5.0 w/ C4 - Stalls in gear

[gfennie77]

Hey guys,

Just finished putting a 1993 5.0 HO in a 1991 Explorer.

When the engine first starts it revs up to about 1800 rpm, then brings itself down gradually... all without me touching the accelerator. Throttle response is excellent, and it idles like a dream at 900 rpm. This tells me that ignition, timing advance, vacuum, computer, etc is all up to snuff (I think).

As soon as I put the truck in gear, it stalls. Can't even keep it running if I floor it - it just bogs down and dies (although the tires 'chirp' first).

I've thought about the EGR and IAC but I don't think that's the problem. All the sensors, injectors, etc are brand new.

Maybe I need to swap the torque converter? (ugh)

Any thoughts?

 

[TarHeel085]

very well could be the torque converter. was the C4 set up for a 5.0 or another engine?

 

[gfennie77]

The C4 & Dana 20 are from a 1977 (I think) Bronco w/ 302. Torque converter is stock (I believe).

 

[Nitrous SSC]

Sounds exactly like the TQ converter.

Your warm up is about right for most 5.0 engines from stangs. A double check on the TPS wouldn't hurt. .95-.99v is where you want to be.

If you have your foot off the brake and go into first can you get rolling?

 

[gfennie77]

Actually it's a little 'funny' - seems that the truck is much more responsive when it is 'cold' than 'warm'. Example: I drive it up and down the street a couple times, then the next time I turn around it stalls and won't restart. Even smells like the engine is a little flooded out. Throttle response goes to ****, and the engine feels very sluggish in general.

I have a BBK adjustable fuel pressure reg (and excellent vacuum). The truck seems to run best (throttle response) when the reg is backed off (unscrewed) as much as possible. Also, this is a 93 HO MAF motor (Windsor firing order) with 24lb fuel injectors and an A3M1 computer (but a C4 trans). Heads, Cam, Crank, Compression are all 'stock'.

Question - is there a difference between 1993 HO and non-HO computers (due to the different firing order?)

When it's 'cold' and in Drive, she idles at about 500-600. When she's warm, she'll stall in the same situation.

Note - the PNR switch (Park, Neutral, Reverse) and the VSS are not installed yet. Should that make a difference here? I thought VSS was for cruise control and that I can bypass the PNR for now...

Hmm.... this could all probably be as simple as O2 sensors. I love EFI. :>)

-Graham

 

[gfennie77]

Update - so here's the plan:
1) Verify that the computer is a "HO" Computer. Should be pn# F3ZF-12A650-??
(EA, EB - Manual)
(FA, FB - AOD)

I don't think the A3M1 is a "HO", so at least two cylinders are getting fuel at the wrong time due to the HO's different firing order.

2) Upgrade the MAF to a 75mm - calibrated for the 24lb injectors (19lb are stock)

3) Get a chip to reward myself for finally figuring it out if everything works. :>)

I'll post here in a few days when all the parts come in...
-Graham

 

[gfennie77]

It's fixed!

1) Cleaned O2 Sensors (they were filthy with carbon from running too rich)
2) Cleaned Spark Plugs (likewise - filthy with carbon)
3) Changed oil (engine had indeed flooded - oil was 'thin' and smelled like gas)
4) Installed Pro-M MAS calibrated for 24lb injectors (*** Main Problem ***)
5) Verified correct computer (All Mustang 5.0 computers will run all Mustang 5.0 engines. It's OK to put a manual computer in an automatic X, but not OK to put an automatic computer in a manual X. E-mail me for details. I've done a LOT of research here.)
6) Fuel Pressure Regulator - fixed leak in vacuum line (***Main Problem***)
7) Made sure that Neutral Safety Switch circuit is OPEN (not 'closed'). Open is 'in gear', closed is 'in neutral' I have a "Manual" computer runinng my 5.0 w/ C4).
7) Set initial timing to 11 BTDC
8) Set idle at about 900 RPM (with IAC unplugged). She sounds good there.

Runs like a champ - pictures (and FREE manual) coming soon.

I will have to change the gears and torque converter, but she's drivable now. Just a little sluggish off the line.

FYI: Jeff @ Ford Racing Parts (586-468-1356) really knows the 5.0 Explorer swap inside and out. He's a great resource.

Next up, chip and throttle body (75mm)

-Graham
gfennie@rochester.rr.com