I've got an old 88 crown vic with the efi 302 in it. It's old enough now that everything has started going wrong over the last few years, and I fix or replace as I'm able, but I'm stumped now. (just to clarify, I had a mechanic look at it, he claimed he spent 23hrs of shop labor on it, and couldn't find the problem. He charged me 1hr of labor and asked me to never bring it back)

About 2 years ago, I was getting what appeared to be a stuck throttle (wide open) which I found were burnt out O2 sensors. I replaced them, but the had a problem with the motor misfiring and kicking violently for the first 3 or 4 minutes after starting. I checked the computer codes with my voltmeter, and got no koer errors, only some stored memory errors from when my O2 sensor was still disconnected.

When I disconnect only the passenger-side O2 sensor, this problem goes away. I checked the sensor's output with my meter, and it seems fine. Secondly, even with the heated sensor, I was under the impression that for the first minute or 2, the computer ignores the O2's anyway while they heat up. What's really interesting, is that after 3 or 4 minutes of highway driving, it feels like someone stomps on the gas. The kicking and bucking in the motor stop, and I've got all kinds of power. From that point on, the car runs fine.

For a long while simply running 1 sensor was a viable option because I didn't know what else to try, but I'd still like to squeak that little extra bit of gas milage out of the motor if I can. Does anyone have any ideas or possible problems and/or things I can check??

 

you could need a tune up, the plug wires could be bad or crossed causing them to arc and draw power. the timing could be off or the chain has to much slack making the timing jump. how many miles on the motor. fuel filter may need changing , a slipping tranny could make you think the motor is messed up. are the o2 sensors the same and were replaced at the same time. the wires are fried anywhere? need to know whats been done to it. because from what you have said most of the basics havent been addressed.
late

 

Plugs and wires were changed about 6 months ago and look like they're routed alright. The distributer cap was changed at the same time to replace the old corroded one. The motor was rebuilt top and bottom end about 18,000mi ago. I had a rebuilt transmission put in 4 years ago (this problem will happen in idle too if you bring the engine speed up a little so I ruled the transmission out). I put a new fuel filter in back when this problem started and it had no effect, and the O2 sensors were both changed at the same time; I didn't put them in myself because they were hopelessly stuck in the manifold, but they appear to be identical units. I've got a dual-roller timing chain, it's pretty solid and when I got the bf-socket on the crank and checked, it seemed nice and tight. The computer module was also replaced at the same time as my O2 sensors. The timing was reset 3 months ago when I had to have the tfi module on the distributer changed; it's computer controlled anyway - set and forget.
As for fried wires, I can't follow the maze of wires to check how they all look, and most of them are contained inside that plastic wrap tube. I did check to make sure of no obvious cuts or melted spots, and where I could get at sensor connectors I checked that the pins weren't shorted with each other or to ground. I also manually checked the resistance on my throttle position sensor, and my coolant temperature sensors - both correct by factory values.

I may have missed some other things I've done. It's hard to keep track of everything.

 

i would still check the timing it should be at 10*btdc with spout removed. maybe even 12*. when you changed the cap did you change the rotor as well. sorry i gotta ask hehe. is that crown mass air? if so your mass air meter could be bad, or an injector could be bad to . whats your fuel pressure at? What kinda plugs and wires are you using.

 

Yeah I got a new rotor to put on there, it was as corroded as the points. I will dig out the timing light and have another peek at it when I get around to it, but I wont adjust it ever.. not after the... unpleasentness of last time - the computer really dislikes you attempting to manually adjust the timing. I'm using Motomaster preimum sheilded or whatever canadian tire calls their most expensive plug wires - They're the reccomended ones for my car in the CT catalogue anyway. Plugs are just standard napa parts, Autolite I think. I've heard people complain that those are junk, but I run them in my sisters 94escort and my mothers 97 crown vic, and they work great.

Unforunately I dont have a fuel pressure gauge, or know anybody that does (Lots of people have the older style, but I don't know anyone with one that'll clip onto that queer connector ford has on the fuel rail). I've suspected my fuel pump for a long time because it occasionally buzzes, but it's done that since '92 and keeps on going - I dont seem to have any lack of power under WOT conditions.

As for injectors, I'm not sure how to check them. The intake covers 3 of the 8 up so badly I can't get at them at all, I know that disconnecting the other ones makes the engine run much worse. Aside from that my only idea was to use a mechanics stethascope and listen to each one. All of them had a very clean and constant ticking as they opened and closed.

And, nope not MAF. Good ol' speed-density system, and like most common and important sensors in that car, they dont look like their replacement parts, and in general aren't mounted where they're supposed to be, so I can't find them. (I spent hours trying to find my pcv and I just can't)

 

the pcv is located on the underside of the upper intake plenum. do you have a haynes manual.

 

I've got the chiltons and a seperate 88-93 ECC-IV electronics book. Unforunately my car seems to be made of a hodgepodge of leftovers from 87 along with new stuff from 88. Almost nothing is where it should be on that motor. That's one of the reasons mechanics ask me to take it elsewhere.

 

sounds like its time for something else to drive man an cut your losses. it could be a lemon

 

The thought crossed my mind, but I like my giant car. I think before I go about replacing it, I'll break down and spend a week or 2 grinding and filling the body to make it worth working on mechanically, then see about getting either a really old motor with no electronics - a carb and 4 vaccum lines, or a new 4.6L kit. I've seen the whole motor and sensor/computer package for sale at not unreasonable prices. At least then I'd know exactly what's what, even if I have to fiddle with making new engine mounts to fit it in.

Thanks for your time - let me know if you happen to think of anything else I can check.