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Registered
Join Date: Mar 2008
Location: Nashville, TN
Posts: 4,053
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you have 7 links but did you set the cam/valve timing properly?
1.4mm intake valve lift on #4 when #1 is at TDC? retarded cam timing can cause low vacuum and a weak engine. advancing brings back the goodness... |
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09-16-2018, 03:48 PM
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Automotive Necromancer
Join Date: Nov 2006
Location: Beantown, MA
Posts: 1,544
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vac leak?
Hi guys, sorry to barge in here, bear with me. Perhaps the low vac is caused by a vac leak. I had one on my engine for months and couldn't find it so believe me when I say they can be tricky. have you tried blocking off the intake manifold and pressurizing it with a hand pump while spraying soapy water everywhere? and i mean everywhere. I know it sounds a bitt odd, but it might be worth a try. also pay special attention to your Idle air controller as it doesn't seem to be doing its job.
I have a 87 so cant speak with authority on your 88 motronic. but IMHO most faults are not in the EMS as much as components the wear out or fail. good luck with it all. 
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There may be nothing quite as expensive as a cheap Porsche: Ruby Red 84 928S : White 87 924s 2.5L NA (Blinky) M44/07-43H10676 spoiler delete - 046/2B - Belts 9/12, Clutch and OC seals 8/08 andd Red 94 Del Sol: Please put your Make, Model and Year in Sig. Try not to break more than you fix. |
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09-16-2018, 05:16 PM
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Registered
Join Date: Jul 2014
Posts: 405
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KD,
I'm gonna guess that you probably considered this but just in case; I saw that you mentioned the TPS, not sure if you set it or tested it, but could the TPS be intermittent when coming off throttle going to idle? Do you have a spare to test with? |
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09-16-2018, 06:56 PM
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In the Fires of Hell.....
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Danno and Paul hit it on the head.
Test Plan #2 showed what was going on. I had tested the TPS idle switch while the intake was out of the car, and it ohmed out as good, as did the WOT switch. Testing it at the DME plug showed that 10% of the time the idle switch was not activating correctly. I had tested this many times before from the engine compartment, by pulling on the throttle cable after the 180 degree wheel, and it was clicking and the TPS seemed to be working correctly. Apparently the cable drag from the gas pedal to the TPS was enough to prevent it from completely closing 100% of the time. I had done the reseal of the throttle body, and when I compared what I did to an 8V throttle body I had laying around, I noticed that the torsional spring was not landing on the stamped arm on my resealed one. This led to a reduced amount of return spring force, and this intermittent problem. Fixed all of that, and so far so good (two test drives, 80 miles on highway and city). Maybe this thing isn't as bad as my initial rant  Thanks all for the help... I am declaring victory on this, finally. Spencer, not really interested in maximizing this engine, as it's for a 19 year old to be a grocery getter. At least it now has a rear sway bar: Who orders one of these cars and only has a front sway bar installed on it? Much more balanced now.
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PCA Instructor: '88 951S - with LBE, Guru chips, 3Bar FPR, 1.3mm shimmed WG, 3120 lbs, 256 RWHP, 15 psig boost Last edited by kdjones2000; 09-16-2018 at 09:10 PM.. |
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09-16-2018, 07:31 PM
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944 Turbo
