When to replace Ignition coils. (2 Viewers)
- Thread starter 2001LC
- Start date
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Replaced all coils (Denso 673-1303) over the past few months, doing two per month. Finished-up with the last two and replaced all plugs w/ Denso Iridium TT (4702). Seemed smoother at speed, but didn't notice much difference in anything else.
Then replaced PVC hose and both little foam mittens. Valve seemed a little sticky, so soaked in solvent and blew out.
Mileage improved about 10%. Idle remains at around 600-750 depending upon temp & hvac.
Still seems a little rough at idle, so I assume it's time to replace all vacuum lines...
Then replaced PVC hose and both little foam mittens. Valve seemed a little sticky, so soaked in solvent and blew out.
Mileage improved about 10%. Idle remains at around 600-750 depending upon temp & hvac.
Still seems a little rough at idle, so I assume it's time to replace all vacuum lines...
fooldall1
Handy Enthusiast
250k Here, have replaced all but 3 original coils and plugs. It may be worth noting that when the cylinder misfire causes a CEL I ALWAYS replace the plug as well.
Still no luck with the issue.
Went to a mechanic friend with a scanner, all parameters in spec, all looks good.
However the next day same stuttering which goes away after about 20 kms. Weird.
Went to a mechanic friend with a scanner, all parameters in spec, all looks good.
However the next day same stuttering which goes away after about 20 kms. Weird.
Dropped the fluid a few weeks ago and replaced it with fresh.
Level was good, will check tonight.
Finally got around to replacing the coils and plugs. Truck is a 2005 with 150,076 with no known issues. Idling at a stop light isn’t always super steady but not rough or bad sounding either. This was more of a PM replacement as I wasn’t sure on the age of the plugs. I’m assuming the plugs have been replaced at some point by the PO as they were NGK plugs. Truck seems to run a bit smoother but the Scanguage is showing similar numbers to before the replacement. The first tank of gas seems to be better though. I’ve been averaging around 16 to 16.5 for my everyday use and hit the half tank mark at 160 miles. First tank was at 175 miles at the halfway mark and I’m over 17.5 mpg. I’ll take whatever improvements I can get.
Want to add a bit more info.
All 8 plugs looked good and were between .042 and .043 inch gap. I know I could have reused them but for the price, I couldn’t see going through the hassle just to put in used plugs.
All 8 coil packs looked almost new. A little bit of brown up inside the boot but the boot was otherwise like new. No discoloration or cracks and they were just as pliable as the new ones. My dad and brother both have 4.7 powered Tundra’s with over 150k miles each so I’m sure they will get used at some point. Good to have spares.
All 8 plugs looked good and were between .042 and .043 inch gap. I know I could have reused them but for the price, I couldn’t see going through the hassle just to put in used plugs.
All 8 coil packs looked almost new. A little bit of brown up inside the boot but the boot was otherwise like new. No discoloration or cracks and they were just as pliable as the new ones. My dad and brother both have 4.7 powered Tundra’s with over 150k miles each so I’m sure they will get used at some point. Good to have spares.
2001LC
SILVER Star
- Thread starter
- #194
I re post what I just posted in the PCV thread for you.
In severe vacuum cases, I'll say YES!
It can cause excessive oil to pass oil ring and carbon up compression ring and foul spark plugs. Even before that it may blow oil into spark plug tubes, filling them with oil. This may affect temp of coil and spark. Vacuum leaks, will alter manifold pressure. So YES, a number of issue can result.
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Thanks. Will this stop after say 15 kms driving?
My thinking is that maybe when the engine is warm, the hose might be closed again.
My thinking is that maybe when the engine is warm, the hose might be closed again.
2001LC
SILVER Star
- Thread starter
- #196
Everything expands when heated. Including intake manifold gasket, which is more of issue in the VVTi engine. It also tightens spark plugs, coil boots, compression rings, etc. Coils on plugs (COP) themselves have more issue when hot as resistance goes up.
I go through the engine and tune. This means checking spark plugs, coils, all vacuum line, clean T-body, air filter, oil& filter, and spray MAF clean with battery disconnected for 20 minutes. Weak voltage from bad battery and oxidation on battery post/clamps can have it's affect also. Toss in a can of 44K (or any good fuel system/fuel injector cleaner) in gas tank.
I go through the engine and tune. This means checking spark plugs, coils, all vacuum line, clean T-body, air filter, oil& filter, and spray MAF clean with battery disconnected for 20 minutes. Weak voltage from bad battery and oxidation on battery post/clamps can have it's affect also. Toss in a can of 44K (or any good fuel system/fuel injector cleaner) in gas tank.
After a recent hunt for 'which one is the failing coil' without a CEL, I learned two things.
- Don't assume the failing coil is the one with the lengthwise crack in it. I had 3 coils with cracks, all of them turned out to be fine. The one that had failed looked pristine (and the spark plug too).
- Even though there are missfires, the CEL might not be on. In Techstream the missfire counter can be monitored. However every few seconds (15 or so?) it resets. So for an occasional missfire it is really difficult to find the failing coil. Every time I plugged in the computer after a missfire, all counters read '0'. So I used the recording function and went for a drive till I felt the missfire and then looked at the data. Not sure why the counter would be reset the whole time. But it would be a lot more convenient if the counter kept increasing till the next engine start.
2001LC
SILVER Star
- Thread starter
- #200
When checking for misfire in tech stream. I find it helpful to put engine under load. This can be done by holding brake on with left foot. Put transmission into gear (i.e. "D"). Then raise RPM with right foot on gas, to 1,500 RPM or so.
Just because a coil looks new doesn't mean it's firing properly. But ones that are crack will not last, nor likely be firing at peak performance.
The really tough part is finding coils that aren't operating peak performance, like as when new. Without the specialize equipment shown in OP.
I've found that if engine is well tuned (i.e no vacuum leaks, tested and rebuilt fuel injectors, new spark plugs, new air filter, clean properly MAF sensor, properly operating OAT & water temp sensor, clean throttle body, de- carboned pistons & valves, proper voltage, coolant system to spec, etc.). I'll smell gas from exhaust after warm up, and when giving full throttle to enter HWY or pass. I'll feel ever so slight hesitation in acceleration. Swap in a new set of coils and gas smell goes away, and acceleration is flawless.
Whereas split coils may still operate and not show misfire. The split is sign of running excessively hot. Heat is the enemy of coils. Two main reason for excessive heat being created in coils IMHO is:
1) Gap of spark plug is out of spec (new is 1.1mm, at 1.3mm they must be replaced). The larger the gap the more current delivered from the coil. The more current produced by coil the hot it gets internally.
2) Spare plugs walking out. The hot gasses escape from combustion camber passed the spark plugs (SP) thread into the SP tube. This heat coils from outside. Additionally as plugs walk out (loosen) they seal (expand from heat) as engine reaches op temp. But once plugs become to loose it no longer seals. Then hot gasses escape even at op temp. As SP electrode (tip) moves further away form optimally firing point and enters thread area of head, the coil keeps delivery more power. This not only overheats coil. But it will blow the spark plug out of the head. A search in mud, will produce pictures/accounts of Spark Plugs blown out of the head.
Spark Plugs that have a brown halo are "typically" slightly loose SP, that expand and seal at OP TEMP. The boots of coils brown and harden.
Spark plugs and coils boots that are blackening, are those that "typically" are so loose they don't seal be expansion at OP TEMP.
#3 coil was the loosest. Notice the blackening of plug and coil boot. This one was very close to blowing out of the head.
Coils and spark plugs (junk Bosch platinum, I'd never use them) are in order. With #1 in upper LH corner and #2 in RH upper corner. The tube oil seal where not leaking:
Just because a coil looks new doesn't mean it's firing properly. But ones that are crack will not last, nor likely be firing at peak performance.
The really tough part is finding coils that aren't operating peak performance, like as when new. Without the specialize equipment shown in OP.
I've found that if engine is well tuned (i.e no vacuum leaks, tested and rebuilt fuel injectors, new spark plugs, new air filter, clean properly MAF sensor, properly operating OAT & water temp sensor, clean throttle body, de- carboned pistons & valves, proper voltage, coolant system to spec, etc.). I'll smell gas from exhaust after warm up, and when giving full throttle to enter HWY or pass. I'll feel ever so slight hesitation in acceleration. Swap in a new set of coils and gas smell goes away, and acceleration is flawless.
Whereas split coils may still operate and not show misfire. The split is sign of running excessively hot. Heat is the enemy of coils. Two main reason for excessive heat being created in coils IMHO is:
1) Gap of spark plug is out of spec (new is 1.1mm, at 1.3mm they must be replaced). The larger the gap the more current delivered from the coil. The more current produced by coil the hot it gets internally.
2) Spare plugs walking out. The hot gasses escape from combustion camber passed the spark plugs (SP) thread into the SP tube. This heat coils from outside. Additionally as plugs walk out (loosen) they seal (expand from heat) as engine reaches op temp. But once plugs become to loose it no longer seals. Then hot gasses escape even at op temp. As SP electrode (tip) moves further away form optimally firing point and enters thread area of head, the coil keeps delivery more power. This not only overheats coil. But it will blow the spark plug out of the head. A search in mud, will produce pictures/accounts of Spark Plugs blown out of the head.
Spark Plugs that have a brown halo are "typically" slightly loose SP, that expand and seal at OP TEMP. The boots of coils brown and harden.
Spark plugs and coils boots that are blackening, are those that "typically" are so loose they don't seal be expansion at OP TEMP.
#3 coil was the loosest. Notice the blackening of plug and coil boot. This one was very close to blowing out of the head.
Coils and spark plugs (junk Bosch platinum, I'd never use them) are in order. With #1 in upper LH corner and #2 in RH upper corner. The tube oil seal where not leaking:
