8mpg and 0-60mph in 22 seconds, something's wrong with my truck
07-09-2016, 02:31 PM
#1
8mpg and 0-60mph in 22 seconds, something's wrong with my truck
The truck is a 2004 Ford F150 Lariat crewcab with 117k miles on it.
The issue is very poor performance and fuel economy. I'm having trouble accelerating, particularly between 20 and 50mph, to the tune of 0-60mph in 22 seconds. My mileage has also dropped from a historical 15-16mph to 8-9mpg. When accelerating (pedal to the floor) the RPM needle climbs very slowly, at the same pace (roughly) as the speed. That, to me, indicates that it's not a transmission issue. When the vehicle is cold, it performs normally, for a brief period, but at operating temp it performs very poorly. There are zero codes thrown.
So far, I've confirmed that the vacuum is normal (steady at 20 in-Hg), the throttle body is clean, the MAF sensor is clean, the air filter is clean, there are no obstructions in the air intake, I replaced the fuel filter just to be sure (easy and cheap), and there are no fuel leaks or oil leaks to be found. I also checked the coolant and it's kinda on the opaque side, but yellow, not bubbly. There seems to be a little bit of buildup along a couple thin vertical sections of the coolant reservoir as well, looks almost like calcium deposits.
I took it to a shop that also confirmed that the spark plugs are good, ignition coils are good, compression is good, timing is spot-on, fuel pressure is good, injectors are clean, and the backpressure test didn't show problems. The shop tech didn't charge me anything because he couldn't find the problem, but he surmised that it could possibly be the catalytic converters even though the backpressure test didn't show issues - he said that the O2 sensor being in the middle of the cat might make it hard to determine if there's an issue with the backpressure test. However, both catalytic converters are brand new, though only $180 muffler shop chop off / weld on deals (Eastern Catalytic, I think). The tech mentioned that there were misfire codes being thrown while he test drove it hooked up to a computer, but none of them were stored and they didn't indicate which cylinder.
I'm at a loss for what the issue might be. I'm going to try one disconnecting the exhausts and running without the pipes & cats connected to rule that out, but I'm not optimistic.
The issue is very poor performance and fuel economy. I'm having trouble accelerating, particularly between 20 and 50mph, to the tune of 0-60mph in 22 seconds. My mileage has also dropped from a historical 15-16mph to 8-9mpg. When accelerating (pedal to the floor) the RPM needle climbs very slowly, at the same pace (roughly) as the speed. That, to me, indicates that it's not a transmission issue. When the vehicle is cold, it performs normally, for a brief period, but at operating temp it performs very poorly. There are zero codes thrown.
So far, I've confirmed that the vacuum is normal (steady at 20 in-Hg), the throttle body is clean, the MAF sensor is clean, the air filter is clean, there are no obstructions in the air intake, I replaced the fuel filter just to be sure (easy and cheap), and there are no fuel leaks or oil leaks to be found. I also checked the coolant and it's kinda on the opaque side, but yellow, not bubbly. There seems to be a little bit of buildup along a couple thin vertical sections of the coolant reservoir as well, looks almost like calcium deposits.
I took it to a shop that also confirmed that the spark plugs are good, ignition coils are good, compression is good, timing is spot-on, fuel pressure is good, injectors are clean, and the backpressure test didn't show problems. The shop tech didn't charge me anything because he couldn't find the problem, but he surmised that it could possibly be the catalytic converters even though the backpressure test didn't show issues - he said that the O2 sensor being in the middle of the cat might make it hard to determine if there's an issue with the backpressure test. However, both catalytic converters are brand new, though only $180 muffler shop chop off / weld on deals (Eastern Catalytic, I think). The tech mentioned that there were misfire codes being thrown while he test drove it hooked up to a computer, but none of them were stored and they didn't indicate which cylinder.
I'm at a loss for what the issue might be. I'm going to try one disconnecting the exhausts and running without the pipes & cats connected to rule that out, but I'm not optimistic.
07-09-2016, 04:03 PM
#3
Senior Member
Any brake smell due to brakes hanging up?
07-09-2016, 07:57 PM
#5
Senior Member
Maybe the e-brake? Sometimes they get hung up.
Fpdm? Could that cause this?
Injectors?
Fpdm? Could that cause this?
Injectors?
07-09-2016, 08:17 PM
#6
Howdy.
This:
... Seems to suggest the problem occurs during the transition from open loop to closed loop operation. In other words, when the front O2's take over with fueling. A competent shop can instrument the front O2's fer laziness / inop.
Another facet of closed loop is - the engine temp needs to reach at least 180-190 degrees, or it may not transition properly. Something as simple as a malfunctioning thermostat ( e.g stuck open) can aggravate this.
Refer to: http://www.fordservicecontent.com/fo...t/OBDSM407.pdf fer ( a lot) more info.
Th abbove is just a s.w.a.g. The lack of pending/stored codes is troubling - misfires are a significant issue if left unaddressed. Don't think the plugs were checked as 'good' unless the mech actually pulled them to see - not trivial on a 2004 with 100K+ miles. Doubtful...They are overdue in any case - Ford specifies 60K R&R on plugs fer that year. Gap growth contributes to random misfires.
Good luck
MGD
This:
"When the vehicle is cold, it performs normally, for a brief period, but at operating temp it performs very poorly.
Another facet of closed loop is - the engine temp needs to reach at least 180-190 degrees, or it may not transition properly. Something as simple as a malfunctioning thermostat ( e.g stuck open) can aggravate this.
Refer to: http://www.fordservicecontent.com/fo...t/OBDSM407.pdf fer ( a lot) more info.
Th abbove is just a s.w.a.g. The lack of pending/stored codes is troubling - misfires are a significant issue if left unaddressed. Don't think the plugs were checked as 'good' unless the mech actually pulled them to see - not trivial on a 2004 with 100K+ miles. Doubtful...They are overdue in any case - Ford specifies 60K R&R on plugs fer that year. Gap growth contributes to random misfires.
Good luck
MGD
The truck is a 2004 Ford F150 Lariat crewcab with 117k miles on it.
The issue is very poor performance and fuel economy. I'm having trouble accelerating, particularly between 20 and 50mph, to the tune of 0-60mph in 22 seconds. My mileage has also dropped from a historical 15-16mph to 8-9mpg. When accelerating (pedal to the floor) the RPM needle climbs very slowly, at the same pace (roughly) as the speed. That, to me, indicates that it's not a transmission issue. When the vehicle is cold, it performs normally, for a brief period, but at operating temp it performs very poorly. There are zero codes thrown.
So far, I've confirmed that the vacuum is normal (steady at 20 in-Hg), the throttle body is clean, the MAF sensor is clean, the air filter is clean, there are no obstructions in the air intake, I replaced the fuel filter just to be sure (easy and cheap), and there are no fuel leaks or oil leaks to be found. I also checked the coolant and it's kinda on the opaque side, but yellow, not bubbly. There seems to be a little bit of buildup along a couple thin vertical sections of the coolant reservoir as well, looks almost like calcium deposits.
I took it to a shop that also confirmed that the spark plugs are good, ignition coils are good, compression is good, timing is spot-on, fuel pressure is good, injectors are clean, and the backpressure test didn't show problems. The shop tech didn't charge me anything because he couldn't find the problem, but he surmised that it could possibly be the catalytic converters even though the backpressure test didn't show issues - he said that the O2 sensor being in the middle of the cat might make it hard to determine if there's an issue with the backpressure test. However, both catalytic converters are brand new, though only $180 muffler shop chop off / weld on deals (Eastern Catalytic, I think). The tech mentioned that there were misfire codes being thrown while he test drove it hooked up to a computer, but none of them were stored and they didn't indicate which cylinder.
I'm at a loss for what the issue might be. I'm going to try one disconnecting the exhausts and running without the pipes & cats connected to rule that out, but I'm not optimistic.
The issue is very poor performance and fuel economy. I'm having trouble accelerating, particularly between 20 and 50mph, to the tune of 0-60mph in 22 seconds. My mileage has also dropped from a historical 15-16mph to 8-9mpg. When accelerating (pedal to the floor) the RPM needle climbs very slowly, at the same pace (roughly) as the speed. That, to me, indicates that it's not a transmission issue. When the vehicle is cold, it performs normally, for a brief period, but at operating temp it performs very poorly. There are zero codes thrown.
So far, I've confirmed that the vacuum is normal (steady at 20 in-Hg), the throttle body is clean, the MAF sensor is clean, the air filter is clean, there are no obstructions in the air intake, I replaced the fuel filter just to be sure (easy and cheap), and there are no fuel leaks or oil leaks to be found. I also checked the coolant and it's kinda on the opaque side, but yellow, not bubbly. There seems to be a little bit of buildup along a couple thin vertical sections of the coolant reservoir as well, looks almost like calcium deposits.
I took it to a shop that also confirmed that the spark plugs are good, ignition coils are good, compression is good, timing is spot-on, fuel pressure is good, injectors are clean, and the backpressure test didn't show problems. The shop tech didn't charge me anything because he couldn't find the problem, but he surmised that it could possibly be the catalytic converters even though the backpressure test didn't show issues - he said that the O2 sensor being in the middle of the cat might make it hard to determine if there's an issue with the backpressure test. However, both catalytic converters are brand new, though only $180 muffler shop chop off / weld on deals (Eastern Catalytic, I think). The tech mentioned that there were misfire codes being thrown while he test drove it hooked up to a computer, but none of them were stored and they didn't indicate which cylinder.
I'm at a loss for what the issue might be. I'm going to try one disconnecting the exhausts and running without the pipes & cats connected to rule that out, but I'm not optimistic.
Last edited by MGD; 07-09-2016 at 08:34 PM.
07-09-2016, 08:51 PM
#7
Senior Member
To me, it sounds like the converters. Get the truck up to running temp. And get a temp gauge. The one with the little red lazer. Point it on each cat. See if 1 of them is significantly hotter than the others.
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07-10-2016, 08:16 AM
#9
But - the OP said they were 'new'?
BTW - that model year used 4 cats, so yeah if the just changed to front two ( and not the rears ), still could be a factor. Apart from the alleged 'backpressure' test coming back 'clean'.
Uncorking the exhaust and/or measuring cat temps are both reasonable testing steps to try.
I admit that I'm not real comfortable with the mech doing the diagnostics given what's been stated so far. Perhaps seek another opinion? I do that with Sawbones all the time, lol.
Good luck
MGD
BTW - that model year used 4 cats, so yeah if the just changed to front two ( and not the rears ), still could be a factor. Apart from the alleged 'backpressure' test coming back 'clean'.
Uncorking the exhaust and/or measuring cat temps are both reasonable testing steps to try.
I admit that I'm not real comfortable with the mech doing the diagnostics given what's been stated so far. Perhaps seek another opinion? I do that with Sawbones all the time, lol.
Good luck
MGD