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  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
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crazy 86 gt

  • Thread starter Thread starter Redtallman
  • Start date Start date Dec 17, 2006
R

Redtallman

New Member
Oct 3, 2004
5
0
0
Dec 17, 2006
#1
  • Dec 17, 2006
  • #1
This car is driving me nuts .!!!!!
the problem "car will crank and dies with the vacume line hook to the map sensor>if i hit the gas it runs but back fire out the exhaust and misses thru range.also i have to feather the gas and it acts as it has delay reaction.

withe vacume line off idles well hit the gas instant roar no delay. but very rich exhaust. 'burns eyes:

came up with 22
o2 sensor lean on bank 1 and 2
tps :SNSign:
 
V

v8only

Active Member
Jul 3, 2003
2,378
22
49
Dec 17, 2006
#2
  • Dec 17, 2006
  • #2
with the map sensor off often it will run, but it will dump tons of gas into the engine. The way it works, the more rpm's, the less vacuum your engine makes, thus with no vacuum, or very little, the MAP thinks you have a wide open throttle condition, and is sending tons of fuel into the motor.

on the other hand, with your o2's, they could either be bad, or your thermactor system may not be operating correctly. When your motor is cold, the smog bypass tubing dumps the air into the cylinder heads, which in turn comes out the headers and into the exhaust. This extra fresh air dilutes the exhaust, and convinces your o2 sensors that the motor is running lean, so it richens up the mixture. When the motor warms up, the air bypasses and goes straight into the cats, and the o2's are happy now and does not richen the mixture at all.

You've got a few places to start. The VERY first thing that I would do is take a vacuum reading. If you don't have a vacuum gauge, go buy one, they're very cheap. A stock cammed motor will make a steady 17-20 pounds of vacuum, 17 being on the low side. Fire the motor up, but leave the map connected, and pull vacuum from an unused port on the intake, or unplug the charcoal canister lead from the front and tap in there.

IF the vacuum is low, you've got a leak, and there is your problem. If it's a steady 17-20 pounds, the problem lies elsewhere.

If the vacuum is good, I'd check the o2's. You could either have o2's that are bad and stuck lean, or bypass tubing that's not switching anymore, and permanently richening it up via the lean signal your getting. That's easy to tell, just pull the rubber lines apart at the Y on the pass side. If the air is coming out the top hose while the motor is warm, then it's not correctly bypassing into the lower hose which goes to the cats.

do report back, let us know what you find. There should be plenty of info here to test the o2 sensors, I believe you can do it with a simple voltmeter, but i'm unsure of the procedure exactly.
 
R

Redtallman

New Member
Oct 3, 2004
5
0
0
Dec 17, 2006
#3
  • Dec 17, 2006
  • #3
very hard to diagnose the problem when i plug in the vacume line to the map its runs for about 2 to 3 seconds then cut off.now the wiring to the map is still hooked up just not the vacume line it seems to run better with vacume line sucking in air even went and got a lincoln speed density map at junk yard still no luck. my other gt is massair so i neverhave this problem before
 
V

v8only

Active Member
Jul 3, 2003
2,378
22
49
Dec 17, 2006
#4
  • Dec 17, 2006
  • #4
well, if it runs with the map disconnected, then plug the map vacuum into a vacuum gauge and start there.
 
8

86bluecobra

Advanced Member
Dec 20, 2004
4,265
12
69
B.C. Canada
Dec 17, 2006
#5
  • Dec 17, 2006
  • #5
it sounds like the maps sensor could be bad but since you tried another one i'm not so sure. Perhaps this car is ready for a carb swap.
 

stang&2Birds

Founding Member
May 4, 2000
2,091
5
58
New England. :-) CT/MA
Dec 18, 2006
#6
  • Dec 18, 2006
  • #6
What codes do you get for KOEO? Sounds like a bad MAP. They go for ~$50-$100. Also, check that the vacuum line to the MAP is good. If you don't get a MAP error on KOEO, then hook up the vacuum line that goes to the brake booster to the MAP (and ONLY the MAP) - use one of those universal vacuum line adapters.
 
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