EGR issue?

[Nighteyez]

Hello all, I am buying a one owner 1985 Ranger with the 2.3 liter and 5 speed manual trans. It has EFI and the owner tells me it has an idling problem after it warms up. When cold it runs fine, but as soon as it warms up the idle becomes erratic. He has replaced the fuel injectors, but to no avail, so he thinks it may be the EGR. I am not familiar with the 2.3 and don't have it yet to do any checking myself, but I was wondering if anyone could tell me what to look for when it gets here. I was thinking maybe a vacuum leak, but that would affect it when it was cold as well as warm. If it is an EGR valve is that hard to get to or replace? If it isn't the valve is there anything else that would cause this problem?

[TigerDan]

It could be the EGR Jim, it's usually not the valve itself that goes bad but rather the EGR passages which get clogged with carbon. Worth checking and cleaning anyway. It's fairly easy to get to:



And look at these related items while you're at it:

http://fordfuelinjection.com/?p=35

http://fordfuelinjection.com/?p=43

Another possibilty is the IAC, which is the solenoid on the opposite side of the pic also at the back of the motor. It controls the idle by opening at closing at the appropriate times (controlled by the ECU) to let air in around the throttle plate. It's also subject to carbon build-up in its passages. More info here:

http://fordfuelinjection.com/?p=39

In fact, it's not a bad idea to clean the throttle body as well. Use a throttle body cleaner in an aerosol can, similar to carb cleaner but not as harsh. Throttle bodies had a factory coating on the inside designed to reduce carbon build-up, which can be dissolved by conventional carb cleaners thus the need to use a gentler throttle body cleaner.

[Nighteyez]

Thanks Dan,

That is good info. And just what I was looking for. When the Ranger arrives I will know what to check for, and where it is located. One other question, the last article mentioned a code checker, where do I get one of those? Any parts store? Or from a stealership?

[tomw]

Code checkers from any parts store - autozone, pep boys, advance, NAPA for about $30-35. Easy to use, or use a VOM.
I'd check the MAP sensor. It uses intake manifold vacuum to modulate the amount of fuel that is injected, leaning out the mix when vacuum is high, and enrichening when vacuum is low.
The IAC would not give you a raised idle when cold if it didn't work. The EGR can be tested by disconnecting and plugging the vacuum line to the diaprhagm. You can also test the EGR by using a probe to open the EGR valve by pushing on the back-side of the diaphragm.
The ETC and ACT sensors (coolant and air temp) can also be sending bum info to the computer, and they won't hardly throw a code unless disconnected. But at lease they are working somewhat as you do get a faster cold idle.
Check the MAP by unplugging it and plugging the vacuum line. It looks like a deck of cards with one vacuum line connection to the intake manifold, and an electrical connector with 3-4 wires. I think it hides under the plastic cover on the passenger side (where you will find the weird shaped code reader connection)
tom

[Nighteyez]

Thanks for the info Tom. Should be able to find the cause of this problem with these suggestions.

[tomw]

I forgot to say that I think if the MAP (manifold absolute pressure) is bad, you can disconnnect it electrically, and it should smooth out the idle right away. I believe that if it gets bogus info, it uses a default setting to 'limp' home. I may be wrong.
I also forgot to say that you open the EGR manually or with vacuum at idle to see if it is functional. It will mess up the idle if you open the EGR and it is flowing gas. If it does not change the idle, either it is plugged or it is leaking gas all the time. 'kay?
tom

[Nighteyez]

Thanks again Tom, and Dan. Now I am just waiting for it to arrive so I can find out just which one of those parts mentioned is the culprit.