Hot engine sputter

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mmcswss

NAXJA Forum User

Location

Washington State

• Aug 25, 2010

• #1

91 XJ started life as 2 wheel drive automatic tranny. Recently installed 2000 engine with nv3550, rubi tcase, dana 44 front nine inch rear. Auto tcc is still intact and connected. Bypassed nss at the harness using the connector off of aw4. Engine runs fine cold (open loop) but when it gets up to temp (closed loop) it has a miss/stutter through out the rpm range. Suspect iac or a temp related sensor. Any thought suggestions. I have located a 91 mt computer and will pick it up when funds become available.iratefla

 

joe_peters

NAXJA Forum User

Location

Grants Pass, OryGun

• Aug 26, 2010

• #2

Check your o2 sensor.

 

NorCalChris

NAXJA Forum User

Location

Central Coast, Ca

• Aug 26, 2010

• #3

Agreed on the o2 sensor. While in open loop the engine is just running off of a preset Air/fuel ration. if your o2 is bad, or slow at switching, you are definitely going to have poor driveability.
Iac problems I have encountered are high idles and stumbling, but you would fell the stumble at idle while cold or hot.

 

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mmcswss

NAXJA Forum User

Location

Washington State

• Aug 26, 2010

• #4

It seems it was primarily the o2 sensor. Still have a slight miss not nearly what it was. I was thinking of 23 lb injectors any thoughts.

 

shawnhancel

NAXJA Forum User

Location

Hubbard, OH

• Aug 26, 2010

• #5

i had this trouble, i was told that fuel tends pre atomize in the fuel injector causing this. if you wrap it in heat shield that may slove it. its helped mine. if its not the o2 wrap it up, see what happens

 

joe_peters

NAXJA Forum User

Location

Grants Pass, OryGun

• Aug 26, 2010

• #6

mmcswss said:

It seems it was primarily the o2 sensor. Still have a slight miss not nearly what it was. I was thinking of 23 lb injectors any thoughts.

Click to expand...

On a stock engine? No. Read Rainman's post and check his chart here: http://naxja.org/forum/showthread.php?t=1027854

 

NorCalChris

NAXJA Forum User

Location

Central Coast, Ca

• Aug 27, 2010

• #7

do you have those injectors already? if so get the stock ones back in. you dont need these on a stock engine. also, a slight misfire can be a bad plug wire, or spark plug.

 

joe_peters

NAXJA Forum User

Location

Grants Pass, OryGun

• Aug 27, 2010

• #8

norcalchris said:

do you have those injectors already? if so get the stock ones back in. you dont need these on a stock engine. also, a slight misfire can be a bad plug wire, or spark plug.

Click to expand...

Or a burnt contact in the distributor cap (I hate those aluminum caps!), or a wobbly distributor shaft, or a leaking injector, or a fouled injector.

You can pull the plug wires loose, then just start them back on the plugs enough for good contact. Hook up a tach, start the engine, pull a plug wire and note the RPM drop, reattach that wire, move to next cylinder--looking for the least RPM drop, that is the weak/misfire spot.

 

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mmcswss

NAXJA Forum User

Location

Washington State

• Sep 25, 2010

• #9

Stumble has gotten worse not better leaning towards iac or bad injector.