Engine acts like it's governed . UPDATE


#1

2005 Jeep Liberty 3.7 V6 Automatic transmission , 4x4 .
I just replaced the engine in this vehicle with another one also out of a 2005 . I bought a wrecked Liberty that still run & drove so I heard the engine run before I bought it . It sounded good & I revved it up several times & it acted fine . Today I completed installing it in my Liberty & it’s good to about 2000 rpm’s then it acts like it’s governed . Holding the accelerator pedal steady the engine rev’s up & down continuously . The engine bogs if I try to run it above about 2000 rpm’s . I don’t have a code reader yet so the codes haven’t been read . Any ideas ?

I just completed the installation a couple hours ago & haven’t done any troubleshooting yet .
Update
Had codes on two cylinders related to spark plugs or coils . Pulled a couple spark plugs & I’m relatively sure they were the originals . Installed a new set of plugs & the 2 plug related codes went away . Engine still acted like it was governed . Had a little squeak so removed the serpentine belt to see if the squeak would go away . Found the belt tensioner bolt loose . Started the engine without belt on & engine will rev like crazy & sounds great . Put belt back on & back to original problem . Unplugged & disconnected wires from alternator & ac compressor & that didn’t help . Took belt back off & engine runs great again . Just came in for a cup of coffee & haven’t searched the internet yet for what might be causing this .
Will be back a little later to see what gets said about this problem .


#2

If the exhaust system is hooked up to the replacement engine, you might want to check if the catalytic converter was damaged when the original engine let go, restricting the exhaust system.

Tester


#3

Park/neutral or drive?

It sounds like you are testing the rev limiter in park/neutral, which is normally 3,500 RPMs.
If there is an active fault in the PCM the rev limiter will be reduced to 2,000 RPMs in park/neutral.


#4

It could be a lot of things,make sure all the wiring is hooked correctly and the engine isnt running in limp home mode,the 3.7 in my Dakota will hit 5500 RPM in gear going up this certain grade,but it does its best in tow mode,in tow mode it was doing 80 mph up afton mtn at 4500 rpm with pedal left so I’m of the opinion your rev limiter is functioning as intended for the most part some vehicles wont rev but about 4k or so in park(which is good thing)You have road tested it ,I presume?


#5

The exhaust system is hooked up & it was running in park & no I haven’t road tested it . I’ve been wanting to buy a decent code reader , reasonably priced , just for my own use . If possible I’d like to stay at about $300.00 or lower . My problem is I can’t make up my mind which one I should buy . Thanks for helping & any more advise is appreciated .


#6

You don’t need a code reader to determine if the cat is bad.

You need to disconnect the exhaust system from the replacement engine and then see if the engine can be revved.

Or remove the cat assembly to see if the substrate is broken up and falls out of the assembly.

https://www.rockauto.com/catalog/moreinfo.php?pk=1398755&cc=1430900&jnid=409&jpid=2

Tester


#7

+11 to Tester


#8

Is the check engine light on?


#9

The service engine soon light is on . I wasn’t only referring to this problem when I mentioned buying a code reader . I’ve been wanting one for some time . I can easily disconnect the y pipe from the exhaust manifolds , I’ll try that & see what happens .


#10

The MIL is the reason for the reduced rev limiter. Cycle the ignition switch from the “off” to “run” position three times, the third time leave it in the run position. The fault codes will be displayed in the odometer.


#11

Thanks , I’ll do that . I just thought of something , There is a vacuum hose that connects to the side of the air box under the air filter . Inside the air box there is a piece of foam that covers the hole the vacuum hose connects to . The piece of foam looked grungy & I was going to take it out & wash it out with gasoline . When I started to remove it , it basically fell apart so I left it out . Was planning to get a new one . Could this be a problem ?


#12

Just did the ignition switch & got 3 codes , P2308 , P0204 & P2314 .


#13

No, that’s not a vacuum hose, it is the crankcase breather hose. The foam is there to collect the oil mist that occurs during acceleration. The fault code may point to a connector that is disconnected.


#14

Looked the codes up , Seems 2 of them are coil or coil wiring problems , cylinders 5 & 3 & the other code is injector related , cylinder 4 . Since the engine ran fine in the wrecked jeep , I’m thinking wiring issues .


#15

From my experience those coil saturation faults indicate that the spark plugs aren’t firing (fouled), possibly caused temporarily by the oil added to the cylinders. Start by examining the #4 injector connector for corrosion.


#16

I have my problem narrowed down to something to do with the alternator . As long as the connector that plugs into the back of the alternator is unplugged the engine runs great . I have been doing a cooling system flush & fill & a few other things & haven’t spent time on the alternator since I found the problem . I updated my original post earlier today & said unplugging the alternator & ac compressor didn’t help but I guess shutting off the engine reset something because now it runs fine until the alternator connector is plugged in . I have another alternator I’ll try tomorrow . The only code showing is P0204 which I believe has something to do with # 4 injector .
If you want to see the update I posted earlier today it’s in my original post on page 1 of this thread .


#17

Would swapping injectors with another cylinder & see if the code followed the swap be one of the simplest things to try first ?