I have been having a problem with my 95 bronco. When I start it cold it idles perfect. As soon as it warms up to normal operating temps, the check engine light starts blinking off and on and the idle goes up and down, then it dies. If I wait about 20 minutes, it starts just fine until it warms up. The check engine light does not stay on. It just goes on and off when it starts idling strange.

My Bronco has the 5.8, automatic and has 117,000 miles. Thankyou very much for any help.

 

Check for codes, you're probably having sensor related issues, most probably the PCV or IAC. And welcome to FTE!

 

I'll second Encho's welcome. Fault codes are your friend here. I'm going to put my money on the ECT or ACT sensors but running a KOEO and/or KOER test will pinpoint which one. If you need information on how to get fault codes from the on-board computer have a look at this link.

ECT - Engine Coolant Temperature
ACT - Air Charge Temperature
PCV - Positive Crankcase Ventilation
IAC - Idle Air Control (solenoid/valve)

KOEO - Key On Engine Off
KOER - Key On Engine Running

 

Thanks for the help guys! I will try the koeo test tomarrow. I will keep you posted. Thanks again!

 

Ok guys, I got the codes.

116-ECT out of self test range

636- TAT sensor voltage out of self test range

111- system pass

Can anyone help me with these? Thanks again.

 

Update- I took the bronco for a drive. It ran great while it was cold. As soon as it warmed to normal operating temp it started running terrible again. I just pulled into the driveway and it died with the check engine light on. I ran the test again. The only code it gave me was,

21- ECT

Could this just be a bad ECT (engine coolant temp sensor) or do you think something else could cause this?

One guy put his money on a bad ECT. Very good call!

Thanks again for all the help.

 

Code 116? Really? Ok... ECT three-digit Codes are 115, 117, and 118 but... that could have changed at some point and not been updated in my information. Regardless, the ECT Code indicates that the sensor was sending a voltage outside of the range that the computer is programmed to read from that sensor. In short, the problem is either that the wiring to the sensor, the connector at the sensor, or the sensor itself is bad. Personally, if you can afford it, I'd recommend simply replacing the sensor.

Code 636 is not one that I would worry about unless you have been experiencing issues with transmission shifting. I would suggest that this Code probably showed up because the transmission was cold when the test was administered.

Code 111 is the one you ALWAYS want to see. Preferably it will be the ONLY one you see when you run the self-tests.

Hmmm, this is odd. But Code 21 is essentially the same as Code 116. Replace the ECT sensor.

The reason I say its odd is because the Ford EEC-IV on-board computers produce either two-digit OR three-digit codes. Not both.

 

Thankyou very much for the help! I will replace the ECT sensor on friday. I will let you know how it goes. Thanks again.

 

greystreak92, I finally got around to replacing the ECT sensor. I installed the sensor, started it up, as soon as it reached normal operating temp the check engine light came on and it died again. I gave up on it and had it towed to Robberson ford shop. They called me up 2 days later and said the bronco runs perfect. They said they cant get it to die and no check engine light, no codes. He told me they have drove it a total of 26 miles and it runs perfect.

I could not get it to leave my driveway when warmed up. It died on me right after I changed the sensor. Do you think it was the sensor that I replaced? Did I just not give it enough time? I dont know what to think.

 

Hi Muley,
I've been reading the thread due to similar issues on my '94 5.8l, and have experienced the same thing as you as far as getting it to the dealer after giving up only to have the truck not duplicate the symptoms. When greystreak chimes in I think he will also conclude that the ect sensor was bad and that the computer had to reprogram itself with the new sensor. Anytime a sensor is changed it is best to disconnect the battery. I think this clears codes and speeds up the computer reprogramming. Mark

 

Thanks for the reply pinggolfer, I did disconnect the battery right before I started it back up. It was only disconnected for about a minute. Maybe I didnt leave it disconnected long enough. Thanks again.

 

A couple ideas. One, there was probably nothing wrong with your ECT sensor. You got the code because the sensor was out of range. Since the engine was cold, it's supposed to be out of range. This is why you have to pull codes while the engine is warm. The check engine light will not go on because the ECT is out of range when it's cold. The ECM expects this.

Two, since you are getting 3- and 2-digit codes, you are probably reading them wrong. I would buy a code reader and that way there is no doubt about what the ECM is telling you. I would suggest an Innova 3145 reader. They are about $30 and the manual alone is worth the money because of all the diagnostic information in it.

There are KOEO codes, CM codes, and KOER codes. The CM codes are what you really need because these are the codes that are stored when the computer notices something wrong when it's running. They are stored for a longer period of time. If a sensor was out of range but isn't now, it will show up here.

I would also check for vacuum leaks. Tubing gets old, dries out and cracks, and the manifold seals are also a common source of leaks.

The most problematic system on these trucks is the EGR. To be honest, it sounds like your problem lies there.

 

Thanks for the help andym. I did pull the codes with a code reader. It was $30 at napa. Im not sure if its the model you recomended. When it read 116 the engine was cold. I took it out and drove it until it died and put the code reader back on. Thats when it gave me the 21 code. The engine was warmed up at this time.

I did have a leak at the EGR valve about a month ago. I took it in to the Robberson ford shop to fix that. They said there was no more vacume leaks.

Thanks again for everyones help.

 

I just checked, my code reader is a innova 3145.