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93 bronco idle surge it idles rough

10K views 58 replies 11 participants last post by  Coleaclark 
#1 ·
Alright guys i checked the codes at autozone and none have came up i have no idea whats wrong it has new plugs new wires IAC Cap N Rotor also a new fuel filter I have searched and search for vacuum leaks and cannot find any timing is on.. Map sensor gets 5 volts when i prb the back end it has about 1.2 i think any ways any help would be greatly appreciated
 
#2 ·
On my '94 I went through four IACs, the first three were "Standard" brand, the fourth was a BWD. Just because a part is new, doesn't mean it is good.
(Ok, now flame me for not getting a Motorcraft the first time.)

A quote from "Big Daddy" Don Garlits from the late 80s after suffering a tranny failure.
"That transmission was brand new, new parts need to be massaged, I hate new parts."
http://www.nitromater.com/nhra/6744-best-drag-racing-comment-ever.html
 
#5 ·
Elaborate your problem. Does it idle rough always? Any other symptoms? Put your Bronco information in your signature so we can help you better. What size motor? Which Transmission? Any mods to it? Look at other people's signatures to get an idea.:thumbup
 
#8 ·
okay last night i got the bronco running fine had all the power back today when i was on my way to get gas it ran fine for like 3 miles than i lost power again and the bad surging came back any help please would be great it.. where are all the main grounds everthing works lights radio etc
 
#12 ·
Have you check for intake leaks at the base of the manifold? A can of throttle body cleaner, as its running spray around the base of intake manifold and where it meets the head, also anywhere there is a gasket on the intake side.. say just behind the throttle bodys, sounds like U have a bad vacuum leak. Also Search for TPS voltage and adjustment here or on Google, should be around 4.5V if i remember at closed position. 93, should be SD system so its pretty basic, measures air flow, and air temperature in manifold along with coolant temp.
The Idle Air Control valve, you can remove leave it plugged in. Have someone turn the ignition on, you should see and feel it buzzing and opening up.
 
#13 ·
I am also having the same problem I have read all the forum that I can I just bought a 1988 ford bronco 5.0 with and rebuilt engine ran fine when I bought it drove it on the freeway at about 65 mph for 2 hours or so when I got home put it in reverse it died since then it has a bad idle surge, once the truck warm up in park it surges from 400 to 1100 then when I put it in drive it will idle at about 1100 rpms at a stop light, then when I tap the throttle it shoots down and almost dies. I checked for vacuum leaks none found.I just changed the IAC today and didn't change a thing. Going to buy a TPS tomorrow to see if that's the problem.I also have new distributor,wires,spark plugs,filters, and I just found three grounding straps not connected can that be the problem if not any ideas???
 
#14 · (Edited)
Main ground is front lower right side of block. Have you tried doing key on engine self test. It's obd1 but can still test itself, a paper clip or one of the cheaply ford Scanners, autozone will do it well as my local store has the older scanner.
I'd bet on tps or air leak.

Post #48

http://www.f150forum.com/f10/88-302-idle-too-high-out-ideas-47966/index5/

Also check PVC valve if it's stuck open.
 
#15 ·
Did you give it a full tune up after buying it? New plugs, wires, oil, filters, etc... to start fresh. Then look it over real good for bad connections, bad vaccum lines, etc... Booba something, or other, did a write up for replacing all vaccum lines in a sticky on the forum somewhere.
Take off the vaccum line from the fuel pressure regulator and if you smell gas replace it. My FPR caused mine to surge after I stopped it, or at a stop sign, or slowing down in traffic. The exhaust smelled like rotten eggs too.

Bad egr flow would cause a Check engine light. I would assume a bad iac would too , but what do I know? I cleaned my old factory iac bottom( non electrical) end, and it works ok.
 
#19 ·
A bad FPR will not throw a code directly, as it is only vacuum operated, no connection to the EEC.
If the diaphragm in the FPR is leaking enough fuel to see it, you would have a very dangerous situation with a lot of raw fuel dumping directly into the intake manifold, I imagine it would indeed run rough just before it exploded.
Take Daves 88's advice and change the FPR.

Most of the codes you posted have to do with the engine being too cold to test. Warm up the engine fully, then rerun the KOEO and KOER test. Read the manual for your tester on how to clear the CM codes and clear them.
 
#21 ·
Have u checked ref voltage and return voltage on tps?
Ref should be 5volts on orange wire and .5-1.0v on green wire at idle.
I just remove dust boot from connector back and probe there. Move the throttle you should see a gradual rise in voltage up to 4.5v. Also check ohms at idle should be at 3k and 350 at WOT.

Take the EGR off and plug the hole to make sure it's not leaking itself.
 
#22 ·
I had that problem. Finally I used a Propane Torch and put a hose on the end of it to search for a vacuum leak. The Vacuum leak showed up on my intake were the Carb Cleaner Spray could not reach. Granted, using Propane like this is a bit dangerous, but if there is a leak, it will show up
 
#29 ·
today i started up the truck and let it warm up and these are the codes i got 116 ECT witch i replaced and no difference and i have a 311 air system not working whats this mean??
Interesting that changing the sensor had no difference, that probably means that there is a wiring problem rather than a sensor problem.

Look at the schematic below, all those sensors go through connector C101. C101 is a rectangular 42 pin connector that usually lives under the cruise control box. Open it up and look at the connectors, you're looking for green corrosion. Could be the signal from the ECT is not making it to the ECM.
You could measure the resistance of the LG/R (Light green/red stripe) wire from your ECT to pin 5 on connector C101. Should be close to zero ohms.



http://www.supermotors.net/registry/media/874102_1
 
#26 ·
Could this because a weak fuel pump?? bad ground??? i have sprayed carb cleaner all over to find a vacuume leak and cannot find anything.. TFI problem?? when i took out my dizzy the round cap inside was missing a screw and also there was rubbing on the side of where rotor sits on the shaft has some play
 
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