Help! Stranded with Surging

[hankallan]

Hi folks,

Seemingly out of the blue, my Suburban surges at idle and underway. It's not driveable and I'm stranded 150 miles from home. Immediately after starting it jumps from 600/700 RPM to 1200/1300 RPM rythmically. I'm out of ideas and have tried the following:

-tightened connections to batteries
-cleaned air filter
-did lift pump fuel flow check - a little more than 1/2 pint in 15 seconds
-replaced fuel filter
-fuel pressure 4-5PSI at idle (though before replacing filter was very abnormally high at 9-11PSI)
-checked for air bubbles right before IP inlet
-checked codes and none currently set but there is an old P0216 still in history

Vehicle is 6.5L Suburban 'F' code. 179,000 miles. Remote mounted PMD.

Any ideas what to check next? After searching this forum and others, it seems some possibilities are: PMD, Accelerator Pedal Position Sensor, and IP. Trouble is I don't know how to diagnose those.

Thanks much for your reply.

-Hank

[JohnC]

It's not driveable ... Immediately after starting it jumps from 600/700 RPM to 1200/1300 RPM rythmically.

What does it do if you try to drive it?


-fuel pressure 4-5PSI at idle (though before replacing filter was very abnormally high at 9-11PSI)

That's bazaar! could be that there's something in the injection pump that is blocking the fuel flow.

Surging is generally either uneven fuel delivery to the injection pump or a sticky fuel solenoid. I suspect you're going to have to put a scanner on it.

[hankallan]

Thanks John - yeah it's not driveable because it does not respond to the pedal. When stepping on it the swings only slightly change from 600 to 1200 RPM to a swing of about 800 to 1600 RPM. Up then down over and over again. Very strange.

I put in clear fuel line before and after the IP and dont see any air bubbles after it's primed. Return pressure is less than 3 PSI and I think that's ok.

At this point I'm trying to find a PMD for sale near me on Cape Cod in hopes of a quick fix. Not sure how to tap into the APP sensors, unless it means shaving the insulation off the wires and even then which ones are on which circuit.

Sure was a lousy time for the Sub to decide to break down. I've got a trailer to pull and 3 kids and a wife to get home somehow. Yuck!

[JohnC]

There really shouldn't be much if any pressure in the return line. It's a sort of drain. Someone else may comment on this, but I'd be a little concerned. You might try momentarily disconnecting the pump return and directing it into a bucket to see if the behavior changes.

I doubt if it's the PMD. They're pretty much all or nothing.

The APP will always set a code if it is at fault. Sounds like the PCM can't control the fuel solenoid. You need a scanner. Look at solenoid closure time.

[6.5TDTahoe]

Check & clean the PMD/FSD/ wire harness for connections and absolute ground. Costs nothing. Benefit: eliminates a possible freaky problem. My 02cents.

[hankallan]

Ok I used OBD-2.com software and got values that seem so messed up I don't know where to start:

http://i4.photobucket.com/albums/y118/hankallan/Scanvalues.jpg

[rameye]

no missed pump references...thats good news anyways!

what looks so outta whack to you?? I'm not a techie but these numbers look kinda OK..

I'm thinking PMD right now....as the main solenoid appears to be behaving..although that 60 mm fuel rate is pretty tall....could be anomaly, artifact, or that a bad PMD allowed it.

been stranded...feel your pain...you will get it going...hope it's nice where you are at!

[hankallan]

Sorry for the confusion with the numbers, rameye. Let me explain them. The "low" and "high" values are what I measured for my truck. The "Reference Value" I obtained from the GM document. So the truck had 1 missed ip cam reference.

What looks whacked to me is the IP Solenoid Closure time stuck at .01. The reference says 1.70 to 1.90 for all RPM's. Also the APP angle and APP voltage values. Not sure about the ESO going on/off, I figured the Reference Value means it should always be ON. Lastly the ETC volts looks out of range. I bolded values I thought were out of whack.

Here's a corrected table:

http://i4.photobucket.com/albums/y118/hankallan/scan2.jpg
thanks,
Hank

[rameye]

Ok That clears up the data table a little...

1 missed cam reference...no biggie for me...my experience is when it goes, it goes big time..

solenoid closure time....that can mean sticky solenoid...or possibly a PMD going south as it drives the solenoid...

as far as the accelerator voltages....if your not throwing APP codes I would not examine them too closely..

I'm not the most experienced with the DS4 and its anomalies...but I sure as hell had to screw around with their "issues" enough..After 2 pump failures..I have learned that the pump starts tossing codes when they die....the PMD doesnt....but it sure raises Hell!

The best "side of the road" suggestions I have....if it was me stuck on the road is...

1) as suggested...clean all ...I mean all grounds...battery connections etc. rear of passenger head to to firewall..etc.

2) spend some time examining the wiring and connectors in the area of the fuel management system...break the connectors apart and inspect them

3) put some lube..2 cycle slick stuff in the tank..if it is a sticky solenoid...this might free it.

4) get a Ditech PMD fedex'd to you and put it on...hope for the best..

and if all else fails....

5) .45 caliber thru the radiator ( makes you feel better anyway!)

[hankallan]

LOL :D that's a good one cause you had me reading intently 'till I got to #5 then I busted up laughing. Maybe I'll just skip right to #5 :eek:

#4 is on order, just not a Ditech D-tech whatever. I'll buy one of the new fangled ones if it turns out to be the PMD and keep the cheap one I ordered as the spare

In the meantime I'll check out the grounds and wiring as you and 6.5TDTahoe suggested cause it does seem related to an electrical problem to me.

thanks for the suggestions
-Hank

[hankallan]

Well, wasnt the PMD - probably. Assuming the used one I got is ok. Same symptoms. So, had the truck towed home. Tow cost: $480 :eek:

Fortunately, roadside assistance covered much of that, but still an ouch.

Also I went over some old scan data and compared it to the most recent. Seems the closure time of .01 ms I got is fine. I was expecting 1.9ms but that spec apparently is for a '94-95 model and the .01 is for later models.

The timing degrees is still way out of whack. My old data always showed it tracking nicely with desired timing, varying only by 1/2 degree at most. With this problem it varies 1-5.5 degrees! Not sure if that's the cause of the problem or just a symptom.

Next thing I plan to do is check the ESO since that was switching ON/OFF and should stay ON.

-Hank

[rameye]

you have to try it with a proven good PMD...

have to rule it out...whats the chance of a second used PMD being no good??..pretty darn good!

my .o2

how bout that crank pick-up?? causes alot of grief when it goes south.

just guessin now! cheap stuff first

[blackshirts]

there is a VERY easy fix for the pmd problem..? if you dont have the relocator kit and you cant afford one or dont want one then(my uncle did this with his 97 2500 4x4 5 speed after his went out 3 times) he simply took the fancy plastic 6.5l cover off the top of the engine and let it look a little rough but the cover trapped the engine heat and over-heated the PMD so he simply took it off which released heat and he never had pmd problems again......he then put it back on and traded it in for a 07 classic 4x4 duramax and the guy who bought his old 6.5 called him 2 months later and asked about PMD problems lol

[hankallan]

Well I'm 90% sure the problem was a bad IP. I replaced it (after 3 days wrenching on it) and now the truck runs fine. I did try a second PMD just in case and no better. The 10% unsure is from a short I found on the ignition circuit. It's still there and the truck runs so I don't think it was the original cause but who knows...

[rameye]

good for you...I guess....cost alot of $$..gotta love hooking those injection lines back up!

[hankallan]

good for you...I guess....cost alot of $$..gotta love hooking those injection lines back up!

Yes that was the hardest part. Pump wasn't too bad at $600. And the labor was nearly all mine so some savings there.

All this talk about $200 special wrenches for the flange / mounting bolts was overdone. Didn't need those. Needed a special wrench for the injector line nuts. The underside two were simply a bear. I ended up using a horsehoe attachment to the socket wrench. But even that was brutal. I think a flare nut wrench would be better. Or what I saw on youtube - some guy ground down and cut open the box wrench.

[MAS1866]

there is a VERY easy fix for the pmd problem..? if you dont have the relocator kit and you cant afford one or dont want one then(my uncle did this with his 97 2500 4x4 5 speed after his went out 3 times) he simply took the fancy plastic 6.5l cover off the top of the engine and let it look a little rough but the cover trapped the engine heat and over-heated the PMD so he simply took it off which released heat and he never had pmd problems again......he then put it back on and traded it in for a 07 classic 4x4 duramax and the guy who bought his old 6.5 called him 2 months later and asked about PMD problems lol

Yah, I hav'nt seen a 6.5 with the top on in I don't know how many years. The PDM will still fry in time. I still think its best to relocate. The popular thing around here is just pulling the harness off of the old pdm still on the pump and it will( with a little coaxing & fish) stretch out enough to mount the heat sink on the two driverside bolts of the to intake. Usually solves the prob. And no extra expence for the relocate harness which is a rip off.(60-80 bucks for three feet of 18 guage wire)

[DmaxMaverick]

Yah, I hav'nt seen a 6.5 with the top on in I don't know how many years. The PDM will still fry in time. I still think its best to relocate. The popular thing around here is just pulling the harness off of the old pdm still on the pump and it will( with a little coaxing & fish) stretch out enough to mount the heat sink on the two driverside bolts of the to intake. Usually solves the prob. And no extra expence for the relocate harness which is a rip off.(60-80 bucks for three feet of 18 guage wire)

Bad advice. Out of the frying pan and into the fire. The PMD is better left on the pump, in this case. You could spend all that coin on a pre-made harness (the cost is in the connectors (which are still proprietary), and labor, not the wire), or extend your own for a couple bucks worth of wire, solder and heat-shrink. The top of the intake, or just about anywhere in the engine compartment is the worst location.

[rameye]

Yes that was the hardest part. Pump wasn't too bad at $600. And the labor was nearly all mine so some savings there.

All this talk about $200 special wrenches for the flange / mounting bolts was overdone. Didn't need those. Needed a special wrench for the injector line nuts. The underside two were simply a bear. I ended up using a horsehoe attachment to the socket wrench. But even that was brutal. I think a flare nut wrench would be better. Or what I saw on youtube - some guy ground down and cut open the box wrench.

I go my local autozone and buy some cheap wrenchs and have at them with my torches and saws...have a whole drawer full of "special tools" I label them so I know what the hell they are supposed to be used for.

15 MM box end as you already know does those mounting bolts quite nicely....I have the ratcheting box ends...more better!! Now sears has adjustable offset ratching box ends...now we are talking!

Glad you're up and running!!

[neo]

So I am very curious about this. I have a similar problem, but with a code of P0004. I have another post asking about this. I have investigated the heck out of it and can't find squat on it. I am wondering if it is not a bogus code, but instead my PMD is croaked. Mine is located in the hold (passenger side) of the bumper with a heat sink from SSDiesel. I figured this would be plenty of cool, but seems this is shortly before I started having probs. It was in the engine bay relocated near DS fender. Is there a better place than the hole in the front bumper? Is that a bad place? The P0004 is the only code. Thanks!