can cause surging if this system is not operating properly. More then likely the purge valve is stuck open which means it is just dumping the vapor into the engine causing the RPM to surge.

Let me know if you have questions. Thanks
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Jun 18, 2020 at 3:06 PM (Merged)
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LEE PULSIFER
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Thanks for the quick reply, however, that is not what I was asking, I have attached another picture. This is actually not my vehicle, but there appears to be a identical problem. The first cylinder directly behind the battery has a hard aluminum flex tube that is dangling (which I really cant see here) and the smaller round thing just behind it has an opening that looks like a hose should be attached on the side facing out. With the motor on, one is blowing and the other is sucking. Do these somehow go together?
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Jun 18, 2020 at 3:06 PM (Merged)
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KASEKENNY
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Okay. Sorry. That picture helps. This is part of the secondary air injection system. Basically is for CA emissions and it introduces air into the exhaust so that it helps cut down on the harmful emissions.

Take a look at this info. Thanks
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Jun 18, 2020 at 3:06 PM (Merged)
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JOEDARE
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My truck loses speed after reaching 60 mph. With foot still on gas pedal, the speed drops from 60 mph to 50 mph -- 15 seconds later the engine picks up fast too 60 mph again. Stepping on the gas pedal has no affect on performance. I have to wait the 15 seconds for the speed to kick back on almost like it is timed? The RMP needle moves up and down from 1000 to 1500. Work done -- TP sensor, gas filter, two new fuel pumps and another small gas filter. Also, it responds like above at 40 mph as well? Something like cruising at 20 mph, but in 4th or 5th gear. The engine struggles - then after 15-20 seconds, engine picks up to desired speed? PLEASE ADVISE. Mechanics in town are a JOKE!

Marc

ps diagnosis my problem correctly and I will GLADLY make a larger donation. I rather pay you then Palm Bay, Fl. mechanics.
Jun 18, 2020 at 3:07 PM (Merged)
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RASMATAZ
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Lack of acceleration,chugging,hesitating,bogging etc. could be caused by one of the following below:

Possibilities: Inspect and test all the following listed below:
Oxygen sensor.
Catalytic converter.
Fuel injectors dirty/sticking.
Mass airflow sensor/Airflow meter.
Throttle position sensor.
Crankshaft position sensor
Knock sensor
Manifold absolute pressure sensor.
EGR Valve
Fuel pressure regulator leaking or defective fuel pump.
False air leakage.
Fuel contamination.
Foul/defective spark plugs.
Open spark plug wires.
Ignition coil/Coil packs defective.
Incorrect ignition timing.
Cap and rotor.

Note:If it doesn't apply disregard it.
Jun 18, 2020 at 3:07 PM (Merged)
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BURGIEDANNY
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Engine Performance problem
1988 Ford Bronco V8 Four Wheel Drive Automatic
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Ide fluctuates from about 500 to 1200 rpm. I've changes the throttle posistion sensor twice and this corrects the problem for a couple weeks and then it starts fluctuating again. Check engine light stays off, however when I unplug the tps. the engine smoothes out and the check engine light does come on. The engine is fuel injected.
Jun 18, 2020 at 3:07 PM (Merged)
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MERLIN2021
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You may have a vacuum leak, get a can of spray gumout, spray the vac lines and maniflod area, when the idle changes, youve found the leak! You want the engine running and spray on the outside but do direct the stream onto the hoses, if it is a vacuum leak, the engine idle will change speed, then you have detected a leak, repair the vacuum leak and see how it runs! If that doesnt do it, you may need a new idle air control valve, it's bolted to the throttlebody. In your case have a look at the throttle plate shaft, it may be worn and moving...
Jun 18, 2020 at 3:07 PM (Merged)
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EDTHEJUNKIE
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My Bronco has an idling problem, it either runs at 200 rpms or it dies. The guy I bought it from swears its a vacuum problem, is there an easy way to test that?

Thanks in advance,
Ed
Jun 18, 2020 at 3:07 PM (Merged)
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BILLYMAC
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hi ed yes ,their are a cpl ways to check for leaks both very risky. you can use a propane torch not lit eng running turn torch on low run around bottom of intake.rpms will rise when you find the leak. again not reccomended unless you are an experienced technician. first check the iac motor this is the idle sensor.two screws hold it on the throttlebody. remove it.hold your thumb over the whole see if you can stableize your idle.if yes iac is prob. if not most likely upper plantum gasket.. be very careful billymac please vote on my response
Jun 18, 2020 at 3:07 PM (Merged)
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YBBOR
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At times Bronco will idle rough, if not warmed up already usually will die. I can tap at the mixture control solenoid, which is no longer "clicking" when idleing rough, and it will start "clicking" and idle returns, but when idle is good I can unplug solenoid and there is no change? Thought solenoid was problem, now not so sure. I rebuilt carb 1 year ago and all has been good till now, choke is good, pull-off is working. Thanks
Jun 18, 2020 at 3:07 PM (Merged)
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JACOBANDNICKOLAS
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Are you sure there isn't a vacuum leak? As far as the solenoid, based on your description, it sounds like that is the problem. However, check for lvacuum leaks.
Jun 18, 2020 at 3:07 PM (Merged)
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MARKOFGRACE17
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85' Bronco II,over 100.000 miles,automatic transmission
4 wheel drive.Fluid leaks: oil around valve gasket & oil pan
A few weeks ago drove about 8miles(20mins) turned of engine on restart idle was stuck and engine ran fast
(without foot on pedal coasted at 30-35 mph) got home cooled about 3 hours ran fine couple of days.then on start up idle stuck drove about 6 miles idle kicked down and ran fine til shut off and re-start. Is this possibly a vacume line problem kicking the idle control solinode off?
HELP!!!!
Jun 18, 2020 at 3:07 PM (Merged)
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RUDPRO
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A vacuum leak could cause high idle. Or maybe it's the idle air control valve. Unplug the electrical connector on the IAC valve. Put an ohmeter across the terminals on the valve. It should read 7-13 ohms. If not, replace it. There is a diode in it so make sure you put the posiive lead of the ohmeter on the vpwr terminal.


https://www.2carpros.com/forum/automotive_pictures/74660_0900823d800b98f7_1.jpg

Jun 18, 2020 at 3:07 PM (Merged)
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CRCBRONCO
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The car sat for almost 3 yrs with only turning the motor over once a month. The car was running fine but now when it idles the car shuts off but then starts right back up when you put it in park are turn the key. Also when it first starting it lets out a high pitch squeal. They could be separate problems but how do I fix it?
Jun 18, 2020 at 3:08 PM (Merged)
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ATKAPARKING
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Yes, it sounds like 2 separate problems. The easy one is the squeal--I don't know where you live, but it sounds like the belt has dried out while sitting. Belt dressing may help, as well as making sure it has the proper tension. The idle problem is a little more difficult. Again, depending on where you live, the gas in the tank can be suspect. You say it starts right back up, but does it die again? I would suspect internal carburetor junk. If you don't know much about these systems, my best advice is to check and replace the fuel filter as necessary, fill the gas tank and drive the truck on the freeway for an extended period of time. If you're still having idle problems, find an old-school shop that has an owner who knows carburetors.
Jun 18, 2020 at 3:08 PM (Merged)