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Matt
Matt, Engineer
Category: Jeep
Satisfied Customers: 20580
Experience:  Honors degree in Mechanical Engineering, worked 8 years as a Formula 1 engine engineer.
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My hc and co are way to gh cant pass emissions 89 jeep

Customer Question

my hc and co are way to high cant pass emissions 89 jeep Cherokee
JA: Sometimes the difference between passing and failing a smog test can be just a few quick repairs. Luckily, the mechanic I'm going to connect you with will have just the information you need to get this fixed fast. How many miles are on the car?
Customer: 257124
JA: Tell me a bit more about what's going on so he can help you best.
Customer: the readings are 935 on hc limit is 220 and 12.25 on co limit is 1.20
JA: Are you hoping to fix this yourself?
Customer: yes
JA: Great! What have you tried so far?
Customer: a new tps new cat oil change and seafoam in it twice once in the gas once in the intake
JA: Is there anything else important you think the Jeep Mechanic should know about your Jeep?
Customer: not that I can think of
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the Jeep Mechanic about your situation and then connect you two.
Submitted: 6 months ago.
Category: Jeep
Expert:  Matt replied 6 months ago.

Hello

This could be a number of things:

Incorrect fuelling due to a faulty water temp sensor. If this is the problem then the ECU will be leaving the car constantly ' on choke' and not reducing the fuelling as the engine warms - so unplug the sensor and clean the contacts on both sides with some switch / electrical cleaner (not WD40) and inspect the wiring for any signs of damage to the insulation especially where it runs over other components and through the bulkhead- if this doesn't help consider replacing the sensor as they're not expensive

Check for exhaust leaks before the O2 sensor as if this has been experiencing an exhaust leak then it will have been running very rich as the sensor will see the extra air pulled in as fresh / lean fuelling and be adding fuel to compensate.

this can lead to catalyst failure as the extra fuel can re-light inside and melt the catalyst

The best way to find an exhaust leak is to run the engine from cold and feel around the exhaust joints with your bare hands - you'll have about 30 seconds before it all gets too hot and you should feel any escaping gas blowing over your fingers

One other thing is to ensure that you're running on the correct grade of engine and gearbox oil as if its too thick or overfilled this will really hurt the fuel economy

Expert:  Matt replied 5 months ago.

Hi

do you still need help?

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