wierd wierd problem we cant solve
#1
03-27-2007, 08:48 PM
Join Date: Oct 2006
Location: Pa
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wierd wierd problem we cant solve
Heres one we have been trying on and off for almost a year to figure out. 1994 F-150 with 300CID fuel injection, straight six, auto trans. When the weather is cold it acts perfect. If the temperature gets above about 70 the engine will start fine and idle fine but if you try to accelerate or gun the throttle before it warms up it will stall. It will restart but runs rough for a minute or so till it smooths out. After it warms up it will run like new. We have replaced the EGR valve and EGR position sensor, Ignition coil, distributor pickup coil, firing module on firewall. plugs, wires, fuel pump, checked vacuum hoses, checked fuel pressure, evacuated the injectors and checked for fault codes (none set). There are 5 of us with a combined 120 years experience playing with this thing and its driving us crazy. The person who figures it out is going to get the all galaxy award.
#3
03-27-2007, 10:40 PM
#4
03-27-2007, 11:47 PM
Has anyone reviewed the cold start stratigy for these engines?
The ECT and IAC are the prime sensors that determine cold start fueling, cold drive away and running until the ox sensor comes on line (closed loop).
The ECT and Iac are actually the same sensor except packged for their applications. The resistance measurements are the same for both vs temp.
Make sure the coolant level is full as a low coolant level affects the ECT signal by operating out of coolant if is it is low.
Unless you saw vaccum being applied to the EGR or it is sticking open, then that areas is not at fault, or see any codes for EGR.
What does the idle speed do? What is the health of the IAC? etc.
.
Not the same, but on our later PCM controlled engines, you can put a vacuum gage in place of the EGR hose connection and raise the idle and actually see the PCM play with the EGR system trying to make the P0400 series emission checks that it normally does on a cold/warm start. Once done the gage fall to zero.
Good luck.
The ECT and IAC are the prime sensors that determine cold start fueling, cold drive away and running until the ox sensor comes on line (closed loop).
The ECT and Iac are actually the same sensor except packged for their applications. The resistance measurements are the same for both vs temp.
Make sure the coolant level is full as a low coolant level affects the ECT signal by operating out of coolant if is it is low.
Unless you saw vaccum being applied to the EGR or it is sticking open, then that areas is not at fault, or see any codes for EGR.
What does the idle speed do? What is the health of the IAC? etc.
.
Not the same, but on our later PCM controlled engines, you can put a vacuum gage in place of the EGR hose connection and raise the idle and actually see the PCM play with the EGR system trying to make the P0400 series emission checks that it normally does on a cold/warm start. Once done the gage fall to zero.
Good luck.
