94 4cyl runs rough when cold

Notes to consider:

1) 94 Camry 4 cyl does not have (OBD II) onboard diagnostic system but OBD I. 2) O2 Sensor is 2 wires, that is no heating ckt involved to ( > 2 minutes to become functioning.) 3) Engine runs on open loop when cold until O2 sensor heats up to 600F, that is, AIR/FUEL ratio is set to a default setting but is not monitored or corrected 4) Once O2 Sensor is functioning (O2 sensor temp > 600F), Engine will enter closed loop and would control AIR/Fuel ratio.

Suggestions: Look for short or excess air entering throttle body that impacts A/F ratio, following are possibilities

1- Air filter but impact is not limited to cold engine 2- EGR Valve stuck open, impact is noticed when engine is cold. 3-

and

running

In news: snipped-for-privacy@tpg.com.au, Peter Jakacki being of bellicose mind posted:

In the old days..... we'd put the car on a scope and check the ignition system for faulty secondary ignition components ... plugs, plug caps arcing, plug wires, water inside the distributor cap ... simple stuff like that. ;-)

--
- Philip @ Maximum Torque RPM

Same thing happens to my '94 4 cylinder occasionally, even though the idle air control valve (and air intake hose) was replaced by the Dealer prior to my purchase of the car. The idle air control valve (IAC) controls the fast idle speed when cold by passing a small amount of air past the closed throttle valve. (Kind of amazing operation really. Computer controlled "step"motor moves a pintel valve to maintain the idle speed at correct values for all conditions.) Sometimes the valve gets gummed up and doesn't open fully to let in more air when cold to create the fast idle necessary immediately after starting. Just take a 10mm wrench, loosen the hose clamp and pull the plastic air intake hose to the throttle body over to one side. Start the engine and let it idle roughly. Spray short blasts of emissions control safe carburetor cleaner into the small rectangular hole on the bottom, just right of center, in front of the butterfly valve. This is the air intake for the IAC. Keep the engine running if needed by moving the throttle cable on the left side of the throttle body. Had to do this again couple of days ago, but will be many months before needed again. Purists will tell you it is necessary to remove the throttle body and IAC valve for thorough cleaning, and you can have the dealer do this for you also. I use a small amount of Berryman carb. cleaner (apx. $3 per can) every six months or so, versus around $80 for the throttle body cleaning, which also is not a permanent cure. To "properly" clean the IAC valve you need to break the seal at the gasket, remove the water lines and cables. Not really a major job, but certainly more involved than one hose clamp bolt and a few minutes time.

In news: snipped-for-privacy@posting.google.com, Daniel M. Dreifus being of bellicose mind posted:

(Purist raises his hand)

EXCUSE me :-)

WHEN you've got highly expensive heated O2 and A/F sensors in the exhaust, it is proper to take throttle body off the car and remove the IAC from the throttle body for cleaning. Anyone who has Berryman'd or Gumout'd an intake tract and then checked a spark plug won't want all that carbon endangering those two ... sometime three exhaust sensors.

--
- Philip @ Maximum Torque RPM

Thanks for your answer. Was wondering about the benefits of removing the IAC for cleaning. Still . . . on the '94 the first (main) O2 sensor is not heated, but more importantly, one is not spraying and cleaning the throttle body and releasing lots of muck into the cylinders or exhaust. If the throttle body needs cleaning, that can be done separately, with the engine off, and cleaning loosened gum with a rag and toothbrush. In that case, the throttle (engine off) is fully opened, with both front and back sides cleaned. The distinction, when cleaning the IAC valve to correct rough running when cold, is that the throttle is fully closed when spraying cleaner. If the engine stumbles further, threatening to die, the throttle is opened slightly to keep it running, but at that point is admitting only air. I'm actually more concerned about admitting unfiltered air, but it is only for a few minutes. Plus, if you learn to keep the blasts of spray cleaner very short, no manipulation of the throttle is required - just wait a few seconds for the idle speed to clear up. Essentially, the only "carbon endangering the oxygen sensors or spark plugs" is the quite tiny amount of gum causing the small orifices in the idle air control valve to stick slightly, because the cleaner spray is directly only into the IAC air intake passageway. You're not opening up the throttle and dousing the whole throttle body in cleaner, just surgically aiming a mist from the little red tube to direct a short spray into the little rectangular holes in front of the closed butterfly valve, and that's really all it takes to clear up the cold idle problem. Keep going, and you might convince me to take the whole thing apart for cleaning next time, but I suspect the results wouldn't be any different. Based on mileage, I did use the OX1 terminal in the DLC1 under hood connector with a digital multimeter last month, just to check the operation of the oxygen sensor and it appeared to be operating correctly, with fairly rapid and consistent switching.

In news: snipped-for-privacy@posting.google.com, Daniel M. Dreifus being of bellicose mind posted:

You've given a bunch of excuses for not spinning off 4 or 5 bolts and a fitting and removing the throttle body to the bench.to do the job right. Duly noted.

--
- Philip @ Maximum Torque RPM

When was your last tune up , how are the plugs and hows it been maintained, could be a bad wire or a bad cilinder .

And ,...........of couorse you've been helpful with this wonderful tidbit.

( yeah, I know I am no more helpful than you were with that post, but It's good for someone to let you know once in a while how much help you've been )

Remove "YOURPANTIES" to reply MUADIB®

It's is not, it isn't ain't, and it's it's, not its, if you mean it is. If you don't, it's its. Then too, it's hers. It isn't her's. It isn't our's either. It's ours, and likewise yours and theirs. -- Oxford University Press, Edpress News

V6 Camry has another Intake Air Control Valve located by DLC1, its part of Acoustic Control Induction System intended to provide high torque at low RPM when in closed position and maximum horse power at high RPM when in open position. A valve to consider for cleaning on V6 engines.