Pinging problem

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Jul 2, 2012 | 11:37 AM

Lilryan

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Pinging problem

i have a 1991 f150 5.0 automatic. i just did a tune up, plugs/wires/cap/rotor/fuel filter/air fitler. it sounds like the truck pings when it is under load. it doesnt do it under wot. part throttle is a problem. the truck feels like it has no power under part throttle, but does pretty good under wot. i havent checked the timing yet, but the truck is bone stock with 167000 miles and i bought it from the original owner. i tried running 91oct in it and it didnt make any difference. so based on that, maybe it is not detonation. i also seafoamed it a couple times and it didnt seem to make a difference. is there a sensor or something that i am not thinking of. the truck still has the two original converters, so i am going to have them removed and put a better muffler on the truck. someone please help me, i am running out of ideas.

thanks
ryan

Jul 3, 2012 | 12:57 PM

White Max

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From: Imperial, MO

I'd start with checking the base timing with the SPOUT removed, as well as checking for vacuum leaks.

Jul 3, 2012 | 03:06 PM

Lilryan

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thanks for the reply. i am going to be doing that once i purchase a timing light. i just discovered that my truck is missing the evr. i am in the middle of doing an egr delete so i will be checking all the vacuum lines then.

Jul 3, 2012 | 09:02 PM

White Max

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From: Imperial, MO

That could have a lot to do with it. At part throttle, the EGR system partially fills the cylinders with inert gas, reducing the amount of fuel required by the engine. Deleting the EGR system on a MAF-based setup isn't too problematic, as the additional air now filling the cylinders is measured by the MAF, and the correct amount of fuel is added. However, on a SD-based setup, the AFR will go lean if the EEC believes that the EGR system is operational when it has actually been removed. You're likely going lean and detonating at part throttle, which explains the lack of power and pinging under those conditions. I'd either recommend tuning the EEC to turn off the EGR, or reinstalling the EGR system.

Jul 3, 2012 | 11:47 PM

Lilryan

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So you think the problem will continue if I delete the egr without tuning the computer. I bought all the Pieces from rjm to do the delete. I bought the plugs for the heads, the egr plate, and the the plug so the sensor won't throw a cel.

Jul 5, 2012 | 07:53 AM

rla2005

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From: Kentucky

Quote:

Originally Posted by Lilryan

thanks for the reply. i am going to be doing that once i purchase a timing light. i just discovered that my truck is missing the evr. i am in the middle of doing an egr delete so i will be checking all the vacuum lines then.

I know from personal experience with my old 1992 F350 w/5.8L engine a disconnected EVR will trigger a hard fault and turn on the Check Engine Light. A hard error will trigger the PCM into limp mode. Your issues may be caused by the PCM operating in this condition.

Jul 5, 2012 | 09:08 AM

White Max

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From: Imperial, MO

Quote:

Originally Posted by Lilryan

The resistor from RJM may correct the issue. If it doesn't, you'll either need a tune or a properly working EGR system. Either way, you'll want to correct the situation immediately, as detonation destroys ring lands in no time.