Recently my car has started developing a strange idle problem when hot. If when the car is up to temp I have to stop at a stoplight for too long, the car will flip into open loop and throw a O2 sensor lean code. Once in this state it idles very rough, lurching the car if I don't take it out of gear. Once the light changes and I drive away, the code disappears and it goes back into closed loop operation.

I was watching with a scanner while it did it the other day, and the temp sensor was reading a 186 - 188 when idling normally and the switch occurs. The temperature goes up slightly when it hits open loop, about 190.

Does anyone have any ideas as to what the problem could be?

BTW, FP is set at 45 psi and I'm running the ARAP bin.

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Black 88 GTA L98
261 RWHP, 345 RWTQ
13.406 @ 103.72 MPH
ZZ4 bottom end, Edelbrock 6085 heads, LT4 HOT cam, GMPP 1.6 RR's, ported stock TPI, SLP 1 3/4" headers, no cat, Dynomax cat-back, Stock PROM
E.T.F.A Member #11

 

Try a heated O2 sensor.

 

Do you really think that's the problem? I only ask because I don't have $80 to just throw at a new O2 sensor. Thanks.

 

Actually, you probably just need a new O2 sensor. Mine did that a few years ago when the original O2 sensor (I bought the IROC used) had 75k miles on it. Swapped in a new 1-wire Bosch (Grumpy shudders) sensor and everything was better. My sensor was slowing down and wasn't giving me readings at WOT last year, so I swapped in a new one and everything's back to normal. A new 1-wire sensor is $35-40 around here...

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Greg Westphal
'87 IROC 305TPI/A4

 

Ok, let me in on the secret, here. Is there something about Bosch sensors I need to know about? Is there a better alternative?



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'87 IROC 5.7l TPI - original owner!

 

Heated O2 (at least 3 wires) = better than non heated (1-wire)
4 Wire heated O2 = better than 3 wire heated O2

The 4 wire sensors have a redundant ground. In the 3 wire application the sensor receives ground from the connection between the sensor and the exhaust (sensor ground NOT heater ground). This can be a problem with high performance coatings, wierd gaskets, various header bolts, etc. The 4-wire sensor ensures a good sensor ground.

Bosch makes the 13077 heated sensor that most people end up using (including me). But, the better way to go is the 4-wire.

Tim

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TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels.
Gunning for NA 11's with bigger cam, bigger stall, and bigger exhaust.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

 

The O2 sensor is new. I put a new one wire Bosch in with the new engine in November, it shouldn't be bad already. But it seems that everyone seems to think the O2 is the problem, so does anyone know the part # for a 4 wire sensor?