86 cown vic 5.0 loss power and stumbles

I just bought this 86 Crown Vic w/ 5.0 fuel injection, she runs great throughout 1st and 2nd, when it shifts into 3rd it loses power, flutters and stumbles until I mash the gas to the floor, it downshifts with lots of power and eases up a bit when it shifts back up to 3rd and has hit about 40 MPH. I had this same problem on my 75 Ford van three on the tree but that was Carburated. I put a new carb on it and fixed the problem. I don't know much about Fuel Injection and all the sensors that come with it. I cleaned the throttle body and installed new plugs, wires, cap, and rotor, changed oil and fuel filter. She also stumbles a bit on the highway and has a vibration that doesn't seem to be coming from the tires or driveshaft. Anyone have a clue at what is going on? Other than that, it runs sweet.


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Is the engine placing any codes? my next guess would be to check the EGR valve, check the shape of it`s current tune up, change the fuel filter.

Does this happen under load at high/freeway speeds? My father in law is having a similar thing happen with his vic as well. It has had a tune up and all looks fine, but stutters while under load, pulling a hill at 65.

sounds like a fuel problem, I'm not so hot with computer controlled engines though. I had a 67 skylark stumble and almost die when you stepped on the gas, I thought that would be the end of me, that drove me nuts. It turned out to be a weak ignition coil of all things.

I used to work at Schuck's Auto supply part time and have seen new or new "rebuilt" parts bad right out of the box just so you know.

good luck

Dan

my Father has a 94 Crown Vic with the 4.6, We were getting a few codes, and it would stumble alot, especially under load. we replaced the sensors the codes said to, problem persisted, and we were still getting the same codes. so I removed the throttle body and found the EGR passage was completely stopped up with carbon, and this stuff had set up like concrete, I poured sea foam on it and let it soak, then chipped it all out, then I removed the EGR valve and cleaned it and it`s passage, ever since then no more problems. The 4.6`s and 5.4`s are notorious for this problem, but any vehicle with EGR that stumbles under light throttle and seems to run fine elsewise the first thing to suspect is the EGR.

Do you know had to read the codes? Let me know if you dont and I'll give you a link. Very simple process. Possibly the TP sensor can give your the same symptoms. Read the codes 1st.

Not sure how to read codes. Yes it stumbles when under load when shifting up. It also does this on the highway. Changed fuel filter and shot some throttle body cleaner in it also. Haven't taken the throttle body apart to clean it. I have no idea what the egr is.

Thats ok, many shops offer free diagnostic checks, if it throws any codes the mechanic will tell you, and he will also tell you what the code(s) mean, so you'll know what parts to buy.

I'm going to try and clean the EGR first. Since I've been driving it more it's been getting better, but still not perfect yet. Is there anything I should be careful of when cleaning it?

just don't eat the carbon. sorry couldn't resist.
I'd just watch what I had to remove to get to it,( vacuum lines, etc )

Go to this site and read the explaination on how to read the codes.http://www.dalidesign.com/hbook/eectest.html

So far I have sprayed alot of throttle body cleaner into it and that has helped alot. So I've pretty much narrowed it down to just cleaning. Thanks for all your help.

Been a while but I've figured out what the problem is. It's the darn AOD transmission. The weak link is in the 3rd and 4th gear setup. Apparently they wear out and can cause this stumbling and lack of response upon trottle. I adjusted the T.V. Cable which was a little stretched out but now it drives alot better. The really annoying thing it does is blows hot air out of the vents when all of my heater contols are set to the off position when I get on the gas to down shift from overdrive to 3rd.