I just bought a 91 formula and I need a little help. The previous owner put in a 350 where a 305 once was and all is not well. The codes show code 42. I am putting in a chip from a 91 corvette 5 speed to maybe help my problems. The problem is that when the car is cold she has plenty of power but won't idle, When warm it pops through the intake and has no power. I don't know if anything else has been changed or not. I am looking for suggestions to my bird fly again. The only way it will run is with the base timing set at 0 degrees.

How do you tell the difference between 305 injectors and ones for a 350?

 

https://www.thirdgen.org/techbb2/sho...hlight=code+42

https://www.thirdgen.org/techbb2/sho...hlight=code+42

 

Both sound like my problem!!! I have replaced cap, rotor ,plugs,wires, distributor, coil, and still have these problems.

 

Sounds kinda like the guy did do a 350 swap, and used the 305 chip and injectors. And since it's a 91 and thus speed density, it doesn't know you have a 350 and you're really lean. When cold it runs richer so it at least has some power. But once warmed up it just noses over lean on you.

If thats the problem, you're in luck. All you need is a chip. Check the sticky post on the top of this board. The change you need is very basic. And in the grand scheme of things, the stuff you need to do it isn't that expensive considering the power it gives you.

The flip side owuld be it's a 350 swap, but he did keep 350 injectors. And because of how the math works out the fuel for this would be close so the problem would likely be elsewhere.

You can figure out what chip is in the computer by pulling it down and looking at the chip. As for the injectors, only way to tell for sure is to pull them and check the part number. If you can get a picture of them though, someone might be able to ID them by the year/type, but not always. Worst case, you have to pull the plenum, which is really easy anyway, and gives you a good chance to port it while it's off.

 

I have a chip ordered for a 350/5speed. I hope this helps. The injectors look just like the ones in my 305 in my other car. I will also be replacing the fuel pressure regulator soon. Can I do this without removing the plemum? As for porting- I don't think so. I need to get this car running soon. Thanks for all your help.

 

The vette chip will not work since you don't have an oil temp sensor. At the least you'll get aconstant SES light from that, not sure if you'll have any other problems.
And besides that, just swapping chips isn't going to help anything. You need the chip and injectors to match. Putting a 350 chip in with 19lb injectors isn't going to work any better than the 305 chip running a 350.
The easiest and best way to completely solve your problem is to get into PROM burning. $200 and 5 minutes and you're ready to go with the added benfit that you can do a lot more down the road. There are no factory chips you can buy that will help your situation without at least swapping injectors, which is going to run you about the same amount of money anyway, and is an uglier solution. I'll break down for you the various things you can do.

-PROM burning equipment. $200, 5 minutes and you're ready to go. Start with a 305 5 spd bin, set the cylinder size for the 350.
- use the stock 305 5 spd chip (f-body), swap in 22 lb injectors. Ugly, but is close
- get a stock 350 A4 chip (f-body) AND a set of 22 lb injectors. From what i've heard this doesn't work that great with a 5 spd though since driveability functions are different 5spd to automatic.

 

The motor in my car is a pull out motor from a junkyard. The intake doesn't look like it has ever been off. All I know is that the engine was pulled out of an IROC. I may already have the proper injectors. Is the oil temp sensor the only difference? I don't think I will get prom burning equipment since my other car won't have tpi and this one will not be modified. I just want to drive my car again.

 

OK, so pull the injectors and verify the part number, pull the ECM and verify the chip and go from there. I already told you how to make it work, but you still don't even know what you have. Guessing is not going to advance your cause. Or are you just in no hurry to actually fix it?

edit: Just thought i'd add that honestly, at this point, you can't take ANYTHING for granted. If you don't check the block casting numbers you don't even know for sure that you have a 350. Unless you helped the guy put it in, you should have NO reason to believe him when he says he swapped a 350 in. That is THE most common lie that people will tell you about a TPI car they are trying to sell you.
Probably not what you wanted to hear, but just thought i'd throw it out there, because it is a very distinct possibility that the problem could have nothing to do with a '350' swap, and everything to do with some other aspect of poor maintenance or just some other problem. This is where the chance aspect of buying a car with a serious problem comes into play. Most people don't do an engine swap and then sell the car unless they know they botched the job. The less you assume, the easier things will go.

 

I checked my chip against my other car and they have the same number on them( don't have them with me right now). I pulled the engine to put an oil pan gasket on it, the casting numbers on the blok were unreadable, but behind the drivers side head was "5.7". The reason I bought the car was because the previous owner could't get it to run right and his wife busted out the hatch. I put a hatch on it, fixed the leaking oil pan and now I am here. What part number am I looking for on my injectors? I am pulling my intake this weekend to change the regulator.

 

if you have really good eyes, you might be able to see the part number on the injectors without even taking anything off. I have one of my original injectors sitting on my desk here, and the part number is wrapped around on the top of the body of the injector on the right side looking at it from the connector side. The 305 injector i have here is 17086542. I forget where the part nuumber was exactly on the earlier styles. Check here: http://members.shaw.ca/s15/Fuel%20Injector%20List.htm for a pretty good list of early injector part numbers. If it isn't there, just do a search on what you see and more times than not somebody will have already posted to try to ID them before.

btw, sorry if i sounded harsh, didn't know you had pulled the engine and all that. You seemed to be dragging your feet a bit like a newbie that thinks we're experts at guessing games

 

It is not that I am dragging my feet, it is just that my time towork on the car is limited to weekends and I am fairly unfamiliar with TPI. I am more familiar with ford injectors that are identified by color. I thought about using the injectors out of my LT1 to get the car running. I am going to put in a new knock sensor as well this weekend to see if that helps.

 

When an engine backfires up the intake manifold, that's a sure sign of running to rich. Either something is up with the ignition and it's not burning the fuel completely in one or more cylinders, or something is convincing the ECM that alot more fuel is necessary. Start checking and/or replacing sensors- maybe in order of ease of replacement (below). Main sensors that affect fuel delivery (at any speed) are the following:

1.) O2 sensor
2.) Throttle position
3.) Manifold Air Pressure
4.) Coolant temp
5.) Manifold Air Temp

1 and 2 are the most expensive, while 3 and 4 are likely the same.

Some simple things to do first are checking the fuel pressure, fuel filter, amount of manifold vacuum (vacuum leaks?), and PCV valve.