I'm currently working on a chip for a friend's 88 L98 IROC. Engine is a 355 with SVO 24lbs injectors, a Comp 214/220 cam, 1.6 roller rockers, TPIS intake, SuperRam plenum and runners, SLP 1 3/4 headers, and Flowmaster exhaust. Many thanks to GregW for his help so far, but I want some more opinions.

Idle in park/neutral is set to 750, and 725 in drive. Fuel pressure is 40 at idle, 46 disconnected, IAC reset has been done, set to 725 RPMs. IAC steps shows 39 at idle. Throttle voltage is .67V, is that too high for a MAF car? I'm using the ARAP chip of course. BLMs and INTs are in the 120-130 range, so its slightly rich at idle. I'm using Diacom+.

The problem I am having is the car will stall when I give it a little gas and then let off. I can bring it up to 1000-1500 RPMs and then let off, and the car will stall and die about half the time. It does this in drive as well. I'm not sure what the three stall saver thresholds mean, but I have them set to 550 (1), 600 (2), and 650 (3) with the disable threshold set to 700. Why is this car stalling??? Thanks for the help.


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1991 Camaro Z28
5.7L 5-Speed (originally 305)
317 RWHP, 418 RWTQ
13.23 @ 107.62 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Member: SoCal F-Bodies
-=ICON Motorsports=-

 

The idle may be a little low for that cam, I run right at 800rpms if that makes any difference. Yes the TPS is a little too high, you should be able to adjust it back down to .54+- , make sure to check all of the basics first, timing, etc...
Have you messed with the pumpshot at all?

Brendan

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1987 IROC-Z L98,SR,EB 6085's,LPE 219/219 Cam, Crane 1.6RR, EB TPI Base, 58mm TB, Stock T5, 30lb SVO, AFPR, K&N, EB TES, Catco Cat, 3" Borla Cat-Back, Accel cap,rotor,distro/other crap, Aluminum DS, 94 Disk Rear, Adjustable Prop Valve, Precision 3.73 Gears, Weld in Sub-Frame Connectors, Hotchkis LCA's, KYB Shocks/Struts, Poly Bushings all over the place, Moog Upper/Lower Ball joints and Tie Rods ends/Idler Arm, Big stereo, 730SD Conversion.

To see the ROC, Check out the webpage Here

 

Timing is verified at the stock 6 degrees. Whats the name of the pump shot table in the $6E code in TunerCat?

 

Shoot, I can't remember the exact locations, I'm sure Glenn will chime in with them sometime. I tried doing a quick search(i'm at work) for them but came up empty handed.


Brendan

 

PS,
The pumpshot table isn't listed in the Tunercat TDF, or atleast the older 6E I have, They may have added it by now. I know the tables are listed in GMPRO though..

 

My car with the big LT4 HOT cam idles just fine at 750, I dont see why this cant idle at 750 too. But mine is a stick and this is an automatic with a 2400 stall converter. I raised the idle to 750 and its a lot better but still stalls a little. I guess I'll have to try 800 RPMs.

 

BTT,Im having a similar problem..IT seems like I have to adjust the IAC/TPS all the time..

Daz

 

Who says MAF cars adjust to mods so much better than speed density?

I raised the idle to 800 in park/nuetral and 775 in gear, and its a lot better, but it still stalls a little. Its seems to stall only when going slow up driveways, now. Crazy thing.

 

have a look at what the 02 reading is when he stalling occurs , you normally find that large overlap cams can cause rich idle mixtures , running them leaner tends to help.
Also look at the BPW and see if the idle logic is throwing fuel in causing overly rich mixtures.

 

I took your idea and ran the injectors down to 40psi and advance the timing..apparently my base timing was waaaaay retarded..just a thought for Kevin..This condition was waaay worse before I changed my MAF though(giving an "out of range" error.

Daz

 

Well I have the LT4 Hot Cam, 2400ish stall, automatic with MAF and a mostly stock ARAP and I can get my car to idle almost flawlessly as low as 500rpm. It would tend to die once in a long while if I gave it a quick rev in gear and let off but that was it. It would idle forever at 500 if I wanted to. I also see that my car runs extremely lean at idle. My O2 nearly goes to 0!! I have the stock 22lbers running at 51psi which gives me palatable WOT performance but I am still lean at part throttle and idle big time (160-170 BLMs and WAYYYY low O2). I just ordered 30lb SVOs and I am GOING TO GET THEM TO WORK DAMMIT!! Even if it kills me..... lol. I think they will help eliminate the part throttle lean issues (which are extremely annoying and cause the engine to surge violently) and with the right rail pressure will not run too rich at WOT. I see some long nights at the computer coming........... lol.....

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1987 GTA L98 MD8
355, TFS Heads, LT4 Hot Cam
My GTA

The Minnesota F-body Club

 

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[This message has been edited by KlayBuRn (edited October 02, 2001).]

 

Matt,
I wouldn't be running your engine that lean. Do you ever check your plugs for detonation? Every have the knock sensor going off? I would definatly wait until you can either get bigger injectors and mechanically halfass it and/or get the prom equipment(if you don't have it) so you can get it running properly.
No being an *** , just don't want to see the motor blow up.

Brendan

 

No worries. I have all the equipment to burn EEPROMs and I am working on getting it to run right as we speak. I am not recording any knock as of right now (I know the sensor is still alive), and it never runs hotter than 175*. Of course, 100 octane fuel doesn't hurt . I know it is lean but I have pulled a few of the plugs and they don't show any signs of detonation and are somewhat getting a brown tinge to them. The entire engine (including all sensors) is only 2K miles old as well. I have done a few things already with rail pressure and lieing to the ECM about injector size with little help on the idle and part throttle lean conditions. I am using WinBin though and all I saw was a place to enter injector size rating @40psi to control injectors with. Every time I change my rail pressure or injector size seems to help the WOT stuff and effect how my mixture is there, but doesn't really get me anywhere on part throttle stuff . That is why I think that a larger volume injector will help me out where I need it and I can work with my rail pressure and injector constants to get my WOT stuff perfect. I am still a novice with EEPROM tuning and not really sure what is going on with my setup as far as the lean condition goes.

Thanks for the help....

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1987 GTA L98 MD8
355, TFS Heads, LT4 Hot Cam
My GTA

The Minnesota F-body Club