lack of vacuum May 20, 2008, 09:22:37 PM how much vacuum is needed for the vacuum modulator to work properly?I am only getting 10 in. ,from the tree ,that the modulator is hooked into. Quote Selected
lack of vacuum Reply #1 – May 21, 2008, 04:06:33 PM nobody?this thing is not shifting properly and I have a hunch thats it is a lack of vacuum.I replaced the vacuum modulator (c5 by the way),checked for vacuum leaks,properly adjusted the tv rod and no luck solving this.the tranny cannot decide wich gear it would like to be in (2nd or 3rd).as long as I stay on the gas,it will shift normally,but as soon as I let off and cruise ,say 30-40 mph,it wants to, down shift ,up shift continuosly?if it is "a lack of vacuum"? what are my options to correct this? Quote Selected
lack of vacuum Reply #2 – May 21, 2008, 04:25:55 PM I don't think your problem is vac... I'd suspect the engine pulls at least 14-15" at cruse and that's enough to keep the modulator "happy"...Maybe the kick down linkage is mis adjusted??? Quote Selected
lack of vacuum Reply #3 – May 22, 2008, 05:15:47 PM Is this an AOD? They have no vacuum modulator.Disregard.....Saw in the second post it's a C5....What Rpm you checkin vacuum at? Vacuum at the tree changes and SHOULD go to almost zero or zero @ WOT with a load on the motor...... Quote Selected
lack of vacuum Reply #4 – May 22, 2008, 05:32:53 PM 800 rpm and yes it does go to zero when throttled.little update on thisI played with the timing last night (set it by ear) will check with timing light tomorrow. I now have much better throttle response and it is shifting good now.the only thing I dont like,the engine builder se et the timing at 15 deg. and I had to advance it even further ,just to get it to run good. if I had to guess,I would say it is around 18 degrees rite now, wich makes me think I may have other issues (valve timing is off)....................little frustrated with it rite now,so I am staying away from it.another thing,the guy that came to the house tonite,to replace the windshield,put a small hole in my perfect dash:flame: Quote Selected
lack of vacuum Reply #5 – May 22, 2008, 05:38:05 PM Is this car carb or CFI? Does it have a spout connector?Quotethe guy that came to the house tonite,to replace the windshield,put a small hole in my perfect dashThat would mean the installation is free and the glass was half price IMHO. Quote Selected
lack of vacuum Reply #7 – May 23, 2008, 08:16:50 PM problem solved.it had nothing to do with the vacuum being low.the problem was the huge coil springs :D they insatall in the distributor at the factory.these things are stiff!!!.I was not getting any advance on my timing (hence the reason I had to advance it so much at idle) just to get it to run fairly good.I ended up putting the lite springs in it ,to get it to advance at 1000 rpm.(idle is set to 900 rpm).set the timing at 10 degrees and total is at 33 degrees.it now runs and shifts like it should..............I am a happy man now. Quote Selected
lack of vacuum Reply #8 – May 23, 2008, 09:55:59 PM Quote from: Chooglin;220411the problem was the huge coil springs :D they insatall in the distributor at the factory.I'll guess no one(on the board) would have diagnosed that one, including myself... Sometimes you just have to be in front of the problem...Glad you got it... Quote Selected
lack of vacuum Reply #9 – May 24, 2008, 09:29:19 AM QuoteSometimes you just have to be in front of the problem...Yup! Good catch! Quote Selected
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