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sprinkles08, ASE Certified Technician
Category: Cadillac
Satisfied Customers: 22986
Experience:  ASE Master and Advanced level certified. Factory trained with 15 years dealership experience
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I have a 2000 escalade with a new crate motor that I

Customer Question

I have a 2000 escalade with a new crate motor that I installed about 6 months ago only about 2000 ***** *****. it was running great but I let it sit for a couple months and the battery went dead I jumped the car it started right up but has been missing and back firing since It sets no codes but has yet to run ev o e and c monitors
JA: Thanks. Can you give me any more details about your issue?
Customer: it idles fine then stumbles sometimes even stalls if i try to drive it misses and back fires
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Submitted: 1 year ago.
Category: Cadillac
Expert:  K. Wiggins replied 1 year ago.

Hello, with it sitting for 6 months the first thing that comes to mind isbadgas due to water absorbtion. Today's fuels with the 10% ethanol are very bad about this. Heet brandmakes a good water removal treatment that you can pick up at most parts stores.

Another thing you may want to check is the fuel pressure. The fuel pressure should be 60-66PSI and not drop more than 10PSI in 10 minutes.

Let me know how things go and we can work further if needed.

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Customer: replied 1 year ago.
I guess my original question was written poorly. I put the new engine in 6 months ago the car was driven a lot for a few months. It has had several tanks of gas . It sat for a few weeks the battery went dead I jumped started it and it began running bad. I did the throttle position sensor resets no real help . It idles fine for about 1 minute or so the misfires (sometimes stalling completely) then idles ok .If I rev the engine it begins to misfire a lot. What is weird to me is it doesn't set any codes at all. Sorry for the mixup on the original question .Also when I put the new engine in I also changed cap, rotor, distributor, and Plugs and wires. I hope this info helps
Expert:  sprinkles08 replied 1 year ago.

Hello and welcome to JustAnswer!

It sounds as if you may have a failing upstream oxygen sensor. A weak upstream sensor heater will cause signal voltage to remain higher than it should be as it enters closed loop operation. This will cause the engine controller to think the engine is running rich and it will take fuel away, causing it to run poorly, backfire, or even die.

Try unplugging the upstream sensors, disconnect the battery to clear the adaptives, and then take it for a ride to see if it runs ok without the sensors plugged in. If it runs ok then one or both of the sensors is bad.