Hello! New to the forum... what a great place! Hope I can get a little help here.

I have a 93 Bronco XLT 4WD that my husband is working on fixing, and he has a problem he can't figure out. You see, it will be driving fine and when I stop at a stop light it will just die. He just changed the air filter, crank case air filter and the pcv valve and we're still having the same problem.

It's like the RPM's are slowing down below what the idle is set at. He turned the idle up to just over 1000 RPM's and it didn't help.

Any suggestions appreciated! Thanks in advance.

 

I also just found this resource group. And found allot of great information and links.
I have a full sized 1990 5.8l Bronco I have been working on … one of the main problems I was having is the Idle would Bounce between 300 and 1000 RPM’s the truck would also stall out. After replacing almost every sensor in the emissions system, I found a faulty fuel regulator valve
Hope this helps.
Glad I have something to offer back.

 

My '93 XLT (5.0 EFI) was having similar problems..stalling at idle. Turned out to be the EGR valve itself.

If you can, possibly go to a reliable mechanic who can hook-up the computer and run an engine diagonistic. Cost probably in the $75 to $100 range for the test but may be worth it

 

For me it was the IAC. Does it have trouble at idle all the time or just when your slowing down?

 

Ksparks,
I don’t disagree with you on the reliable mechanic, however I took my Bronco to several different mechanics including the Ford dealer. The all put it on the computer and told me it was everything from the O2 sensor, EGR valve, IAC, throttle position sensor. I replaced all that and still had the problem. I guess there are no codes in the computer that point to the fuel regulator valve, a friend pulled the vacuum hose and there was gas dumping into the injectors, the rest of the computer was trying to compensate and giving all the wrong errors.
Just my little experience.

 

He should definitely start by pulling the codes. You can buy a cheap (but adequate) code reader from Autozone for about $20, or you can get Autozone to do it for free -- but then they will try to sell you the parts associated with whatever codes show up. DON'T BUY THE PARTS -- yet!

The codes are just a starting point and when combined with the other symptoms will point you in the right direction. As an example: if you receive a code for EVP out of tolerance, Autozone will probably try to sell you the EGR valve and the EVP. When the problem might actually be a vacuum leak that is not allowing the EGR to open as much as the computer is expecting -- a very common problem with the Ford system.

I suggest you get your husband to check the codes and then report them on this forum -- with whatever other symptoms you are seeing.

 

Ok, first off, if he ran the idle stop screw IN to increase the RPM's you will need to fix that. The stop screw is NOT an adjuster for the idle. It ONLY keeps the throttle plates from sticking in the bores of the throttle body. Since each throttle body is machined, there are subtle differences that require the screw for factory setting of the stop location.

Second, the problem has all the earmarks of a dead or dying IAC solenoid. Located on the passenger side of the throttle body it has a three wire connector and it controls the amount of air through the intake at idle. Hence, the name Idle Air Control solenoid. It may just need to be removed and cleaned really well. If cleaning has no effect, replacement is fairly easy. You will need to provide the Ford dealer with the calibration code from the driver's door jamb so they can hand you the right one.

Once you are certain you have a functioning IAC, the idle stop screw needs to be reset. With the IAC disconnected and the engine at op. temp, the truck should just barely run and die within a few seconds of it turning over. If it doesn't, back the idle stop screw off until it does. Shut the truck off and restart it to make sure the setting is correct. Once the stop screw is set, reconnect the IAC and disconnect the battery for 5-10 minutes to clear the computer. Reconnect the battery and go for a drive for an hour or so to let the computer relearn everything.

 

It has been my experience that when you have driveability problems like hesitation before takeoff, the EGR system isn't working right. The surging idle
and sometimes the stalling sympton may just be the IAC or Air Bypass Valve as some of us call it.

Do pull the codes to find out what the ECU says.

then go from there....and get back to us.

 

another problem could be a vacumm leak
at idle you should have approximately 20Hg of vacumm
idle is very sensitive to a leak

 

Great! There are a lot of good suggestions here.. thank you all for being so helpful!!! I'll take all this info to my husband and report back. I sure appreciate it. Have a great evening!

 

you can do a quick test for the IAC ....get some throttle cleaners...pull air intake hoses off TB.....start truck....and pray the whole can in both intakes....you will have to raise idle while doing so..to keep engine from dying..if the idle smooths out...after spraying...then the IAC is dirty...you can try cleaning..but replacment is the best

 

Hey everyone, has the problem been solved? I ask because my '96 5.8L Bronco runs good except it has a strange, almost miss at idle. There are no codes stored in the computer and I have changed the fuel filter, air filter, spark plugs, wires, cap and rotor. What do you recommend trying first?

 

The IAC only has 2 wires not 3. The TPS has 3.
JImmy