Hello, looking for some help with my 1987 f-150 with 4.9 i6 EFI automatic.
it's been a series of symptoms finally resulting in no start. they may be related or not, hoping you can help. really wanna avoid having it towed to a garage right now.

I got the truck 1.5 yrs/~15k miles ago, at which time I did starter, solenoid, flywheel/ring gear (whatever you call that huge wheel), distributor, plugs wires filters etc.. probably more that I'm forgetting. always ran great, very reliable.

began having trouble this winter where starter wouldn't engage in the cold. (nightmare flashbacks to replacing flywheel...)
had to leave key on for a good minute before cranking, and then it would engage. also struggled to stay running after cold start, had to give it gas till it had run for a few minutes and warmed up. after warming up, ran like a top and no issues idling. the sluggish starter and start-stall symptoms became gradually worse all winter and didn't improve with warmer temps.

finally noticed interior lights and radio fluctuating, so replaced alternator and battery.
fixed the starter issue, but not the cold-start idle. truck would start right up but stall immediately without throttle. if not given throttle for long enough, would enter a surge/rev cycle and eventually stall. if given throttle till it smoothed out, would then idle and run great.
if truck was parked then started again fairly soon, usually idled ok, but not after sitting for an hour or more.
as a shot in the dark, tried a new IAC, no change.
eventually started to notice a VERY faint and random/intermittent hesitation/stumble(?) generally at higher speeds. but not every time I drove it.

finally, last week after a drive 1.5 hrs each way, with noticeable and increased stumbling at highway speeds, truck stalled close to home, while coasting at about 30 mph. (truck runs so smooth I didn't even notice at first.) has never stalled while driving before.
now cranks but won't start.

got it home, changed fuel filter, and ignition coil.
can definitely smell gas when cranking and fuel pump sounds the same as it always has.
took out and visually inspected spark plugs, distributor cap, and computer circuit board-- no smoking guns. plugs have faint orange patina (which is good according to the charts?) and wires look brand new.
visually checked grounds and found no obvious issues.
vaccuum lines seem fine and can't detect an audible leak.
had a new pcv valve and engine coolant temp sensor not long ago.
has always been pretty bad on fuel consumption (may have been better when I first got it, but now it's ~11-14 mpg) haven't noticed a dramatic change.
*a side note, dashboard battery guage has always read consistently high at 17-18 but never in the red. it didn't change after alt replacement, so I chalked it up to inaccurate gauge. maybe I am wrong?
truck has never shown a check engine light and I can't get it to flash codes using any of the methods I've found online/forums.
haven't tried TPS, MAF but wondering if any of these would lead to a no-start. doesn't seem likely to me.
next most obvious component is ignition module but it looks newer like the distributor and it's pricey so I haven't done it yet.
as you can probably tell by now I'm somewhat of an amateur driveway-mechanic. it is probably either something obvious I am overlooking, or something requiring actual diagnostics...??? I am a little bit at a loss as to the next step, and trying to avoid throwing more parts at it than I already have.


UPDATE I got a spark tester and remote starter button, cranked engine and no spark anywhere
UPDATE replaced ignition control module and TRUCK STARTS but has same immediate stall problem, can be coaxed into idling with throttle but eventually stalls. please help what is causing the idle condition??

PLEASE HELP, I need my precious work truck back, THANK YOU!

 

First see if you have spark at the plugs.

 

Yep that would be the first and as a check you could spray a little starting fluid in the air intake and see if it will try and run. If not no spark but best to pull a plug or 2 and check.
The other thing to do is check for codes on the computer as it should tell you what is going on.

If no spark I would look at the TFI unit in the dist. the wires go into.
They have been known to go bad and motor just stop running and not start again.
I have also heard they can cause some issues like you have before they stop working.

The other thing to cause no spark is the PIP (forget the name but the pickup coil) in the dist. I have seen posted go bad but a code would show this.
Dave ----

 

Thanks for the reply-- update, I got a spark tester and remote starter button, no spark anywhere-- dist to plugs or coil to dist

 

Thanks for the reply-- update, I got a spark tester and remote starter button, cranks but no spark anywhere-- dist to plugs or coil to dist

 

UPDATE replaced ignition control module and TRUCK STARTS but has same immediate stall problem, can be coaxed into idling with throttle but eventually stalls. please help what is causing the idle condition??

PLEASE HELP, I need my precious work truck back, THANK YOU!

 

The ICM did it have the same color wire holder at the body? Was it you that said it was black?
Most are blue so wonder if you got the right one to start with.

This stalling was the motor cold still or up to temp?
If up to temp I would check idle speed then timing.
If cold check carb choke setting and fast idle speed for starters.
Dave ----

 

How's your fuel pressure?

 

new ICM was identical to the one removed, gray and mounted on the distributor. it didn’t look old, not sure why it failed.
no carb 1987 EFI fuel injected. already did idle air control valve.

another update: I applied an intake sustem cleaner last night, AND taped a cracked corner i found on the plastic air intake/filter housing. this morning the truck started and actually stayed idling on its own for a minute before stalling, which is a big improvement. it runs great when running, all stumbles gone and never stalls en rte.
but, generally when starting from cold the truck wants to stall until it’s warmed up.
(already did eng coolant temp sensor)

 

I don't know why but was seeing 78 truck not 87
Being 87 & EFI you can pull codes to see what the computer had to say it needs.
Dave ----

 

[QUOTE=saltytrucks;19298449]new ICM was identical to the one removed, gray and mounted on the distributor. it didn’t look old, not sure why it failed.
no carb 1987 EFI fuel injected. already did idle air control valve.

another update: I applied an intake sustem cleaner last night, AND taped a cracked corner i found on the plastic air intake/filter housing. this morning the truck started and actually stayed idling on its own for a minute before stalling, which is a big improvement. it runs great when running, all stumbles gone and never stalls en rte.
but, generally when starting from cold the truck wants to stall until it’s warmed up.Check for intake manifold gasket leak, when cold the engine shrinks a bit and causes vacuum leak and as engine heats it expands and seals the leak.

Common problems with iron blocks and plastic or aluminum intakes.