It feels like the ignition is cut off momentarily then back on and if I keep the pedal down it cuts off again and will do this several times then clears up and takes off. Seems to do it only in low (AOD). Full or low tank same thing. Sometimes worse than others like when I just pulled off the freeway. Anyone have a similar experience and (hopefully) an answer?
EFI bogs on launch
Jim_Williamson
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It feels like the ignition is cut off momentarily then back on and if I keep the pedal down it cuts off again and will do this several times then clears up and takes off. Seems to do it only in low (AOD). Full or low tank same thing. Sometimes worse than others like when I just pulled off the freeway. Anyone have a similar experience and (hopefully) an answer?
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1,851 Posts
Jim,
Have you done any mods to the engine (cam, heads, intake, injectors)? I've been fighting this (along with a couple of other issues) for awhile. But I've got a fairly modified engine -- trick flow head, E303 cam, BBK intake, 24 lb injectors, etc... After getting rid of the dreaded idle surge, I have a fairly decent bog at throttle tip-in. I've got a wide-band O2 sensor in the car at the moment, and my bog is the car is going significantly lean as I hit the throttle. It takes a couple of moments then the Air/Fuel ratio is back to where it belongs and the car takes off like a bat outta....
But if you've got a fairly stock 5.0, then you don't have the same problem that I'm fighting through.
Have you done any mods to the engine (cam, heads, intake, injectors)? I've been fighting this (along with a couple of other issues) for awhile. But I've got a fairly modified engine -- trick flow head, E303 cam, BBK intake, 24 lb injectors, etc... After getting rid of the dreaded idle surge, I have a fairly decent bog at throttle tip-in. I've got a wide-band O2 sensor in the car at the moment, and my bog is the car is going significantly lean as I hit the throttle. It takes a couple of moments then the Air/Fuel ratio is back to where it belongs and the car takes off like a bat outta....
But if you've got a fairly stock 5.0, then you don't have the same problem that I'm fighting through.
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Alot of the idle surge is due to the car running way too rich, and the computer is trying to compensate with the Idle Air Bypass and timing, and it's just way too far off for the adaptive learning to deal with. When I put on the wide band, I idle was somewhere around 11:1 AFR. The car just did not want to idle unless, I bumped the idle upto about 1200 rpms. I've messed with several of the function and tables to the the idle fairly stable....but still dealing with the lean tip-in issues.
The location of the MAF is important due to airflow charateristics. If it's close to any corners, the flow profile flowing though the pipe will be different at the outside of the corner vs. the inside. My MAF is slightly off of 12 o'clock, and that's probably where some of my problem is, but the E303 cam is notorious for idle surge.
The location of the MAF is important due to airflow charateristics. If it's close to any corners, the flow profile flowing though the pipe will be different at the outside of the corner vs. the inside. My MAF is slightly off of 12 o'clock, and that's probably where some of my problem is, but the E303 cam is notorious for idle surge.
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Thanks for the responses. Mine is stock with the exception of Edlebrock heads. I didn't have this problem when I first installed the 5.0 but only noticed it about a couple months ago and I have 14,600 on it now. Hmmm
Several years ago I had a '94 T bird with a 4.6 that was doing the same thing... it got to the point where it was very hard to get it moving. I called my brother in law mechanic and he asked me to unplug the MAF and see what happens. I did so and the car practically burned rubber... Bottom line was I had a bad MAF. I'm not sure if this will work in your case, but might be worth a try.
If you run an oil type filter (like K&N), the oil can get sucked in and coat the maf element, which can cause this phenomena as well.
Electronics cleaner works great to clean the maf element.
Another thing to check is cleanliness of the throttle body. I like to use WD40 on the throttle body to clean it up.
Also check your tps. Voltage at idle should be just under 1V (0.96V to 0.98V seems to work really well).
Good luck!
Electronics cleaner works great to clean the maf element.
Another thing to check is cleanliness of the throttle body. I like to use WD40 on the throttle body to clean it up.
Also check your tps. Voltage at idle should be just under 1V (0.96V to 0.98V seems to work really well).
Good luck!
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