96 v8 starting issue

[bigcrunch]

Is the MAF sensor in the plastic duct work between throttle body and air filter?

Or after the throttle body?

1996 V8 5.0

 

[williams.cory]

between air filter and TB

 

[robertoa1a]

On the MAF there are two small filaments that occasionally need cleaning. Being that your problem is intermittent (on and off) I would rule out things that would cause a steady problem.

On a regular basis, How often does your engine start normal vs crappy?

The valve under the battery and the one above the tire can be purchased for about $20 each, but lets not go blowing cash yet.

When you'r at a stop light do you feel shaking in the engine, only sometimes?

 

[robertoa1a]

Do you feel engine vibration in the steering wheel at traffic lights, but only sometimes?

How many times out of ten does it start up fine vs. crappy, would you say?

I would rule out things that would cause an "all the time" problem as this one is intermittent (in and out).

The valve under the battery isnt the one to be conserned with. I believe its the one above the spare tire that causes the problem. It's a $20 thing, but dont spend money yet.

 

[2000StreetRod]

MAF sensor DTC

Will MAF sensor issues give a trouble code?

The PCM checks the MAF sensor output voltage to see if it is within normal limits (0.2 to 4.8 volts). It also compares the MAF sensor output with the TPS output. The PCM sets a DTC (P1121) if the Load > 60% and TPS < 2.4 volts or the Load < 30% and TPS > 2.4 volts. It is very difficult for the PCM to detect a dirty MAF sensor.

A dirty MAF sensor will not cause an intermittent problem.

Have you tested the TPS output?

How fast after turning off the ignition does the fuel pressure bleed down to zero?

 

[robertoa1a]

As far a engine codes go on a '96, you don't get one unless there is a catastrophic failure or a part is physically missing. The PCM is way under sensitive.

 

[bigcrunch]

Do you feel engine vibration in the steering wheel at traffic lights, but only sometimes?

How many times out of ten does it start up fine vs. crappy, would you say?

I would rule out things that would cause an "all the time" problem as this one is intermittent (in and out).

The valve under the battery isnt the one to be conserned with. I believe its the one above the spare tire that causes the problem. It's a $20 thing, but dont spend money yet.

-I feel a vibration in the steering wheel rarely. When it does I tap the gas pedal goes away.
- crappy starts about 3 out of 10.

 

[bigcrunch]

The PCM checks the MAF sensor output voltage to see if it is within normal limits (0.2 to 4.8 volts). It also compares the MAF sensor output with the TPS output. The PCM sets a DTC (P1121) if the Load > 60% and TPS < 2.4 volts or the Load < 30% and TPS > 2.4 volts. It is very difficult for the PCM to detect a dirty MAF sensor.

A dirty MAF sensor will not cause an intermittent problem.

Have you tested the TPS output?

How fast after turning off the ignition does the fuel pressure bleed down to zero?

-I have not tested the TPS, will do that next. Is there a documented process?

-the pressure will drop to from 30 to 0 in about 60 seconds, then most time it does not drop.

 

[2000StreetRod]

TPS check

The PCM relies on the TPS to determine closed throttle for idle and all other throttle positions for acceleration or deceleration. Testing the TPS is easy and costs nothing. With the electrical connector connected to the TPS backprobe the wiper contact (gray/white wire) and the return (gray/red wire). Connect the positive lead of the voltmeter to the wiper probe and the negative lead to the return. Switch the ignition On but do not start the engine. The voltage should be approximately 1.0 volts with the throttle closed. Slowly rotate the throttle plate to WOT while watching the voltage reading. It should increase smoothly (with no dropouts or jumps) to at least 4.0 volts at WOT.

 

[williams.cory]

at least 4.0 volts at WOT.

I thought a perfectly dialed in TPS read 4.96v on WOT? At least between 4.8-4.9ish

 

[bigcrunch]

I checked the TPS, voltage up to 5 at WOT.

However before I pulled the explorer to the garage to check it,

There was the no start again, it had been sitting for 20 hours since I last ran it yesterday, 37f outside. First thought was no fuel in the fuel rail.
What I did after my first attempt cycle the ignition key 5 times without starting it I could hear the fuel pump run for 2 seconds each time, I think it shuts off with no start, on the sixth time turned it all the way to hit the starter and whalla it fired right up.
I think fuel related????
I have a new fuel filter(Purolator) just not installed it yet, lots of cold, rain and wind in Ga right now will do so Sat am.

thanks for the help,,,,

 

[williams.cory]

get that filter changed ASAP!!!!! takes 5 minutes to change it....really easy. Go outside and change it right now!! LOL.

you said its never been changed...how many miles on the truck?

let us know what happens!

 

[bigcrunch]

it must have 235,000 +, odometer stopped working,,,,

 

[2000StreetRod]

DTCs P0123 & P1120

I thought a perfectly dialed in TPS read 4.96v on WOT? At least between 4.8-4.9ish

If the TPS voltage exceeds 4.80 volts the PCM sets DTC P0123: Throttle/Pedal Position Sensor/Switch A Circuit High Input and/or P1120: Throttle Position Sensor out of range

 

[williams.cory]

If the TPS voltage exceeds 4.80 volts the PCM sets DTC P0123: Throttle/Pedal Position Sensor/Switch A Circuit High Input and/or P1120: Throttle Position Sensor out of range

I was reading somehwere (I think Mustang forums) that 4.96v was the best setting. they went into detail telling you to get a dremmil and shave where the bolts go through on the sensor, so you can tilt the sensor just a little bit to give it a different reading when its mounted back up, and to fine tune it to 4.96-4.97.....? I wish I could remember where I saw this at.... Maybe I miss understood something...or the guy writing the thread was smoking something strange!! LOL

 

[robertoa1a]

There is slack in the throttle cable on most of ours effecting WOT. Look behind the throttle pedal. That's a whole orther topic though.

My truck has the exact same problem only not as severe.

Half of the time the engine starts perfect the other half of the time It takes excessively long to start.

I was thinking that the check (back flow preventer) valve on the fuel pump was leaking down when the truck sits for a while. This one has been throwing me through a loop for a year now.

My next step is to check the evap system. I will be doing that tomorrow.

 

[bigcrunch]

Changed the fuel filter today. :thumbdwn:

When I disconnected the filter inlet line, I could see the brown stuff in the gas coming back out. Full of rusty crap. It left a brown spot on the concrete, I captured some in a bottle once I got the filter out.
When I changed the pump 1 year ago tank did not have that in it, I always go to newer gas stations in my area to avoid this.
I figure some of that crud got past the filter into the injectors and regulator possiblly making them stick open every so often.

I thought about it all day I must have pumped at a station that had rusty tanks with no filters at the pumps on my trip to Denver 2 months ago. Thats when it started.

I have pics, but cant post them here????,,,

 

[williams.cory]

well that sucks!

to post pics, you have to upload them somewhere like photobucket.com or some free site like that. then you get a specail "code" to post on here

 

[bigcrunch]

http://s307.photobucket.com/albums/nn315/bigcrunch69/?action=view&current=101_0009.jpg

http://s307.photobucket.com/albums/nn315/bigcrunch69/?action=view&current=101_0004.jpg

 

[williams.cory]

Here you go.....You take the image code and put it in here....But either way works just fine