surging problem

JNJ-Z · **Posted:** Sun Oct 04, 2009 6:25 pm

is it normal at 45mph, when my jeep shift into over drive that the motor
surges up and down? it seems to go away at 50 or higher! i didnt notice it before i changed my exhaust. any ideals????

Jeepjeepster · **Posted:** Sun Oct 04, 2009 9:53 pm

Are you talking about the jerking when it locks in 4th? Normal unless its getting worse or something. Lock out O/D till you get above 50mph and it'll be better.

JNJ-Z · **Posted:** Sun Oct 04, 2009 10:01 pm

thanks jeepjeepster,-its the engine thats surgering (the rpms)

Jeepjeepster · **Posted:** Mon Oct 05, 2009 9:39 am

ohh, the rpms are going up and down? Are they slowly changing or are they bouncing? Sometimes the torque wont know what to do if you give it a certain amount of gas and it will partially unlock and lock but its hard to feel it, you can watch the rpms slightly change on the tach.

JNJ-Z · **Posted:** Mon Oct 05, 2009 7:27 pm

yes thats it, the tach moves up and down

JeepinJarhead03 · **Posted:** Sun Oct 11, 2009 5:19 am

mine does that but:

only below 70 degrees ambient

and only within 15 minutes of starting

and ONLY on 87 octane

KJWildman · **Posted:** Sun Oct 11, 2009 7:36 am

Sounds like maybe the trans is beginning to slip in OD. How many miles on the KJ now?

JeepinJarhead03 · **Posted:** Sun Oct 11, 2009 1:13 pm

it's not a slip only happens when you coast in a gear that it would typically not be in if your foot was on the gas, happens in non-od gears too

3.7's are known for surging and idling weird

plus alot of people forget with all those fancy wires and things under the hood to inspect and replace their vaccume lines as necessary

mine's only done it once since the pcm/tcm upgrade but it used to do it pretty consistantly but only under the conditions that i previously stated

BugginKJ · **Joined:** Mon Jul 06, 2009 7:35 pm **Posts:** 4576

JNJ-Z wrote:

is it normal at 45mph, when my jeep shift into over drive that the motor
surges up and down? it seems to go away at 50 or higher! i didnt notice it before i changed my exhaust. any ideals????

I don't know what year yours is (too lazy to read today or find out) but I know for the 42RLE trans they have a TSB for torque converter repalcement and flash to help ease that problem........

JeepinJarhead03 · **Posted:** Sun Oct 11, 2009 3:13 pm

dunno if it's specific to the 42 , i've got the 45 and it did it prior to the B&G upgrades and i've had it do it since then atleast once

i hate to guess but I think it's nature of the 3.7 and it's timing / spark knock handling

unless i've completely misunderstood the OP it's an 'idle' surge while coasting, about 250rpm twitch with about a 1 second interval

JNJ-Z · **Posted:** Sun Oct 11, 2009 8:01 pm

thank you all, i posted an update in the bad transmission post, the stealership told me that i need my computor reclaibrated because i had p225 tires now i have p235 tires does this sound right???and when it shifts into overdrive its at the wrong speed

JeepinJarhead03 · **Posted:** Mon Oct 12, 2009 2:42 am

i appologize if i totally misunderstood what you were talking about, our vehicles will do weird things when our tire sizes aren't calibrated

ugh. electrical

surging problem

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