the.green.machine

I posted this on a couple other forums too btw and I'm new to posting online so be gentle please. My issue is:

1995 f150 5.0 4x4 with 240k miles

symptoms;
. 1. Slight miss at idle.
. 2. Will not accelerate unless throttle is darn near floored, and maybe 1 out of 10 times it will seem to function as it should.
. 3. CEL comes on but only intermittently, never at idle.
. 4. Exhaust seems to blow out much harder than my 92 with the 300 and my friends 2006 with the 5.4L.
. 5. Catalytic converter seems too hot to me.

checked;
. 1. Plugs (all good and getting spark)
. 2. All vac lines look good, no hissing.
. 3. Timing is perfect.
. 4. Spray carb cleaner all around vac lines, egr, intake and even the plugs with no change in running.
. 5. Fuel pressure (34 key on and about 37 psi running)
. 6. Compression in tolerance of Haynes manual, I forget what they all were but we're withing 10% of each other.
. * tried to pull codes btw, will not show codes at idle and I think the diagnostic port for the obd 1 is messed up, have tried with and without obd 1 scan tool

The following are all things that have been replaced (for give my part swapping, as I couldn't pull codes it was kind of a best guess scenario).

Replaced:
. 1. EGR
. 2. FP Regulator (old one was bent where vac. Hooked up anyways.)
. 3. TPS
. 4. IAC
. 5. Fuel Filter
. 6. Throttle body gasket
. 7. Air filter
. 8. MAF
. 9. Battery (kind of unrelated as old one was shot anyways)

the next things on my list to try (unless you fine folks here can help) is to try a new coil and I may hollow out the catalytic converter since it seems to me like it gets much hotter than it should. After this I am at a complete loss (more than before). I've tried not to just throw parts at it but nothing is seeming to workout right. Its a truck I bought from a friend and he is at a loss too. Any help would be greatly appreciated.

vjsimone

(1. Slight miss at idle.)
Cold Idle or Warm Idle?

Does the initial Cold Start Idle rise up to 1800rmp for 30 seconds and then drop to 1000rpm then drop to 600rpm when warm?

(2. Will not accelerate unless throttle is darn near floored, and maybe 1 out of 10 times it will seem to function as it should.)
Yeah, possible clogged exhaust. I’ve seen a double lined Y-Pipe bubble inside and block exhaust.
Injectors not being pulsed from computer.

(2. All vac lines look good, no hissing.)
( 4. Spray carb cleaner all around vac lines, egr, intake and even the plugs with no change in running.)
This is not a 100% check for verifying vacuum leaks.

(. * tried to pull codes btw, will not show codes at idle and I think the diagnostic port for the obd 1 is messed up, have tried with and without obd 1 scan tool)

You may have a wiring issues from your OBD connector to your Computer.
If you cannot retrieve codes then your computer may be corrupt, making it suspect for your other issues.

Recommend you test your OBD connector for Power, Ground & Continuity to your computer.

Does the TPS output voltage = .94-.97vdc when throttle is closed ?

Did you replace your Cap and Rotor?

the.green.machine

Seems like the miss only starts once the RPMS have dropped down after initial cold start, and yes the RPMS step down as they should.

I didn't even think about injectors! I will clean or replace as needed, can't belive I didn't think about it.

I know it isn't 100% way to check, I also stuck a piece of hose to my ear and didn't find any hissing, will check again though. Have a better way without a fog machine?

For the OBD1 etc, the 2 center bottom pins in the EEC bring about 2.7 VDC, and the single wire is .1 ohms to ground. Can you verify these voltages?

TPS voltage is within range yes

And although it doesn't mean it can't be the problem, the cap and rotor are less than 3 months old, also the plugs and wires and the plugs look as they should when I checked them.

Thank you for the response, I'll gladly try anything at this point so thanks.

vjsimone

You can disconnect the half dozen or so Vacuum lines going to the Throttle Body & Intake and cap them. Don't know the 95' but there are about six one the intake vacuum "tree", and another one tucked under the throttle Body, on my 85, it goes to the Gas Tank Vent Canister.

The two that need to stay connected are the MAF Sensor & Fuel Pressure Regulator. I would run a new temporary vacuum line from these devices to 2 of the intake ports, (2 less you have to cap) and cap the others. This will eliminate all your existing vacuum lines in the equation.

I like to plug in my vacuum gauge to one of those ports as well (1 more less to cap). You can tap your gauge in before you start this process to base-line how your vacuum is acting currently

Crank it up from cold start, see if it make a difference, if so, put the vacuum lines back one at a time to see which one has an issue. Starting with the Brake vacuum line, Fuel Pressure Sensor, then the MAP, and then the rest of the lines.

http://shop.advanceautoparts.com/p/d...7388/9110159-P

vjsimone

Check voltage on the STI self-test connector, this is the single wire (separate wire) next to the test connector. "Self-Test Input" (STI) should be +5 volts dc.

My STI connector has +5vdc when the key is turned on.

the.green.machine

The 302 in my 95 doesn't actually have the MAP, it has the MAF and it is new. The MAP is what I thought it was too but looked and found there isn't one on this truck. I live 2 hours away from where the truck currently is and if it didn't keep looking like rain I'd go try these, hopefully tomorrow but probably gonna be thursday or Friday. My friend is going to replace the coil for me since it is at his house and I'm gonna ask him to try your suggestion with the vac. Lines, but he works all the time so he may not. I really appreciate the advice and will try anything.

the.green.machine

Alright, I'm going to try and test wires resistance, may have corroded. Thank you

the.green.machine

What are the symptoms of a bad DPFE??? Doing some research and found someone with a similar issue but not in good detail.

vjsimone

I have no experience with the DPFE, but loads of info out there; I believe it has a vacuum line as well.

http://www.ford-trucks.com/forums/34...fe-sensor.html

Chris_1

iTrader: (1)

DPFE tells the computer how much exhaust gas is being recirculated; the computer then compensates the fuel air mixture accordingly. A bad signal from it would cause an issue.
But I didn't think they had them on F150's till 96 - maybe yours does though ?