thomasev

Hi all..

I need some assistance..Link is a downloadable Datamaster logg.

http://dl.dropbox.com/u/52503631/first.uni

I have installed a Innovative wideband lambda in my Vette. The engine is a newly build 383 stroker, Trickflow heads and cam. The tune for the car is done by PCM4less.

Picture of one of the spark plugs is here : https://lh5.googleusercontent.com/-Q...5-k/2012-05-12

The readout from the lamda says that car is going far too lean. For the moment I have only 1 gear (some problems with rebuilt transmission). I did a small testdrive today and logged engine data with TTS Datamaster. The Innovative lambda sonde shows a AFR about 16-17 (which is to lean). The AFR when engine is idling is even higher (above 20).

Fuel pressure is about 45-50 psi..

Injectors are 32 lb/hr (Bosch design III from FIC) and the all measure 17.3 ohm..

I do not understand all datamaster readings. Can someone please help me and give me some feedback. Dont know if fueltrim values says anything about AFR..

Rebuild is here : http://thomas-chevy-c4.blogspot.com/

vettef6

The DataMaster log doesn't work.

Did you get a mail order tune?? Had one from them, the engine died out on me all the time and never ran as it should have.

thomasev

Yes, I got a mail order tune from them. This is the second tune from them. The first one was OK (before rebuild motor). AFR on that one was 12.4 (350 cid and a comp.cam). I might just drop that tune in see how AFR is.

Where did you get your tune?

85MikeTPI

What year is your car? DM has different IDs between 92-93, and 94-96 cars

thomasev

It is a 93 mod LT1. The DM version is DM35xDA..

USAsOnlyWay

Doesn't Alvin do free re-burns to dial it it? I'd send both your logs to him and get a new chip.

HOWEVER, where is your wideband located and does it seem to match up with the datalog BLM/INTs?

I ask because an exhaust leak before the wideband will make it look leaner than it actually is. So if you have the bung after a junction, you could be seeing that effect. Just make sure that isn't a problem before you dig too deep into this.

85MikeTPI

We do need to know this.. According to the datalog, your left bank (Drivers side) is running lean, while the right back appears to be running ok. Could be a bad injector, injector plug, spark plug, plug wire or exhaust leak on one of the left hand cylinders

You do know you have a canister purge error code too? Not sure if you're getting too much air in the purge line if it's hooked up, or if its not hooked up and not tuned out..

thomasev

I have sent PCM4less my DM log - waiting for him to respond ;-) Dont know if I have some problems with vacum as well.. The lambda is placed just before the muffler on the passenger side. And yes there are some exhaust leaks before the lambda. I will stop them and see what happens about AFR readings..

And thanks for your replies - the members at US Corvette forum is as always, very responsive ..

Best regards,
Thomas

thomasev

The canister purge is not in use. I will email PCM4less info about that and they can make another tune without it..

Thanks for info, learning every day ;-)

USAsOnlyWay

Better yet can you move it up into the header collector or at least in the y-pipe before the cat so there is only one junction before the o2. Similar to where the factory front ones are. Another thing, are the exhaust leaks new? I notice you said it was fine on your old tune?

I don't know if you have cats, but if so, multiple leaks + cats could mean your tune is just fine.

A single leak ahead of an o2 sensor in the y-pipe can cause AFR drift of 1.5-2 at WOT. Your scenario sounds like it could easily cause it to drift from 12 to 16.

Good luck and let us know what Alvin says. He will be looking at the BLM/INT data.

thomasev

I have Melrose longtube headers and BB-Tri flow 3" exhaust. No cats. The car has been dynoed before commencing this project including measuring the AFR. It was the workshop which did the dyno, that welded on a nut for the lambda sonde. The exhaust setup is not changed since then. The AFR readings then was about 12.5 - so if I manage to stop any exhaust leaks I should get OK readings.
The O2 sensors connected to the ECM is located at the collectors. I dont how accurate they are compared to the heated sonde from Innovate. The stock O2 sensors (which are new) are not heated..

I will report back about what Alvin (I suppose he is PCM4less ;-)) says about DM log..

USAsOnlyWay

So the leaks were there when you got the 12.5 AFR reading at the same port?

Then it is at least partially your tune. If they leaks are new, they could be a contributing factor.

It sounds like you are on the right track with Alvin checking. Do let us know what he says.

thomasev

Leaks are new.. Car is at workshop right now for fixing second and third gear (TH700R4) - probably a servo which is responsible for shifting gear which causes the problem..

I will fix the leaks on Tuesday when getting the car back from workshop. In the meantime I probably have a respons from Alvin/PCM4less as well ;-)

I`ll post results here, thanks very much for responses to my thread..

Best regards,
Thomas

thomasev

Have been in contact with PCM4less - waiting for an answer from them. Anyway - I have fixed exhaust leak (at least to a minimum). Stil I think the engine is somewhat lean.

In open loop the AFR is 11.2 - 11.4. As soon as engine goes into closed loop AFR is between 15 - 16. When accelerating AFR goes down to about 14 (and maybe 13). A fellow corvette friend asked me what about fuelpump? Dont know how old my fuelpump is - but as long as AFR in open loop is quite rich I dont think there any problems about fuelpump not delivering enough..

Will post answer from PCM4less when it comes. I might ask him for a tune which gives me a AFR about 13-14?

Regards,
Thomas

STL94LT1

thomasev

Got an reply (and new tune) from PCM4less... He says "Here is a new file for you. Something is off somewhere. What injectors are in the car? What is the fuel pressure? What is fuel pressure under wide open throttle?"

"Something is off somewhere"... Can anyone with knowlegde about Datamaster and logging please have a look at the attached DM log and help me out? I have asked him what he mean about this ...

http://dl.dropbox.com/u/52503631/andre.uni

krackenvette

With the 92/93 the IAC can be bad and cause a false lean as it will cause more air to come in. The IAC will not give you a code. It needs to be unplugged at a minimum and read with an ohm meter. I had an IAC "leak" as it was broke for a long time, but since there was no code, I never knew it. It is a controlled vacuum leak after all. There are write ups within this forum showing you how to test the IAC. Alvin is pretty good.

USAsOnlyWay

This.

I think what Alvin is getting at, is that you are running quite rich at idle but yet going lean on WOT. At idle you are using FAR less fuel than at WOT, so if you have a pinched fuel line, clogged fuel filter, dying pump etc that limits your flow under high demand, this fits and could explain a problem of an overly rich tune still going lean at WOT (which is what I think Alvin is getting at.)

thomasev

Thanks, I will find the write ups about IAC and test it ;-) Hopefully Alvin can provide me with some info what he see in DM log and an idea what might is not correct. I will check the IAC, thx.

thomasev

The injectors should be OK, I have measured the resistance of all and the are OK. Before commencing my rebuild I used injectors in old LT1 (stock engine) and they were fine then. The fuel filter is replaced. I also changed fuelr egulator (to an Aeromotive type) a few years ago. I also have another one (a new Accel regulator). I will drop that in an see what happens. I have not replaced the in tank fuel pump, I might as well change that on to?

The FAT part at idle is in open loop. As soon as closed loop idle is also somewhat lean...