Hi I’m working on a 97 Ranger 2.3. I’ve been trying to figure this issue out for a while now.

ISSUE: when I fire up the engine, it cranks and fires right up. The idle goes up to about 2k then slowly works it’s way down. The engine sounds good and no missing. As it lowers idle it continually goes down and dies. If I hold the throttle at about 1500 rpms for a few minutes it will eventually hold and then run fine until I turn it off again.

REPLACED:
IDLE AIR CONTROL VALVE
MAF SENSOR
TPS SENSOR
INTAKE AIR TEMP SENSOR
WATER TEMP SENSOR
O2 Sensor. (Upstream)
Fuel Pump and Filter
intake gaskets and all intake components cleaned.
Injectors checked and cleaned.
Misc vacuum hoses

Ive recently discovered if I disconnect the vacuum hose off of the fuel pressure regulator it runs good. I’ve read that means it’s being restricted air and the vacuum leak is giving it more air. I cannot figure out where it would be “restricted”

any help would be GREATLY appreciated

-Justin

 

So has the FPR failed then? can you see any fuel in there where it shouldn't be? (FPR is a vacuum thingy)

 

I haven’t seen any fuel in the line. Would the regulator let it start up as normal and just kill it?

 

FPR's going out tend to make a mess of idling and starting, can also affect response off closed throttle.

 

Alright guess I’ll replace that next. Fingers crossed! Thanks

 

I've seen so many variations on problems that were "kind of related" and turned out to actually be related to (and caused by) the FPR going out, it's worth doing if the problems are related.

 

Well I slapped on a new FPR and nothing changed... still the exact same problem.

 

Bummer :(

Is the IAC working correctly? Pull it's plug when the engine is idling normally, the revs should go down a few hundred.

Have you run any smoke tests for vacuum leaks?

 

So its a new IAC (Duralast) but I was curious if it was maybe just a bad one, so i bought another one (Borg Warner) and it made absolutely no difference. I tried running it with IAC unplugged, it was much different, wouldn't even begin holding idle. Fires right up and quickly falls flat. With IAC plugged back in it fires up then has smooth idle but just slowly lowers rpms until imminent death.

 

So that should rule out the IAC then.

Vacuum leak test next - gotta do one myself, idle is a little high (i think) though i'm also unsure if my fan is operating correctly.
Just not thought through how i'm going to do a smoke test yet.

 

Yeah my vote is on vacuum as well.. just gotta find it.

 

Have you checked for any pending codes? Does your engine have 2 Water temp sensors? One for the gauge and one for the pcm?

 

Its throwing codes for running rich, codes for the upstream o2 sensor and maf sensor. On the two temp sensors.. do they have different plugs? I have two sensors on the same water line, they have different plugs. When I ordered a new one, it only came in one option.

 

On further research it looks like I have two, and it looks like I replaced the one for the gauge. Sooo that gives me hope... In the morning I'll check the OHM difference when hot and cold and see if its registering much of a difference. (Any idea how much the difference ohms should be?)

 

You need to address the codes for the o2 sensor and MAF sensor before doing anything. If you already replaced them, then you can clear the codes. It could be a long time before the PCM does it for you. I'm assuming the codes were there prior to you replacing the items correct?

 

Yes it was prior to replacing them.

 

Yup, gotta clear them then; disconnect battery negative for 3 minutes with the headlights turned on - turn off headlight switch and reconnect - that should be enough to clear them.

 

Ok ill do that. I pulled my temp sensor and tried testing it with my ohmmeter, its not registering anything, even if I place it in hot water. I've read that means it is bad. I'm gonna pick another up and clear the codes, maybe ill get lucky. Thanks for all advice