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forsaken82 06-18-2013 05:05 PM

bucking sputter at operating temp
I have a 94 4.0 with 160k on it. It sputters,bucks and jumps once it reaches operating temp. So far I have changed tps, o2 sensor, coil, dist cap and rotor button, fresh oil and gas, sea foamed intake, ran a propane torch with no fire over the vac lines with no idle change. Any ideas?

Garyk 06-18-2013 05:40 PM

Check your temp sensor. If ecm thinks engine is cold it will make it run rich..

forsaken82 06-18-2013 06:33 PM

Wouldn't that cause my gauge to read off too? I assume your talking about the coolant temp sensor

Redrider94 06-18-2013 06:45 PM

The temp sensor is in the t-stat housing, the ECM uses this sensor to make adj to the fuel system. This sensor has two wires to it.

The temp sending unit is what the gauge uses, it is located on the drivers side rear of the engine by the end of the fuel rail kinda under a bundle of wires. This sender only has one wire.

forsaken82 06-18-2013 07:04 PM

Valucraft/TruGrade/Coolant Temperature Sensor (SU326VC) | 1994 Jeep Wrangler 4WD 6 Cylinders S 4.0L MFI |

This one right?

goatman 06-18-2013 07:38 PM

Is it at any rpm, or just going down the road, or just idle? Mine sputters around at idle because the TB and IAC are dirty. It has a hard time exactly modulating how much air it is getting at idle so it hunts around. Need to get some carb cleaner and go to town.

forsaken82 06-18-2013 07:45 PM

Its just under load. She idles perfect.

jokerchief462 06-18-2013 10:32 PM

Plug wires??? You will see them sparking in the dark.

Ecu sets the timing and fuel mixture based on inputs. So the temp sensor or some if your wiring maybe.

kik 06-19-2013 05:59 AM

It sounds like you have a bad/weak fuel pump. You're probably not getting enough fuel pressure under load.

forsaken82 06-19-2013 06:03 AM

I thought fuel pump too but it doesn't do it all the time. Seems to go through spurts.

forsaken82 06-19-2013 06:59 AM

Gonna check fuel pressure. 45-55 psi right?

forsaken82 06-19-2013 08:17 AM

checked fuel pressure. its sitting about 52-53psi, bought a temp sensor while i was there. ill let you know if it did anything after i drive home for lunch.

going to the lake camping this weekend so i need to get it fixed.... im gonna hate it if i have to take my charger. its just not the same!

forsaken82 06-19-2013 11:46 AM

Still doing it. Seems to get really bad if I hit a bump while it is doing it.

forsaken82 06-19-2013 12:59 PM

another forum suggested the cps, could this cause it without throwing a code? only code im actually getting is speed sensor which i dont understand since i replaces it already.

forsaken82 06-19-2013 09:27 PM

Disconnected cps cleaned connections and packed with dielectric grease. No sputter on way home... if i was a betting man id bet it will be back but we will see after a longer drive tom.

forsaken82 06-20-2013 12:56 PM


CHL 12-02-2013 12:18 PM

I'm having a similar problem, what and where is the cps?

rhd_yj 12-02-2013 12:48 PM


Originally Posted by CHL (Post 6512170)
I'm having a similar problem, what and where is the cps?

On the transmission bell housing at around the 11:00 position (if your looking from back of the tranny to the front) 2 bolts hold it on and you should follow the wire through the firewall and should see a clip around the fuel rail

CHL 12-03-2013 03:57 AM

Thanks rhd.

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