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EGR valve could case start/idle problems

1875 Views 1 Reply 2 Participants Last post by  B10alia
One item to watch is the EGR solenoid-transducer unit on this vehicles like the 1994 Caravan 3.3L. It is energized to prevent use of EGR in most operation, but if the solenoid fails EGR might operate which can hurt start and idle (depending on logic of the use of exhaust backpressure in this vehicle’s EGR configuration, should be low at idle). My unit appears to work correctly.​

It is a simple solenoid so can be energized to test that vacuum is blocked. Conveniently I have a 12vdc memory holdup tool to test some devices away from the vehicle. (It holds 8 AA batteries, plugs into the lighter socket. I suppose if I made some conductive spacers I could reduce voltage close enough to lower voltages to better test devices Oh, I must have a surplus battery holder for four AAs.))​

Some contemporary Chrysler vehicles do not involve exhaust backpressure, this one plumbs it from the base of the EGR valve, another configuration also does that but has a simpler lashup to control vacuum to actuate the EGR valve – no solenoid. The EGR valve is organized the right way – closed until energized, unlike the solenoid. However the tube to sense exhaust backpressure from the base of the EGR valve is probably prone to clogging by carbon in the throat of the EGR valve.​
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If the solenoid is the same arrangement as the one in the 2.5 TBI motor, the mode of operation can cause failure. In order to regulate the EGR flow, the solenoid pulses on and off, resulting in a lower vacuum over a given period than straight ported vac. Of course, over the years, all that pulsing tends to wear out the diaphragm inside the assembly, eventually resulting in full vac to the EGR valve at all times.
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