URGENT TECH HELP NEEDED- Bronco II stalls/dies

[RICHARDG]

Hi all,
Here's the problem: Bronco II dies after running (or idleing) for EXACTLY 25-30min. Runs like a top (NO engine firing/"missing") with good idle & acceleration for 25-30 mins. then engine "lugs"/chugs (like spark or fuel starvation) & just dies. Does NOT blow any smoke, leak any oil. engine temperature is NORMAL. "check engine" light comes on after ~ 20min at idle, just before it dies 5 -10 min later at the 25 - 30 min mark.
IF I disconnect the vacuum hose that runs between the air filter & intake manifold then the "check engine" light DOES NOT come on BUT the engine still dies at the 25 - 30 min mark.

History & tech specs:
> 1990 Bronco II 2.9L fuel injected. 76K ORIGINAL miles
Engine DOES NOT have a MAF or EGR sensor.
Truck was garaged for ~ 10 yrs.
> New parts installed:
Fuel pump, fuel filter, FPR (fuel pressure regulator), air filter, plugs, plug wires, TFI (distributer ignition module) thermostat.

> Troubleshooting procedures & maintenance checks performed:
ACT sensor cleaned & resistance checked OK.
IAC cleaned
PCV cleaned & checked OK
TPS checked OK
Throttle body cleaned
Coil resistance checked & spark jump checked OK ( ~ 1"" + )
Distributer cap & rotor checked OK
Alternator voltage output IS STEADY ( DCv) checked OK @ ~ 13DCv at idle RPM. (output voltage DOES NOT INCREASE with higher RPM )

>Possible causes issues/& other miscellaneous symptoms identified so far:
Base Idle Adjustment - Cant set/get the engine to idle below ~ 1000 - 1,100 RPM ( factory spec is ~ 850 - 950RPM)

?? - RF headlight "dims" with right turn signal engaged (NO other light/turn signal dimming, NO engine RPM decrease/ dying)
??? - Alternator gets very warm (hot?) the longer the engine runs.

SOoooooo...... the question is...
Whats causing the engine to die ?
?? MAP sensor is bad ?
??? ECM malfunctioning ?
???? other ?

Any comments/help appreciated
Thanks
richard

 

[vwa1]

When the engine stalls like that, are you able to restart it right away?

If you have the means, it might be a good idea to hook up an inline spark tester and a fuel pressure gauge and watch them when it starts to stall. If one or the other drops out right as it stalls, at least you will be narrowing it down.

Have you tried checking the codes? You should have something stored if the check engine light is coming on consistently. You can check them with a jumper wire and a test light. Here's a link with the procedure and a list of DTC's http://www.extreme-check-engine-light-codes.com/Ford OBD1 Decoder.htm

also, you may have 3 digit trouble codes, cant remember for sure. Here's a link to those http://www.therangerstation.com/tech_library/3digitcodes.shtml

 

[RICHARDG]

Hi vwa1,
Thanks for the reply.

NO cant restart till the engine "cools down"....~ 30 mins... then it restarts easily.(Again engine temp never exceeds "normal")... Will run again for 30min... then... dies again at ~30 min. mark.

Cant pull the ECM codes myself....cant locate the EEC 60 pin connector under the hood....also (pre 1996 models cant be done for free at local Autozone stores.) and the mechanic shops want $50 bucks just to pull the codes for 5 min work.

Any other suggestions?

 

[SenorNoob]

Look for the plastic connector just to the rear of the truck from the battery. It doesn't have anywhere near 60 pins. (That'd be the ECU connector behind the passenger side kick panel.)

I see you've replaced the TFI, did you use thermal paste on it? Also, new doesn't necessarily mean good.