Fixed Idle Problem. Got logs too!

[david-b]

Hey all;
It was finally warm(er) here today, so I decided to fix my car. Replaced the IAC and the TPS. The car has not been starting when cold, and idle has been very rough. With the sensor and motor replaced, it idles a whole lot better now. Very smooth. It's not cold, so the cold test really didn't come into play. I hope that solves that problem too. When driving, the rpm drops very quickly down to idle, which was being logged at 766-800rpm.

Since I was logging, I wanted to post some logs to see if these look good. I wasn't full on the throttle, but hit high 80s on a short expressway. Please tell me if these readings are good for what I was doing. Thanks

Load


Fuel


Timing


Speed


What do you think? IS the timing and fuel good?

[crunchymilk55]

well from a 4g63 perspective they look damn awful. Your fuel trims drop way low, and your timing curve has a HUGE dip in it. But I don't know how to tune a nt. I don't know what they're supposed to be.

[SilvrEclipse]

You might want to post your logs on 2gnt, they would probably know more about them.

[david-b]

Why would the fuel be bad, and the timing cut low like that? What are possible problems caused by this? (Even if it is a 4g63 perspective)/ Thanks

[crunchymilk55]

well, from a 4g63 perspective, the fuel should be a steady line, maybe a bit leaner at higher RPMS. Yours is all over the place, see how it jump around? The timing curve looks fine except for that huge dip, usually caused by knock.

[david-b]

So knock will cause the timing to change, correct? I have to look into on what would cause that. I should have posted my rpm log too. The timing actually drops when I take my foot off the gas, then shoots back up for some reason.


What would cause the fuel to be like that? Thanks

FYI - I jumped on the Canook's ass for talking shit on NTs when he's on a NT forum. Also replied to your post. Maybe there will be more, quality information later on. Don't judge 2GNT based on the random shit-talker.

Thanks.

[david-b]

So, changes in timing, like spikes or dips, is because of knock, correct? So what causes knock? Low octane gas? If I use premium, and/or octane booster would that possibly eliminate knock then? I'm thinking out loud, and it seems like garbage, but what can be done about that? Thanks

Originally Posted by david-b

So, changes in timing, like spikes or dips, is because of knock, correct? So what causes knock? Low octane gas? If I use premium, and/or octane booster would that possibly eliminate knock then? I'm thinking out loud, and it seems like garbage, but what can be done about that? Thanks

While the ECU retards timing in the event of knock, it typically does so well after any damage would be have ocurred. If you run a well-maintained machine, you shouldn't have to worry about knock given the level of modification you have going on. Stock fuel system is not going to give you issues based on I/H/E. Perhaps, you might get a tank of ass gas, but chances are you would know that right off.

Keep in mind that the ECU uses input from CMP, CAS, MAP, and even CLT to determine how much fuel to inject, when to inject that fuel, and finally to light it off. It's a constantly changing environment, based on TPS, engine load, ambient air temperature, vehicle speed and what you had for lunch.

I wouldn't be worried about it. The variations you see in your logs are just the ECU making adjustments on the fly. While it's fast, it's certainly not the type of computer that is going to be beating Kasparov at Chess. Know what I mean?

[kjewer1]

I just want to make sure everyone is aware that he was not at full throttle on these logs according to the initial post. On the turbo cars, and I would expect on the NTs too, we would only be concerned with WOT logs as far as AFR and timing go. At cruise and idle the ECU messes around with things constantly and there isn't much to see that's going to be helpful.

[david-b]

So should I do a run and post the logs of that then to get the full feeling for it then? With it being new years, I cant do that this weekend. Every cop is out after me... (already had a breath-alayzer test already). I will do a run on full throttle, and post the logs from that a little later then. Then we can take it from there.

[crunchymilk55]

o yeah sorry I didn't read you weren't at WOT

start in 3rd gear at 2000 rpm and floor it to redline