casias

iTrader: (1)

After installing an Ly6 which retained stock tuning and VVT in a 1999 Dakota R/T, we experienced a frustrating issue that took a while to diagnose. Case is as follows:

LY6 installed in 1999 Dodge Dakota R/T:



Truck was performing well through over 500 miles of testing. As we began to finish up the little things (final installation and welding of exhaust, routing of electrical, coolant lines, routing of wiring), we also installed an aftermarket oil cooler from summitracing.com:



This had 1/2 inch aluminum tubing, and was connected to the original oil cooler tubing from the donor 2007 GMC Sierra 3500 with compression clamps and short sections of rubber tube:



After the final work was done, we immediately noticed drivability issues and poor idle and low speed cruise, with an increase in exhaust drone and bogginess. The issue would clear up somewhat during hard acceleration, but would "cough" at about 4500 rpm. Lifting the accelerator caused loud burbling.

We checked for vacuum (19 mmHG) at idle, checked for leaks, disconnected the MAF sensor wire to force the ECU into Speed Density, and cleaned the throttle body. No exhuast leaks were detected, but we removed the manifolds (including the upstream O2 sensor bungs) and water tested the joints. Very mild seeping was noted at the welded joints, which was repaired.

The problem continued. MAF was ultimately replaced, as was spark plugs and O2 sensors. Wideband showed mostly lean conditions 15 - 15.5 at idle, not less than 14.5 at hard throttle. STFT was all everywhere and LTFT could be in a range from -7 to 20 % in both banks, during a drive, but almost always symmetrical.

We did note after the addition of the oil cooler, the oil pressure at the sending unit (upper rear block), dropped from a range of 40-50 psi, to a range of 24-40 psi. But this was in the minimum specifications in the service manual.

Ultimately, it was realized that the oil cooler has adequate tubing size, but a pinch point at the intersection of the rubber hose decreases the size by more than half, and decreasing flow exponentially. The cam was not phasing correctly as a result.

.

Replacing the block off plate, that allowed unrestricted oil passage immediately restored normal running.

I just wanted to post this, as I searched and found little discussion about the problem. It appears this can happen in any LS engine with VVT that has an aftermarket oil cooler.

Has anyone else experienced this?

Jimbo1367

thanks for sharing. I may be in the same boat someday. I do think that once the oil cooler was installed and the problems arose, I would of tried to undo the change, bypass the cooler with as little oil cooler hose as poss. Yeah, I would think at would be a long shot, but would be worth the effort.

I seen you posted this pic in another thread and glad to see it again. Do you have a build thread? Looks like a Very clean install !!!

casias

iTrader: (1)

Thanks. Hoping this will help alleviate frustrations for some people. We focused so much on the LTFT and STFT, O2 sensor, fueling and vacuum and exhaust leak issues, we overlooked this.

Build thread will be coming soon. Truck runs great, meeting our expectations. I want to make sure we are 100 % before I post a full write up.But so far, a great improvement in these great little trucks.



I'll post some pics in the hybrid section.