Cokie907

I've got an 89 5.7 liter here in East Tennessee with 176,000 on it. I bought her for 2 grand and she ran great for about 10,000 miles until all of the sudden, she started running rough. I pulled the plugs one day to see what the story was....boy what a chore! All the plugs looked normal except for cylinder 2 which looked a bit fouled. No matter, I just cleaned it and swapped with cylinder 1 then took her for a test ride. The car ran fine but all of the sudden started bogging out. I limped to the side of the road and parked her in a parking lot.

The next day I tried getting her home but as soon as the engine warmed up (after about 1 mile) it started bogging again. No power. The car has since been towed home and the symptoms remain. I've jumpered the ALDL to get codes but there are no codes. I've replaced the fuel filter and tho the one I took out was cruddy and rusty, that didn't do the trick! My only other recourse is to replace the fuel pump? But it comes on when I turn the key and makes its humming noise. Perhaps I should get a fuel pressure tester and check my fuel rail pressure? That would be a start I guess.

Working on a Fox Body Mustang was soooo much easier!

Forgot to mention that while I was under the car sweating my *** off to get cylinder number 6's spark plug out, I yanked a wire out of the block. I was able to re-attach that wire but am not sure if that might have caused my problems. What does that wire do anyways? :-)

musclecar70sfan

iTrader: (1)

Bad fuel injectors. My car was doing the same thing once. Do you know if your engine still has the original injectors?

Cokie907

One detail I failed to mention is that the motor will idle all day (albeit a bit rough) but when I step on the gas....it just bogs and almost stalls. The fuel injectors are the originals as far as I know.

Am I to surmise that the fuel tank has built up a good bit of rust from condensation over 20 years and that rust has made its way to the injectors? I couldn't believe the rust that dumped out of the fuel filter when I changed it out. Amazing...

Maybe I should throw a can of chemtool in the tank and see if that will clean the injectors? Or maybe some Seafoam. Couldn't hurt...

musclecar70sfan

iTrader: (1)

Sure you can try that but if they're the original injectors, I'm willing to bet that they're the culprit since they all start going bad at around this point. Try the resistance test on the injectors. The coils inside the old injectors deteriorate from age and that increases their electrical resistance to the point they barely function. I don't remember what the numbers are supposed to be but people have done this here countless times so I'm sure you'll find them. And my car did the same, the LB9 would idle OK, and would bog and die when you hit the gas. Then you couldn't get it to restart until the engine completely cooled.

Cokie907

I now know why the spark plug in cylinder #2 was loaded with soot. Checked the resistance on those injectors tonight and got the following:

Cylinders 1,3,5,7 all 16.5 or 16.6 ohms
Cylinder 6, 8 - 16.5 ohms
Cylinder 2 - 4.2 ohms
Cylinder 4 - 11.5 ohms

I guess I should be replacing the injectors for cylinder 2 and 4? I wonder if the car will run properly after that...hmmm. I'd like to hope so.

musclecar70sfan

iTrader: (1)

that's probably your culprit. and these TPI systems are like old christmas lights.... 1 injector goes bad and the rest go down with it!

hawgranch

Aslo check your ignition control modual.Have it tested at your local parts store.

southbay08

At this point chemtool is not going to be the answer, if anything you may cause more issues. Just remember, fuel additives/cleaners work, we actually carry seafoam and techron, but they are sometimes a temporary fix, and it also depends on the condition of the injectors. When you use these cleaners you may be cleaning out your fuel system but whatever "gunk" is in there will be flushed directly into the screens/filters of the fuel injectors.
In your case, the resistance on 2 of your injectors indicate coil failure... definitely on cyl 2, and cyl 4 is on the way. Coils cannot be repaired.Trash the injectors and get yourself a set of bosch lll's...you will be very happy....guaranteed!

www.southbayfuelinjectors.com
516-492-6504

danziger

Yep. I'll third the vote for injectors. Replace them all at once instead of piece-meal. I learned that the hard way...

ninetyone

iTrader: (2)

hope you didn't pull out your knock sensor wire. Should be 2 wires there. One is for your secondary fan (black)the other is knock sensor(blue). I used to work on 5.0 Ford motors too. Yes much easier to work on! LOL Anyway, If you pulled out that knock sensor wire, the car will have NO power and run like crap. Make sure it is connected tight, especially that plastic connector that attaches to the knock sensor. Make sure you have a tight connection there. If not, it will trigger a code 42.I am going to have to vote towards bad injector(s). Not that hard of a fix. You will have to remove intake plenum and runners and disconnect your fuel line in front of your throttle body.

Cokie907

Thank God for this site and the folks on it.

I just got done with the replacement of my fuel injectors and the car fired right up on the first try. It starts quicker, idles smoother and runs like an absolute champ. No more bogging whatsoever.

I must say the project went quite well and I feel like I understand my ROC a heck of alot better now after fiddling with all them hoses.

Now it's time to start saving up for a paint job I guess.