Help with Mustang Engine troubles

ronclark · Apr 14, 2014

I am having some trouble with my 94 Mustang with a 3.8L

A few months ago i replace the heads after blowing a head gasket. Its been running great until a few weeks ago, on a long trip back home it felt like i lost a cyl.

I pulled the codes I am getting P0305 ( Missfire on cyl 5)
I pulled the injectors and have them cleaned and thy were pretty dirty. It is running better but I am still getting P0305 and P0714.
What do not get while live mentoring the OBDII when it drop out of closed loop it runs horrible, and at random times it will go in and out of closed and open loop.
Closed loop runs perfect.

When i did the heads i replaced the spark plugs and used Motorcraft, wires and the coil place since it was out of speck.

What am i missing? :icon_confused:

hoosier1104 · Apr 14, 2014

Did you put the wires back in order? I seriously doubt you have burnt up your cat like I have.

ronclark · Apr 14, 2014

hoosier1104 said:
Did you put the wires back in order? I seriously doubt you have burnt up your cat like I have.

I'll double check, the coil pack is labeled. IF that is it ill feel dumb.

hoosier1104 · Apr 14, 2014

Mistakes happen. There could be a flat spot in the wires. Might want to check the wires to make sure they are not pinched.

ronclark · Apr 14, 2014

I just checked wires before my way to work, there are all in the right spots and nothing pinched. I still have all the factory wire holders so none of the wires are pinched or touching.
On go the search....

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hoosier1104 · Apr 15, 2014

Check to see if you are getting spark on cylinder 5. Just because you replaced the coil does not mean if could not have been a OBF.

ronclark · Apr 17, 2014

Well i check the plugs and wires thy all look good and were thy belong.
Spark is plenty hot
fuel pressure at idle is 31psi and unplug the regulator it is at 40psi
The Vacuum is rock steady at 21in. hg at idle.

I am starting to wounder if my cam sensor might be going me the problem since it controls the injector timing.

any other ideas?

hoosier1104 · Apr 17, 2014

That could be a probable cause. If it is going bad, it will cause the injector pulse to be off.

ronclark · May 3, 2014

The Cam sensor did not help. I found some really bad vacuum hoses, so i replaced those and a leaking EGR tube.
I installed new O2 sensors, since i read coolant eats them and thy have 170k on them anyway.
I have to say the car is running better, but still right.
I am just not sure were to go next or just give up and drop it off at the dealer.

SenorNoob · May 4, 2014

I really hate to say this but, I'd check out the compression at least on that cylinder and one to compare it to. It'd have been very easy to have mis-torqued something and caused a problem.

ronclark · May 4, 2014

SenorNoob said:
I really hate to say this but, I'd check out the compression at least on that cylinder and one to compare it to. It'd have been very easy to have mis-torqued something and caused a problem.

One of the first things I did after I got misfire on cylinder 5 and I have 170 to 165 psi across all cylinders.
I was wonder if it might be that or a valve since it was intermittent.

ronclark · Jun 19, 2014

I have a update. i got tired of messing with the problem and dropped it off at a shop. so after 3 days of having the car there telling thy found a pinched wire that goes to the injectors ( there telling me is common problem) and the ECU needs to be replaced. there quoiting me a price of $800 to get that taken care of, Something I really cant afford right know.
I checked a few part houses and it seems i can get a ECU between $125 to $225 depending on the calibration code.
Anything i should look out for? pick in pull had two 94 in there lot I was thinking of taking a chance and see if there 5 speeds and go that route at $50.

SenorNoob · Jun 19, 2014

ronclark said:
...I was thinking of taking a chance and see if there 5 speeds and go that route at $50.

This. I'm sure you can find one here: http://www.car-part.com/

Help with Mustang Engine troubles

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