Ok guys, I'm still chasing my heavy throttle miss, and am trying a few more smaller things before I yank the injectors outta this thing again. I keep reading about cross-firing between 7&8, and now even saw something about 1,3,5, and 6.

So, my question is two parts:

What's the best way to route the wires to avoid the cross-fire? (I really hope I don't get 5 engineers answers on this. If you want 5 ONLY ways to do something, just ask 5 engineers. I'm permitted to say this, I'm an engineer.)

How do I do this without making the wires look like a bear's butt sewn up with a grape vine?

Does anyone have a sketch or photo of the wire routing that looks decent and avoids the cross-fire issues? My assumption that the longer wires need to go to the rear cylinders is obviously not right, because they don't fit there very well either. There's no numbering on the Motorcraft wire set that I have, unlike the original equipment wires, or the Motorcraft set I put on my '86 T-bird (3.8L V6), so if I have the wrong assumption about the longest wires going to the plugs farthest away from the dizzy, maybe I'm creating my own problems?

I'm getting really anxious about this miss, because the truck is my daily driver, and I have to go across the only significant mountain on I-65 in Alabama twice every week. I don't want to kill my truck really dead by destroying the engine with this miss.

When on level ground or under light throttle, it runs sweet. Start up a significant grade that lasts more than about 15 seconds, and the sputter starts. If steep enough, or if it lasts long enough, the sputter turns into a dead miss until I get over the top and start back down hill. As soon as the throttle backs off, the miss cleans up again. Timing's dead on at 10 BTDC, new wires, new cap, new rotor, new plugs (before anyone starts pointing at 'em). Does exactly the same thing with Motorcraft plugs as it does with the Bosch Platinum II's. I cannot link the problem to ignition unless it is the cross-firing issue. I don't hear any pinging or rattling before the stumbling starts, which us usually the first sign of poor fuel, lean burn, or timing too advanced. I think the EEC may be detecting the knock, and retarding the timing as it's supposed to before I get a chance to hear it. Problem is, it can't correct enough for the miss, which brings me back to either plugged up injectors or constipated cats. When idling, it's got the tiniest bit of a stumble, and I don't feel the normal vibration on acceleration in 1st or 2nd that would indicate a burnt valve. I can gouge it in 1st or 2nd, and it doesn't miss a beat, but I don't want to send the pistons into orbit by trying to stay in it long enough to see if the problem starts happening. 3rd gear, and yeah, I start getting a slight stumble at about 50 mph or so. 4th or 5th, well, any time I wanna, I can make it stumble or miss. The miss is certainly worse with higher RPM and heavy throttle (highway speeds) than low RPM driving like city traffic and lugging the engine in upper gears.

My theory is, when I start up hills, the EEC is detecting spark-knock and dropping the timing. This would answer for lousy mileage, and absence of audible pinging when the miss starts. I've put the light on it, and yes, when I first pop the throttle open, the timing drops retard first before advancing. It does advance, though, which would explain the smooth running under light load. The plugs have little or no ash deposits, indicating a very lean running engine. None has any significant difference to the rest.

Any suggestions or diagrams would be appreciated on routing the wires. A picture's worth a thousand words, for sure.

 

exhaust clogged or o2 sensor bad.

 

Try changing the wire positions. I think that you are going to have to experment. If it works I am sure you can make the new routing look good.Not every vehicle will respond the same way. I read the post regarding wires crossing between spark plugs 7&8. It worked for a lot of guys, but not everyone. I had bad pinging a week ago and was going to start messing with the wires. I tried the next higher octane fuel and the problem disappeared.

 

im chasing this prob too mine comes and goes might be gas???? blocked egr nothing when i have no ping runs great then just poop out first and second gear runs fine hit third feels like it missing .......as my o2 is welded in and i have duels with headers and flowmasters im thinking need a chip to richen up mixture 4 these????????? plugs look like a lean burn i moved wires one day and it ran perfect 4 a few days then reverts to old crap????? im standing here beside old paint with this.......im thinking of changing vacume canister on fenderwell and intake gasket

 

Thanks for the recommendation, but I'm burning a tank every week now as it stands, getting about 250 miles out of 18 gallons (~14 mpg). 200 of that is interstate 65 between Birmingham and Decatur, AL. If I could figure out how to make it run on water, I would, just to cheat the greedy oil companies out of a few pennies. I couldn't afford to feed this thing on middle or premium grade, and besides, it's not a ping. It's a dead miss under load. At least one cylinder, if not two. Dunno if you saw my post in another thread, but I recently put a fuel pump on because of poor response to vacuum change. In addition, within the past 6 weeks or so, I've replaced the plenum gasket and cleaned the TB and IAC. I'm sure it isn't the IAC causing this problem, because it's from about 1/2 to WOT where I get the miss running highway speeds. If at low RPM, e.g. 40-45 mph in 5th, and I stick my toenails in the main bearings, it isn't a dead miss, but a very definite stutter and spit until I let up on it. The problem also seems to be worse after the temp gets up enough for closed loop, i.e. after the EEC starts leaning back on the fuel. I probably should have spent more time on the injectors, but, alas, got in too big a hurry. The little screens don't seem to be available locally, so I didn't pull 'em out at the risk of damaging one and not getting it back in. Ford dealers seem to be happy to sell me entire injectors, but no filter screens. I'm thinking new air compressor, another TB/Plenum gasket set, O-Rings, TPS, and side grinder cut-off discs are gonna be some of my purchases this weekend. I've been avoiding pulling the Y pipe to check the cats, simply because I'm sure I can't see down in the pipes, and it looks like it'll be a bear to pull out due to having to remove the tranny tail crossmember. If I pull it, I'm gutting the cats. 138K, they've done their job. No emissions testing here, so can open 'em up, gut 'em, and then weld the cans back together so it looks like they're still there. Should make for an interesting sound with a big hollow collector and resonator behind shorties and into a stock muffler. When I have a little more cash reserve, I'll get someone to build me some custom down pipes and hang a 2 in 2 out FlowMaster on it and stick the pipes out the side in front of the right rear like the Lightning package.

One thing I tried today, was downshifting to 4th at the bottom of the hill that gives me so much grief in 5th and let her snort at 75 mph. Even though the RPM was a lot higher, the throttle wasn't open as much because of lower gear giving me less engine load, so less intake and exhaust flow. More interesting, the miss wasn't nearly as bad, just an occasional light sneeze. I could tell there was a power imbalance in the cylinders too. Repeated the process on a couple other hills that also give me grief and got the same results. So, this is strongly pointing at mixture or exhaust problems. Truck runs beautifully up to about half throttle, and has ever so slight a stumble at idle. I can live with a light stumble at idle, but not a dead miss at highway speeds. Ping, yeah, I could fix with a slight timing adjustment or a little booster in the tank. But, I've run 93 in this truck, and it ran a LOT worse than it did on 87. Then again, that tank of 93 could have been what stained my fuel pump with rust. Tank was clean as a whistle inside. (well, a new whistle). Since repairing the plenum leaks, my city mileage has gone way up (about 12-13) because I can use the upper gears without it bucking and trying to tear the tranny and dif out. Based on another test I ran on the HEGO, the mixture's gotta be out of wack pretty severely for a long time before it's gonna give me a code. I drove 8 miles from cold engine in 100 degree weather at 60-70 mph before it finally turned on the CEL with the HEGO disconnected.

I really should write up some of these test procedures and post 'em for everyone. I've found some really neat ways to check fuel delivery, just by experimenting. Being a field service engineer, and spending 25 years learning to adapt and overcome on systems I had nothing to work with, I've got a little bit of an edge on the novice mechanic. I asked a dealer how they check the fuel pump, and they never mentioned using the pump test on the DLC. I did it using the pump test connection, and a vacuum pump to simulate engine vacuum to the FPR. Makes the work a lot cooler and a lot less dangerous.

Still hangin for any other ideas ....

 

As far as the wiring goes I've had good luck with Motorsports vs Motorcraft wires for HOs & 5.8s. They are numbered & have a good length. The best way to inexpensively loom them for functionality is with wire ties rather than the orig clips. Take one 8-10 inch tie & go round all 4 wires leaving to one bank. Then take 2 smaller 3-4 inch ties and go around the first tie between each adjacent wire, pulling them tight a bit at a time. This will allow you to space the wires as far apart as you wish ( while staying paralle over the VC ) and curve them down to the plugs, where you can cross them as needed, say 7&8. Can't beat the cost & they won't work loose from fatigue like the plastic clips.

 

I managed to come up with a scheme for routing the wires, and it turned out looking pretty good. Best of all, my heavy throttle miss went away!!!!. Bitten by the cross-fire gods, I guess. I've been chasing this problem for WEEKS. After seeing DO NOT and DO place 7/8 side by side, mine wasn't working as is, so I shuffled 'em a little. The wires for 7/8 were plenty long, so in the first loom, I ordered the wires 8,5,6,7. Over the valve covers, I turned 5 and 8 toward the front of the engine. 6 went straight down. I looped 8 back under 5 and 6 along the VC, behind the dip-stick brace and the coil bracket brace, and in the bottom hole of the 2 wire loom on the VC Stud. 7 went through the top hole and turned down, so this crossed 7 and 8, as well as kept them apart through the routing. No more dead miss (doing the hamster dance now).

I still have a very mild stutter at idle, which I attribute to the garbage we're getting for fuel now. I don't care where you buy it, it's gonna be the worst slop the oil companies can ship and still call gasoline. When ya get huge puddles of condensate out the tail pipe in mid summer, it should be a pretty good indicant of how much water content there is. I'm not missing any coolant, so I know it ain't me putting the water in it. I took the truck out on the interstate where it seems to have it's worst problems, and it would climb up to 90 MPH pretty quick in 5th without the normal sputtering.

I still think the cat's may be a little constipated, albeit a vacuum test doesn't show it. Revved the engine and held it at about 2000 RPM, and vacuum came back up to 22 inches. But, there still seems to be a bit of power loss on hills. Be that as it may, I went up one in 4th today that I've barely been able to make it up in 3rd for a long time.

 

That is great news about the plug wires. I have had the same cat for 14 years and only replaced it because I couldnt meet emissions. When removed it was perfectly clean inside but I guess the converter part was tired and I couldnt get the hc,s down to pass which the new converter did. Performance was not affected. I guess I am trying to say that if looked after these things can last a long time. The honey comb substate inside mine had a light cream color slightly darker than a new one, and when held up to the light you could see right through it end to end. Once in a blue moon mine will idle rough and almost stall. But it happens so infrequentlly and lasts only 15-30 seconds I am not to concerned.I expect this as the truck is 18 yeas old with 385,000 kilometers.