High idle and flooding when warm?

1996 Cherokee 4.0 is having issues again. The engine starts and idles fine when cold, but now if I start it up after the engine has been warm, it is flooding. There is a fuel smell at the exhaust and requires the accelerator pedal to be floored to start. After start it idles at 1000 rpm. Any ideas as to what I should do? Could this have been caused by a defective gasket when I replaced the Idle Air Control motor last week? The only code currently being shown in the computer is code 17, engine staying too cold. Engine never really gets above 160 degrees when watching the gauges. Any thoughts as to what I should do?

Check the coolant temp sensor. If the truck thinks its too cold out it will puke fuel to compensate. Bad or broken connections can cause the sensor to read antarctic temps.lol

If you have access to a scan tool with live data, you should be able to see it rather quickly.

If you're not getting above 160 you probably need a thermostat as well.

There is also the possibility of a leaking injector.

P.S. check coolant level too.

Thank you! Will swap it all out tomorrow! Coolant level is right and the mark and the right color thankfully.

Cessnapilot89 said:

Thank you! Will swap it all out tomorrow! Coolant level is right and the mark and the right color thankfully.

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Get a thermostat from the dealer. Little pricey but work extremely well. Most aftermarket stats are junk.

That fixed it! There was a 160* fail safe type installed. Jeep runs great now!

Cessnapilot89 said:

That fixed it! There was a 160* fail safe type installed. Jeep runs great now!

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Woohoo!!

I'm working on finding a source for those MotoRad High Flow thermostats in the aftermarket. Some guys on CF are in the mix also.

Tentatively, we're thinking the 2000-195 MotoRad is the one we want.

cruiser54 said:

Woohoo!!

I'm working on finding a source for those MotoRad High Flow thermostats in the aftermarket. Some guys on CF are in the mix also.

Tentatively, we're thinking the 2000-195 MotoRad is the one we want.

Click to expand...

I get the feeling that flow rate is a bit tricky. More isn't necessarily better. I noticed my 96 was warming up slow, but when it did eventually warm up it would go into the aux fan temperatures a lot earlier than I was used to. Considering the outside temps (75-80 F) the aux fan coming on seemed a bit premature, more so than usual and I was used to. In effect it was warming up slower and reaching a higher than normal temperature at a lower ambient than I was used to.

My OEM thermostat was junk, it had actually broken into two pieces. But it did leave me wondering how having a basically open flow (no thermostat to speak of) could cause the motor to get hotter quicker, with the same outside (ambient) temperatures. The only logical explanation I could come up with was that the rate of flow through the radiator had something to do with it. It seems logical that time (coolant inside the radiator) has some effect on how much heat it can radiate. Like I said, more isn't necessarily better, it's finding that magic *balance* that gives the better results.

More airflow is unlikely to upset the balance as the thermostat will regulate the flow. More radiator surface area is unlikely to upset the balance as the thermostat will regulate the flow. But messing with the flow may upset the balance, it may just flow too fast through the radiator. I'm sure there is some *buffer* but I'm guessing there is a tipping point. The only reason I can think of for my temperatures going higher with no thermostat is the increasd flow was causing my issues.

Well, it appears the HighFlow MotoRad may not be the same as the factory unit. So, until we know more down the road, use factory stats.