Engine/Transmission (1998.5 - 2002) Intermittant Miss or surge under heavy, hard pull

[klaybus]

I thought he had a bad EZ so I sent it back to Edge and upgraded to a comp to fix the intermittent miss I had. To trouble shoot the problem I unplugged the "bad" EZ and the problem disappeared. Problem solved! Nope! I installed the comp minus tapping the wire and hooked up his 5r to go camping this weekend. While pulling I-90, Snoqualmie Pass the symptoms are back when rpms are 1800-2000 and worse with more rpm's. Running on flat ground no miss what so ever. Without the comp on there is no miss either. Bad comp... . could be but, my best guess is the vp... ... . Anyone have any incite to offer? Same symptoms with the new Comp that I had with the EZ & now at 198k miles on the original VP I'm thinking maybe it's on it's way... . Electrically perhaps?

Suggestions PLEASE! I've been given the OK by the CFO to replace the VP but would like some confirmation prior to throwing money at it with no real evidence it's going bad.



Thanks,

Clay

 

[ROADWARRIOR]

Have you checked all of the MAP sensor connections? I had one pin that was green from corrosion on my MAP plug from my Comp box and it gave me a similar style miss.



Dan

 

[DLGonzo]

I had the same thing last week. Started missing only at High rpm under load, but quickly worsened untill I couldn't run over 1200 rpm. no e/g light so I unhooked comp with no improvement. Used a scan tool and found p0122, and p0123. Had to replace APPS. problem fixed and running better than ever, of course with the comp back on. I would however investigate thoroughly before replacing APPS. At $400 from the dealer, I'd want to be sure.

 

[DLGonzo]

Hey, just read you signature and it doesn't say anything about a Fuel pressure gauge. Before you do anything else change fuel filter and check pressure if you can. A bit of water or beginnings of plugged filter will show those symptons. Also what Roadwarrior said. Buy a couple packets of dielectric grease from the Autozone counter and apply to all edge comp connections. Good Luck

 

[rweis]

Seems to happen under load.



Sufficient fuel volume and psi (gauges), I just read your sig, the Walbro should be able to provide fuel supply just fine, westach fp should be ok.



APPS certainly a possibility



VP44 advance piston a possibility especially at higher rpms. How do you deal with ulsd lubricity?



Have you ever changed your VP44?, if so when (ie brass advance sleeve vs steel sleeve)



Almost sounds like when the advance piston has to go to a more advanced position (heavy load & higher rpm) it is getting fouled or there are deposits in the advance piston sleeve preventing it from going to the requested degree of advance.



Almost sounds like a VP44 heat issue. Hot VP44, malfunctions (like computational problems at high rpms, ie VP44 heat issue). Cool VP44, fine.



Bob Weis



I would OAT cool the VP44 first, cool return fuel second, change the nylon line between the engine T and frame fuel return line third, DrawStraw definitely (probably should be first choice).



I tow 13k and fuel temps increase a good bit when towing (loaded) and also increase with RPM (ie your symptoms > 1800 and worse the > the rpms also your symptoms).

 

[klaybus]

FP not a problem I'm sure. I will check map sensor plug as well. Don't have access to a scan tool to check for codes & my 99 I can't cycle the key. Hmmm... Advance piston, maybe but wouldn't it miss without a EZ or Comp or would it be because the boxes use even more advance? Hmmm... .



Thanks,

Clay

 

[DLGonzo]

Yeah, Westach FP. Why would I ever think that was a fuel pressure gauge in you signature. I shouldn't be on here when I'm sleepy.



Autozone or similar should be able to hook up a scan tool to check for codes. My '98 misses out on the cool OD code check too.

 

[rweis]

Part of the idea in the advance is you normally use it in a certain range and wear happens there but it is also very contaminent free there because the piston works that area alot.



Then you want to move the piston to a area beyond where you normally use it (the timing boxes) and if there is contaminent there it impedes the piston or the fit is tighter and it has trouble making the transition from the tolerances of the worn area to the tolerances of the tight area and then the requested advance angle is not able to be met within the time limit (. 00x seconds I think I remember reading the x range being 1 - 5), and symptoms show up.



If deposits get built up in the advance piston I have no idea how to get it cleaned out short of replacing the pump.



I think I would use a good lubricity of some type and see if that makes any difference in getting the fit to take effect better. There are a couple of threads on studies on the need of lubricity additives to ulsd and which additives are "better than" ... It is a HFRR study.



The PSG is a circuit board. One of my drives is to keep the PSG (and the whole VP44) as cool as possible (with OAT blower and return line fuel coolers). My thinking is the cooler it (they) is (are), the larger the fit tolerances are because the mechanical fit has not been aggravated by internal pump component thermal expansion. The concept is fairly involved because you have to rebuild the entire fuel system and design it for flow and cooling purposes.



Keep it cool and keep it lubed. Cool has a LOT to do with rpms, slow down and keep the rpms down. I would not tow during the hot part of the day as OAT has a lot to do with the keeping it cool. I bet you could tow in the morning < 90* OAT at 55 mph (rpms < 2000) and be ok. Day heats up and symptoms show up. Speed up and symptoms show up. I would also keep tank no less than 1/2 to use it as a heat sink for the return fuel.



Bob Weis

 

[JTruelove]

Could be a bad ground wire too!

 

[klaybus]

I replaced ground to neg of batt & will see if this helps.

 

[DCreed]

I've had the same problem. I was going to check MAP. runs BEST on hot dry days, terrible bucking in the rain. I run the SMARTY/TSTpm3 Comp.

 

[klaybus]

LONG....Observations made on the return trip home.

Well, we made it home. I've got kind of a wierd synopsis so baer with me. Empty, Comp on (no VP wire-tap) truck runs great! For just 275s & an EZ truck is snappy, blows some good smoke, boost at 28-29 lbs & overall performance pretty damn well. From a dead stop with the pedal to the mat the truck accelerates very well up to 3200 rpms where it shifts to the next gear. No miss what so ever & pulls hard through all the gears. Accelerating & cruising truck performs well.

Coming Westbound over I-90 with the 5vr in tow I would experience the miss\surge upon any acceleration or hill. When I was nearing the top of the pass I had to come out of OD & go to 3rd direct. I was at 2500 rpms going 52mph as I came over the pass with no missing what so ever.

Here's the part I don't get... . Empty, truck runs great! Pulling at high rpm's no miss what so ever with the box on or off. Pulling an incline or pass in OD the surge\miss appears & my power disappears causing me to down-shift out of OD where my rpms increase substantially & speed decreases substantially. However, miss\surge disappears!



Clay