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2000 Mercury Sable: Replaced A/C Compressor pulley bearing, now car will start but dies immediately

I am completely lost now, spent alot of time trying to get the pulley off to replace the bearing, finally got that done, turned on the car, and it dies almost instantly unless i have my foot on the gas… it runs really rough until i rev it up to at least 2K, any answers would be appreciated

maybe your compressor is seized up and that caused the bearing to go? and it may be drawing too much current for the car to run properly?

Remove serp belt. Does car start ok?

Check connections to the idle air control valve. Clean it and the throttle body if not done recently.

Concur w/ Stoveguy , need to eliminate the new pulley as the cause. It’s usually possible to run the engine w/out the s-belt for a short time, one minute or less. Not too long, esp if water pump is driven by s-belt. Don’t want engine to overheat.

removed serp belt, same result, starts, revs go up and drop, engine sputters once or twice and dies, i can smell a strong exhaust smell, seems like rich exhaust like its trying to run rich, dont know if thats just a side affect of whats actually wrong or not. When i do start it and put my foot on the gas it runs very rough and sputters until i get over 2k, but will not die until i let off and the revs drop all the way down.

side note…i did have to drop the front of the sub frame for the engine so i could get to the compressor, had to drop almost 8 inches but i looked for any hoses or cables loose, didnt find any

I’m wondering if you cracked something in the exhaust system in the process, and now outside air is getting into the exhaust stream. That would confuse the ECM to no end. It would think there is too much O2 getting through the combustion process, so it would enrich the mixture by injecting more gas. But no matter how much gas it injected, it wouldn’t work b/c the O2 – when there’s an exhaust leak – is not coming from the cylinders.

It could be lots of other things too, but that’s something to consider at least. Given the prior work you’ve done, the most likely cause seems like it would be that you forgot to reconnect something, or something fell off or became disconnected. With so much stuff in modern engines, sometimes something like that can be looking for a needle in a haystack.

You just have to eliminate the possibilities one by one. Have you read out the diagnostic trouble codes yet? You could have some stored even if the check engine light is off. Your experiment to temporily remove the pulley seems at least to eliminate the AC compressor or any of the other accessories on that pulley, so that put you ahead of the game. Get those trouble codes read out and if there’s any there, folks here will help with the interpretation. Best of luck.

I towed the car down to oreillys and had them put the diagnostic on it, there were no trouble codes at all, he even started the car and kept it running by upping the throttle and it still had no codes, i jacked the car up and checked as much of the exhaust system as i could see or feel and didnt feel or see any signs of damage to the exhaust, all the connections were in line and looked for a 3rd time to see if there were any loose cables or hoses but like you said, needle in a haystack, after i got no info from the diagnostic i just took it to a mechanic that my roommate uses all the time, he says they are very fair and competent so we will see what they come back with

thank you all for your info and ideas, they gave me somewhere to start and i appreciate that
if i have any other issues i will definately be coming back here first

While not always true in every case, an engine that will not idle or run at low RPMs but will run acceptably well with the pedal depressed could mean a vacuum leak.
I wonder if dropping the engine that much split a vacuum line. No codes for this.

Other possibilities could be that dropping the engine stressed a wire connector on the TPS or IAC valve, etc and the problem is related to that. It’s possible to have a TPS, IAC, or EGR problem with no codes present.