Werid bucking
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Werid bucking
Hey everyone, got a sorta odd one on my hands, I've always noticed my truck had a little bit of a buck to it since I first started driving it but lately its been doing allot of sitting due to a long drive to work and high fuel prices, however in recent days with it down to a much more affordable level I have been driving it allot more but I've noticed this low rpm bucking is getting worse. It only does it after I let of the gas to slow down and I get back into it to pick speed back up, does one or two little but noticeable bucks and then accelerates like normal. Any ideas? I'm stumped. Thanks in advance Shadow.
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Been about ten months since they were last changed out, they are durlast brand wires. How would I go about testing them to find out if that is the case? Ohm meter I assume? Or just replace them with a good quality set?
Lead Driver
Joined: Dec 2012
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From: Tennessee
I ran through a bad batch of Motorcraft wires about 10 years ago , We could not get a good set . No problems now though . You can ohm them out but may not show a problem . I would try a new set myself .
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Whenever I get the chance I may just invest in a good set of ford racing plug wires just to get the hassle of cheap autozone wires out of the way.
New User
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mine did that for about 10 years. 
when it did, i just let off the gas and it stopped. mine felt like tranny rather than fuel, spark, etc.
when it did, i just let off the gas and it stopped. mine felt like tranny rather than fuel, spark, etc.
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Logistics Pro
Joined: Mar 2005
Posts: 4,698
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From: Mexico, Missouri
Ohming out the plug wires is a good start. I would check and clean the cap contacts of carbon.
Next would be to check fuel psi. Fuel filter. Another shot in the dark is the EGR valve pintle isn't closing fully when coasting and as you start to accelerate, its pulling in exhaust gases, giving you the apparent bucking. Also, there is more vacuum when coasting, letting off the throttle, so higher vacuum would draw in more air if there were any intake leaks or a leaky EGR valve or gasket.
Next would be to check fuel psi. Fuel filter. Another shot in the dark is the EGR valve pintle isn't closing fully when coasting and as you start to accelerate, its pulling in exhaust gases, giving you the apparent bucking. Also, there is more vacuum when coasting, letting off the throttle, so higher vacuum would draw in more air if there were any intake leaks or a leaky EGR valve or gasket.
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Logistics Pro
Joined: Mar 2005
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From: Mexico, Missouri
Simple jumper wire or paper clip. Then start counting the CEL flashes. This is the most widely asked and I can't tell you more since I never had to do it, but once, years ago. Google is awesome for videos posted and others have posted their videos so others here could decipher. When I bought my truck, I also bought the Innova Eqqus 3145 code reader to make things easier.
I never thought to ask if you checked codes, but it should always be the 1st step.
Post back with your findings.
I never thought to ask if you checked codes, but it should always be the 1st step.
Post back with your findings.
Fleet Owner
Joined: Oct 2005
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From: Kentucky
Warm up the truck then do this: Fuel Injection Technical Library » How To Run a Self-Test
Or purchase a code reader such as the Equus/Innova 3145
For reference: Fuel Injection Technical Library » 2 Digit Self-test Codes 11-32
Or purchase a code reader such as the Equus/Innova 3145
For reference: Fuel Injection Technical Library » 2 Digit Self-test Codes 11-32
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Alright not sure if I did this right but I did get the codes for the key on engine off and when I come back from town I will do the key on codes. Here is what i got. 212 431 212 431 1 132 32.
Fleet Owner
Joined: Oct 2005
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From: Kentucky
Probably should be KOEO: 21 24 31 21 24 31 11(spacer flash) CM:32 32
Code 21 (KOEO): ECT out of self test range 0.3 to 3.7 volts.
Code 24 (KOEO): ACT sensor out of self test range 0.3 to 3.7 volts.
Code 31 (KOEO): EVP circuit below minimum voltage of 0.24 volts.
Code 32(CM): EVP circuit has intermittently failed below minimum voltage of 0.24 volts.
Codes 21,24 can be caused if you did not warm up the truck before runing the tests or the ambient temperature is very cold.
The key codes to focus on are 31, 32. This indicates the EGR valve may have a collapsed diaphragm or spring.