1986 F150 5.0 hard to start,will not idle

[85lebaront2]

Gee, I remember that headache. I spent a weekend in Falling Waters WV getting it solved.

Maybe Gary could add that into the idle setting information.

[1986 F150]

85lebaront2 wrote

Jeff, Jim, the 1985/86 5.0L EFI system is not like the 1987 up systems, The idle stop screw setting is very touchy on these. The EGR system starts to function just off idle (Matt's drove both of us nuts). In the right front corner behind the battery is a set of solenoid valves:

Two of them are for the EGR valve, the other two are for the Thermactor system. If the TPS voltage is too high, the EGR pair will chatter and the EGR valve will try to open, which kills the idle, followed by closing where it will pick up again.

The idle may be raised to get around this. One item we did discover, aftermarket sensors do not always react the same as OEM Ford ones, he had a Standard TPS and could not get the closed throttle voltage low enough. A Motorcraft one solved the problem.

I did not hear any chattering from the EGR solenoid valves. I'll do a voltage check on the TPS. I just can't see the TPS suddenly going out, as like I mentioned before, it idled in gear fine before I replaced a bad TFI module (I had it tested and it was shot).  I don't know what else to try,  am getting close to the end of my rope. Can't afford to dump much more money into it

[ArdWrknTrk]

I'm never about parts swapping and always about diagnosis.
Take some readings from the TPS and if it's out of range slack off the the stop to see if you can get it back where it belongs.

The fuel regulator was obviously a big issue that needed replaced before any other trouble shooting.
You might find closing the plate up will help since there's not gas going everywhere now.

Do you have an accurate meter?

[1986 F150]

ArdWrknTrk wrote

I'm never about parts swapping and always about diagnosis.
Take some readings from the TPS and if it's out of range slack off the the stop to see if you can get it back where it belongs.

The fuel regulator was obviously a big issue that needed replaced before any other trouble shooting.
You might find closing the plate up will help since there's not gas going everywhere now.

Do you have an accurate meter?

I have a digital multimeter I bought  from a tool bin at my local hardware store a few years ago, it's as accurate as it can be I guess, it'll have to do.

[ArdWrknTrk]

Digital is good as long as the battery is fresh.
Let us know what you find!  

[grumpin]

1986 F150 wrote

85lebaront2 wrote

Jeff, Jim, the 1985/86 5.0L EFI system is not like the 1987 up systems, The idle stop screw setting is very touchy on these. The EGR system starts to function just off idle (Matt's drove both of us nuts). In the right front corner behind the battery is a set of solenoid valves:

Two of them are for the EGR valve, the other two are for the Thermactor system. If the TPS voltage is too high, the EGR pair will chatter and the EGR valve will try to open, which kills the idle, followed by closing where it will pick up again.

The idle may be raised to get around this. One item we did discover, aftermarket sensors do not always react the same as OEM Ford ones, he had a Standard TPS and could not get the closed throttle voltage low enough. A Motorcraft one solved the problem.

I did not hear any chattering from the EGR solenoid valves. I'll do a voltage check on the TPS. I just can't see the TPS suddenly going out, as like I mentioned before, it idled in gear fine before I replaced a bad TFI module (I had it tested and it was shot).  I don't know what else to try,  am getting close to the end of my rope. Can't afford to dump much more money into it

You said you replaced the TFI Module. It could be bad out of the box. Can't trust aftermarket parts anymore. I'd be leary of OEM anymore.

[1986 F150]

ArdWrknTrk wrote

Digital is good as long as the battery is fresh.
Let us know what you find!  

TPS test results: 5 volts between orange wire and black wire
                         1 volt between  dark green wire and black wire

[ArdWrknTrk]

More good news!

I might try to back the idle down to see if that keeps the transmission from loading the engine in gear.

Curb idle for automatics is shown in gear (with the vacuum advance capped and wheels chocked) on the emissions/vacuum sticker attached to the radiator support.
But you might look to the 'manual in neutral' setting to get an idea of engine speed if you can't yet do it engaged in drive.

[vjsimone]

1986 F150 wrote

ArdWrknTrk wrote

Digital is good as long as the battery is fresh.
Let us know what you find!  

TPS test results: 5 volts between orange wire and black wire
                         1 volt between  dark green wire and black wire

Hello Jeff, (following) how is this going ?