Well, I've been at a complete loss regarding this particular issue with my truck. It isn't seriously impeding driveability, yet, and I want to head it off before it becomes a serious issue. I've spoken of this issue on FTE in the past, but I'll try to describe it as best I can here.

When I start the truck cold, it starts just fine. the idle is slightly rough (very very barely noticeable), and the voltage gauge is low. According to Torquepro, the voltage hovers around 9.3 or so. If I just let it idle for a minute, then it slowly creeps up to the 14.3 where it should be. Sometimes I'll depress the throttle to try and get the voltage up quicker, and about half the time when I do this, the voltage will start bouncing between that "low" value and the "normal" value, about once per second, and then it will eventually stay at 14.

The more important issue is this: After a cold start, if I put my foot to the floor, it will rev up quick, and then start falling off, even though I'm keeping the throttle pegged. It will do this a handful of times to me, whether in park or driving, and then suddenly drive normally. During the period where the RPMs are falling while the throttle is depressed, I've noticed that it kind of makes that same sucking sound that the EBPV makes. But, the EBPV is unplugged. And the new concern is, I noticed today that if I peg the throttle and then get off of it immediately, the RPMS fall below idle speed and the truck starts bucking and tries to die, and then after a few seconds will smooth out and return to idle.

I've tried watching the vitals with Torque Pro during this, and can't seem to find an anomaly. However, that doesn't necessarily mean much because I'm still learning what "good" values are.

Does anybody have any suggestions? I don't know if the voltage issue and the running issue are related, but I need to get them resolved ASAP before they become serious, as I cannot afford to be without it.

Here are videos I recorded of each issue:

 

Bump for the morning crowd.

 

The voltage issue is normal, that's the glowplugs kicking in and out.
why are you starting it and flooring it is the concern?

 

I normally start it and then hold the throttle down for a "high idle" so I don't have to let it sit and run for fifteen minutes. If I don't, then it does that thing where it loses RPM as I'm driving, which is dangerous on the road. I can pull out on to the road fine, and then try to get up to speed and it'll go to 10 MPH and then start dropping RPM. Not cool.

Yesterday while I was sitting there, letting it "high idle" with my foot, for whatever reason I stuffed my foot into it quick. Dunno why. But when the RPM dropped and it started to stall out, I got concerned. Cold or not, it shouldn't do that.

 

Changed the fuel filter lately and have you checked the filter bowl?
how high are you reving it up?

 

Filter has not been changed, and I have not checked the fuel bowl. You can see in the video how high the tach is going, about 2400 rpm or so.

What am I looking for when I check the fuel bowl?

 

The voltage fluctuation is NOT normal. The GPs should NEVER cycle on and off like that. At the very least, you have an electrical problem, possibly associated with the GPs. Hard to say if that's related to your cold run problem, however.

 

I've seen my 97 GPR cycle OFF-ON before. Usually will always wait for the GPR to turn OFF before driving. However, occasional I'm in a hurry and drive immediately. Not always but sometime the relay starts cycling as indicated by the voltage gauge, probably once every second or so.

From the manual ...

The glow plugs are self-limiting glow plugs and do not require cycling on and off. (The glow plug relay will only cycle on and off repeatedly when there is a system voltage condition greater than 14.5 volts.)

 

And system voltage greater than 14.5 volts is NOT normal.

 

I know you state the ebpv is unplugged but is it still closing on its on on start up? Someone had this problem a while back. Wire it open and see what happens. Also what madpogue said is my findings also. If you have not done so replace the glow plug relay and see what happens. If not that ,It could be a pcm grounding problem. If I am wrong with any of this someone feel free to correct me.

 

Mine has done it ever since I bought my truck over 150k miles ago.

 

Interesting, I didn't realize that the EBPV could still close when it's unplugged. Maybe that's what it is, it definitely sounds like it. I'll see what i can do to wire it open.

As for the glow plug relay, is there some way to test it before replacement? I don't mind buying new parts, but i don't want to replace it if it's not verifiably bad.

 

Yes, It should not close. but like I said someone had that problem a while back. I can't remember the thread but I do remember reading it. Use a volt meter and see if you are getting 14.5 volts.

 

The only way I know of getting over 14.5v would be alternator related. IDK

 

According to Torque Pro, my voltage sits right at 14.3-14.4.