sweet-94z28

iTrader: (30)

My 1994 started a new one yesterday. It stumbles while I idle when the car is in closed loop. As soon as it hits open loop and the air pump shuts off, it idles perfect. Any ideas??? I really wanna get this thing fixed. I have checked all the vacuum lines, no leaks. I put on a new EGR valve and that made no difference so I don't know what to do???????

infinitebird

iTrader: (11)

Well first, I think you are a little confused. Open loop is the initial mode when you first turn the car on. Closed loop is after it has warmed up and starts using the O2 sensors. So the transition is open to closed, not the reverse. And changing from open to closed loop has nothing to do with the air pump.

Formula350

iTrader: (3)

Even I confuse the two. I figured it's "Open" to the sensors when the car warms up, and "Closed" when cold, as in not receiving info from sensors. I've been trying to burn in what the correct way is heh.

Onto subject at hand: Since Closed DOES talk to sensors, it could be a few of them. IAC, O2s, possibly temp sensor or IAT and maybe the TPS.

infinitebird

iTrader: (11)

you're still confused lol.

open/closed loop ONLY has to do with the o2 sensors. It has no effect on those other sensors. They all function pretty much the same in either mode. open loop just means only the o2 sensors are ignored, those other sensors are still used.

Formula350

iTrader: (3)

Huh... ok then lol I mean, I knew the IAC and TPS still worked no matter what, but he said during idle, so I figured it was during idle at ANY time.

sweet-94z28

iTrader: (30)

Well, my car shifts perfect and the TPS shows good voltage. I am leaning toward the IAC myself. GM cars always throw a code if an O2 sensor has an issue (at least thats my experience from work).

Formula350

iTrader: (3)

Not always, mine didn't. TOTALLY bad, yea, but if they're still sending a signal I think the ECM/PCM assumes it's still game on.

infinitebird

iTrader: (11)

On my formula, both my o2 sensors were totally dead, and I had no code. It was only from a datalog I could see they were dead (and it acting up at part throttle). It's been my experience that more often than not it will NOT throw a code.

Formula350

iTrader: (3)

I'm surprised totally dead didn't even do it, that's sad :\ Thankfully my scanner basically is a build-in data logger and real time reader. So usually once a ride I check and see what everything is reading.

sweet-94z28

iTrader: (30)

What would you guys consider a low/dead reading for these O2 sensors? My one side does run higher than the other. The car does appear to run richer because it does have a bit of smoke out the tailpipes when hot. Its not a lot, but just a little puff every time I hear it hit a cylinder. I just don't wanna put another 140 bucks in it right now for new delco O2 sensors. IDK if there is a cheaper brand to buy.

Formula350

iTrader: (3)

They should run around 650-850mv normal driving (I think is the normal range, might be lower to 850, but not much).

sweet-94z28

iTrader: (30)

I think my left one was much lower than that. I'll have to investigate this tonight. It almost feels like it is missing too. I might try new coils because I have 4 extras at home. The delteq IMO gets too hot in the locations they call for.

Formula350

iTrader: (3)

I've said it in another thread, electrical components (basically computer parts) don't like heat. IF it has any sort of processor, then heat can cause it to become unstable and spit out the wrong information, or in the case of a real computer, crash/lock up. But since it's all hardware, that can't happen What DOES happen is components fail, and then you have to replace parts :\

If possible, I'd relocate it.

infinitebird

iTrader: (11)

No, if it never goes lower than 650 it is dead.

It should vary between 100-900 very rapidly in normal cruise part throttle condition.

infinitebird

iTrader: (11)

It is dead if it does not constantly vary between low 100s to high 900s (450 being the midpoint).

If it just stays around one small range of values all of the time it is not working correctly.

sweet-94z28

iTrader: (30)

Well the left O2 sensor is reading a tad bit low (75ish at idle to 400 at WOT). The right one reads 100 at idle and 800 at WOT so the left one is lagging a bit. The MAF was throwing some really crazy high numbers for idle so I cleaned it. The car runs so much better. It runs better than it ever did before. I never cleaned it before because of the risk of screwing it up. I still will get an O2 sensor and a set of plugs and throw in it because they were last done at 40,000 miles (with ACDelco 100K platinum). The car is now approaching 115,000 so I think it is time to try some new ones. Any suggestions???

infinitebird

iTrader: (11)

400 at wot is completely wrong. should be high 800s to low 900s.

sweet-94z28

iTrader: (30)

I'll get a new left one and put it in next week some time. Any type of plugs you guys really like on a mostly stock car that will not be spraying. I am thinking AC Rapidfire platinum or NGK iridium. Not sure though

infinitebird

iTrader: (11)

might as well replace both. if one is bad the other will soon be anyway assuming they are the same age etc

sweet-94z28

iTrader: (30)

OK, I'll get my tires and then the O2's I guess. My damn RF tire is chopped really bad. I just had it aligned and it pisses me off. The tires have at least 30K miles left in them. I got some BFG's on the way so its all good. Money is just a little tight because gas is raping me right now (3.85 for the good stuff).