Rich in Florida (new to TRS) need help

[rraff19]

Need some help here.. 1989 Ford Ranger, 2.3 - having an issue with the idle and it's getting worse, also bad shift points, bad acceleration. Had these problems for a year and then problems disappeared after installing new ignition module, new cam shaft sensor, new ignition switch due to truck died and would not restart. after replacing these parts truck started and ran excellent for 3 months, all problems are back and are worse. Tonight replaced battery and alternator due to battery light started coming on. Idle jumps from 300 to 1,500 rpms and is almost stalling after it slams from 1,500 to 300rmp, this happens at idle and idle jumping all over when driving. Just bought new idle air and ignition module to recheck and made no difference, so I reinstalled 4 month old parts. Checked vacuum lines and replaced all lines coming out of vacuum module. Any help would be appreciates. Thanks

 

[RonD]

Hi, welcome to TRS

'89 Ranger 2.3l, automatic

Engine idle should go up to approx, 1,500 on cold engine start, then drop down to about 1,000 after a few seconds, as engine warms up if should end up at 750-800 after a few minutes.

You should have the DIS module with dual coil pack and 8 spark plugs, so no adjustment for spark timing.

Computer uses CKP(crank position) sensor to determine rpms via DIS module, CKP usually works 100% or is dead, not usually intermittent.
CPS(Cam position sensor) is used for fuel injection
Computer uses IAC(idle air control) valve to control idle rpms.
While engine is idling unplug IAC valve, if idle stablizes then computer was opening and closing IAC valve either because computer has gone looney toons or it is getting bad info about rpm.
If engine stalls or idle is still all over the place then computer was trying to stabilize idle but can't.

Coil packs on these can get flaky, but can be tested with ohm meter
Google: Ford coil pack testing
good video out there.
Doesn't matter it its a 4 or 6cyl coil pack testing and results are the same

Does your engine have an EGR system, faulty EGR system can cause exhaust gas to enter the intake at the wrong times, during idle this can cause rough idle that can go up and down as computer tries to stabilize it.
Unplug vacuum line on EGR valve check if line has vacuum, it shouldn't, plug it if it does, see if idle stabilizes.
Then test EGR system.

Any time you change or clean a sensor or any part really you need to reset the computer.
Unhook negative battery cable for 5 minutes to get a reset.

Has the Check Engine Light(CEL) come on?
Does it come on when you turn key on and then go off?

Just seeing if computer is working as it should, because the automatic should be computer controlled, also check that the vacuum solenoid line is good.

If you post in this subsection you will get more people seeing your post
http://www.therangerstation.com/forums/forumdisplay.php?f=84