Help with High MAP at cruise

[Protec]

Gents -

Have a LS3 /L9H transplant into a 2011 Jeep JK with a 6L80e automatic transmission.

Truck idles just fine with normal MAP readings but when I drive it the MAP is over 85kpa at cruise!!!! This is sending it into enrichment mode and its just dumping fuel into it.

Again, at idle all parameters are perfect, O2's MAF freq, everything looks like a perfect LS3...


We have looked for possible causes such as a plugged exhaust and the like but we cant find any problems... There are no codes in the computer or transmission.

Anyone ever experienced this before?

Any help would be appreciated.


Thanks,

J

[joecar]

Post tune/log files.

[J.Abbott]

You know I am thinking about doing the same swap. I love Jeeps but I had to sell my TJ. I just could not put my kids in the back seat and feel safe. I am looking a 4 door JK though and then doing a LS motor swap.
So with your issue, What is the offset on the MAP in the PCM. Are you sure this is correct. If the MAP cal is off you will have issues. Is the cam in this LS3 stock?

[Tre-Cool]

sure it's not running with a couple of less cyclinders?

[Ryan W.]

What size tires and gears in it? It strikes me that the LS JK's I have tuned were up there a bit at cruise but I don't recall them being quite that high. I'll have one of them this weekend and will check that for you if you want

[Protec]

Sorry so late getting back to this.

Turns out the cats were bad that were supplied in the Y-pipe. changed to a new set and with the exhaust opened up now it ran much better. Had some tuning issues that needed corrected and now its a great driver.

Thanks for the help!!

Very much appreciated.


John-

[jims68]

What size tires and gears in it? It strikes me that the LS JK's I have tuned were up there a bit at cruise but I don't recall them being quite that high. I'll have one of them this weekend and will check that for you if you want

Ryan,
What kind of MAP readings are you seeing in the jeeps with the LS's? I have a 08 with a 11 5.3 6l80, 3.5" lift and 35 nittos. No heavy armor and have even put the stock shroud back on the front. I have been fighting what seems to be a rich condition, exhaust being black and poor mileage 12 mpg mixed and it doesn't seem to matter how I drive it! Changed CAT'S and put on a Magnaflow exhaust, sealed the intake from the engine bay, IAT's are close to actual but heat soaking is present even with a wrapped charge tube in traffic. Have had Black Bear do some tuning for me with logs from above changes. They thought it was incomplete combustion and recommended running only premium fuel. The tuning has brought the performance up greatly, but 0 effect on mileage. When monitoring MAP kpa any type of incline that allows motor to hold a high gear low rpm yields 80 plus kpa readings consistently. I know these tires are a considerable drag along with the box I am driving but something seems to be a miss! Cylinder deactivation is turned off, long term trims balance out nicely, short term trims operate correctly, only thing I see is high MAP and high CAT temps. Cruising they hang around 1500 plus and I have seen this indicates a rich condition. Smoked motor, EVAP system and exhaust and have found nothing. Idle the MAP is a consistent 36 kpa. Runs nice but black exhaust and mileage are stumping me!

[Ryan W.]

It's been about a year since I have done one but I will see if I can find the logs Monday. 12mpg sounds right from what people have reported back to me.

[joecar]

Ryan,
What kind of MAP readings are you seeing in the jeeps with the LS's? I have a 08 with a 11 5.3 6l80, 3.5" lift and 35 nittos. No heavy armor and have even put the stock shroud back on the front. I have been fighting what seems to be a rich condition, exhaust being black and poor mileage 12 mpg mixed and it doesn't seem to matter how I drive it! Changed CAT'S and put on a Magnaflow exhaust, sealed the intake from the engine bay, IAT's are close to actual but heat soaking is present even with a wrapped charge tube in traffic. Have had Black Bear do some tuning for me with logs from above changes. They thought it was incomplete combustion and recommended running only premium fuel. The tuning has brought the performance up greatly, but 0 effect on mileage. When monitoring MAP kpa any type of incline that allows motor to hold a high gear low rpm yields 80 plus kpa readings consistently. I know these tires are a considerable drag along with the box I am driving but something seems to be a miss! Cylinder deactivation is turned off, long term trims balance out nicely, short term trims operate correctly, only thing I see is high MAP and high CAT temps. Cruising they hang around 1500 plus and I have seen this indicates a rich condition. Smoked motor, EVAP system and exhaust and have found nothing. Idle the MAP is a consistent 36 kpa. Runs nice but black exhaust and mileage are stumping me!

Post logs.

Sounds like you're having to open throttle further due to lack of power.

Check MAF sensor to see if MAF sensor under-reporting, and clean it with MAF cleaner.

Check for the presence of misfires.

Check that cats are not clogged.

Check air filter.

Check that all spark plugs fire correctly.

Check that injectors do not leak.

Check rail pressure and check that FPR is not leaking internally.

[jims68]

It's been about a year since I have done one but I will see if I can find the logs Monday. 12mpg sounds right from what people have reported back to me.

Thanks Ryan for getting back to me. I kind of think it is shifting out to fast. At 35 40 mph it is in 6th gear and lugging at 1200 rpm's. Funny thing is highway it will get 15 to 16 mpg. Let me know what you find out and thanks again.

Jim