1987 Toyota Supra Car Idles very rough for 2 Seconds on col

Z2TT

MEMBER
1987 TOYOTA SUPRA
6 CYL
2WD
AUTOMATIC
62,000 MILES

Hi,

I have a 1987 Toyota Supra with a 2.0L Twin Turbo engine (1g-gte). When Turned on the car will idle extremely rough for about 2 or 3 seconds, then rev upto normal speed (1800 RPM On cold starts). This does not happen when the engine is warm, only on cold starts.

- Battery Is new and Fully Charged, Cranks fast
- Each Cylinder has equal compression of 170 PSI
- Have checked for vacuum leaks, none
- Air Filter is clean
- No ECU Errors
- New Ignition Leads
- Spark Plugs are not fouled

If I have my foot just resting on the gas pedal, it won't hesitate on cold starts for the first 2 or 3 seconds, otherwise it hesitates, but doesn't do it when the car turned on when the engine is warm, only on cold starts.

Car does not give any other problems, so I assume the engine is in good condition, never hesitates or misfires in normal driving, but just on cold starts. Some people would say this is normal, however my other Supra with the same engine did not do it.

So I think it could be something ECU or Electrical related.

Thanks for any Help, If you have any questions or information that I should provide then please ask.

2 Replies

RASMATAZ

MECHANIC
75,992 POSTS

Check/Test the coolant temperature sensor, idle air control valve, throttle position sensor and airflow meter.

Was this

answer

helpful?

Yes

No

Saturday, May 2nd, 2009 AT 3:38 PM

Z2TT

MEMBER
3 POSTS

Hi.

1. How would I test the coolant temperature sensor? I assume it's working as when I start the car up, the indicator for the temp shows that it's cold, and as the car warms up and reduces it's idle speed, the coolant temperature rises until it is in the middle, from that I assume it's working.

2. I was told that I should clean up the contacts on the coolant sensor plugs and cables, as the Idle air control valve uses the readings, so I cleaned up the contacts and still does not help. Now if the Idle valve is dirty inside, by that I mean has oil deposits, that would cause it to stay partially open, I heard that this would cause high idle, but I have never heard anybody say that it can cause hesitation on startup, however can a dirty ISCV valve cause hesitation on startup, if so I would like to know why, just so I know exactly what is happening.

3. How would I test the throttle position sensor?

4. My airflow meter is a Flap Type, it has no hotwire inside that can get fouled, is there anything on it that should be checked?

Thanks.