Help Needed Jumping tach at startup? Not the CPS!

[hheynow]

Recently when I start it the tach jumps from 500 to 1000 rpms and back down and up and the truck shakes. When I press the go pedal the idle smooths out at just over 500 rpm. I just changed my CPS five minutes ago but still have the jumpy tach at idle ONLY AT START UP. My fuel filter was just replaced so I think I can rule out fuel restriction. Thoughts?

 

[7.3turbodiesel]

Problem with your ipr valve maybe?

 

[95_stroker]

Richard, next time before you start it, pull the plug on the HPOP. Almost sounds like you have a low reservoir.

 

[hheynow]

I thought the '97 had a check valve to prevent HPOP reservoir draining?

I think I narrowed it down to a fuel restriction. A bit more background info. When the truck died (wouldn't restart) in the post office parking lot the other day (just prior to my tow home) I noticed the 12 inches of J30R9 fuel hose just prior to the fuel pump had sucked itself shut under vacuum. When I got home I replaced the hose and changed the fuel filter. BTW, I'm running B99 very late in the year so gelling is a real concern at dawn. It started right up. The next time I tried to start it I noticed the romp as the tach jumped. Once I pressed the go pedal and revved it up it settled down to a perfect idle. So today I decided to trace the fuel line for a restriction and I found my Vegtherm Mega (a 12" aluminum tube with a small bore used for 12v vegoil heat) had a huge glob of goo inside. I got my rifle bore brush with the steel brush tip and cleaned the inside of residue and rinsed with B99. I think it will solve my problem but it's not put back together yet. I really should have checked and cleaned the Vegtherm Mega when I replaced my fuel pump a few months ago. Seems that this item clogs once per year.

 

[95_stroker]

I thought the '97 had a check valve to prevent HPOP reservoir draining?

Yeah well, things fail from time to time yanno?

I think I narrowed it down to a fuel restriction. A bit more background info. When the truck died (wouldn't restart) in the post office parking lot the other day (just prior to my tow home) I noticed the 12 inches of J30R9 fuel hose just prior to the fuel pump had sucked itself shut under vacuum. When I got home I replaced the hose and changed the fuel filter. BTW, I'm running B99 very late in the year so gelling is a real concern at dawn. It started right up. The next time I tried to start it I noticed the romp as the tach jumped. Once I pressed the go pedal and revved it up it settled down to a perfect idle. So today I decided to trace the fuel line for a restriction and I found my Vegtherm Mega (a 12" aluminum tube with a small bore used for 12v vegoil heat) had a huge glob of goo inside. I got my rifle bore brush with the steel brush tip and cleaned the inside of residue and rinsed with B99. I think it will solve my problem but it's not put back together yet. I really should have checked and cleaned the Vegtherm Mega when I replaced my fuel pump a few months ago. Seems that this item clogs once per year.

Now you tell us the rest of the story.....

 

[hheynow]

The latest rest of story. Gosh I hate throwing parts at her. After changing the CPS and GPR the truck still had the romps at startup. Then I tried starting it in neutral. Bingo...beautiful smooth idle with no romps. Started it again in park and the romps returned. So my problem is the transmission range sensor aka MLPS (manual lever position switch) aka PRNDL switch.

I can't find such a part on JOAT's parts page nor am I certain of Ford's term for it. I know it's a sensor outside the tranny. Anybody know what I'm looking for or a P/N?

So I had two issues. The sucked in fuel hose due to the VT clog and a truck that doesn't like being started in park. But I tell ya, since cleaning out the goo clog and replacing the fuel hose the truck drives like a bat outta hades. Still bone dry from my fuel pump install.

 

[action4478]

So that's the Mercedes you were telling me about ...

Running veggie in it too?...

 

[trackspeeder]

The latest rest of story. Gosh I hate throwing parts at her. After changing the CPS and GPR the truck still had the romps at startup. Then I tried starting it in neutral. Bingo...beautiful smooth idle with no romps. Started it again in park and the romps returned. So my problem is the transmission range sensor aka MLPS (manual lever position switch) aka PRNDL switch.

I can't find such a part on JOAT's parts page nor am I certain of Ford's term for it. I know it's a sensor outside the tranny. Anybody know what I'm looking for or a P/N?

So I had two issues. The sucked in fuel hose due to the VT clog and a truck that doesn't like being started in park. But I tell ya, since cleaning out the goo clog and replacing the fuel hose the truck drives like a bat outta hades. Still bone dry from my fuel pump install.

You can get the MLPS from any parts store.They run about $45 bucks or so.

The part is on the left side of the tranny. Located on the manual shift lever.

You will need the funky little tool to set it. I think you can get that at any parts store too.

 

[hheynow]

So that's the Mercedes you were telling me about ...

Running veggie in it too?...

Yup
Yup, as of Thanksgiving.
It's so slow and green like a turtle I just had to name him Yertle.

 

[hheynow]

You can get the MLPS from any parts store.They run about $45 bucks or so.

The part is on the left side of the tranny. Located on the manual shift lever.

You will need the funky little tool to set it. I think you can get that at any parts store too.

Ordered it (F7TZ-7F293AA) from Ford for Monday delivery.
They call it a neutral safety switch or transmission range sensor.
Having it installed. Some things I just won't mess with.

But until then, starting it in neutral works just fine with a perfectly smooth idle.