XJ "Dieseling" after new Sensors - JeepForum.com
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post #1 of 9 Old 01-20-2020, 11:58 AM Thread Starter
legendslayer
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XJ "Dieseling" after new Sensors

I also have a 93 XJ that's my daily, i was getting poor milage so i tuned up the engine new champion spark plugs, wires, distributor cap, air filter and sensors TPS, MAP, IAC and cleaned up the throttle body abit, but the engines been running really rich since.
alot of the parts were mid range ordered off rockauto, never economy brand but never premium either

the tail pipe turned black at the tip and a i experience i extra 4 - 5 engine cranks after killing the ignition when the car is warmed up
sometimes the car idles at 1500 rpm in park

Kinda lazy let this issue slide for awhile took me like a month to install a ball joint on my other jeep haha
i still have all my old sensors to try to switch one out for comparison
not really sure how to tell which ones bad or "under performing" however

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post #2 of 9 Old 01-20-2020, 01:50 PM
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The rule-of-thumb in mechanics-world is to put back whatever you changed until the offending part is exposed. But I would suspect the MAP as it is basically a vacuum gauge telling the computer how much of a load is on the engine.

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post #3 of 9 Old 01-21-2020, 06:25 AM
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I'm gonna bet the tube/hose from MAP to intake manifold has a leak from being disturbed.

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post #4 of 9 Old 01-23-2020, 07:28 PM
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it should have engine code.
O2 sensors usually last about 100k miles.

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post #5 of 9 Old 01-24-2020, 10:31 AM Thread Starter
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Quote:
Originally Posted by car6car View Post
it should have engine code.
O2 sensors usually last about 100k miles.
I don't have a check engine light on and its a 93, So OBD1 not 2, They don't really make consumer OBD1 Live data code readers.
not to mention the header, exhaust and sensors have less then 10k miles threw them

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I'm gonna bet the tube/hose from MAP to intake manifold has a leak from being disturbed.
taped all the hoes up, made sure they were all attached, not seeing any immediate differences

Quote:
Originally Posted by Fourspeedman View Post
The rule-of-thumb in mechanics-world is to put back whatever you changed until the offending part is exposed. But I would suspect the MAP as it is basically a vacuum gauge telling the computer how much of a load is on the engine.
2 people mentioned MAP, maybe mines a lemon, the one in there right now is a Spectra Premium part ID MP102
Would a poorly sealed exhaust manifold cause any of these issues?

https://www.rockauto.com/en/moreinfo...%2BPPsdyoCi3ob

Was like 30 bucks, maybe ill try a third one?

Last edited by legendslayer; 01-24-2020 at 10:43 AM.
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post #6 of 9 Old 01-24-2020, 11:32 AM
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yes an exhaust leak would skew o2 sensor readings possibly causing them to see a lean condition, resulting in eng adding fuel.

speaking of fuel - ck fuel pressure with a gauge?

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post #7 of 9 Old 01-24-2020, 04:31 PM
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Taped up the hoses?
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post #8 of 9 Old 01-24-2020, 11:32 PM Thread Starter
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Originally Posted by jtec View Post
yes an exhaust leak would skew o2 sensor readings possibly causing them to see a lean condition, resulting in eng adding fuel.

speaking of fuel - ck fuel pressure with a gauge?
Now that you mention, i did put a new Wix fuel filter with the tune and sometime later down the line the Fuel Pump Ballast Resistor physically broke in the engine bay, the same ones in there still, pretty sure its just wired together at the moment and not bypassed. engine doesn't stay on with out it. Talking it out with you, i realize this could be a culprit. I'll have to go pick up a gauge to check the fuel rail tho.

i installed the exhaust manifold months before these issues arose and have had inspections since then with no mentions of a leak, so for now ill rule out the exhaust leak but will consider it heavily.

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Taped up the hoses?
Only temporarily but i wrapped some thermotek automotive tape around most of the vacuum lines and tubes in a poor mans attempt to seal any leaks.

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Last edited by legendslayer; 01-24-2020 at 11:45 PM.
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post #9 of 9 Old 01-25-2020, 08:15 AM
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With it idling, spray some carb cleaner around the vacuum lines. You'll find it.

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