Driveability help please

Strokesstitches

New member
Good morning all. I need a little help figuring out a weird idle concern if possible. Being a tech for 30 years I know how much this can be a pain to figure out without being present with the truck, but maybe someone has a thought.

I rescued this 94 Lightning from a 7 plus year sentence of sitting in a field, with tons of rot and rodent damage. I gave up a brand new truck to make this my driver and I am in love. It's a dream to own this. The truck now runs great for the most part. I've replaced so much due to sitting and rodents, etc.

The truck idles great but has a somewhat hard start sometimes but then will idle great in park or neutral. Sometimes when sitting still in gear the engine will lope constantly, from approximately 500-900 rpms. It's more of an annoyance then a problem, but obviously I still want to fix it. I have a new IAC. I've actually been thru a few of them cause of parts store listings. I've had my Ford parts department guys help with numbers, hence me trying numerous units. No vacuum leaks that I can find, amongst the new parts thanks to damage from getting chewed on, etc is distributor, ignition module, ecm due to corrosion, map sensor, egr position sensor and probably more.

I'm kind of stumped and maybe just need a fresh opinion.
 

FMOS Racing

PSI=:-D
I Support the NLOC
That kind of behavior is typically a vacuum leak, or it's running lean (and that's usually from a vacuum leak).

Check vacuum, check fuel pressure, follow the procedure to set the idle without the IAC and set the TPS to less than 1v.

That's about all I know of as a first shot spitball!
 

R&RFord

Member
I'll will add that at this point in the in the trucks life cycle it never hurts to remove the computer and inspect the board for damage, including pregnant or leaking capacitors.

What IAC are you using? It will not work right if you have the wrong part installed...
 

Strokesstitches

New member
I've got a new PCM because there was internal issues with the original. I've got 3 different IAC valves that make it do the idle surge at different intervals.
 

bumperquip

Active member
Why the transmission filter?

Poor/low/irratic idle and/or stalling upon transmission engagement is a typical symptom of a clogged or otherwise failed or improperly seated automatic transmission filter.

At a minimum the trans pan should be dropped and the proper seating of the filter should be checked.

Based on the history of the truck, as explained by the OP, replacement (and proper/secure installation) of the trans filter is recommended.
 

RU$$ELL

Member
Poor/low/irratic idle and/or stalling upon transmission engagement is a typical symptom of a clogged or otherwise failed or improperly seated automatic transmission filter.

At a minimum the trans pan should be dropped and the proper seating of the filter should be checked.

Based on the history of the truck, as explained by the OP, replacement (and proper/secure installation) of the trans filter is recommended.

Thanks, I need to see if mine wonders in gear. I have not driven it much because I don't have tags on it yet. In park it goes from about 950-1050. I assumed I had a vaccum leak, or the idle needed to be reset after the new intake gaskets.
 

Strokesstitches

New member
I installed the IAC mentioned by R&RFord and it made a huge difference in starting. The idle is better but still has some bugs. I'm gonna check the timing, etc then I will update. Baby steps in bringing this girl back to life.
 
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