Alright, I have posted something similar to this in the past, but I hadn't out any miles on the new motor yet to really break it in first. I have since put about 1300 miles on it and feel it is broken in enough. Anyway, on to the point.

I have a 355 4 bolt main block I had built a while back now but kept the 305 HO heads for it. It also kept the 19lb. injectors. I have all the 305 to 350 swap parts taken care of including: knock sensor, PROM for a 350 auto., etc. I even had a burn made a while back from TPIparts.net that was supposed to account for the eliminated EGR valve, no cold start injector, VATS disable, and the 19lb injectors. However, that PROM actually gave me more issue with runability than the stock 350 chip I have, so I left the stocker in there. It seems to run a bit rich though which seems funny considering it has 19lb injectors and a 350 chip (350 runs a 24lb. injector right?)

Anyway, the car starts right up and idles and drives, never stalls at lights or anything, but it seems rough at cold start with the idle. It could be the cam as the cam was a peanut 305 cam ground to 350 lift and such numbers and now I'm sure has a bit more duration (ie slightly mild cam). All vacuum lines are good and all sensors were replaced or checked good when the build took place. When it is warm it seems to run a bit smoother, but is still rougher than stock. Now I am sure it will run rougher as the mix matched parts are not stock running off that stock chip. But is there any way to really tune this car for the setup? Will the laptop program and chip burning software be able to account for all the variables in this case?

The car is a strong car and reliable as the day is long. i have never had an issue with it stalling or not starting, but I feel it could idle a bit smoother perhaps and not quite so rich. Or is this rough idle due to the cam and that's that and the rich is just rich? Any input would be appreciated. Thanks.

 

People on this board have run the 19# injectors on a stock 350 with out any issues, using the 305 chip. Some said it ran better. Do a search.

stock 350 had 22# injectors.

19# injectors with 22# stock 350 chip will run lean.
Injector constant set higher than injector actual flow = less fuel/lean. Computer o2 closed loop will try to correct to 14.7 AFR

19# injectors with 24# on the chip runs very lean.

what are the cam specs? lumpy cams can idle rich.

 

Also, the computer is expecting the cold start injector to be there, and richen the mixture a bit. You are probably a bit lean at cold start.....

 

That's what I mean...it should be lean, but it is running rich. The cold start is just on the intake, not the actual engine or computer as it is an '89. I guess the 305 the genius put in there before me before I put the 350 block back in was out of an '88 or earlier with a cold start. It shouldn;t be accounting for it though should it? Also, in Florida, cold start is really like 70 degrees :-p

 

As far as the cam numbers, it is a stock 350 cam number for lift and lobe, but the grinding process to achieve that number with a 305 cam I think required grinding the underside of the cam lobe which would essentially increase the duration right?

And if the stock 350 had 22# injectors, than that is probably what the PROM is feeding the car for injector pulse info. I just would think that if anything, the car would run lean and it runs rich. It has new sensors all the way around and should not be reading like negative 40 degrees or anything that might make it run rich. I don't know. I think the idle may just be the cam...and if a mild cam can make a car run rich at idle, than that may just be what it is. Like I said, the car starts and runs fine. Just seems to be rich is all and have a slightly less than smooth idle is all. I appreciate the reponses.

 

What is indicating that it running rich at idle? smell, black smoke, black plugs, tail pipe, mileage?

stock cam should not make the idle too rich. more duration would. did the grinder give you any paper on the cam numbers?

check around for a stock 305 memcal for that year car. to try.

Get the car scanned at idle to see pulse width, blm's, rich/lean. Maybe you will get some insight as to what is wrong.

 

Thanks...I will do that next time I'm at the shop. I think it's rich because of the smell and mpg. I think I'm averaging around 10 mpg right now, maybe 11. Also it smells pretty rich. I will try and locate a stock 305 auto. PROM. What throws me is when the 305 motor that someone had in there before I put the 350 back in, they had a stock 350 auto PROM in the ECM, according to the numbers on it anyway. It seemed to run fine...aside from the terrible racket it made from the spun main bearing that is.

 

I am running 24# svo at 50# with stock 88 chip. idle is alittle rich (no stalling or fowled plugs) gas mileage is 15 town 20 highway.

Got this by running a tired maf (only reads to 187 gr/sec). It ran the best of the 4 I had to pick from. lower maf numbers make for leaner running. The bigger injectors and fuel pressure are offset by the lean Maf.

Will be getting tuning equipment soon so I will reset the consants, change to a 255 maf and tune from there.

 

I think you should conntact the guys rom tpis, or do you have a hot rod shop around your area?? when you start swappin and mixing parts it can become a headache and a half!!. To me something sounds off with the cam. What are the cam specs and are the valve springs matched to that camshaft?? sounds more like your rough idle is cam related but I don't know your specs so I can't be certain

 

Do you guys think a 305 PROM will really help in this application? Right now, it has a 305 HO intake setup on it with a cold start injector, but I think I have that disconnected or removed; 305 injectors, but I have the 350 knock sensor, ESC module, 4 bolt main block, and it has been bored .030 over as well as had the cam ground to 350 specs but using a 305 cam to start before the grind which is why I think the duration is longer. So it is kind of a 50/50 mix match right now one way or the other. Basically, would it run more or less the same on the stock 305 PROM as it does on the stock 350 PROM or worse? Would it be in my best interest to just take it to a tuner shop and have them fiddle with it as I have none of the equipment to properly tune it?

I would like it running perfectly if possible before I really get serious about selling it. I like a car to be in as close to tip top shape as possible as I hate having someone else's problems handed down to me when I have no history on what has been done to the car besides what the previous owner says.

 

No one has an idea if this PROM would help or not? Even a speculation or a maybe and why or why or not would help. I just don't want to buy a 305 PROM and have the same issue if not worse occur, just to satisfy a curiosity or a "maybe it will run better", if you know what I mean...

 

Here is your challange

#1 the 350 chip is more than likely set for 22# injectors. If you post the numbers off the memcal in the ECM, somebody can help you verify this.

#2 Without running a scan on the car while it is idling, this is just a big guessing game. There are 25 differant outputs to the data log. Which one should we pick?

#3 The more accurate the information the better the help can be. Things like how many people have worked on this. has it been rewired. have all the connectors been verified as to tight and plugged into the right spot. All grounds hooked up and vacuum lines. has all adjustable settings been verified to factory spec's.

There are about 50 things that can cause a rich Idle. Which one????

you want definant answers to I don't feel good whats wrong questions.

Good Luck in your quest for knowledge. I can't help you sorry.

 

It doesn't really matter anyway. I have asked countless questions and given all sorts of detailed information about the issue and my car to get the same "did you do a tune-up...that might help" answers. I know you are not one of those and are just trying to help, but the more info. I give, the less of a response I ever get. I'm just frustrated.

And to verify the application for everyone then, so I can still get zero response to any of my questions, the car has all new vacuum lines, no leaks. No cat., no exhaust leaks, no intake leaks. The PROM is a stock 350 PROM out of an '89 Trans-Am auto MAF TPI car...I can get the number, but it probably won't matter. Grounds are all good as well as anything that might have ocuurred due to age as the car has been gone through top to bottom sicne I got it and rebuilt everything for the motor rebuild and interior swap, etc. Wiring is good, any issues fixed long ago. I am the only one working on the car right now. It is 10:43 AM and am facing north. The sun is brightly shining and a dog just barked behind my shop. Hope this info helps.

 

Not to interfere, But I would get rid of the MAF sensor and repin your ECM and put in a 1227730 Speed Density ECM with a AUJP ECM then use a MAP Sensor. They are actually alot easier to program.. You might also want to consider going to MOATES.NET and getting all the necessary software and hardware and hanging around DIY ECM threads. To program your own ECM isn't hard, but takes some basic smarts.. It is extremely hard to get an exact tune for any engine if you buy the pregrammed chips. I learned that lesson after asking 1000+ questions.

Hard Ware Needed
**************************
Chip Piggyback Adapter
Moates Autoprom or Ostrich
Laptop
Chips and Ribbon Cable
Couple of misc parts

Software Needed
**************************
Tunerpro RT (Free)
Flash~N~Burn (Free)

C.A.T.S. Computerized Automotive Tuning Software Costs $$$$$
but you can get same thing accomplished.

 

It's not butting in...it's an answer to what would help. The only problem is I am going to sell the car relatively soon and don't want $1000+ in just programming it when it runs alright now, just not perfectly is all. I am starting to think there are too many mix matched things for a simple PROM burn or tuner shop visit even to fix and it would be more economical to swap the entire intake over to a 350 with proper 350 fuel injectors and rail, no 9th injector, etc. I just had this stuff from the previous motor and didn't have the money...nor do I now really...to buy all those 350 parts. I kick myself too because I had some 350 injectors, but they were used, so i didn;t keep them around. Unfortunately, the result is it will be harder to get to run right until I do. I was just looking for a speculation on whether the 350 chip or 305 chip would be a better stock base program for the car to run on based on my specific application as the entire intake system is off of a 305. I wasn't after exact written in stone definite solutions, just opinions on what might work or not work based on people's personal experience.

 

I wasn't sure what your intentions were. If you were planning on keeping, then I would go the full route and buy whats needed to get~er~done! But, you don't have alot of options as to what you can do to get it fixed right. Most of your problems currently sound like a good ECM tune can fix them. When I 1st started altering my engine, I quickly learned that I just couldn't change this or that without consequences. Not too long ago, I had a good friend sit down with me, and taught me alot of the basics to tuning. I am still not 100% on top of where I should be. But, I am close. I now have another brand new engine and all new components on this next install. So, Back to the drawing board for programming again. But have a good idea of where and start and what to modify in the Prom. I did the drastic change from a 7165 MAF ECM directly to a 7749 ECM with a $58 mask. I am still awaiting for Scannerpro to be completed so I can tune in Real Time. Tuner Pro R/T and the Boosted 7749 ECM don't like communicating with each other. I have to use my Scap-on Scanner MT-2500 while driving, then tune from there.

 

Maybe I'm misunderstanding something...but...

Are you running a Cold Start Injector AND an '89 PROM?

If so, that's your problem...just unplug the CSI harness and I'd bet you'll be okay

 

Well, the 9th injector is there and has fuel to it as you can't really eliminate it without fabricating something to block it all off which I didn't have time for at the time of the build/install. However, there is no electrical connector to it as the car was not designed for the cold start injector and the PROM is also out of a post cold start set-up. So it should not be firing as there is no signal...unless of course the thing is leaking all the time from a bad seal or something.

 

It's possible the CSI is leaking, only way to make sure is to pul lit and cycle the FP on and see if it holds pressure...but you're correct, if there's no wires plugged into the intake from it, it shouldn't be causing any problems...assuming it's good.

So, you're back to just running the stock chip?

If so, you probably need some tweaking, as the 305 heads will put your CR in the 10 to 1 range or so, plus thay have smaller valves (asuming you didn't upgrade), so it's kind of a mismatch...higher CR, less flow...that 083's would have been.

Most definitely though, it can be tuned, it's just a matter of learning the PROM tuning and buring a zillion proms, or biting the bullet and spending the bucks on a dyno-tune.

You seem to have you **** together, i/e sensors replaced/tested...and really, the only thing on cold startup that could affect things...would be the MAF and the CTS....might have issues with the IAT readings

I'd suggest first getting a scan program or scan tool and post INJ pulsewidth, MAF readings/etc on startup...also too, once warmed up and in closed loop, post the O2 readings, see if it's doing the crosscounts, or just diving off up or down..etc.

 

You have such a mesh/mash of parts, its very hard to know whats going on. As 8Mike9 said, to really get to the bottom of it, you need to run a scanner.

One more point: I thought that in '89, the cold start injector was removed. To get the extra fuel that the CSI provided in earlier years (like my '87), the start-up fueling was increased. But, I guess that this would not have anything to do with running rich on a cold engine.

What is the fuel pressure, as Mike asked, and do you hold fuel pressure. Attach a fuel pressure gauge, and just turn the key to the on position, do not start the engine. What does the pressure peak at, and how long does it take to go to zero?