Recently found out my car has a 350 tpi swapped in instead of a 305.

Since I thought it was a 305, the injectors I put in a few years ago were 305 injectors, and installed an AFPR (set to 305 psi). I also found that there was no knock sensor installed so I put one in. (I would always get check engine lights (later found out it was a knock sensor code) but I never was able to scan it and find out.) The ESC module was for a 305 as well.

So last week I installed stock 350 injectors, couldn't get my harbor freight fuel gauge to work so I left fuel pressure alone. Immediately after doing the injector swap, I get a MAF code. Car ran perfectly fine, but the check engine light was always on. Replaced the MAF, code went away, but immediately get an ESC code. Car ran like ****, wants to stall in gear, often stalls when I don't have foot on the gas. Replaced with a 350 esc, does better but still bogs a little when going into gear. Stalled again but only once.

Do yal think replacing the 305 knock sensor with the 350 knock sensor will solve this? Or do I need to get a 350 computer as well...I looked at my computer but can't tell if it's 305 or 350. I also don't know about the prom..if that's inside the computer or separate..or what.

 

Need to find out if its a 305 ecm chip or a 350. Changing injectors size will change fuel amount going into motor unless chip is changed to reflect this.

Also the 350 should have a different knock sensor than the 305 so make sure it matches. Sounds like a tune problem but could be some other mechanical/electrical issues. I'd start with making sure the prom/chip is correct for a 350. Need to read the 4 letter code on it and look it up to see what motor its for. If its a 350 motor and has a 305 prom, look for a factory 350 chip on the classifieds on this site.

 

Bogging sounds like too much fuel. After u replaced the 305 injectors with 350 ones, what did u set ur fuel pressure to? Set it to 43.5psi. That is factory 350 spec. You are actually better off running 305 inj at a higher fuel pressure though,but it's ok now cause u might as well use the 350 injectors. Oh, and ohm them with a multimeter and check their resistance. The ecm' are the same between 305 and 350's. Just make sure you have the proper 350 prom chip in there now. Just make sure u use 350 knock sensor, injectors, prom chip and u can eliminate those from being culprits.

 

Installed 350 knock sensor..helped. iac then took a **** so replaced that. Helped so much. No stalling no bogging until an hour later it bogged again. Set to 305 fuel pressure ...my gauage wont work couldn't change it. Still no idea what chip prom or computer. Thanks folks. On the scanner it was bouncing between rich and lean I assume that is normal from searching. Would I fix everything by throwing a 359 computer in?

 

i told u what to do. take off ecm cover and look at the prom chip. Get some numbers off of it. Set ur fuel pressure to 43.5 psi.

 

There is no difference between 305 fuel pressure and 350 fuel pressure. Stock pressure with the vacuum line disconnected in either case is 43.5lbs. At idle with the vacuum line connected you'll probably see 38-ish.

 

Is there a prom from another GM car (like a car common in the junkyard) that will work like the 90-92 guys can do with the 7730?

 

Any 87-89 TPI 350 car should have a prom to work for you. can keep the computer the same, just need a 350 chip and memcal from the 350 TPI car. There are several different codes out there.

 

yeah 87-89 350 tpi prom from a 165 ecm.

 

you need to look for codes again and see what you get after you install the prom too.

 

crap, no 350 cars in any junkyards here...was hoping I could find one out of a beretta or something like the 7730 proms...guess i'll have to find one somewhere else. Damn

 

What did they swap in in from? If the original engine was an L03 the fuel pump also needs to be upgraded.

 

no idea what/where/when the motor was swapped from.

the heads say 14102193 my friend said it is "‎193 is light duty ultra swirl port truck heads" Don't know if the heads and block have been swapped.

original motor was a 305 tpi.

I'm guessing they just bolted up a 350 block, threw a tpi intake on it and rehooked all the 305 harness/sensors/computers/injectors

 

Keep in mind that the 89s eliminated the cold start injector. If your setup has one, either make sure you get a chip for an 87-8 or if you get a chip fir an 89, remove the cold start injector and cap off the back of the fuel rail.

 

Good point. Forgot about the injector.

Sounds like they got a truck 350 and put the 305 stuff on it. If thats the case the L98 bin may work ok but the truck has different heads and cam than the L98 so it may still be a tad bit off perfect. MAF should correct just fine tho

 

thanks folks

 

edit: never mind, found a friend who has prom burning stuff...anyone know where I can find a stock 87-88 350 auto trans prom file to upload?

 

I have an 89 5.7 prom in here...with a brand new MAF sensor and now I can't get rid of the code 33. from what I read here: https://www.thirdgen.org/forums/tech...ible-code.html

Do I need to get rid of the square relay connectors and wire in the rounded off relay style connectors? (if possible)

Autozone showed the same part numbers for mafs 86-89 5.0 and 5.7 (fbodies...vette was diff number)

Or switch to an 87 5.7 fbody prom maybe? At a loss here...fighting this car all year long.