I have a friend that bought a 97 F150 4.6 about a year ago. It recently started spark knocking horribly so they got the plugs changed and replaced all four o2 sensors. Now the spark knock is back very bad under load and the engine misses really bad. Any ideas? Maybe a knock sensor? Haven't had a chance to see if the CEL is back on. (It was showing a code for o2 sensor before they were replaced.) Any input is appreciated.
Need help with 97 F150
- Thread starter SubyRoo
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May want to do a piston soak or run a can or two of combustion chamber cleaner through it. I had a 1998 F150 with the 5.4 in the shop earlier this week. It was in for some bad coils, but has also been burning oil, I replaced a collapsed PCV elbow and sprayed a can of MOPAR combustion chamber cleaner through it to clean the oil out of the intake. The customer said it helped with the spark knock problem he has had for a while.
The MOPAR cleaner was less than $7 a can at my local dealer.
The MOPAR cleaner was less than $7 a can at my local dealer.
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Originally Posted By: eljefino
I'd take a look if it's running lean and if something like the MAF is screwed up.
X2.
I'd take a look if it's running lean and if something like the MAF is screwed up.
X2.
It could be clogged or weak injectors, or the fuel pump could be on its way out. You have to have a very serious misfire for the CEL to come on. How many miles are on it? If the wires and coil packs are original I would replace them immediately. If you still have a misfire after this I would look at the injectors. The spray holes on the injectors are insanely small and the smallest bit of crud can cause a problem. It sucks I know, as even reman injectors are not cheap, but this may be what your friend needs to do to sort it out.
does it have wires oil coil packs? Wire problems show up under load, especially lower rpms.
carbon buildup can cause predetonation. Seafoam or similar treatment would be best--- heck go old school and just dribble water, it works. if not comfortable (and if you like the neighbors) then have an induction cleaning service done by a shop.
Lean fuel condition cause cause this as well, which I'd put less likely on the list - filter, check pump pressure, dirty injectors, lazy map/maf.
carbon buildup can cause predetonation. Seafoam or similar treatment would be best--- heck go old school and just dribble water, it works. if not comfortable (and if you like the neighbors) then have an induction cleaning service done by a shop.
Lean fuel condition cause cause this as well, which I'd put less likely on the list - filter, check pump pressure, dirty injectors, lazy map/maf.
Originally Posted By: Rob_Roy
Originally Posted By: eljefino
I'd take a look if it's running lean and if something like the MAF is screwed up.
X2.
X3, will throw lean codes and cause spark knock if MAF is dirty...
Five minutes and a can of spray cleaner fixes 49 out of 50...
Originally Posted By: eljefino
I'd take a look if it's running lean and if something like the MAF is screwed up.
X2.
X3, will throw lean codes and cause spark knock if MAF is dirty...
Five minutes and a can of spray cleaner fixes 49 out of 50...
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Originally Posted By: TFB1
Originally Posted By: Rob_Roy
Originally Posted By: eljefino
I'd take a look if it's running lean and if something like the MAF is screwed up.
X2.
X3, will throw lean codes and cause spark knock if MAF is dirty...
Five minutes and a can of spray cleaner fixes 49 out of 50...
x4.
Originally Posted By: Rob_Roy
Originally Posted By: eljefino
I'd take a look if it's running lean and if something like the MAF is screwed up.
X2.
X3, will throw lean codes and cause spark knock if MAF is dirty...
Five minutes and a can of spray cleaner fixes 49 out of 50...
x4.
DFPE sensor cured years of chronic pinging / spark knocking on my 01 Taurus.
It kept causing the engine to run lean all the time.
It kept causing the engine to run lean all the time.
A faulty ERG system will do this [part to mid throttle].
Advanced ignition timing, running too hot, bad coolant sensor, TPS, MAF, jumped timing chain, are all possibilities.
Narrow it down? That's why mechanics exist - to look and diagnose.
It's tough over the internet.
Advanced ignition timing, running too hot, bad coolant sensor, TPS, MAF, jumped timing chain, are all possibilities.
Narrow it down? That's why mechanics exist - to look and diagnose.
It's tough over the internet.
^^^So right, you are unlikely to get a correct diagnosis over the Net.
And diagnosis is the key to any repair. Don't want to just throw parts at it.
And diagnosis is the key to any repair. Don't want to just throw parts at it.
Originally Posted By: SteveSRT8
^^^So right, you are unlikely to get a correct diagnosis over the Net.
Well, I generally agree with that. Here you have a handful of actual techs/former techs/really good parts guy who are on the ball, and a lot of wannabes that should read and not type.
'97 4.6 with pinging/detonation/miss on accel. First, pull codes, look for lean codes on both banks, or a combination of both rich and lean codes. If you can pull data, look at fuel trims. Rich at idle, lean on accel means there is a 99% your MAF is kaput. If you suspect a MAF, unplug it, cycle the key a few times and go for a drive with it disconnected.
Misses on light accel usually due to wires. A bad MAF will usually cause a "bog" on accel. You got to have a really bad MAF to get an actual lean miss. FoMoCo isued a lot of PCM updates for pinging.
If you confirm a faulty MAF, great. If not, post back and I will get out the "H" manual.
^^^So right, you are unlikely to get a correct diagnosis over the Net.
Well, I generally agree with that. Here you have a handful of actual techs/former techs/really good parts guy who are on the ball, and a lot of wannabes that should read and not type.
'97 4.6 with pinging/detonation/miss on accel. First, pull codes, look for lean codes on both banks, or a combination of both rich and lean codes. If you can pull data, look at fuel trims. Rich at idle, lean on accel means there is a 99% your MAF is kaput. If you suspect a MAF, unplug it, cycle the key a few times and go for a drive with it disconnected.
Misses on light accel usually due to wires. A bad MAF will usually cause a "bog" on accel. You got to have a really bad MAF to get an actual lean miss. FoMoCo isued a lot of PCM updates for pinging.
If you confirm a faulty MAF, great. If not, post back and I will get out the "H" manual.
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