Brandon2350

I am hoping that by posting this question, I can clear up a few questions I have. Vehicle-1993 rs. I have swapped out the stock 350 tbi with a 355 which has been balanced / Blueprinted, around 10:1 cr and fairly mild cam installed 6 deg. advance all while using stock ecm. I built this motor 10+ years ago so I really dont remember the exact cam or compression specs. (never was fired. recently pulled apart to inspect though) I want to say that it's between 375-420hp. Heads are ported 194's. Stock intake modifyed to bolt to heads. When this mongrel is idling, it is gassy and smokes black like hell, comes out of it above 1500. Idles (hunts for a better word) around 900 rpm up to 1200 rpm. real loopy. runs worse when up to temp. This is where i'm having trouble: From what I've read, a bigger cam should have leaned out the mix, not richened it. I have tested the map voltage and even installed an adjustable voltage cut out(which didn't seem to help any) Was told that the gear drive could be causing the problem with knock sensor, but I am under the impression that this wouldn't be relavent until it was in closed loop. Same for the O2 sensor I believe. Someone,Pleeeease help me. I'm not afraid to atempt programing. I would rather atempt to do it rather than sub it out. I'm sure this is a simple problem for someone with more knowledge on this subject than myself. I just need someone with some solid info to point me in the right direction

steve8586iroc

Sounds to me like you have to big of a cam. Check your vacuum at idle, rather while it's trying to idle. Usually a low vacuum signal makes the map sensor tell the ecm that the engine is under a load and or trying to accelerate, so it's richening the mixture, even though you arn't going anywhere. You also need to check for vacuum leaks.

Steve

JPrevost

One easy way to tell if it's timing, unplug the knock sensor and stand there with a timing light to verify the timing is about right. If you're running a stock chip or anything sold on e-bay then I can think of LOTS of reasons why the car runs so bad. Ask any TPI speed density guy if their stock ecm ran good, HA. Good and great are so far and imbetween. If you don't have the time to mess around with the TBI and do your own chips you are better off going to a carb and mechanical dizzy. It's kind of like school, there is the easy quick cash way if you get out early and then if you're in it for the long run you'll be well rewared with the smarts and eventually the money. Yes, TBI will save you on gas milage if you tune your own chips not to mention closed loop makes certain you aren't running dangerously lean or rich.

Brandon2350

STEVE, Thanx for your reply. I plan on doing some of this testing this weekend. I am quite excited about this project. I will definately stick with the tbi unit. For me, the part that makes this project fun is the learning aspect. I know Jack about computers and tbi units. I do know engines and carbs though. For me, taming this beast is part of the fun.

JPREVOST, I plan on doing some testing / troubleshooting this weekend. Steve has mentioned items that I am also going to check out. You mentioned timing / knock sensor. To clarify your suggestion, Am I to let the car warm up, check timing, remove the wire to the knock sensor then recheck timing? When it comes to computer control and tbi's, keep in mind that your talking with Barney Rubble here. If the timing remains constant, or if it should fluctuate, what should I be looking for? I am definately sticking with the tbi unit. For me, switching to a carb would be giving up. Taking the easy road. Yah, I could pay someone to burn a chip for me, but how much fun would that be. Nobody will treat your car as well as you treat your own. I am striving for perfection. As well as the satisfaction of knowing that " I did it". I love learning new things. It's even better when you learn something that you really enjoy.

steve8586iroc

You might also want to reset you cam back to 0 degs or even retard it 2 to 4 degs. If this combo is really capable of making 375hp you are going to run out of fuel and air with the stock tb and injectors, at the very least you need a Holley 670 or 454 tb with 80# injectors and a lot of tuning ie... chip burning. I see that your running the stock intake and I assume stock exhaust manifolds as well. That alone should be enough to give the engine fits I would think. But you still have to determine weather your problem is electrical (ecm related) or mechanical (parts combo). Hope you get it running good soon.

Steve

Brandon2350

[QUOTE=steve8586iroc]You might also want to reset you cam back to 0 degs or even retard it 2 to 4 degs. If this combo is really capable of making 375hp you are going to run out of fuel and air with the stock tb and injectors, at the very least you need a Holley 670 or 454 tb with 80# injectors and a lot of tuning ie... chip burning. I see that your running the stock intake and I assume stock exhaust manifolds as well. That alone should be enough to give the engine fits I would think. But you still have to determine weather your problem is electrical (ecm related) or mechanical (parts combo).
Steve[/QUHope you get it running good soon.
OTE]
The project was put on hold for a bit due to everyday hecktic life, a divorce and all that fun stuff but now i'm back at it and would like to share with all where i'm at and to ask for some advice.

By the way, I'm burning my own chips!!!!

It does idle now and thats all I'm focused on at the moment. I am going at this very carefully and methodically where as I'm not very knowledgable with this. I have had to adjust the fuel tables and timing tables (leaned the fuel considerably and shuffled the timing tables around to match up somewhat with my map) to get a decent idle but it's still not what it should be. For example, I still have to mash the pedal to get it started because I havent quite figured out what table would reference this condition and when, but for every chip I burn and data log I create an index card describing the changes made to that chip along with a brief description of how it ran on the back. I've burned 12 chips or so within the last month. My ecm is 16168625 with the E_6 definition file which I have not found much info on regarding it's tables and their functions either. It was only used in 1993 from what I can tell and tuner cat didn't have a calibration help file for it.

Alright, now the fun stuff:
It idles around 750 - 775 RPM in closed loop. (I haven't done much with open loop yet. At idle the manifold vacume is around 10 - 11". The cam is still installed 6 deg. advanced and the exhaust manifolds are also stock. The other day I wanted to double check the distributor to be sure the timing was set correctly before going too much further as it's been a while since i've worked on it. As it set idling I pulled the timing connector and within a few seconds or so it stalled. My closed loop blm's are all around 128 even though the O2 mv stays around 800-900 and the tps runs around 150. (knock was disabled, AE values were raised above tps threshold as was egr just to simplify things while I tune idle ) I'm guessing the Inj BPW may be set too large and the timing is correcting for this?? Shouldn't I still maintain an idle(or somewhat of an Idle) when the timing connector is disconnected? Any thoughts on this?