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Mar 16, 2004 | 08:48 PM

jamesgs47

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Joined: Feb 2004

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From: Southeast Virginia

Missing under load

Hello everyone. I'm new to FTE and I think this is one of the most helpful sites I've ever been to.

I have a problem that is driving me cazy. My 88 F150 5.0 5spd 4X2 has started missing under a load. The truck is basicly stock with a 92 Mustang 5.0 roller cam, Mac equal length shortie headers, rear converter removed and dual exhaust with no mufflers. The missing started out just once in a while but it has become all the time. I've used the search funtion and read everything posted about this and tried everthing that sounded like it would cure it.

1. Tune up- plugs, cap, rotor, wires, fuel filter, air and crankcase filters, cleaned IAC and EGR vavles.
2. Checked for any codes. Code 31, replaced EGR posision sensor. This fixed the problem until the next day and it was back. Code 31 set again. Found and repaired coroded ground for ECM at neg. battery cable, no change. Disconected vacume hose on EGR valve, no change. Replaced EGR valve, still no change.
3.Checked fuel pressure. KOEO 38PSI, KOER 32PSI. Filter in tank switching module has been removed.

This is becomming a bit expensive. Does anyone see something I'm over looking?

Thanks James White

Mar 16, 2004 | 09:07 PM

RLKBOB

Tuned

Joined: Mar 2004

Posts: 281

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From: Petersburg, MI

Did you check/set the timing?

Mar 16, 2004 | 09:10 PM

MJD

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Joined: Aug 2002

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From: South Dakota

My pickup has a barely noticable miss when under load. It is not really a rhythm and it feels much like I am hitting a small bump in the road. I would like to know what it is, but since it is no big problem, I am not too worried. My friend thought that it might be the torque converter when he rode in my pickup, but since yours is a stick, that couldn't be the problem. I am going to check the timing on my pickup when I get the chance.

Mar 16, 2004 | 09:12 PM

jamesgs47

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From: Southeast Virginia

Sorry, Iforgot to mention that. Yes 10 degrees BTDC with the spout disconnected.

Mar 16, 2004 | 09:19 PM

RLKBOB

Tuned

Joined: Mar 2004

Posts: 281

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From: Petersburg, MI

How old is the O2 sensor? You set the timing with the spout disconnected and the engine warm right?

Mar 17, 2004 | 06:38 AM

jamesgs47

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From: Southeast Virginia

O2 sensor is about 2 years old. timing was set with engine at opperating temp.

Mar 17, 2004 | 07:14 AM

ASH

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Joined: Jun 2003

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Did you test the EGR vacuum regulator (EVP or DPFE)? If it is not functioning properly, it will affect the EGR valve and position sensor. Check out Fordfuelinjection.com for testing procedures. I think this is the problem with my truck. Their wasn't a local dealer who had the part, so I am still waiting for it to be delivered.

Also, if the O2 sensor has more than 30k miles, you may want to consider changing it. Maybe try a good fuel injector cleaner, that's at least an inexpensive try at the problem.

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Mar 17, 2004 | 01:41 PM

jamesgs47

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Joined: Feb 2004

Posts: 17

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From: Southeast Virginia

Problem solved! I pulled the plugs back out to do a compression check and found one cracked. New plug installed and it runs like new. Thanks for the help.