94 4.0 V6 poor idle/ dies when in gear

[Shokie1555]

Hello my 94 4.0 V6 recently had the pcm fuse go bad so I switched it with the ac fuse and it started running again but the problem is it runs horrible and with misfires and when I put it into gear it wants to die and I have to keep my foot on the throttle. Any ideas?

 

[RonD]

I assume this is fuse #4, 30amp, in the engine fuse box?

If so this powers most of the engine systems, and the PCM
There is a PCM relay in the engine fuse box, it sends fuse 4 power to the PCM and the engine systems when key is ON
Systems powered by PCM relay and fuse #4
PCM
Ignition coil
Ignition module(EDIS-6)
6 fuel injectors
IAC Valve
EVAP solenoid
EGR solenoid
MAF heater
If automatic trans then 2 solenoids in trans

So most likely one of these caused the fuse to blow
Most obvious are PCM, coil pack and injectors if engine is barely running

I would put in a 15amp fuse and see if it blows with Key OFF, wait 5 minutes
Then turn on key and see if fuse blows

 

[Shokie1555]

It was the pcm power relay not the 30A #4 C171

 

[RonD]

".......recently had the pcm fuse go bad so I switched it with the ac fuse...."

So the PCM relay wouldn't close with the key ON and you replaced it with...........??

AC Relay..........or ??

 

[Shokie1555]

I replaced the PCM Power relay wth the WOT cutout relay

 

[RonD]

And the engine was running fine prior to this swap of relays

And how did you diagnose PCM relay issue, was that your first guess with a Crank but no start?

Or did you do any testing with volt or OHM meter?
Or test spark or 50/50 test?

 

[Shokie1555]

Yes it was a crank no start

 

[RonD]

And so what did you do?
What tests?

 

[Shokie1555]

Before I switched the relays I tested the spark,fuel,compression and i had all of those so i thought it was a dead PCM so before i bought a new one i switched the relays and it started but it ran horribly and with misfire.

 

[RonD]

You wouldn't have Spark or Fuel with a failed PCM relay, you would have compression

So wasn't the PCM relay for sure
PCM relay powers coil pack for spark and fuel pump relay for fuel pressure, so if you had spark and fuel pressure, then PCM relay was working at that time

So the crank, no start, wasn't PCM relay

Did you remove spark plug wires?
On the coil pack they should be this way
3 4
2 6
1 5
front

The 5 6 4 side gets me every time
Follow each one over to its cylinder, because they can get mixed up at the spark plug end as well

 

[Shokie1555]

No I did not remove the spark plug wires

 

[RonD]

1994 4.0l running poorly can be:

I assume spark plugs looked OK since you saw them when you did the compression test
Dirty MAF sensor, clean it, shouldn't cause a no start though
Low fuel pressure, test it, 30-35psi is expected, can cause a no start
Clogged exhaust system, can also cause a no start, i.e. potato up the tail pipe trick, can be tested for with vacuum gauge

All best guess as there is not alot to go on

 

[Shokie1555]

The MAF was cleaned and the exhaust blew out and the engine is running it just runs horribly

 

[Shokie1555]

Also brand new injectors and i put new gaskets between the fuel plate and lower and fuel plate and the upper

 

[RonD]

And you have checked the firing order on the coil pack, and then checked it again, and then checked it one more time

When was the last time you got gasoline in the tank?
"Bad gas"(has more water than usual) will cause what you describe