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Hello everyone, I have a 1993 LX 5.0 retired police interceptor. Its got bbk 75mm TB and air sensor, edelbrock performer intake, not sure what cams were put in. The guy who had it before me put just about every bolt on piece you can get out of jegs, he did some things to engine but not sure what exactly.

Anyway its pretty quick i managed to beat a ford lighting by about a car length. In the 2 years ive owned it i havent had any real problems with it just small parts until now. Im having a problem i cant seem to diagnose on my own without just changing all kinds of parts. About 3 weeks ago i got in cranked it up and took off, well it felt like i had a bulldozer hooked up to the bumper. It didnt want to go and when i gave it some more gas it backfired up the intake. I stopped and reved on it a little sounded fine, then took off and no problems for 2 weeks. Now it starting doing it again, for the last 3 days it does this, but while its studdering trying to go if i press the clutch it sounds fine but in gear it studders. This might last about a minute then clears up and car is back to normal. It does it cold, hot... i cant make it do it, its all random. I was thinking maybe my fuel pump, gauge reads about 55 pounds though, and under a load it builds pressure (havent been able to try while car running funny) I changed TPS and fuel filter about 6 months ago, im not sure if its the original distributor, havent tested it yet. Timing is right too.

Any help would be appreciated, thanks.
 

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If you haven't already did this change your o2 sensors. My car did the exact samething over the summer and thats what I did to correct it and for sensors try getting them right from Ford I haven't had any luck with Bosch.
 

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About a year ago i checked codes because my engine light comes on and off randomly, they pointed to o2 sensors but i checked them with ohm meter and values were correct. Do you think its worth checking them again or could they be bad even though they dont look it?
 

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Last time i ran codes i was having issues with idle, i got these 14, 16, 41, 66, 91. I changed my TPS before i figured out that my Throttle body had some slack in linkage, i fixed it and cleared up the 14 and 16 codes. Today i ran codes again and it gave 33, 41, 63, 66, 91. I changed my plugs and right away knew i was running lean from old plugs.

I also put in another fuel pressure gauge and ideling it sits at 33psi, if i throttle it drops to about 31psi. Not running the gauge goes up to about 36 then slowly climbs to 38psi after about 45 seconds. I checked the wires in the MASS they are clean, the TPS is fairly new havent checked voltages yet, and havent checked out 02 sensors yet. Is my fuel pump acting normal?
 

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Fuel pressure should go up when you rev - with the vacuum line on the regulator. And when you pull that vacuum line, at idle, the pressure should shoot right up to 39(stock) or whatever it's set for. 55 is too high. Sounds to me like the pump. It'd be nice to have some dyno rollers or a remote gauge to monitor pressure under load.
Check your vacuum line for the EGR(33).
Set your new TPS, 63 is voltage too low.
The 41 and 91 are the lean condition.
You could call the previous owner and ask if he ever did the pump.
 

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Clean your MAF sensor. Was having the exact same problem with my '93 cobra. Look at the wires... should be shiny silver. If they're not... carb cleaner to clean... brake cleaner to remove residue... perhaps a VERY gentle q-tip for stubborn stuff.

It was so nice to have my cobra back from the pig it had become.
 
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