I own a 2014 LT 4WD model with 5.3 Liter Flex Fuel motor with 231,000 miles. Purchased new in 2014, one owner. At 225,000 miles the engine was making odd noises, oil pressure at idle was around 15 to 20 psi and would not rise above 30 psi (first 200,000 miles highway oil pressure was 40 psi) and dealer wanted to replace lifters along with oil pump. Estimated cost was $3900.00. That made no sense, so I tried to locate a crate engine replacement. No joy. Even Jasper had long lead time for an L83. Then the transmission lost the oil when the line to the cooler detached when driving down the road. (The Jeezus Clip popped off.) Had serviced but shifting was harsh. So found a salvaged 2015 engine/transmission combo with 65,000 miles.

Removed the engine, and transmission, replaced both, checked engine oil pan and transmission lubricant pan for debris. All golden. Added fluids and started it up. FIrst thing noted was a cylinder misfire. OBD-II check revealed the number one cylinder was misfiring. So decided to grab the ignition coil from the old engine and buy a new replacement later. Problem solved, until the road test. The engine miss returned intermittently and was most noticeable when encountering slight incline in road. Obtained an OBD-II test set that would operate mobile and during test drive, it was noticed that Cylinder # 8 was frequently misfiring and cylinders #2, 4, and 5 occasionally misfired. So grabbed another ignition coil and solved the misfire issue on #8. While this radically improved driveability, the occasional misfires of #2, 4, and 5 can be felt. It was then I noticed that the shape of the ignition coils on the old engine (rectangular) were different than the coils delivered with the salvaged engine (circular).

In digging around for differences on the engines, references kept popping up about differing dwell times for the rectangular and cylindrical ignition coils. That info indicated the cylindrical coils required a longer dwell time than the rectangular coils and if not set for the cylindrical coils, that intermittent firing would be a problem.

My questions at this point are:

1. Do differing shape ignition coils require differing dwell times?
2. If differing dwell times are required, how does one set the required dwell time?

The rectangular ignition coils are purported to be manufactured by Mitsubishi while the rounds one are of Delphi manufacture. Right now I am leaning towards transferring the remaining ignition coils on the removed engine to the installed replacement engine, but it would be nice to know if differing coils require differing dwell times.

Redd

 

That's a good question, but I haven't worked on a Flex-Fuel motor so I am unable to help you, at present. We have a couple of Professional Auto Technicians who might be able to help you, however.

 

The fix is in. I should have used the original ignition coils from the failing engine.

More information was found that indicated the coils have differing Dwell Time specs and going from the smaller (2014) rectangular coil to the larger (2015) cylindrical coil will result in misfires due to the 2015 coils needing a longer dwell time setting. Interestingly, the cylindrical coils are considered a better product by many, but the problem is, the computer from the salvaged vehicle was needed. From what I was able to find, the dwell time is part of the smog emissions lashup and changing the value is made deliberately difficult. I was told by one shop that even if I was able to change the 2014 ECM dwell time to work with the beefier coils on the (2015) replacement engine, that the next time a Chevy dealer connected to the ECM, that the factory defaults would be set and changes I made would be discarded.

So the good news is I am down to one cylinder misfiring and the ignition coil on that cylinder is one of two that were noted to have splits in their plastic housing. Since the OEM part is available for about $25.00 per coil I decided to order a set of eight and change them all out, as the originals that came with the vehicle have nearly a quarter million miles of service behind them. I do a lot of long distance driving and the $200.00 replacement cost pales in comparison to the cost of towing, and typical dealership charges.

 

I'm glad you found the problem! Good work!

 

did not know that...good info.
since you changed the engine...you need to do a crankshaft sensor variation relearn...if you don't do this...the pcm will set misfires dtc at high rpm.