AudiSport4000

Ok, it mainly pertains to the Motorgeek thread below. In the past when a car would run crappy when just started I would (maybe I was told by somebody) disgregard the O2 as the culprit, since the car is cold and ECU hasnt started to look at the O2 reading yet. But judging by what Natrix said, the O2 could be the problem, so it has my confused.

Can some experts shed some light on this for me?<ul><li><a href="http://www.motorgeek.com/phpBB2/viewtopic.php?t=25075">http://www.motorgeek.com/phpBB2/viewtopic.php?t=25075</a</li></ul>

boxerfan

The old ones used to rely on exhaust gasses to heat them up. Newer ones have a heating element to help them reach operating temperatures sooner. I'm not familiar with how soon the ECU looks at the data but if it is looked at right away in a newer car that shouldn't matter. Wait for it to get warmed up and then test as usual. Probably best not to rule it out until it is checked properly.

AudiSport4000

In my posts I was ONLY referring to the older Audi engines, nothing new at all (the car in question was a 4kq).

If Nate is correct then whenever somebody posts a bad running car at startup or when cold, we should be looking at the O2 as a culprit. That doesnt make sense to me.

Pre95

Before the car has run, turn the key over to just before ignition (so all your lights and fuel pump come on). Let it sit for 15-30 seconds. Reach under the car and feel around the o2 (the bung its in, the exhaust tubing, and maybe the o2 itself but could be blazing hot by then...). Obviously if it's warm/hot it's self heating.

Poor running when cold would point me more so towards vac leaks, cold start valve, and A:F ratio...

ddg=shinebox racing

I had to convert my car to a 3 wire when I used the 5-3-1 4000q exhaust manifold and downpipe.

AudiSport4000

All 4kq's Ive seen are all 3 wire.

Katman

But in the caSE of JT, ecu doens't look at o2 until warm.

(As I know, when I had a really bad o2 sensor)
Would work fine for a bit, then when warmed up, would die. DIsconnecting the o2 sensor fixed problem.

Sensor had died when I went through a big puddle, and was putting out ~3v, totally confusing the ECU. O2 sensors never put out more then 1V, so it must have crossed over to the heater power somehow.)

As undoing his o2 sensor didn't do anything, I'm betting on that guy having the 'bad temp sensor' problem.. :-)

AudiSport4000

That was the first thing I asked, along with the ground on the intake manifold. He says that sensor is fine, so who knows.

Only reason I posted this was due to the O2 information Natrix posted. Didnt make sense to me that the O2 was the guys problem if it persisted when the motor was cold.

Katman

sensor = fine means what?

Depends what he did to test it.

From what we know from posts, the 'base mixture' is 'sort of' ok, as it runs with the dpr wiring undone (actually, it should run a bit lean then). so something is still up..

Only way DPR makes mixture rich is from temp sensor, 02 sensor, or altitude sensor.

So pick one of them as a troublemaker... :-)

AudiSport4000

I told him to look at the intake manifold ground and that coolant temp sensor. He said "it was fine", so I almost would feel like an azz if I said "well, did you properly test it?"

Thanks for chiming into that thread though, your insight is always awesome to see when it comes to this stuff.