Still lacking throttle response!!!
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Still lacking throttle response!!!
OK guys....so far I have replaced the MAF and DPEF sensors, the EGR valve, cleaned the air filter, reset the computer. None of these things have fixed my lack of throttle response.
When I listen to the exhaust and intake upon getting on the gas it sounds like its being muffled too much and hesitates for a second and then starts to go. There is no chance of spinning the tires or beating another truck off the line. It cruises fine and drives okay under cruising conditions but when I want to gun it to pass someone or to get a jump off the line, the truck just sucks wind.
The truck is an '02 F150 with a 4.6L. 3" cat back exhaust, Airaid intake, Hypertech tuner. 156k miles.
When I listen to the exhaust and intake upon getting on the gas it sounds like its being muffled too much and hesitates for a second and then starts to go. There is no chance of spinning the tires or beating another truck off the line. It cruises fine and drives okay under cruising conditions but when I want to gun it to pass someone or to get a jump off the line, the truck just sucks wind.
The truck is an '02 F150 with a 4.6L. 3" cat back exhaust, Airaid intake, Hypertech tuner. 156k miles.
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I didn't notice this "hiccup" until a few years ago when I installed an aftermarket intake. I've never been able to spin the tires but I think the response tapered off when I installed the intake. Too much air?
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I've cleaned the throttle body but I don't know how to check the injectors. I plan on changing plugs this weekend as my routine maintenance. It does sound like the truck swallows too much air and is ready to stall out for a split second and then accelerates very slowly.
Lead Driver
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Things to do are take the tuner off and see what you have.
Then check to see if the PCM is controlling the ignition timing.
There is a plug link to test this.
Set up an inductive timing light and sence off an injector cable and reference a point on the crank pulley to case.
Remove the plug and check the timing no longer moves with changes in rpm.
This proves the PCM is or is not able to control the timing.
No control retards the timing about 4° fixed and should make the motor run like a turd as well as get very poor fuel mileage.
Another thing is the cat back may have caused a loss in low end torque by upsetting the factory exhaust tune as odd as it may sound.
Putting these after market items on does not gaurrentee more power until the motor is wound up to take advantage of the lesser flow loss that is not there at lower speeds with the stock system. Stock muffler was big for a reason.
Good luck.
Then check to see if the PCM is controlling the ignition timing.
There is a plug link to test this.
Set up an inductive timing light and sence off an injector cable and reference a point on the crank pulley to case.
Remove the plug and check the timing no longer moves with changes in rpm.
This proves the PCM is or is not able to control the timing.
No control retards the timing about 4° fixed and should make the motor run like a turd as well as get very poor fuel mileage.
Another thing is the cat back may have caused a loss in low end torque by upsetting the factory exhaust tune as odd as it may sound.
Putting these after market items on does not gaurrentee more power until the motor is wound up to take advantage of the lesser flow loss that is not there at lower speeds with the stock system. Stock muffler was big for a reason.
Good luck.
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Someone described my truck as acting like it had a turbo lag without the turbo acceleration. I'd have to agree.
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Former ******
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From: Salt Lake City, Utah
Have you checked you fuel system? New filter? Have you tested the fuel pump? Sound to me like its starving for fuel. This doesn't seem consistent with a clogged cat.
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I'm not sure how you test a fuel pump but I did replace the fuel filter though about a week ago. My trucks found its power through higher rpm's but still a little less than desirable at lower rpm's (ie: off the line). I've had some feedback from some people who think it could be the opened up 3" exhaust. I thought a had a rattle coming from my cats but it turned out to be a broken exhaust mount under the end of the transmission. Bear, tell me again how to recover more low end through exhaust.
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I really have this feeling its getting too much air. I loosened the air filter while it was running and began pulling the filter away from the flange (allowing more air to get through) and the truck was starting to bog out and when I would put the filter back in place the truck would recover and run fine. I then pulled the filter completely away from the flange and it stalled (too much air).
Cargo Master
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From: Olathe
I really have this feeling its getting too much air. I loosened the air filter while it was running and began pulling the filter away from the flange (allowing more air to get through) and the truck was starting to bog out and when I would put the filter back in place the truck would recover and run fine. I then pulled the filter completely away from the flange and it stalled (too much air).
Lead Driver
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Normally taking the air filter out/off or whatever cannot cause a 'to much air' condition at idle.
Reason is the throttle body plate and air by pass control the air flow and it's not that much at idle. You can't influence this with the air cleaner assuming the opening is not being totally blocked.
It sounds like you have an issue right there with the air tube assembly 'after" the mass air meter.
It may be allowing air to enter after the air meter and becomes unaccounted for air ' unmeasured'. This will be signalled to the PCM and upset the idle due to improper signals.
Normally an engine that gets more air will increase in RPM not stall.
This is the way cold start-high idle works by the air bypass allowing more air to pass.
Fiddling with the air cleaner and getting the result you do indicates you must be pulling the air tube apart somewhere passed the mass air meter and causing upset.
It's a sealed system past the air meter..
Reason is the throttle body plate and air by pass control the air flow and it's not that much at idle. You can't influence this with the air cleaner assuming the opening is not being totally blocked.
It sounds like you have an issue right there with the air tube assembly 'after" the mass air meter.
It may be allowing air to enter after the air meter and becomes unaccounted for air ' unmeasured'. This will be signalled to the PCM and upset the idle due to improper signals.
Normally an engine that gets more air will increase in RPM not stall.
This is the way cold start-high idle works by the air bypass allowing more air to pass.
Fiddling with the air cleaner and getting the result you do indicates you must be pulling the air tube apart somewhere passed the mass air meter and causing upset.
It's a sealed system past the air meter..
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If thats the case then I'd question whether or not if the MAF sensor (if I'm remembering the right thing) you replaced is good or not or that its actually sending anything to the ECM. Another thing if it seems like its getting too much air have you tried a higher octane gas?
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