Hello and I apologize about the long post!

My 98 2.5 5spd manual (197k miles) will randomly begin to bog and die while driving. Truck throws no codes at all, and it is completely random. It always starts right back up no problem once I pull to the side of the road. this morning while cruising at 70MPH I felt it beginning to bog down so I pulled to the slow lane and eventually made the next exit and pulled onto the shoulder. I keep a scangauge plugged in so when I pulled over I had a pending code - P1131( Lack of Upstream to the Heated Oxygen Sensor Switch). No hard codes at all.
I did notice this morning that the truck seemed sluggish when leaving my house, but it may have been in my head.

I have owned it for the last 3 years and this is what has been done to it:

-New fuel filter about 20k miles ago
-Timing belt, water pump, plugs and wires replaced about 30k miles ago(preventative maintenance)
-New ignition coils(Amazon specials) about 10k miles ago, courtesy of a cracked coil pack
-New crank sensor(Amazon special) about 15k miles ago - truck threw the code for it
-Mass airflow sensor cleaned regularly (last done 2k miles ago at last oil change)

The PO did replaced the fuel pump at about 145k miles with a white box brand from a local store.
I did hook my gauge up and tested the fuel pressure and it passed all tests with flying colors except the drain back test. it would lose about 10PSI every 15-20 seconds after the pump and engine were shut off. truck had 62PSI while running/idling and held it even when rev'd to 3k RPM.

I did look at my inertia switch this AM and noticed that one of the smaller wires was broken on the harness. I unplugged it with the truck as the truck idled, and the truck died. plugged it back in and it fired right up. I tried knocking on the inertia switch with the truck idling and came up with nothing.

The truck will idle all day long and I cannot recreate the symptoms at all.

I have tried the "wiggle test" on all of the wires and have had no luck at all getting the truck to act up.

I should also note that the truck has done this since I purchased it, but very very randomly. It has been about a year since the truck has done this. In the last week or so it has shut off 5 times now while driving.


Any input is greatly appreciated.

Thanks so much
~Florida Dave

 

Welcome to the forum

Try a vacuum gauge on the intake
18" to 21" is expected

You may have a partially clogged exhaust, i.e. a Cat or muffler that has loose parts inside that are shifting around and then reducing the flow OUT so engine power drops and eventually stalls
After stall, and no flow, the blocking part falls and it runs OK again
Wild guess
You can tap on Cats and muffler with rubber mallet or wood and see if any rattles show up

Vacuum gauge will show if pressure in exhaust is building up at higher RPMs, hold RPMs at about 2,500 and vacuum should be steady, if its slowly dropping then clogged exhaust

There would be no code for clogged exhaust
Fuel pump stopping would cut engine off instantly, no bogging, it would be like turning the key off


Computer issue and no codes
Do a sanity test
Unplug a sensor and start engine, see if computer sets correct code
Plug sensor back in and unplug another and see if sets correct code
This doesn't test if the computer is OK, but it does test that it can set correct codes

 

RonD

Cat has been removed but I will go tap on the muffler to confirm there is no blockage at all

I plan on hooking up a vacuum gauge this evening or tomm first thing.

I am wondering about the ECM also.... Great idea to try and just unplug something to see what happens. That is quick and easy and I will try it this evening.

Thank you again.
~Dave

 

Well I wont have time to hook up my vacuum gauge until tomm after work, but I did just drive it 17miles with no issues at all. Im in FL so it is about 20 degrees warmer now than early this AM.
I also was running my AC full blast on the way home. I am trying to think of what could be different.

I tapped on the muffler and had no odd sounds at all, I believe it is flowing just fine

I also tested the CEL by unplugging the IACV and it set the correct code… i then cleared it and unplugged the MAF and again it tripped the correct code. The CEL definitely is working

I will report back once I get my vacuum gauge hooked up.

thank you!

 

Well. Hooked up my vacuum gauge yesterday. Everything seems relatively normal with exception of it bouncing around 21 at idle. I have a couple videos I will attach.

truck drove awesome yesterday, but it did die on my about 20min ago while in 3rd gear cruising. I could feel it starting to stumble and i knew it was coming. While still rolling I fired her right back up no problem! Still no codes and no other signs other than it stumbling and then dying.

 

my apologies. here are the 2 videos. the shorter video is what the truck would do at idle randomly. seems fine under a load though.

 

 

Update -

NEW SYMPTOM - Truck does not idle down or try to stall when I unplug the IAC valve. (NOTE- This truck was bought used at 174k miles and not sure what the PO did, but it looks like somebody messed with the throttle stop screw at some point before me)

Still no codes

I have been chasing these gremlins for a while now.... truck won't even make it around my block without stalling and barely running. new symptom is some serious pinging going on (you can hear it in the video).

I also smoke tested and the only two spots that had a leak was the IAC valve cap and a tiny bit of smoke around the throttle body shaft.

In the last two weeks I have done the following:

New Motorcraft plugs
pulled upper intake and TB when doing plugs and confirmed the EGR is not blocked with carbon or anything
unplugged coil packs one at a time and truck continues to run no problem.

For the lift of me I can not find a vac leak - the smoke test should make it obvious, but it does not.

anyhow...here are the videos...


Smoke Test

https://youtube.com/shorts/Md58AZ8CP6g?feature=share


Driving around Pinging and dying

 

Pinging means a lean air/fuel mix in most cases
Computer expects 60psi fuel pressure at each injector in a 1998 Ranger, so it can calculate correct open time for each injector
If lower than 30psi there would be issues, but there should be Lean codes if under 45psi

You can readjust anti-diesel screw(throttle stop) by warming up engine, let it idle, then unplug IAC Valve
Turn anti-diesel screw counter-clockwise until engine is barely running, about 600rpm on a 4cyl
You are done
Plug IAC Valve back in, Idle should go up to about 750rpm for manual trans, 800rpms for automatic

If idle doesn't go down when turning anti-diesel screw then either IAC Valve is stuck open or you have an intake air leak, PCV Valve, power brake booster?

Gasoline engine RPMs are always controlled by air flow, fuel is added based on that air flow
If you just add more fuel you will get a slight increase in RPM but then engine floods out
So RPMs are solely based on air flow into the intake, usually just thru the throttle body/throttle plate, but in the case of fuel injection the IAC Valve is also used to add air because there are no Jets to suck fuel from, like a carburetor had


RPMs can also be increased by spark timing, but in a 1998 there is no access to that, and incorrect spark timing can also cause pinging, but this would be a computer issue not something you could correct
You can use an old time timing light to see what current spark timing is being used

 

I'm surprised with all you did, you never checked the fuel pressure or change out the fuel filter, especially since you can get it to stall repeatedly and quickly. To me sounds like a dying fuel pump