93 Mark, strange start issues after sitting

A

Alkymark8

Registered
for a day or two, the engine is hard to start and I have to hold the pedal to the floor to get it to start and the black smoke rolls out of it for a few mins and it runs poorly for a bit. Any ideas?
 
Sounds like you may have a (some) leaky injectors, and its dumping all the fuel in the lines into the intake when you shut it off. After you shut it down, there is a residual fuel pressure of about 40 psi. You might want to dump some injector cleaner in the gas tank each of the next few fill-ups.
 
I have run two tanks full with injector cleaner and haven't let it sit but it smells really rich when idling and gets crappy milage I am getting about 16 mpg, what could cause the fuel pressure to go up? I replaced the reg last year and I have not checked the psi just thought I could look for something prior to having it tested.
 
Alkymark8 said:
I did, and got an egr sensor code.
Click to expand...

The EGR is normally closed at idle so I doubt that is the source of your issue.

The ECT(Engine Coolant Temperature) sensor could be bad causing a richer than normal fuel mixture.

You can understand the different strategies of the PCM by looking here.
 
driller said:
The EGR is normally closed at idle so I doubt that is the source of your issue.

The ECT(Engine Coolant Temperature) sensor could be bad causing a richer than normal fuel mixture.

You can understand the different strategies of the PCM by looking here.
Click to expand...

Is that the one for the temp gauge?
 
I'm not sure, but I believe there are codes for out of range. It could be bad, i.e. reading always cold, but not 'out of range'. So the answer to your question is yes and no.
 
Well I checked the fuel pressure and it was about 35psi and held after I shut it off, so my next question is where is this sensor located that goes to the ecu???
 
If your looking for the coolant temp sensor that communicates with the PCM it's on the coolant crossover tube that sits in front of your alternator.

There are two, one on each "down leg" of the crossover tube.

The passenger side sensor is the one for the PCM and the drivers side is the one that goes to the temp gauge in your dash.

they aren't expensive nor hard to replace
 
I picked one up and going to put it in and do the sea foam dealio too. I did get a code for low egr flow, would that effect milage?
 
Yes, EGR troubles can cause fuel economy problems.

I had to replace my DPFE sensor and EGR tube and the mileage came right back.
 
Oops, sorry, I missed this post.

The EGR tube is located between the EGR valve (near the drivers side of the throttle body) and the drivers side catalytic converter. Mine had a hole in it.

The DPFE sensor measures the difference in pressure before and after the orifice in the EGR tube.

The DPFE sensor is bolted to the back of the driver's side head.

Here's a photo of my old tube and DPFE sensor that is connected with the 2 small hoses.

egr.jpg
 
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