1991 ranger starts but dies immediately

[timmis]

hey guys this is my first post so ill try and make sure i include everything. I have a 1991 ford ranger 2.3 i4 with a 5 speed M50D-R1 trans. i recently got the truck back on the road after being parked for about 5 month due to a very illusive ignition problem. however, after fixing that i was able to drive it for about a week. off rip it had idling problems. right after starting the truck i would have to rev it for about 60 seconds before it would take over and kinda idle on its own. the idle would surge to 1500 and then randomly drop to about 500, just above stall out ( too the point where at night the headlights would get super dim with the crank of the motor) this only occurred while in neutral or at a stop. as the week progressed the issues were becoming more apparent, stalling at stops, long cranking times at start up, jerking and bucking while driving at constant speed. the weirdest thing to happen happened on the last day i drove it, (last Sunday) it died at a red light and took twice as long to crank as normal. then when it finally did start it was like the motor was running at half capacity.it was running, but it sounded very weird and with pedal to the floor it wouldn't pass 1500rpm and i couldn't go over 35 mph. highest gear i could get into was 3rd. after driving about a 1/4 mile like this i pulled over and turned the truck off, waited 5 minutes and started it and it was fine, well back to how it was, operational. its been parked sense sunday. i replaced the TPS, IACV, (both brand new) and MAF(off a running ranger same year) and no change at all. both coil packs are new(replaced within last month as an attempt to solve illusive ignition problem), spark plugs and wires, (again same time as coil packs) fuel filter was replaced around same time as coil packs, have a new crank sensor but haven't installed it. also just replaced the upper intake manifold due to a crack in it with an upper intake off a 1991 ford fox-body mustang with the 2.3. I AM SO STUCK any and all input and advice is welcome please and thank you

~Tommy

 

[tomw]

Borrow a fuel pressure tester, and check fuel pressure AND delivery volume. The pressure could be fine, but the volume shipped could be too low to allow proper running.
Most testers have a valve you can open to bleed off the pressure and capture some fuel in a container. Run the pump for say 30 seconds, and measure how much is in the can. Multiply by 2 for volume in a minute, and then by 60 to get volume per hour. Most pumps are measured for capacity in 'gallons per hour', and the previous will give you that number.
tom

 

[timmis]

UPDATE:

replaced EEC relay and replaced battery terminals and cleaned leads. did nothing to solve my issue. the fuel pressure is right around 24psi which is fine. the motor fires right up if i let the fuel pump prime but will not idle. if i mash the gas a few times it will respond (sometimes) and it'll rev up and then die. the exhaust smells very rich leading me to think its an air issue. so far the TPS, IACV (replaced this week brand new) and MAF (used off another ranger that was running. cleaned today with MAF cleaner) have been replaced but none of the three have made any difference. i unplugged all intake sensors i could think of, MAF, IACV, TPS, EGR, and i even took the intake tube off. primed the pump and it fired up and idled at 2k fine. let it run for 5 minutes not one miss or stall. i am so lost please if any one has any idea as to what this could be let me know asap. or if any one knows how to adjust the idle from 2k to like 800 rpm with no computer running the intake let me know

 

[RonD]

Welcome to TRS

So fuel pressure engine off is 24psi and engine running is about the same

On the 2.3l Lima dual spark engines, only the Exhaust side coil pack and spark plugs work when starter motor is cranking the engine.
Intake side doesn't start working until engine starts, 400+ RPMs
Just FYI

Spark is run by the ICM(ignition control module) mounted to the front side of intake.
It runs spark on it's own, and passing on spark timing to the computer so it can time fuel injectors.

IAC(idle air control) Valve is needed on all fuel injected engines because there are no Jets to suck fuel out of, so can't used an idle screw.
So to keep correct air/fuel mix computer needs to adjust RPMs.

If idle is at 2,000RPMs then you have a MAJOR vacuum leak.


Just to recap, your starting and dying issue is over?
But RPMs are now stuck high?

 

[timmis]

Thank you for the reply. no unfortunately, currently i am still having problems with it not wanting to idle. it will only idle on its own when i disconnect IACV, TPS, MAF, and EGR. when all four of those sensors are disconnected it idles at 2k rpms. however throttle response is perfect. just the high idle. i am trying to figure out what is causing it to not idle. as said IACV, TPS, and MAF have been replaced along with EEC relay and battery terminals. is there another component that im missing that controls the amount of air the engine brings in? ( running very rich, this is why im sure its air related)

 

[RonD]

Well Air sets RPMs not fuel

If you add more fuel an engine will stall, flood out
If you add more air RPMs go up, thats what a throttle plate is for, opening throttle plate allows more air in so RPMs go up

So to get to 2,000RPMs you need to add more air
Unplugging the IAC Valve should cause it to Close, shutting off most of the air passing thru its air passage.

On the throttle linkage there is a screw that "looks like" an idle screw, it isn't, its and anti-diesel screw, prevents "run-on", it can also be used to adjust TPS minimum voltage to under 1 volt.

Adjust this screw so it is not holding throttle plate open at all, for now

Pull off power brake booster hose and plug that port on intake
Do the same for PCV hose

These should be the only two hoses large enough to cause 2,000 RPM air leak

Not sure about the 2.3l intake from Mustang and IAC valve, if mounted backwards IAC Valve could be sucked open by engine vacuum so wouldn't work, and would cause 2,000rpm minimum

 

[timmis]

okay i will try blocking off the power brake booster hose and the pcv valve. but is the truck even drivable with out the brake booster and pcv? and the IACV is oriented the same was it was when i pulled the old one off. it will only fit one way. there is a port on the underside of my throttle body that has a short piece of rubber hose that looks like it might go to a breather some where? its not plugged or anything literally just found it when i pulled the throttle body off. but i dont see the other end of the tube so maybe its always been like this? and also thats exactly what the motor seems to be doing is flooding when it stalls. that would explain why if i try and start it right after stall out it cranks for like 10 seconds or more. and the rpms constantly jump. with all EEC intake sensors plugged in i have to constantly feather the gas to keep it alive. holding it steady to the floor will stall it (flood it) and if i dont give it anything at all it'll stall. when im feathering it the range is from about 1000 to 1500 rpm however the tach will consistently drop down to 500 or lower and jump back up, and the exhaust will hickup or sometimes put off a bad backfire. you guys are definitely helping me make progress. going to try and pull codes tonight ill post what i find.

 

[RonD]

If you unhooked sensors then you should have lots of codes

If you think the engine is flooding out then maybe you have a stuck open injector or failed Fuel Pressure regulator(FPR)
FPR has a vacuum hose attached, check that hose for gasoline or gasoline smell, replace FPR if fuel is found in that hose.

All fuel injection computers have a "Clear Flooded Engine Routine"
TPS needs to be hooked up
Turn on the key
Press gas pedal down to the floor and hold it down all the way
Crank engine to start

It should NOT start, should not even fire
If it does then you have fuel leaking into intake

With key on TPS gets 5volts from computer
At WOT(wide open throttle), gas pedal to the floor, TPS will send computer 4.5volt to 4.9volts
If RPMs are 0(engine off) and TPS is above 4.5volts, computer will start "Clear Flooded Engine Routine"
This leaves spark on, but shuts off fuel injector pulses, so there would be no fuel in the intake while cranking, so No Start, unless there is fuel leaking in.

If engine fires, RPMs will increase above 400 so computer will start injectors, exit "Clear Flooded Engine Routine"
If you let up on gas pedal, same thing happens, computer will exit "Clear Flooded Engine Routine"

 

[timmis]

ok thanks for the reply ill give that a try

 

[tomw]

On older models, the port & hose on the underside of the upper intake manifold(where it is 'horizontal' immediately after the throttle body) is either the PCV port or the carbon canister port. If it is open to atmosphere, there's your supply of air for a 2k rpm 'idle', along with hard starting and stumble and dying when cold(at least, if not all the time).
Plug the hose, or connect it where it belongs. It should show on the vacuum diagram on the radiator support.
tom

 

[timmis]

okay. i will plug that tube and see where that gets me. however, i would still like to find the source of the original issue, why it wont idle. what would keep a 1991 ford ranger 2.3 from idling? IACV brand new. TPS brand new. MAF new. Fuel pressure is good. Spark is good. could it be my ECU not communicating with the sensors correctly? i have never had this issue with this truck before. always idled fine unless there was sometime obvious like a melted spark plug wire or something.

 

[RonD]

IAC, TPS and MAF were most likely OK, so changing them wouldn't fix a mechanical problem.

The computer systems on vehicles are fairly well monitored, i.e. the OBD code system
Replacing sensors or controls without cause is OK, nothing wrong with new parts, but they can't fix a problem they didn't cause.

Idle, throttle plate closed, has the lowest air flow and produces the highest Vacuum in the intake, so idle would be when any air leaks would effect a running engine the most.

All engines run fine...............until they don't, that's the nature of all problems

 

[timmis]

amen to that lol. im going to go through and install new gaskets throughout the intake system and see if that helps. currently waiting on a harmonic balancer because i f'd mine up trying to take it off to change the crank-sensor (figured it couldn't hurt had a brand new one laying around.) still haven't gotten to reading the codes but will definitely post my findings.

 

[ghostkchr1990]

I'm having the same issue. I know this post is old but did anyone ever figure out the problem?

 

[Ncompton]

Pleasee tell me you found the solution to this issue??? I’m having the exact same problem and can’t figure it out, have replaced multiple different things now & need help!