What's causing my car to lope?

K

KJSupra

New Member
Feb 10, 2008
22
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So.CA
Hey everyone,

I've been searching for awhile to find out what's causing my car to lope. However, I couldn't quite narrow down the answers so I decided to ask everyone here...

Here are my details:

1989 Supra Turbo Automatic

Mods are very simple:
-Blitz SS BOV
-3 in. CAT back exhaust
-New NGK Plugs

My observations:
-There are NO codes.
-All the vacuum lines seem to be intact.
-There's a small crack on the turbo inlet pipe.
-O2 sensor needs to be replaced (Smog mechanic told me this while ago)
-Worn out/loose catalytic converter
-When I try to accelerate, the RPM goes up to about 3000RPM~3500RPM and my car starts to lope and doesn't want to go any faster.
-When I keep trying to accelerate, a black-ish smoke comes out of the exhaust...

My guess is that my car is running too rich/lean because of bad O2 sensor but I'm not exactly sure...

Any input from anyone is greatly appreciated. Thanks for taking your time to read this. :icon_bigg
 
CajunKenny

CajunKenny

PULL MY FINGER. PLEASE!
Nov 15, 2007
3,255
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Washington
Yup. A plugged cat would do it. Does it run fine when it's cold then gets worse the more you drive it? If so, my bet is the cat.
 
RazoE

RazoE

Boobs/Boost, my favorite
Jun 13, 2006
4,946
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Los Angeles
www.cafepress.com
you're always going to run a little rich in a stock 7m, but with a crack in the turbo inlet pipe you're going to be running VERY rich if metered air is escaping..

get it fixed ASAP...
 
C

Crypton2006

New Member
Jun 26, 2006
294
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Phoenix Az
RazoE;1239503 said:
you're always going to run a little rich in a stock 7m, but with a crack in the turbo inlet pipe you're going to be running VERY rich if metered air is escaping..

get it fixed ASAP...
Click to expand...

A crack in the turbo Inlet pipe (accordion hose) will cause a lean condition not a rich. Air escaping after the turbo will make it rich. Have you checked for a boost leak?
 
K

KJSupra

New Member
Feb 10, 2008
22
0
0
So.CA
Thank you everyone for your input! I really appreciate it.

In regards to the last question, I have noticed a slight drop in boost pressure; about 4-5psi at max...
 
C

Crypton2006

New Member
Jun 26, 2006
294
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Phoenix Az
KJSupra;1240196 said:
Thank you everyone for your input! I really appreciate it.

In regards to the last question, I have noticed a slight drop in boost pressure; about 4-5psi at max...
Click to expand...

There is a thread on here somewhere about how to make a boost leak tester. Maybe someone has a link for it or search for it.

Or if your real brave ( im jokeing now) You could chock the front tires and have a friend do a huge burnout as to build boost and you can go around your intercooler pipes with a spray bottle with soap and water and try to find it that way, but that would probably end in death..lol
 
C

Crypton2006

New Member
Jun 26, 2006
294
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0
Phoenix Az
RazoE;1240378 said:
or just rev it up to 4k in neutral...
Click to expand...

That won’t work. That turbo may be spooled but not actually making boost. Boost is relative to resistance.

If you drive along a flat road at 50 miles an hour in 2nd gear your turbo will be spooled but not actually making boost. then slowly start going uphill you will notice you being to make positive pressure. That is what is called turbo lag, Being above the threshold (where turbo actually spools) going from vacuum to positive pressure (or the time it takes to go between).
If you floor the car in neutral and rev it to 4k it will make boost for a second and quickly go away. That is because the engine is fighting resistance to rev up quickly but as soon as the engine reaches said rpm the resistance is now gone thus loosing boost.
 
K

KJSupra

New Member
Feb 10, 2008
22
0
0
So.CA
Ahh, I see. Yes, that was quite informative. :icon_razz

Thank you everyone. I'll check my car again and let you guys know what happens.
 
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