Engine/Transmission (1994 - 1998) bucking issue

[Moparsean]

Hello there fellow cummins lover's! I have an issue that is starting to get on my nerves. But first,the vehicle is a 97 dually 12 valve,automatic with high miles,429,000 of them. It has a boost elbow,a torque plate supposedly,I didn't put it in,and 330 hp injectors. I can get 35 psi no problem. The turbo is stock and everything including the injection pump appears to be factory. This was run comercailly for years over the highway. The trans I had beefed up and i use nothing but amsoil in everything. The truck ran well before I added the injectors recently. Now I sometimes get a bucking sensation at 70 mph or so under light to moderate throttle. It will do this when lock-up comes in as well,but not all the time on either case. Seems worse if i had run it that day hard,or it was very hot out that day. ( i have 2 trans coolers,one under the bed with a fan blowing on it) This condition happened to me before,but I would change the filter and I was good,but not this time. My thoughts is the converter... do you think its slipping? The trans guy put a "MIddle of the road" unit in,I know its not a billet one. Is it possible I melted this one,or warped the plate in there? Is the pump starving for fuel? The lift pump is new too. Hard to tell if its engine or trans causing this,it bucks hard when it does do it. Thanks guys for reading this,any ideas would be great. I would hate to go back to my stock injectors if its in the engine,it runs sweet when its not doing this :-laf

 

[Matthug]

Check your fuel pressure. Mine bucked with light throttle low RPM and it turned out to be a bad overflow valve. I only had 10 PSI fuel pressure at idle and about 18 or so at 2000 RPM no load. Now it's 23-24 PSI at idle and 34 PSI at 2000 RPM.

 

[JPittinger]

Check the throttle springs? The inner one on mine was broken and bucked like crazy with 370s.

 

[Moparsean]

Yes,and they seem good, (the springs). Ideas are always good though for sure. I agree that it is most likely (Man do I hope!) that it's the fuel pressure. I have no way to test it,have a gauge,no adapter. This thing likes a clean fuel filter often,so I think it may have been low with the stock injectors,but not showing up as much. This upgrade is making it buck now,mostly at light throttle,going into lock-up,worse at 68-72,worse still when its hot out or i have driven it hard. I can drive around it most days, (on the pedal or speed) but its not right. As i listen to advice from all of you (thanks by the way) and look on the net,it seems you guys are right on. I will go to cummins monday and get one. Wish me luck. I WILL post when i get it in,hopefully they have one in stock,looked all over the net,no luck unless you call them,can order on via a web site. tst has them,but they are out of stock. I'd pay a high price to have one mon or tuesday. I love my rig,and I want it right. Like i said it runs like a clock when its not doing this most frustating thing! I'd hate to go backwards on power,we will figure it out together eventually. Mine does take 3-4 seconds to fire,some one mentioned to me in this forum that his did the same and he described exactly to me what mine is now doing going down the road (his was a overflow valve issue). Its something cheap and easy to try for sure!

 

[Matthug]

I bought my overflow valve from Piers, it was in stock. But cummins should have it.

 

[Moparsean]

Hey guys,I've still got the issue,although I did gain a very small power increase,so i'd say its weak (the old overflow valve) If I take it out of lock-up on my dash switch (i can remotely select open,locked,or normal) The shaking/bucking goes away. Could the added power increase be too much for this "middle of the road" converter? I'd sure hate to be wrong and spend 2K on a new one,if thats not it. Didn't have this issue till I did these injectors,has anyone had issues with these 330 bosch injectors? Tonight after driving home from work I took the inspection cover off the trans to look at the converter. Its just a painted grey converter,not a billet,didn't see a name on it . Do you think something is warped in there now? Paint isn't burnt off,but I could't touch it at all really. What are syptoms of a failing converter clutch. The pan was much cooler,i could hold my hand right on it. I know they get hot,but wow was it hot. The first run of the day,this issue is almost non existent,until I go over the speed limit or get on it hard,then it rears its ugly head. Really bad when I am light on the throttle,engine /tans hot,and going into lock-up. Then it does it again around 70 or so,depending on how i push on the pedal. Even when it does do it,i can drive around it via speed or pedal position. I'd say its more of a shaking. The fluid looks great still,and no clutch material on the stick. I'm going nuts. anyone live in Nh that can second opinion this fist hand? Of course ideas are always welcomed by all. I do not want to go back to the trans shop,he takes for-ever and I can put a better one in if this is it myself... . so i KNOW whats in it. It is suppose to be beefed up inside,It has a Bd 2 stage valve body and steel plantitary set. Like I said though,I want to be sure thats it before i spend all that cake!

 

[KingS]

If you havn't had it done yet have you timing bump up I but injectors in mine the other day with dv's and got a miss plus the truck shudder somtimes like the transmission is slipping but everybody sad its my timing it to low for the fuel amount I will know on mine tomorrow for sure I am having mine bump up but I would give it a try.

 

[Moparsean]

PLEASE let me know if this cures yours or not. I was told that because my HP/torque is more,the pressure to the lock up disk may be less,due to the fact I push less on the pedal,and this may be causing a torque converter shudder. I positively have hated my converter since I got it back from the trans shop,the last one was way more effecent,cuz i lost power. So i'm going to R&R that for a billet unit anyways,i've made my mind up. My issue relates to heat. Been cooler the last few days,and it has not been as bad.

 

[KingS]

I had a plugged injector on mine also now its fixed and yea you could be to much for you convetor Question though what is you altenator gauge been doing lately when I had my old trans rebuild a couple year ago I could make the torque convertor shudder once it was locked in and each time I stepped on the pedal it shudder for a few second turned out my alternator was going out and I didn't know it and it was sending a charge to the regulator in the computer on are truck the regulator is in the computer and the electrical charge was messing with the lockup part of the computer I found this out when the alternator died 5 months later and changed it and the shudder quite call dealer and they said they had seen it happen before. sorry for long post

 

[Moparsean]

I'm thinking I may have a new injector issue as well. Mine engine quivers at different rpm just sitting in my driveway. There may be a miss at load. I'm going to try a guy that rebuilds them. he says he can do a better job than new. The ones currently in there are from a guy on e-bay. Maybe they are seconds? Or maybe just a bad one in there somewhere. Alt voltage seems normal and steady. I have heard of that as well. This issue occured with the new injectors. If it was there before I didn't notice it like this. Out of curriousity,where did you get your injectors? Got mine from EIS the first time.

 

[KingS]

Jon Link J. L. machining out of Conklin, Mich. he is a wizard at injector and dv's and great priced