Shaking at light throttle

[madman1234509]

Trying to help my friend diagnose a problem with his truck. It has the basics, spartan with deletes, egr delete with no waste gate, and a precision converter. The converter was just put in because he thought this shaking problem was due to the converter slipping, which ended up not being the case.

The problem: Cruising down a flat road, between 55-65 mph, at light throttle, the truck will sometimes begin to shake violently. Almost as if the tires are way out of balance or the drive shaft is getting ready to come out of it. As soon as you give it a bit more throttle it goes away.

The truck is is the 210 tow tune, late lock I believe. It started doing this with its previous edge tuner on it as well, they thought maybe because the edge didnt ramp up the transmission line pressures that it fried the converter. The truck isnt a street monster, only used for DD, towing, and plowing. I know people have had problems with this in the past, some pointed towards their aftermarket fuel rails. Has anyone else had this problem and successfully diagnosed it to something other then the fuel rails (which this truck doesnt have)?

 

[Dzchey21]

Yep or dual fuelers, doesnt totally rule out a fuel problem

Check the fuel rail pressure, monitor it as a sweeping gauge, if it bounces like crazy then its something in the fuel system.

The next step i would go is the fuel temperature sensor, its in the fuel filter housing, unplug that and see if it goes away.

Also try and different tune.

 

[WoodBoy]

Mine truck is having the same problem. Only with my current preloaded IDP tunes except extreme X. My emailed tunes do not do it and my gearhead tunes do not do it. My truck is something computer controlled because it did not start until I flashed my truck to an older strategy to get rid of the oil level wrench light problem that the 3.01 version had with xrace and the new ford flash. I monitored FRP, TC slip, and there was something else, all these went crazy whenever the shaking with occur, but it was due to the frp bouncing. I do not believe it is mechanical. Its the way the hpfp and frp is set at light throttle and your truck not liking it.

 

[madman1234509]

Odd. So you think its in the tuning? Im going to go for a ride in the truck tomorrow to see what he is talking about.

 

[Dzchey21]

yeah more than likely, there is something that triggers the PCV and VCV valves in the pump to fight eachother, i dont understand it, my race truck still does it sometimes and i cant get it to stop

 

[madman1234509]

Odd. I dont recall my truck ever doing this on older versions of spartan tuning. I wonder if there is something in these newer versions of tunes that programmers are coming out with that is making these truck do this.

 

[Dzchey21]

I also wonder if its a pump issue VDO vs Seimens ect

 

[BFT]

Mine would do it if I had an empty trailer and would do it on a larger tune with no load

 

[MINK]

Mine does it.....unless I run my Gearhead tune ...I also have ported rails though.

 

[Jeff@Spartan]

I run our newer engine files. No shaking once my ported rails were removed.

 

[WoodBoy]

Odd. I dont recall my truck ever doing this on older versions of spartan tuning. I wonder if there is something in these newer versions of tunes that programmers are coming out with that is making these truck do this.

Im 98% positive its in the tuning or something like Dustin said.

Now symptoms like BFT stated I have also seen happen with an empty gooseneck. You can tell the difference between the two. The frp surging is much more rapid than the bucking from touchy throttle like you would experience with a empty trailer.

Get the strategy info (Engine P/N) off the tuner and pm me and I will relay I will talk to Shane and Eric some more this week

 

[gman1]

I believe it is a tuning issue. My stock truck with Spartan tuning no issues. IDP on X-street stock truck = FRP surging. Twin K16s 110s IDP X-street FRP surging. X-race no problems. Twin K16 110s gearhead tuning no issues.

 

[madman1234509]

Thanks for the offer Woodboy. But I think my buddy is just going to live with it. I rode in the truck yesterday and its the same exact thing my truck does at light throttle with hardly any load between 55-65 mph . Frp jumping all over on the dd. It will start to shake, let off the throttle at all or push on it and it goes away instantly. Same exact thing my truck does, and I have ported rails. Both trucks have the latest Spartan tuning. I run the 275 tune daily. He was running the 210 tow. I had him switch to 250 late lock and its more manageable but it does still happen at just the right load/throttle/speed.

I'd get you my p/n but my truck is in storage right now and with work I won't be able to get to it for a week or two

 

[WoodBoy]

I went back and read the first post and IDK why i thought you said he was running Eric's tuning. I still believe his problems are as I stated

 

[madman1234509]

I don't doubt it's tuning one bit. Esp when my truck does exactly the same thing as my buddies. And many others have posted about it over the last year or so. I've just gotten used to driving around it

 

[White_monster]

What's fuel temp?

 

[madman1234509]

Mine fuel temps are always normally between 90-100 if I recall.... I've never seen very high fuel temps on my truck. Not sure what his were.

 

[Jeff@Spartan]

I did notice a little shaking the other day between 45-50 MPH with our 210 tune loaded. It was prior to lock-up. I only started noticing it with my new tires though, so I have just assumed it was the tires. When I had Nitto 420's on the truck, I never noticed it. I didn't monitor rail pressure to see what it was doing. I know it wasn't touchy throttle related either because the 210 tune has a very dead pedal compared to the bigger tunes.

 

[webb06]

Axle wrap? Mine used to buck when I had a gooseneck on when going on a bumpy road. Put on pmf traction bars and it went away. Don't know if these are the same symptoms just throwing this out there

 

[4tonGT40]

Very well could be a transmission "slipping" issue. We had a similar issue with a customers truck that did the exact same thing you are describing. Baiscally If line pressure is weak or clutches are wasted, the clamping force applied in the clutch basket isnt enough and the packs start to "chatter" internally, this causes the truck to shake violently like you are describing. To test this Put the truck on a slight hill upward from a dead stop take off normal/slow and then once you get going about 10-15 MPH lay into harder. If the tranny is to blame you should replicate the "chatter" Hope this helps.