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91 Seville Running Horrible...

2351 Views 21 Replies 8 Participants Last post by  Unforgiven33
91 Seville with 4.9

Lately it has been getting poor gas mileage and the exhaust smelt rich and the smell was coming into the car. So had it diagnosed and changed out the front O2 Sensor, ECT Sensor, Thermostat, Spark Plugs and Distributor Cap. Still ran rich and got poor gas mileage. Now it has begun to run extremely poorly. It barely gets to 20 mph and it doesnt even have the power to get up a hill and it gets about 4 miles per gallon. So it's been taken to a few shops to try to figure it out and none of them know.

Then today it was taken to another shop and when they went to pull it into the shop, it wouldnt start. Turned out both the injector fuses had blown. So now its home and no shop in the area can tell me whats wrong with it. Since the injector fuses blew, I am starting to suspect them. No check engine lights. It did backfire once, so this thing must be running SUPPPPER rich.

Basically, anyone have any ideas? I am mechanically inclined. Next things on my list to do are to test fuel pressure, then pull the rails off and see if any of the injectors are leaking by when the fuel system is primed, and then to do a spray pattern test on them. Am I headed in the right direction?

Also, with regards to the distributor, I did trace all spark plug wires to the right spot in the right firing order. My question is that one the distributor cap, right side there is a 3 wire plug that plugs up into the cap and then a little white plug with a single red wire going into it that plugs next to the 3 wire plug, but there is then a spot open next to the white plug that it looks like a wire should go into, but i can't find any stray wires that go there. Is that spot supposed to be open next to the white plug or am I just not finding the wire?
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As mentioned, these early Rochester injectors are a weak point on these engines. Since you are blowing injector fuses, I see no reason to start blindly probing other areas. I wouldn't even bother going through the hassle of looking for leakers yet. Use the evidence you are given. Don't guess.

When the injectors fail, the injector coils create a short or open in the circuit. That's what the fuses are for, and most likely why they've expired in your case. Leaking injectors, a leaking FPR, nor a clogged CAT will blow fuses!

To check the coils, get a multimeter. You will be checking their resistance. Set the multimeter to "ohms" and probe the blade connectors on the injectors (you can also check the injectors at the harness connector near the distributor if you keep track of wire color). Polarity is of no concern here. You should find readings somewhere between 12 and 18 ohms. Anything with no resistance, or infinite resistance is a failure and will need replacement. Also check for proximity between injectors - for instance, if most injectors return 12 ohms, but one returns 18 ohms, suspect the 18 ohm injector even though it's technically in range.
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Any high impendance 19lb injectors with the standard dimensions of our Rochester are viable replacements. The Ford 4.6 injectors, made by Bosch, work great in these engines, and have a much higher reliability rate. That said, many have done this and I agree that its a great option. Also, I don't recommend you waste time replacing them one at a time. The low resistance you've measured is creating high current draw through the injector circuits, causing the blown fuses. Keep running it with them, and you could damage the injector drivers in the PCM, leading to more repair. Just replace all that have tested bad with correct replacements, or all 8 with a different type used set, such as the Bosch.
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