RPM drop

[Defective]

When my engine RPM's come down after driving or just revving, they take a big dip down to like 400 or so, then it bounces back up to normal range. It's annoying because it dims my headlights at stop lights and it kind of looks like I'm flashing my lights at the drivers in from of me. Any ideas what this is?

This is a '96 w/ 4.0 & 5spd.

 

[srteach]

Check amperage output from alternator. Then check for vacuum leaks.

Slow engine recovery could be caused from vacuum leaks, or the alt may be having issues with regulation of power.

Post if you find the problem ... it helps others.

 

[BUGNUT]

I had the exact problem this morning on my way to work, as well as the oil pressure gauge dropping to near 0 psi and the check engine came on. Not a good start to the day. Since I work across from a Ford dealer I drove there and had them check things out. Its raining here at the moment and we expect a very wet weekend, not very nice weather to do the trouble shooting myself outside. Any way the dealer called me at work and told me the oil pressure sensor was defective. I told them to replace it. The low idle and stalling was caused by the IAC (air idle control) module. Its mounted on the air intake housing.

The dealer charged me $22.00 for the oil sensor and $154.00 labour to install it. Can you believe it, $154.00 to screw in a sensor. I guess thats cheaper than a seized engine.

For the IAC they wanted $285.00 and $103.00 labour to install it. I told them to just fix the oil pressure problem and leave the the rest.

 

[B30004X4]

I am having this same problem. So the IAC is usually the problem for this?

 

[charlie268]

Same problem

I had the same problem for about 2 weeks and just could not find the answer till this past Thursday. On my way home from work the battery light came on very dim at first and I looked at the batter gage and I could watch it dropping to the L. Made it home to my local garage and tested the charging system it sure enough it was the alternator. I have a 2000, 4wd, 4.0, auto 5 spd. You could notice this with the overdrive on or off but it was more noticeable with the overdrive off. Like I said it took probably 2 and a half or 3 weeks to show up with the light and gage dropping