Engine Runs Rough (misfires) under load
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Engine Runs Rough (misfires) under load
Hello, and thanks in advance for your advice.
I'll first describe history and symptoms, and present several alternative solution paths I have thought of so far to solve the problem. I'm very interested in your opinions, reactions to the history and symptoms, and your suggested solution paths.
History and Symptoms
I've owned a 1997 F150 V8 since second-hand purchase about 2000. Currently, just about at 100,000 miles. I have an auto transmission. Has run perfectly, use Mobil One, do my own maint. checks as per Ford manual at recommended times, careful owner.
Engine and Truck has run perfectly for 4 years between April 2000 and April 2004.
In 1991, my son and I damaged the tranny pan and solenoid pack using poor judgement during a hellacious mountain off-road run over rocks. Replaced tranny pan and solenoid pack myself, and all has been well since.
After perfect running during a trip to AZ this last April, I washed and waxed the truck, and used Gunk engine clearner followed by a pressurized garden hose to clean engine thoroughly.
The use of Gunk was probably a second episode of poor judgement.
(Last year, I cleaned engine with substantilly higher pressurized soapy spray gun at a car cleaning garage, with no problems. No Gunk was used last year.)
Engine starts normally, but under load my truck bucks: on level or slightly downhill surfaces at cruise speed, no problem; as soon as truck runs on slight or major up-hill grade in any gear, passengers are treated to clearly uneven engine performance, as if one or more cylinders is misfiring. The ride can become very shaky.
Bucking is reduced if I shift to second gear going up a steep hill.
Engine check light is on continuously, but during bucking episodes, engine check light is flashing.
All other engine performance is normal; engine starts easily and immediately, cruise control fine, tranny works as normal, fluids normal, etc.
First thought was that water got into wiring, and after driving for a day on return from AZ to CO, it would go away. That did not happen.
Three careful visual checks of all wiring, pulling gently on spark plug cables failed to find any loose wiring or any obvious visual problem.
Two stops at Ford F150 Dealers during CO return resluted in following comments: "Check for loose wiring; electrical system is wet and will dry; you can drive the truck, and not worry about further damage to engine even though engine is running unevenly; you can drive the remaining 600 miles back to CO and not worry; when you get home, go to your Ford Dealer and pay the $80 to $100 just to have their computer run a diagnostic to see what the 'engine check' light means."
Completion of the trip to CO, and about 8 weeks of sitting with short drives (2-3 miles) around town, and the uneven engine running continues. No change with time since "engine cleaning" in AZ. Bucking is reduced if I shift from Drive into second gear while driving up-hill on mountain roads.
Possible Solution Paths
1) Get a computer to run the diagnostic: I hate to hand over $100 to a Ford Dealer/Service Center just to run a computer diagnostic on my truck. Since I plan to own the truck until 2016, I would rather invest in a hand held computer ($300?) that plugs into the Ford and do my own computer diagnostics, now and in the future. Where can I buy such a computer at a reasonable price, or can I run a cable from my home PC (after sofware is installed) out to the driveway where the F150 is? This solution path is to run the diagnostic, and then go from there.
2) Forget about running the computer diagnostic, and work on solving the problem. You can unhook the battery for 20 Mins once the problem is solved, and the "check engine" flashing message will be erased, anyway:
a) Replace all the spark plugs, since the truck is at the 100,000 mile point, and the Ford manual says to do this now anyway.
b) Try to find out where the places are that Gunk may have gotten on the sensors, and clean the sensors. Here, we assume that Gunk is somehow fouling up a crucial sensor, which, under normal conditions, sends data to the engine's computer. A fouled up sensor is the cause of the problem. (Here, I am open to your suggestions as to which sensors I should check, where they are located, how you get at them and the technique you use to clean one or more of them).
c) You must have missed a wire that was loosened by the force of the hose when you cleaned the engine. (Here, I would like your suggestions as to how to find a possible loose wire, and how to be sure that one or more wires is properly connected.)
d) Here, I am open to other suggestions you may have as to the cause of the problem, and tests I might run to find the problem and correct it (without a full blown computer diagnostic of the 'check engine' flashing light).
Thank you for reading my post and contributing suggestions.
My best,
Peter
I'll first describe history and symptoms, and present several alternative solution paths I have thought of so far to solve the problem. I'm very interested in your opinions, reactions to the history and symptoms, and your suggested solution paths.
History and Symptoms
I've owned a 1997 F150 V8 since second-hand purchase about 2000. Currently, just about at 100,000 miles. I have an auto transmission. Has run perfectly, use Mobil One, do my own maint. checks as per Ford manual at recommended times, careful owner.
Engine and Truck has run perfectly for 4 years between April 2000 and April 2004.
In 1991, my son and I damaged the tranny pan and solenoid pack using poor judgement during a hellacious mountain off-road run over rocks. Replaced tranny pan and solenoid pack myself, and all has been well since.
After perfect running during a trip to AZ this last April, I washed and waxed the truck, and used Gunk engine clearner followed by a pressurized garden hose to clean engine thoroughly.
The use of Gunk was probably a second episode of poor judgement.
(Last year, I cleaned engine with substantilly higher pressurized soapy spray gun at a car cleaning garage, with no problems. No Gunk was used last year.)
Engine starts normally, but under load my truck bucks: on level or slightly downhill surfaces at cruise speed, no problem; as soon as truck runs on slight or major up-hill grade in any gear, passengers are treated to clearly uneven engine performance, as if one or more cylinders is misfiring. The ride can become very shaky.
Bucking is reduced if I shift to second gear going up a steep hill.
Engine check light is on continuously, but during bucking episodes, engine check light is flashing.
All other engine performance is normal; engine starts easily and immediately, cruise control fine, tranny works as normal, fluids normal, etc.
First thought was that water got into wiring, and after driving for a day on return from AZ to CO, it would go away. That did not happen.
Three careful visual checks of all wiring, pulling gently on spark plug cables failed to find any loose wiring or any obvious visual problem.
Two stops at Ford F150 Dealers during CO return resluted in following comments: "Check for loose wiring; electrical system is wet and will dry; you can drive the truck, and not worry about further damage to engine even though engine is running unevenly; you can drive the remaining 600 miles back to CO and not worry; when you get home, go to your Ford Dealer and pay the $80 to $100 just to have their computer run a diagnostic to see what the 'engine check' light means."
Completion of the trip to CO, and about 8 weeks of sitting with short drives (2-3 miles) around town, and the uneven engine running continues. No change with time since "engine cleaning" in AZ. Bucking is reduced if I shift from Drive into second gear while driving up-hill on mountain roads.
Possible Solution Paths
1) Get a computer to run the diagnostic: I hate to hand over $100 to a Ford Dealer/Service Center just to run a computer diagnostic on my truck. Since I plan to own the truck until 2016, I would rather invest in a hand held computer ($300?) that plugs into the Ford and do my own computer diagnostics, now and in the future. Where can I buy such a computer at a reasonable price, or can I run a cable from my home PC (after sofware is installed) out to the driveway where the F150 is? This solution path is to run the diagnostic, and then go from there.
2) Forget about running the computer diagnostic, and work on solving the problem. You can unhook the battery for 20 Mins once the problem is solved, and the "check engine" flashing message will be erased, anyway:
a) Replace all the spark plugs, since the truck is at the 100,000 mile point, and the Ford manual says to do this now anyway.
b) Try to find out where the places are that Gunk may have gotten on the sensors, and clean the sensors. Here, we assume that Gunk is somehow fouling up a crucial sensor, which, under normal conditions, sends data to the engine's computer. A fouled up sensor is the cause of the problem. (Here, I am open to your suggestions as to which sensors I should check, where they are located, how you get at them and the technique you use to clean one or more of them).
c) You must have missed a wire that was loosened by the force of the hose when you cleaned the engine. (Here, I would like your suggestions as to how to find a possible loose wire, and how to be sure that one or more wires is properly connected.)
d) Here, I am open to other suggestions you may have as to the cause of the problem, and tests I might run to find the problem and correct it (without a full blown computer diagnostic of the 'check engine' flashing light).
Thank you for reading my post and contributing suggestions.
My best,
Peter
Technical Article Contributor
Joined: May 2004
Posts: 6,509
Likes: 6
From: Georgia on my mind...
A flashing check engine light means you've got a catalyst damaging misfire (read: raw fuel is getting dumped into the exhaust because a plug isn't firing) My guess is water found it's way into a plug well(s) when you steam cleaned the engine.
In the interim, you could tote the truck to Autozone and get a freebie code check. My guess is you'll see P0300 (Multiple random misfire) or a specific misfire code for a cylinder (P0301, cylinder 1, P0302, cylinder 2...)
In regards to scan tools, you could if you really, really wanted to, buy the real deal Ford NGS that dealers use for about $2600 new. Or, you could do like I'll do someday when I pay off these @#!@$!@!!! credit card bills, and buy anAutoDiag for about $450. You'll need a PDA, but it looks awful impressive for what you pay. Covers powertrain, restraint, and ABS, PID monitoring, and all sorts of other goodies that I'm gonna stop mentioning before I buy one right now myself.
Run it down to Autozone and get the freebie code check and let us know what you got, and we go from there in the meantime.
In the interim, you could tote the truck to Autozone and get a freebie code check. My guess is you'll see P0300 (Multiple random misfire) or a specific misfire code for a cylinder (P0301, cylinder 1, P0302, cylinder 2...)
In regards to scan tools, you could if you really, really wanted to, buy the real deal Ford NGS that dealers use for about $2600 new. Or, you could do like I'll do someday when I pay off these @#!@$!@!!! credit card bills, and buy anAutoDiag for about $450. You'll need a PDA, but it looks awful impressive for what you pay. Covers powertrain, restraint, and ABS, PID monitoring, and all sorts of other goodies that I'm gonna stop mentioning before I buy one right now myself.
Run it down to Autozone and get the freebie code check and let us know what you got, and we go from there in the meantime.
Technical Article Contributor
Joined: Oct 2003
Posts: 1,490
Likes: 0
From: Topeka Kansas
Member
Joined: Jan 2009
Posts: 22
Likes: 0
From: Putnam County NY
2000 5.4 p0300 p0302
Just finished a head gasket job. Installed r4e built heads and put everything back together. Ran truck fine till I took it on the road, it is chugging and running rough. Drove it until I got the codes, p0300 and p0302. Some history. We installed new plugs and the COP are global and are one year old. Last year had a similar problem with light on, light blinking. Got it to a shop and the error had cleared and I was told the injector #2 was likely clogged and cleared itself thus no error. How likely is it the injector is the problem here? I am open for suggestions.