Sudden change of Pressure Switch [SCPS].

manual says onloy on 1985 model year but appears my 1984 has it.

mounted on fenderwell- pass side [US version] in front of radiator overflow tank---- familiar vacuum switch bell shaped. vacuum line comes from top of warm up regulator and plugs into bottom of SCPS. 2 prong electrical connector plugs into top.

Had idle and stalling problems, pulled vacuum and plugged it off at top of warm up reg and pulled electr plug on top of SCPS and shorted across connectors. Much improved running and idle. If remove short then idle goes up to 1200 or so.

Appears to be bad SCPS... but printed manual is sparse on usable info.

Anybody have to deal with this before? For those with manual a picture is on 19th page [out of 23] in Section 14-100

Thanks in advance!

__________________
dloveless

1984 500 SEL [131K]-
1991 GMC Sierra 4X4 XC [162K]- War Pony.
2004 Jeep Liberty Limited [8k]- wife's sled- Belle.