Mike and everyone else,

I recently put a Jasper remanufactured engine into my '97 4.6L and need to know if I need to have the chip reburned to match this engine? Seems to be running just fine, but also sucking down the gas pretty quickly. Could this be the breakin period, or is the chip reading the previous engine and applying to the new engine?

Thanks in advance...Scott

 

Hi Scott,

As long as they supplied a pre-2001 4.6 (meaning not the 2001 & newer 4.6 that has the PI cylinder heads, different pistons & the COP ignition system), and as long as they did not reflash the PCM to a different code or replace it (and neither of those should have been done, so that should not be any issue), then you do not automatically need program changes just because the engine was replaced.

Now with regards to your fuel mileage issue, I really can't give you one set answer there, as there are no accurate before & after mpg numbers in your post, just your observation that it seems to be "sucking down the gas pretty quickly" - which, while that may very well be accurate, doesn't really tell us much. Don't get me wrong, I don't doubt your mpg may have dropped, but without firm before & after mpg numbers (to the tenth), we just don't know just how much it's dropped.

So it might be getting the mpg it should, or it might not - generally speaking, no, a new engine should not reduce mileage significantly, especially over a motor with a blown head gasket. While it can take 4000-8000 miles to get the full power & mpg from a brand new motor made over the past decade or so, no, a new engine really shouldn't make enough difference to where the gas gauge drops any quicker from a visual standpoint.

SO I don't think that a significant mpg drop is just from the new engine - though I could be wrong, as I just don't know **how much** that mpg has actually dropped - I suspect the problem may be elsewhere, and probably has multiple components to it.

You may very well have other issues, such as worn O2 sensors (and if they have more than 30K miles on them, they're in need of replacement, though that is not mentioned in the owner's manual or any automakers maint. schedule), or the coil packs & plug wires may be worn out, and any number of other issues - especially the fact that it's winter, and with extremely few exceptions, virtually everywhere in America (including southern California, most of Florida, etc.) reformulated fuels are in use which will *always* cause mpg to drop every year during the "winter" months - even in locations that don't see freezing temperatures. Winterized (or "reformulated," etc.) fuels usually cause a drop in mpg of 8-10% or more. You can easily lose 2+ mpg to winter fuels, and more.

Jasper is a good company generally speaking, they make decent motors & transmissions, so I don't see any inherent problem there. Unless it's blowing blue smoke on startup and has more than 5% variation in cranking compression from one cylinder to the next, the motor itself is not your problem - I suspect a combination of ignition, O2 sensors & winterized fuels are most likely the actual culprit.

Figure that O2 sensors with more than 30K miles are ready for replacement (just replace the 2 upstream O2's, don't worry about the downstream units), and if *any* component in that ignition system, from the coil packs to the plug wires to the plugs themselves have more than 40K miles or 3 years (whichever comes first), then the ignition system needs maintenance - if that is the case, call us as there are much better quality ignition components than stock, for less money, and they'll last longer, too.

I hope that info helps a bit, & enjoy your new engine!

Good luck!

 

Hi Mike,

Thanks for getting back to me...and going above and beyond just answering the original question.

Regarding the gas milage, perhaps it was a gut reaction to the change in seeing my girlfriends car gasgauge drop so slowly in comparison to my trucks. And, like you say, we are in the winterized gas season so milage is going to be lower.

They did not replace it with COP engine, though I don't know the specific year. The also made no mention of reflashing or replacing the computer.

Actual milage to the tenth on this last tank was 12.8 which is pretty close to what the previous engine was getting.

I have changed the O2 sensors, plugs, wires and coilpacks within the last two years. And while the milage didn't improve with those changes, they didn't decline either. I still have to do a thorough cleaning of the intake and related components but that will have to wait until the spring.

Thanks again for your response. It's always greatly appreciated.

Scott

 

Hi Scott,

You're very welcome, as always.

Sounds like you've been doing good maintenance, that's very nice to see - so many people ignore the O2's & ignition systems!

Just out of curiosity, did you use OEM plugs, wires & coil packs?

If so, that could be why you didn't see an appreciable mpg gain (assuming the comparison wasn't skewed by different fuel or a different source, or a reformulated fuel, not the same driving conditions, etc., etc - you know, all the basics. ). Just to let you know what we typically see with our ignition upgrade package, as compared to brand new OEM parts we usually pick up 12-14 HP and usually at least 0.5 mpg to as much as 1.0 mpg in many vehicles, depending on exact gap setting, etc. - and even more once they have about 30K miles or more on the original stock ignition parts - just FYI........at any rate, very glad to hear you're taking such good care of it!

Looks like they gave you the correct motor for the pre-COP 4.6's, so all should be just fine tuning-wise.

Good luck & have fun!