Miss at low RPM and heavy load

[tktrain]

Here's a drivability issue that has been dogging me for one heck of a long time. At about 3/4 throttle, just short of enough to cause the trans to downshift, I seem to be getting a miss or shudder. It feels like a plug misfiring or a lean miss. I notice it at roughly about 2200 to 3300 RPM, and I can't feel it at higher RPM's or at full throttle. I don't notice it during warm up while in open loop, either. The MAF is clean and I don't have any codes showing.

I am open to suggestions on where to start. I put this under modified due to my truck being pretty far from stock.

 

[mace]

re

I had the exact same symptoms. Had a pinhole in one of the spark plug wires. Never arced in the dark in the driveway, no codes. Just under load, and at 45-50 mph, and occasionally when it was raining. Could not see anything obvious. But when i replaced the wires, I found the tiny pinhole. They were silicone taylor brand too. Maybe I weakened it on installation, maybe a defect. i dunno. Couldnt believe i didnt get a misfire code.

 

[tktrain]

It almost seems like a cracked insulator on a spark plug, but I would think it would throw a code for misfire. I had a 24V DOHC 2.5L contour with this problem a couple of years ago and it turned out to be a cracked plug, but I really hate to just replace parts without knowing for sure. I guess I need to invest in a data logger to see if it shows a miss while accelerating. I would think it would set a pending code at the very least. I've been threatening for quite a while now to invest in the software and interface box to link to my laptop.

This has really been frustrating. If I could sort this one out I think I'll have everything where it needs to be on this machine.

 

[mace]

re

yea i couldnt believe it didnt throw out a misfire code. i mean, it was a damn misfire ! But it didnt, and I have seen the misfire code on other occasions. I'm serious, the pinhole was just that, and on the bottom part of the boot. not detectable until i one by one took them off and found it. I then bent the boot, it cracked, and you could see the tiny "wormhole" the arc was taking. might take some time to inspect them, but you may find it. and you might only have to replace one wire

 

[tktrain]

Thanks for the response Mace, I'll give the wires a good going over this weekend since I don't have to go to work after today until January 2nd.

I think I'm still going to break down and get the data logging soon, I think it will be a big help in the future.

 

[tktrain]

Update: I put a set of Autolite double platinums in yesterday gapped at 0.054" and the problem seems to have diminished somewhat, but the problem is still there. The old plugs, Motorcraft double plats, had about 75K on them and a couple of them had some deposits, 7 & 8 in particular. I'll post pictures soon. My OEM wires need to be replaced next, they have about 75K on them also. I'm torn between Taylors ans Auroras.

 

[MountaineerGreen]

Definitely check plug wires, mine had the same problem, I had a bad plug wire. Don't buy borg warrner replacements, they suck.

 

[mace]

re

i had the problem with the taylors, but i cant say if i stressed the wire installing, or if it was a defect. I ended up with bosch 8mm wires. they seem fine. i now have half taylors, half bosch installed, with 4 spare bosch's. i wouldnt use the bosch plugs though; many problems reported.

 

[tktrain]

Update: The #8 plug wire was bad, I temporarily reinstalled the #8 from the original set of wires that I replaced at 40K miles. The problem appears to be gone! I have a set of the blue Taylors on order, I should get them in by the end of the week.

 

[mace]

re:

awesome. i finally helped someone a little bit in here . it's always the other way around haha.

 

[tktrain]

Well, my blue Taylor 8mm Spiro Pro wires just arrived! These guys truly build a good looking product. Of course, for $100 they better look good and perform great. I really like the dark blue jackets with the black coil pack clips and the gray plug boots with fire sleeves.

 

[mace]

re :

They do look great dont they. I like the blue. I still have 4 in use. I did have the one fail, but I think that can happen to any silicone wire. Theyre pretty soft...The pic shows the hole. the hole was alot smaller originally, but has gotten a little bigger from showing people. the cracks happened when i twisted it off for inspection.

 

[Turdle]

Well, my blue Taylor 8mm Spiro Pro wires just arrived! These guys truly build a good looking product. Of course, for $100 they better look good and perform great. I really like the dark blue jackets with the black coil pack clips and the gray plug boots with fire sleeves.

they came with socks???
Where did you get them?

 

[Turdle]

the hole was alot smaller originally, but has gotten a little bigger from showing people

That is what my second girlfriend said!!

 

[mace]

re

hahahaha i walked right into that one hahaha

my kit came with 4 socks

 

[tktrain]

My wire set came with four of the fire sleeves as well, on numbers 3 & 4, and 7 & 8. I installed the new Taylors this morning and I am very happy with the way that it went. The new wires are within about 1/2" +/- each of the length of the OEM wires. The new wires have completely solved the miss issue I have had as long as I can remember. I have had the issue through basically the life of two sets of OEM wires. I can honestly say that I didn't know that this truck could run this well! I always kind of figured that I had picked up a slight lean condition as a result of all my mods. Who knew!

I do have a request for the Taylor people however: please put cylinder numbers on the wires like the OEM wires have. It makes installation nearly foolproof when they have numbers! It's not a huge big deal, but it sure would be nice to have.

Mace: regarding your plug boot failure, did you use dielectric grease on the plugs when you installed the wires? Without it the silicone boots will almost become a part of the plug and they will be almost impossible to get off without damaging the boot.

 

[mace]

re:

i used the grease, but sparingly. maybe too sparingly. but they werent fused to the plugs, though. I think I just got a bad one. The 4 still there are now 18 months with no trouble. looks funny though, half blue, half grey haha

 

[ProjectAviator]

I have never been impressed with Taylor wires. I put a set on my 70 GTO and had problems with 2 of the wires. Never had problems with Accel or MSD ( Ford racing wires are MSDs)

Tim