Chasing a misfire on D1

[rappo999]

OK, first of all - I want to THANK everyone on this forum, you all made my Summer project much easier!!!

I was "given" a 1997 D1 with 137k miles on it by a "friend" of mine, it was sitting on his lawn for 3 years. I have a 16 year old son and we spent the summer rebuilding it. (brake rotors, pads, exhaust, plugs (2x), wires (2x), multiple oil changes (sitting oil was gunked up), seafoam treatment, battery, pcv valves, MAF cleaning, throttle body cleaning, multiple interior cleanups, etc...

As of now, it is all running and running almost well. Through the summer, at various stages, I was getting multiple random misfires. After a few oil changes, some aggressive driving, changing plugs and wires twice (because I did not read enough the first time, here is where I am...

I have Champion copper plugs (I think 322) and Kingsborne 8mm wires. All checked, re-seated, etc. I can drive the car for 100 miles on and off the highway with no issues. Then, I will get the check eng light back on. P1316, P0300, P0305 show on my reader. I can reset the light and drive for a while but it will happen again. Always Plug 5. I pulled Plug 5 and it was wet with fuel one of the times. I dont have any other issues, no smoke, not any bad smells, etc.

I brought it to a "real" mechanic and he did some addl testing, checked compression for that cylinder, said it was 140. He did not check others for comparison, I can do that this weekend. His opinion is that the coil might be bad, he thinks that it is not getting spark intermittently.

When the code is not being thrown, the engine is really smooth. Between the recent multiple oil changes and the seafoam via brake booster vacuum, there are no ticks or pings, it is very smooth and starts instantly, etc. Even when the code is lit, the engine is smooth. I might feel a little stutter occasionally but it is hard to tell.

If it weren't for the code, it would be great.

My thought is to get an Ebay coil pack and give it a try. They are $50-$75. I know it will be used, beat up, etc but my theory is that it is not likely to have the same error as mine (if it is at fault). If #5 did not code out, then it points to the original coil pack. If I get lucky, I have solved the problem for $50. If there are other ignition problems but not on #5, then I know to get a new coil pack.

First question obviously is does anyone have any suggestions? Am I correct in thinking that coil pack is the next place to look.

Second question is, if I replace the coil pack, do I need to do anything else? Timing, etc? or is it a "replace and drive"?

This might be stupid, I might be overlooking something simple, I am learning as I go...

Any help will be much appreciated.

Thanks a lot!

JAson

[Spike555]

Its not the coil pack, those things last forever.
I am leaning towards the VSS (vehicle speed sensor), it sends the road speed signal to the speedo and ECU, when it starts to go bad it sends a false signal to the ECU, if the ECU thinks you are going to fast (110mph+) it will kill spark to the engine one cylinder at a time to slow you down.
The "A" typical fault is really rough running on acceleration, climbing hills, etc. along with a MIL for multiple random misfires.
When it gets bad enough the truck will be virtually undrivable.
The way to test this is to unplug the VSS and drive it and see if the problem continues.
The VSS is located on the output shaft of the trans.
The only other thing it could be is a sticky valve, but one would think that would stick all the time not one in a blue moon.

[rappo999]

Thanks a lot!

I will check that out. I did notice that the spedo is off by 5mph. Do you think that might be further evidence that the VSS is going bad?

I will disconnect the VSS and drive it around to see.

Thanks again.

[Spike555]

ALL of the DI speedo's are off by 5mph.

[rappo999]

Todays Update...

So I pulled the VSS wire last night and drove about 40 miles between last night and today. Car seems to be running better but check engine light came back on. I checked the freeze frame data - which I am not very familiar with and will research. (Also note that the gas mileage is worse that I could imagine even for this car, might be less than 8MPG)

Only code so far is P1316

FF Data:

Fuel 1: CL
Fuel 2: CL
Calc Load %: 42.7
ECT Deg F: 86
STFTB1: 3.9
LTFTB1: -3.9
STFTB2: -11.7
LTFTB2: -3.9
Eng RPM: 920
MPH: 0

I will research bur if anyone can help, please let me know.

Thanks again

[Spike555]

Your front O2's are bad, they are running in continuous closed loop, which means in basic terms...full choke all the time.
Replace your front O2's, Amazon has the best price.
Make sure you get the exact fit NOT the universals.

[rappo999]

Ordered the O2 Sensors. I will install next weekend. Thinking I will leave the VSS disconnected for a while. If codes go away with the new O2 sensors, then I can reconnect to see if things come back. This isn't a truck, it is a Rubik's Cube!

[Spike555]

Just to clarify I got it backwards, closed loop is normal warmed up and open loop if "full choke".

[rappo999]

I think it is solved!

Looks like it was coil packs. I installed a new (used) coil pack over the weekend. No check engine lights after 100 miles and all emissions sensors are good - first green light on the code reader since I got the truck. Fingers crossed, it is at my mechanic getting stickers...

Thanks to all for the help. Still a lot to do but it is driving very well!

[ihscouts]

Stickers cause misfires.

[Piranhaboy]

just had to replace my bank of coils. two were cracked and someone tried to stop the spark loss with a gob of silicone on each bad coil. i have a donor disco where i hauled the coils out. they aren't too difficult to remove if you take them all out together on the bracket. i even replaced the coils with the old ones still attached to the wires. i removed each wire at a time and pulled out the bad coil bank sliding the replacement down in its place. not difficult if you lie on top of the engine