''01 SC2, Al flywheel, OBX header, K&N cone filter on stock intake pipe.


Having an issue with the car stumbling (misfiring?) on throttle tip-in off idle, especially when it''s warming up and hasn''t come up to full temp (which is alot of the time with how cold it''s been lately). Any ideas? This makes the car really hard to drive until the engine has some heat in it. If in neutral and you stab the gas quick the engine stumbles before it revs up. Also, when cold the revs drop very quickly between shifts until it''s warm.


When starting sometimes the engine will barely run, needs some throttle to "clear out" for a few seconds before it''ll settle down and idle smooth.


Any ideas?


I was thinking the TPS could be bad, but I''ve got no SES light codes. Coolant temp sensor seems normal according to the temp gauge on the dash. Once warm the engine runs pretty well, but I can still detect the off idle stumble, especially when first rolling out.


Thanks everyone.

 

Any ideas guys?

 

??Maybe a badMass Air Temp sensor ??

 

Have you replaced original ECTS? If not, replace ECTS and connector.

Throttle body been cleaned lately?

 

Coolant Temp Gage works fine... no erratic needle movements or anything like that. Do you think the sensor could still be bad? Why replace the connector? Corrosion?


Going to clean the TB this weekend if I get a chance, maybe the idle circuit is bunged up?

 

Stable needle does not guarantee correct temp reading from sensor. Original resin tipped design are known to crack and provide bogus temp readings to PCMusually that coolant temp is too cold. This causes engine to run rich and will create the type of behavior you are experiencing.

As for connector, yes, corrosion here is a killer and will hose the reading from a brand new sensor.

 

Makes sense... is it possible the IAT could be doing the same thing? On my ''96 SL2 the IAT and ECT were interchangeable, I''m assuming the same still holds true on the ''01.


Cleaned the throttle body on Saturday, wasn''t really that dirty to begin with. Made absolutely no difference... [img]smileys/smiley7.gif[/img]

 

I think I''m going to replace the T-Stat at the same time... I don''t think the T-Stat is the problem, but the car seems to have trouble keeping hot air coming out of the vents when it''s this frigging cold out (-20C).


Planning to do this weekend, I''ll post the results.

 

UPDATE:


Ireplaced the ECT, IAT and T-Stat this weekend, now she runs like a dream! I think the original advice to change the ECT was right on the money, I only changed the IAT and the T-Stat at the same time because it was convenient to do it at the same time. Now the coolant temp gauge reads at 3/8, right where it should (before it was warming up to about 1/4 and staying there). I had good heat, so I think it was the ECT and not the T-Stat, especially since the car starts properly now and doesn''''t stumble on throttle tip-in any more. Now I can back out of a parking spot without touching the gas again!


Thanks for the advice guys![img]smileys/smiley2.gif[/img]Edited by: superspeeder

 

BTW, the T-Stat is a PITA to change with the rad shroud and air conditioning compressor in place, but it can be done. Make sure the seal on the t-Stat housing doesn''t move before you get it in place, though!


Another thing... just because you''ve drained the coolant from the system doesn''t mean there''s no coolant left in the motor! Lots of coolant pours out when you remove the T-Stat housing, and even more pors out when you pull the ECT out of the head... I ended up jamming the new ECT in place to stop the flow of coolant onto the floor. Big mess, but getting the car running right again is more than worth it.


IAT and ECT are the same sensor. My ''01 already had the new brass tipped ECT sensor in from the factory, and it was bad (the cause of all my problems listed above), so don''t assume that just because you have the brass tipped sensor that all is well! I did replace the IAT at the same time (it was the older plastic tipped sensor), so it could have been faulty also, but I doubt it since it just sits at ambient temp all the time.