97 Thunderbird 4.6L - Engine shuttering after rain

Elderwolf · 07-25-2009, 02:59 PM

I have a 1997 Ford Thunderbird with ~140k miles on it. It has been running great until we got a huge amount of rain 3 days ago. I thought the car was fine until I got on the main road and acceleration cause the engine to stutter and shake and just give no power. I got an engine light, and immediately pulled over to get the code (I use a ScanGauge II). I had P0308, misfire in cylinder 8. I cleared the code and limped to work.

When I arrived at work I found that the weather stripping around the firewall/hood area had been pushed off by the water. It seems that around Cylinder 8 had possible been flooded with water since the car was parked nose down on a hill. I only saw a little water pooled on the fuel injector on Cyl. 8. I look around the spark plug and there was no water, the boot was air tight. I took off all wires to let them try in case, and pulled the plug on 8, it was clean no water, the hole was dry except for some oil due to my valve cover leak.

When I got off work the car would get a little more throttle before doing the same. Before I could only use about 20% throttle, now i could use 30% and felt safe pulling out without getting rear ended. Now the car is about 40% throttle, and the engine only sputters a lot, but gets enough RPMs to kick down a gear, but still shaking. 3 days it has dried out, and I cannot figure what might have got wet. Here is a list of things I've tried.

Checked Fuel Pressure Regulator - Air Tight
Checked Plug 8, no water in well
Reset Engine Codes
Unplugged battery for ~2 hours
Changed Fuel Filter (No sign of water in gas, let gas sit in a jar)

I'm using Motorcraft Platinum Plugs replaced about 5k miles ago, Motorcraft Wires replaced about 10k miles ago. Coil packs were checked with multimeter about 2 months ago.

Do any of you have an idea what the cause might be? There are limited electronics in that area of the engine.

BroncoJoe19 · 07-25-2009, 03:13 PM

Seems to me that you know enough about what to look for. Are your wires long enough that you can swap wire 8 and 7?
OR you can test their ressistance with an ohm meter.
AND you can look under the hood in relative darkness for the spark arching outside the wire. (spraying a little water sometimes helps.)
WD-40 is a good dryer.

The miss does not have to be spark,
you can try swapping around the injectors and see if the miss follows it.
You can put a long screw driver to you ear, and listen for the injectors to click open. A mechanics stehoscope would be better.
You can use a noid light to see if the injector is getting a pulse from the PCM.

The coil was good two months ago, but you didn't have a problem then.

Hehee... so you already knew all this stuff.. smack yourself in the head, and figure it out.
Later you can reward yourself with a dish of ice cream, or a beer.

Elderwolf · 07-25-2009, 05:41 PM

BroncoJoe19,

Thanks for the quick reply. Unfortunately I forgot to mention that when I did have the engine code it was flashing, not steady on. And after I cleared it I never saw it again. So I don't think it will come back right now. Also I may sound like I know what I'm doing, but the only experience I have is general maintenance and my handy Haynes manual.

I checked the resistance on the Fuel Injectors and all seemed within spec (13.5-19.0 via the manual). Though I noticed there was still a pool of water around injector 8, so curiosity got the best of me. I tried to get all of it out of the well with a paper towel, then I loosened the fuel rail on that side and extracted the injectors. The #8 injector was wet all the way to the o-ring and covered with black gunk. I cleaned it all off with another papertowel, then reinstalled it to the rail, and put that rail back in. It didn't seem to improve anything, but I noted (accidentally) that if #8 was not plugged in, it ran just about the same. If I left 8 hooked up and unplugged another injector, then it ran worse than when 8 was gone. I'm thinking this is enough validation to replace injector 8 though the resistance seems good. I don't have a long screw driver, stethoscope, or a noid light.

taz4x4150 · 07-25-2009, 06:00 PM

Try cleaning the injector with something like a spray cleaner or swish it around in a cup of gas. You may not have all the black gunk out of the spray tip. Also, have you tried switching the injector to another position?

BroncoJoe19 · 07-25-2009, 07:29 PM

Elderwolf,
So here I am once again the position of the blind leading the blind. Taz makes a good point.. try cleaning the injector.
Consider this... if you have a dead cylinder it is dead due to a lack of combustion... no spark, no gas, no air, no compression.
BY disconnecting the power to the injector you just confirmed that it was dead, you didn't eliminate any of the other reasons.

You still need to determine if it is a lack of spark, fuel... etc.

I never pulled an injector, but I do know that there is an O ring, and that they sometimes need to be replaced. I suspect that your O ring is bad, and that allowed the gumm to collect as it did. Does that make sense?

BroncoJoe19 · 07-25-2009, 07:30 PM

Taz's suggestion of switching it to another postiion is one way of testing the injector itself. IF the missfire moves with the injector it is malfunctioning.

SC Car Dude · 07-25-2009, 07:44 PM

If you determine that the injector itself is the problem I think you should try lightly sanding its terminals and spraying the harness connector with WD-40 (then wipe and let dry) before buying a new injector. The connection may just have gotten a little corrosion when it got wet. This is cheap and easy to try.

Elderwolf · 07-27-2009, 07:00 PM

I tried to clean the injector several times, and it seemed that the engine would run only slightly worse when it was unplugged, but a lot worse if another cylinder was unplugged. Based on this and the fact nothing else was wet, I bought a new injector. This did not fix the issue. It seems the problem is trying to get worse.

I tested my coils and i'm getting 14.56 K-ohms for the pairs (Secondary) and 11-12 on the Primary. My Haynes manual says it should be 13.0-14.0 K-ohms for the Secondary and 8.0 - 9.0 ohms for the Primary. Is this too far out of range? Both of them are reading this, and I would expect if it was a problem, I would be having more than the initial misfire in cylinder 8.

BroncoJoe19 · 07-27-2009, 08:12 PM

You might try this. Pick up a new plug, connect it to the #8 wire and crank it, see if you get spark.

I know that there was a problem with the 5.0 and 5.8 engines, that the wires needed to be reouted properly or they might induce a spark from each other, or something like that and they would missfire. Does the 4.6 engines have the same problem? Could it be that his wires are too close together, or are running too parrallel?

Elderwolf · 07-27-2009, 08:49 PM

I'm fairly obsessive about my wires not touching, and have double checked this. After owning many Chevys with this problem, it's the first I try to avoid. I went out tonight and did not see any arcing. I'm certain it is getting spark though, as unplugging that cylinder makes it worse. However, I'm not sure if you can get a low spark, or too high of a spark that would cause this. I'm going to the parts store in the morning and see if they let me measure the resistance of a good coil pack to compare to mine.