 another FI mystery to chew on, something to do tonight |
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| drewvw |
 Jun 26 2006, 07:28 PM
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#1
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new england car guy  Group: Members Posts: 1,631 Joined: 24-February 06 From: Boston, MA Member No.: 5,630 Region Association: North East States  |
my car runs pretty good, don't get me wrong....but its not perfect and the fact that its varies so drastically with temperature drives me a little batty.
so here goes 1) Cars runs awesome in extremely hot (80s-90s) weather and runs a little worse in the 60s-70s and stumbles all over the place like its too lean when its mid 60s or below. 1) I've timed it, pertronix, ignition seems to be in good working order. 2) Replaced intake temp sensor (thanks evil) and the ohm readings are the same, no change except if I unplug it altogether and then the stumbling stops do to it running more rich. 3) CHT measures 3057 when its cold and 57 when its hot. Seems to work fine 4) I discovered the MPS has been opened up, as the epoxy is gone. 5) edit: I've redone and clamped pretty much all of the vacuum lines 6) only varible seems to be outside temperature solve my mystery and win a prize! |
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| bd1308 |
Jun 26 2006, 07:32 PM
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#2
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Sir Post-a-lot Group: Members Posts: 8,020 Joined: 24-January 05 From: Louisville,KY Member No.: 3,501 |
your BIG varibale is that someone dicked with your MPS. Hope it was someone who knows what they're doing, or else your drivability problem is staring right at you.
b |
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| krazykonrad |
Jun 26 2006, 07:44 PM
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#3
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Senior Member Group: Members Posts: 1,127 Joined: 21-February 06 From: Canton, GA Member No.: 5,610 |
Mine does the same thing. RUns great when hot, not so well if its cool or rainy. I'm tracking down (multiple) vacuum leaks. THis has helped a lot.
Konrad 72/4 |
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| drewvw |
Jun 26 2006, 07:53 PM
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#4
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new england car guy Group: Members Posts: 1,631 Joined: 24-February 06 From: Boston, MA Member No.: 5,630 Region Association: North East States |
oh yeah....i have shored up the vacuum lines too, i will add that. It is looking me in the face, that damn MPS.....I am going to try and turn it a bit more rich gradually and see if that makes a difference. |
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| SirAndy |
Jun 26 2006, 08:12 PM
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#5
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Resident German Group: Admin Posts: 41,658 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
QUOTE(drewvw @ Jun 26 2006, 06:28 PM)  solve my mystery and win a prize! what shape is your wire harness in? i had all sorts of trouble with my 1.7L. bit the bullet and bought 2 junk engine harnesses and made one good one out of three. ran like new afterwards ... what i found, some of the wires had broken inside the hard plastic covers, impossible to see from the outside! i cut *all* the hard plastic and inspected all (and replaced the broken) wires, then put the wires back into the plastic and taped them shut with electrical tape. used a voltmeter to verify *all* wires were working correctly. took me a whole saturday afternoon, but it was well worth it. if your harness is still the original, you'll be chasing ghosts forever and spent cubic $$$ on replacing parts that don't need to be replaced. i'm certain 90% of the FI related problems people have are due to cracks and such in the wiring harness ... (IMG:style_emoticons/default/wink.gif) Andy |
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| G e o r g e |
Jun 26 2006, 08:24 PM
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#6
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Dr Group: Members Posts: 1,905 Joined: 20-September 05 From: Southern Cal Member No.: 4,832 Region Association: None 
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(IMG:style_emoticons/default/hijacked.gif)
Andy what harness or harnesses are you talking about specifically? just the ems harness? |
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| drewvw |
Jun 26 2006, 08:33 PM
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#7
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new england car guy Group: Members Posts: 1,631 Joined: 24-February 06 From: Boston, MA Member No.: 5,630 Region Association: North East States |
Thats a good point andy....I've though about the wiring harness, it looks to be in good shape but like you said who knows...
could outside temp be effecting that? I just read a thread in the archives about popping out the exhaust on decel. I forgot the mention that. Next step is to check for exhaust leaks and see what happens when I adjust the idle mixture. problem is, I am nervous about messing with it too much. It runs so well when its warm, thats a job for the winter.... more suggestions welcome and thank you all.... |
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| SirAndy |
Jun 26 2006, 08:33 PM
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#8
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Resident German Group: Admin Posts: 41,658 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
QUOTE(maddeye @ Jun 26 2006, 07:24 PM) Andy what harness or harness are you talking about specifically? just the ems harness? ze engine harness. the one that sits on top of the motor and gets all the heat and after 30 years all the wires are brittle and brake ... (IMG:style_emoticons/default/sad.gif) Andy |
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| bd1308 |
Jun 26 2006, 11:23 PM
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#9
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Sir Post-a-lot Group: Members Posts: 8,020 Joined: 24-January 05 From: Louisville,KY Member No.: 3,501 |
Good luck Drew!
these cars always need something.... (IMG:style_emoticons/default/laugh.gif) Mine needs L-jet. b |
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