<![CDATA[Brake booster = bad idle???]]>So I have had this problem for quite some time now....The car will idle fine until it reaches a good operating temperature. Once it warms up to normal temp, the idle becomes erratic in this way: Idles fine for 4-5 seconds, stumbles and drops down to about 400 rpms for .5-1 second, then picks back up to fine for 4-5 seconds in a cyclish fashion. Anyway, today I am bored for a bit so I start troubleshooting by plugging vacuum assisted/dependant devices....the first thing I unhook and plug is the brake booster....low and behold the idle is fine. Now I realize its possible for boosters to be "bad" but my brakes feel "ok" (they are a bit mushy)...and it just seems to me that a bad brake booster would lead to erratic idle at all temperatures. Any input anyone?????

Sean

]]>https://fargostreet.com/topic/6790/brake-booster-bad-idleRSS for NodeThu, 28 May 2026 22:23:59 GMTTue, 20 Jun 2006 04:43:15 GMT60<![CDATA[Reply to Brake booster = bad idle??? on Fri, 23 Jun 2006 06:16:18 GMT]]>The IAC slider in the ecu might be off now trying to compensate for that as well. Try resetting the ECU, I don't think it will matter, but give it a shot.

If anything we can adjust the IAC in the eeprom at a later date.

]]>https://fargostreet.com/post/105805https://fargostreet.com/post/105805Fri, 23 Jun 2006 06:16:18 GMT<![CDATA[Reply to Brake booster = bad idle??? on Thu, 22 Jun 2006 22:26:41 GMT]]>Well I replaced the check valve with another one, made the "stumbling idle" go away. In the process of replacing it, the idle dropped from where it was set to about 500 rpms, indicating there was some sort of leak from the unit. Now the idle is fine, but I am having a bit of trouble getting it dialed back to 750. Should I be resetting the ecu or anything else beofore/after adjusting idle on the TB?

]]>https://fargostreet.com/post/105758https://fargostreet.com/post/105758Thu, 22 Jun 2006 22:26:41 GMT<![CDATA[Reply to Brake booster = bad idle??? on Tue, 20 Jun 2006 20:01:07 GMT]]>agree with dave

]]>https://fargostreet.com/post/105411https://fargostreet.com/post/105411Tue, 20 Jun 2006 20:01:07 GMT<![CDATA[Reply to Brake booster = bad idle??? on Tue, 20 Jun 2006 19:49:14 GMT]]>Could just be the diaphram in the brake booster has a leak, that would do what you describe as well.

]]>https://fargostreet.com/post/105406https://fargostreet.com/post/105406Tue, 20 Jun 2006 19:49:14 GMT<![CDATA[Reply to Brake booster = bad idle??? on Tue, 20 Jun 2006 18:07:33 GMT]]>I'm going to try to replace the check valve with a known good one and see if that fixes it, apparently I've read that if they have moisture in them they can get quirky, and I have also read that the check valves themselves can go bad. I'll post results this evening.

]]>https://fargostreet.com/post/105394https://fargostreet.com/post/105394Tue, 20 Jun 2006 18:07:33 GMT<![CDATA[Reply to Brake booster = bad idle??? on Tue, 20 Jun 2006 05:12:53 GMT]]>Check valve backwards? You wont have shit for brakes if it is, but check that.

]]>https://fargostreet.com/post/105341https://fargostreet.com/post/105341Tue, 20 Jun 2006 05:12:53 GMT