StevenK

iTrader: (1)

Hey guys, I've finally got the time to sit down with the car and work with it to try and get all my problems I've been having fixxed. This thread is intended for me to keep track of what I should be doing, and to get input from the smarter people that like to help out here. I'll start with the car setup and how it is currently running.

1991 Z28, L98 Motor with t-5 tranny swap. All stock motor except a Holly 52mm TPI, stock exhaust.

Currently when I get in the car and cold start it, it requires me to give it a little pressure on the gas pedal to get the motor to turn over, once it catches, it will typically idle around 800 with a surge of maybe 200 RPM, warm starts are fine. Driving around in parking lots, not using much gas, or letting it idle around in 1st will sometimes make the car surge or give you whiplash, but it seems totally random. I'm currently running 93 octane gas because I was noticing alot of spark retard, I still get a little, especially in the lower RPM areas, but it seems the lower octane gas was causing it to pull out over 10 degrees at times, now its less than 3 degrees most of the time. When I look at the histogram of driving, its mostly pink or red, showing me the car is running rich, and that I need to pull out fuel (assumption). I would also think I need to pull out a little timing in the lower RPM areas seeing as it doing it by itself.

Link to Files

Mike115.bin - My current .bin, it was made by Mike (1bad91Z) just as a starter. Its basically just a stock chip with the IAC learning and temp stuff changed from what I understand.
Also in the list are some log files from today:
Cold_Start_Jan18.uni - Cold Start, first run of the day, just to see if there is anything in there to help show why I am having cold start problems.
Warm_Start_Jan18.uni - Warm Start after the car had been sitting a few minutes and went into closed loop. I will use this to tune the VE for the idle to try and get rid of some of the gas smell and hopefully help the idle surge.
Warn_No_IAC_or_Timing.uni - Pulled off the Timing wire (brown), gave the IAC 30 sec to reset in field mode and disconnected, set min idle to around 700RPM. Not sure if this is any use, but for some reason, with no IAC or computer controlled timing adjustments, it still surges.
Warm_Reset_IAC.uni - Reset everything, started it up again and let it idle after reseting the IAC. The idle was still surging, and on the previous start (I forgot to hit record) it surged about 200 RPM for around 20 seconds, then out of nowhere surged down to 400 RPM, back up to 1500 a couple of times, then died. That was the only time the surge made the motor die today.
Long_Drive_jan18.uni - This is a pretty long log, me and my dad drove across town and I had him watch the laptop while I drove. This is where I came to find the lower RPM spark seems off, and the lean condition. Also, after the car was warmed up and we had been driving awhile, everytime I would stop at a light or push the clutch in, the car would refuse to idle anywhere near the programed number, mostly around 1200-1400 RPM.

This post is getting pretty long, so I am going to post now and add replies as I think.

-Steven

1bad91Z

iTrader: (1)

Steven -
I cant remember all that I changed on that chip. I think I turned off VATS, EGR, and a couple of other things, along with setting up the .bin for a manual tranny. I'll try to take a look at it later on today or 2morrow.

RBob

iTrader: (1)

Vacuum leak? Also check the TB to plenum interface, the IAC passage moved some time along the way.

RBob.

StevenK

iTrader: (1)

Okay, I went ahead and burned the chip and did a cold start just now. After a couple of turns of the starter, the engine fired and idled really low for a couple seconds, surged, and died. Turned the started again, 5 seconds maybe and it started again, low idle but continued to run until closed loop. As the engine got a little warmer, the idle came closer to where it is supposed to be. Didnt really surge much if at all. Now looking at the scan, I am seeing my IAC at 160 (which is IAC park in the chip). Does this mean the IAC is not doing its job at all? Why did the engine die on the first start? Also I am noticing that the 'L-Term C Counts' are stuck at 118, what does that mean? The car did still smell a little rich when I sniffed the exhaust, but it does seem better.

The only changes made were fixxing a mistake in the injector constant from 24 to 22 lbs, and I took the VeMaster changes from my Jan18 log to change the VE tables, it only changed cell 4 from what I can tell.

I uploaded the log of my cold start run to my files page for you guys to look at....Link. It is the 'Cold_Start_Jan19.uni' file. I'll also attach an image of the screen just for the people that don't have datamaster handy.


-Steven

StevenK

iTrader: (1)

Truthfully I have no checked for a vacuum leak, I do not hear any hissing noise from under the hood. What is the best way to check for a leak, should I get something flameable and spray around the engine and hoses, or is there another method you prefer? I personally put the Holly TB on with a fresh gasket and tightened it down, so I am pretty sure it is not leaking, again, should I test that somehow?
What do you mean by the IAC passage moved? I did clean the lower IAC plate and all that when I changed the throttle body, and then put it on with a fresh gasket.

Thank you for taking your time to give me ideas and feedback RBob.

-Steven

1bad91Z

iTrader: (1)

Post a pic of the closed loop idle datamaster log.

StevenK

iTrader: (1)

Also, another concern I have which I think might have something to do with the idle surge is the 'Inj BPW' field is moving between 1.3 and 1.8 and not staying static, is that a problem?

Uploaded 'Warm_Start_Jan18.log' which is a closed loop idle. Attaching screenie also.

-Steven

1bad91Z

iTrader: (1)

You are probably stuck in cell 4. You need to change CCP purge percentage to 0 %.

Then we can work on VE.

RBob

iTrader: (1)

The reason I suggested a vacuum leak is that as you stated with the exception of the TB everything is stock. The surging is an indication of a vacuum leak.

If the only change has been the TB that is where I would start. There could also be a leak between the plenum/intake/runners too.

The only tuning change really required would be additional AE due to the larger TB. Other tuning can help, but I can't see it being required to fix the surging.

RBob.

1bad91Z

iTrader: (1)

Which one of the AE tables in TC do you modify and what part of the table? Just add 5% in the idle area RPM's ?

I thought you just had to play with IAC constants to fix a surging idle?

StevenK

iTrader: (1)

I assume you mean to do this? or do you mean something else?

StevenK

iTrader: (1)

Sorry to sound like a newbie, but could you explain this more, or show me a link to a thread that does explain it? After I find and fix the surge I will do this step, so no rush if you don't feel like typing it out now.

-Steven

1bad91Z

iTrader: (1)

Nope, you need the updated $8D TDF from tunercat to see the constants that you need to change.

StevenK

iTrader: (1)

Okay, I do not appear to have a vacuum leak, I just did a test and its about 18-21 at idle. (for anyone wondering how, pull the vacuum line off the break booster, took me forever to figure that out). On the first start it cranked, almost started then died. Second start it cought and slowly found its way to the correct idle, it idled about 550-650 for about a minute, then sat at a good idle with slight surge to closed loop. After that I did a warm start, started fine, no major surges, I then revved it up to 5500 twice to show the vacuum readings.

Me being the dork I am, I grabbed my digital camcorder and filmed a cold start while doing the test just so you guys could hear the surge I am talking about.

Uploaded 'Cold_Start_Jan20.uni' and 'Warm_Start_Jan20.uni' which are logs of the run today. Uploaded two video files of the car running during those logs also. First is from cold start, and the second is a warm start with the 2 revs.

Click here to download

-Steven

Kat

iTrader: (4)

So far outta the few SD cars that I've changed over to manual I had to set the base idle at the throttle body. That cured the stalling out problems when first being started.

HTH's

Kat

1bad91Z

iTrader: (1)

My car acts a little funny on a cold start only since I put the six-speed in. It doesn't bother me. Once she warms up, the car idles nice and runs like a raped ape!

Greg

It sounds like to me that you need to open the throttle blades more. The 160 steps you are seeing is way too high, it should be around 20-30 at a warm idle. When you open the throttle blades more it should also help the cold start. It's not idling high or hardly starting because the IAC is open as far as it can all ready. Open those blades and make sure the TPS is at .54 when your done.

StevenK

iTrader: (1)

Sorry for the lack of updates lately on this thread, my t-5 gear linkage broke and I had to pull it out and get the tranny rebuilt. Kinda hard to test the can without a tranny, lol.

The only reason I havn't opened the blades more like suggested by greg is it seems to totally screw up the idle once the car is warmed up. What I mean is....I get the IAC counts really low...5-15 at cold start idle, and it keeps a good idle at 800 or whatever is commanded. Then I take off and drive around for 20 minutes, and the next time I stop at a light or whatever and i'm at 1400-1800 idle. Why would that be? Also, I don't know if its a computer commanded problem or a physical problem with my gas pedal cable, but sometimes when I stop at a light, I idle at 1100 RPM, and if I 'blip' the gas (in other words tap on it slightly so that the rpm flare to 1400 or so RPM) it will go back down where it supposed to be. Any ideas?

Thanks again to the people posting and giving me ideas on what I should be doing, hopefully one of these days i'll get my baby purring the way it should.

-StevenK

JP84Z430HP

Why not just start with a .bin for a manual application? You could always move your current spark and fuel tables to it.

Are there some other features you want to keep from the .bin you already have?

Just curious!

StevenK

iTrader: (1)

I just used this one as a starting point because it is the one Mike made for me. The chip i had before mike's was a 305 5-speed chip with the fuel/spark tables moved over, and I was having a big surge problem. Mike's chip fixxed most of the surge.....

JP84Z430HP

Now I understand!

1bad91Z

iTrader: (1)

Steven, you drive a pink car!! lol , j/k

Your pics dont do the car justice.

But anywho, how's it running and are you feeling well since the op?

Mike

StevenK

iTrader: (1)

Thats Power Pink to you Mr. Weak Rear-End!

Yeah, I made that sig while i was in the hospital, didn't have much to work with on the laptop, but it got rid of the boredom for about 10 minutes.

I'm feeling tons better, just waiting for the muslce and stuff to heal so I can lift stuff and start working on the car again without getting a hurnia (sp?).

I'm gonna have to come spend the day over at your place sometime soon, this surge/unpredictable idle is pissing me off. The 93 octane got rid of most the knock, and if I ever get around to tuning the BLMs some more, i'm sure that would just about get rid of em.

ttyl.

Steven