For the past week or so, the idle in my Ranger has been lower than normal, and sometimes the motor seemed to struggle to stay running. It also did not seem to idle higher when colder which is something I thought it was supposed to do. Well, today I experienced my first "Check Engine" condition so I hooked up a scanner and code 1507 came up.

I understand that code 1507 is related to the IAC valve. I've read the posts about IACs and related error codes and most times replacement of the IAC valve is the solution. However, before I go out and get a new IAC I am wondering if there is anything else I should do. So far I have:

1) checked all hoses and lines for vacuum leaks (none that I could see/hear);

2) disconnected the wiring clip from the IAC while the engine was running to see if it made any difference in the idle. It did not.

3) shook the wiring clip (while connected) to see if some kind of short or break was occuring (no difference in idle).

Can anyone think of anything else I should check before forking over the cash?

Thanks for any suggestions....... Rock

 

You can try cleaning the IAC valve first...

 

Bob,

Thanks. I was thinking about doing that. I'm also gonna test the electrical connections with a tester. Surpisingly, Haynes manual has some info on checking the IAC connections, resistance, etc.

Question though: What is best way to clean the IAC? I was gonna just use throttle body cleaner and compressed air but I read that Ford recommends against even cleaning it at all and Haynes warns against using solvent to clean it.

 

To be honest Rock, I've never had to clean one!

Sorry!!!!

 

I poked around the Ranger Station and got some info on cleaning the IAC. I had the right idea, but I need to use a cleaner that's safe for the oxygen sensors.

I'm not getting my hopes too high. From the threads that I read, there was just a few cases where it helped, and more cases where it did not help. But I agree it's worth a shot.

I checked the IAC plug and the voltage and resistance seem to be within limits.

I've already cleaned the MAF and the IAT sensor in the intake air tube, so these items hopefully won't be contributing to the problem.

Finally, I learned that there is a "table" of values that the computer uses to maintain proper idle and that the computer can get all screwed up (idle wise) when something malfunctions. So I tried resetting the computer, but to no avail. If I do get a new IAC valve I will have to do the same thing so the computer can adapt to it.

 

Cleaned the IAC today. Also cleaned out the PCV hose and put in new PCV valve, which were a little dirty.

No change in the idle problem. Still idles too low. Once the motor is warm it's not a problem, but it's a pain when it's cold b/c then I have to give it some throttle. The motor runs fine in all other respects.

Dealer wanted $115 for an IAC and NAPA wanted $55. Guess which one I went with? Should be in tommorow. Hope it resolves the problem.

 

Rock, sorry cleaning didn't do the trick.....good luck with a new
one!!!!

 

I replaced the IAC today with a new one and reset the computer. When I started the engine, I knew that things were better immediatly . Actually, it was idling a little high at first but the truck had been sitting for a while so it could have been that. Anyway, I figured that I was gonna have to drive around for a period in order for the computer to relearn the proper idle. So, I set out on the road.

After about an hour of city and highway driving, stop and go, etc (on purpose) I've had a nice consistent idle. Accordingly, right now I am a happy camper!

HOWEVER, not to rain on my own parade, but I think the real test is gonna be after the engine gets really cold overnight and I give it that initial frigid start in the morning. If that's OK, then I'm gonna scan for codes, just to make sure.

A note: The new IAC from NAPA came with its own gasket, but there is already a thin rubber gasket that sits in the upper intake manifold where the IAC bolts on. I did not take any other gasket(s) off so I elected not to put the new one on. The IAC itself looked exactly the same as the old one.

 

That's great news Rock, congratulations!!!!!

 

Thanks Bob. I think I'm in good shape. I just got back from another ride in the Ranger. It had been sitting out in the cold (around 30 degrees or so) for several hours so I'm pretty sure I did a "cold start" in technical terms. The truck idled at about 1200 RPM for a while and then after it warmed up I was getting a consistent idle at about 900 RPM. As far as I know, the computer figures out what the best idle is based on vehicle load, ambient temperature, age and wear of motor, and some other factors. So if it decides to give me those RPMs under those conditions, who am I to argue!

 

Rockledge,
how did you reset the computer?

 

Disconnect the negative battery cable, and touch it to the positive cable for a few seconds. This will discharge the capacitors in the PCM, and reset it. NOTE that you ARE NOT shorting the battery, you are just connecting the negative battery cable (which is off the battery post) to the positive one....