Took me almost 50 years but I got my first IROC Z yesterday (86) . The guy I bought it from rebuilt the engine since it was already torn apart when he bought it and said he couldn't get the TPI to work right so he changed the intake manifold and put a new Edlebrock 4bbl carb on it.


It runs but is hard starting and once warms up it idles too high and really stumbles in gear with your foot on the brake. I have not yet tinkered with it but he gave me almost all of the TPI parts he took off. I would really rather have fuel injection for this car since we have a big swing in temperatures here from season to season and I am not good at tuning carbs. Plus I'd like to keep the car as stock and original as I can.


Looks like he left all the wires and wiring harness in the car as well as the computer. He bored the engine .30 over and bought a new cam he described as "one step above stock."


So...would you try to tune it up and stick with the carb or go back to the TPI? I can't wait to start working on the car but I don't want to waste money and chase my tail.


Thanks for any advise...

 

I'd go back to tpi. Or move to a quadrajet. Why live with the downgrade to an Edelbrock carb?

 

I'd prefer the TPI too. what resources would you recommend to make sure I have all the right parts to complete it and put it all back together correctly? I have the throttle body, plenum, fuel rails, injectors, tubes, all that but it looks like there are still some things missing. Where can I find a manual or exploded view of all the parts? I'm a little lost...

 

Check the classified boards or ebay and the like for a factory service manual. Otherwise do google searches to find pictures of just about everything. People here are pretty helpful too. It's probably going to take you awhile it figure out what you'll all need if you've never dealt with tpi before.

 

Thanks! I have plenty of time. Bought the car for my son as a project we can work on together until he gets his license over a year from now. I still love them and can't wait to get her going, for selfish reasons...

 

Congrats. I am also almost 50, so I know you have the patience to get this right. Go with the TPI, it has a lot of great attributes, like good torque and beautiful looks. And even though it's not the highest powered FI setup, it is original to your IROC.


My son bought his GTA 5 years ago. We tinkered with the TPI at first to get some of the wrinkles out, but it's been running smooth ever since. Lots of good info on this site for TPI, read lots before you start.

 

Tpi is the way to go in my opinion since the harness is still in the car, off the top of my head you'll need the old distributor and will need to figure out what he did with the fuel pump. This forum is the best possible place for advice and any questions you have. There's also tons of write ups on the swap you're doing so search around and you'll find out everything you need to know, good luck

 

I'd tune it up and get it running right first. No doubt. Don't start adding NEW parts to an engine that isn't running right. You'll NEVER get it straight! Chasin' gremlins forever. That being said, I'd personally prefer to eventually swap the TPI back on. Harness/electrical can be tricky, but you say it's still there? That's a BIG plus. ...and as Tyler mentioned, fuel. Somehow the pressure would've had to have been dropped a LOT for a carb. If he KEPT the EFI pump, and used a regulator to drop the pressure for the carb, you can just remove the reg and use the intended pump. If he removed it, and replaced with a traditional mechanical pump, then of course you'll need a pump capable of provided the much higher EFI pressure. Other than that, the only tricky part might be a tune to handle the new cam, however, the MAF (mass air flow) system used from 85-90 is much better at handling minor upgrades compared to the later 91-92 SD (speed density system). I can't be sure without cam specs, but I can't imagine a mild cam for a 305 would be too much for the system. ...when the time comes, explain the cam/tuning situation in a dedicated post, but I think you'll be ok. Other than that, it's really just bolting on parts!

I didn't overcomplicate it, did I? LOL.

 

Go with the TPI

 

Thanks for the replies guys.. I took a real close look at it last night and it looks like he just unplugged everything and pushed them aside. All the plugs for the injectors are there and a mass of plugs for all the sensors I imagine. He did tell me he put a fuel pressure regulator on there so it's still using the stock fuel pump. (good news there)


I also talked to a guy that programs the chips and he said if it's a mild cam it shouldn't be a problem. I just need to figure out which plug goes to which injector, etc...


time to make room in the garage and get started but I'd really like a factory service manual..I'll keep looking. Thanks!

 

On the injector harness, left side and right side. Bank/batch fire. So if it runs on the left, just connect them to the closest injector, it don't matter

 

Good news on the regulator, better than dropping the tank by far.

 

Yeah but I noticed the fuel gauge is not working...? Bad sending unit you think or is there something else I should check first? Could that have anything to do with all the TPI wiring disconnected?

 

Probably the best investment in the car that you can make.

http://www.ebay.ca/itm/1986-Chevy-Ch...2a982d&vxp=mtr

The wiring diagrams alone are worth the price. The Haynes manuals (or the like ) just don't cut it if you're going to get deep into the car.