So I've been thinking...

[Unofficial]

I'm having some problems with my '87. To start off, it's a TBI. One of the problems I have is that my engine light will come on after flooring it for long periods of time, like getting on the interstate, or just having fun. I have a 350 with the 305 throttle body unit and computer. I'm pretty sure that the 350 isn't getting enough fuel from the 305 injectors when it's being floored. Hopefully changing to a 350 TB and ECM will fix that. Also, if I'm driving at about 20-30mph, my RPMs will fluctuate about 300RPMs. I was talking to a friend and he thinks it's my throttle position sensor. He explained to me what it does (in detail) and I was thinking that's probably what my problem is. Has anyone ever replaced theirs or had a similar problem? I want to fix these things once spring comes around, and wanted some more advice, guidance, etc...

[Blazin]

Pull the codes, sounds like they might be one and the same problem.

[VileZambonie]

Check the codes like Blazin said and yes you need to be calibrated for a 350. If you are running too lean you're going to ruin your engine.

[dirtmod0]

I have seen a few trucks that had the problem after switching like you did You need to recaliberate the ecm or get the 350 prom should get you fixed up

[Unofficial]

That sucks, hopefully I haven't done any internal damage to my engine, it has less than 2,000 miles on it. I was convinced that the computer would eventually know to supply more gas to the engine. I realize that it's impossible when it's wide open, but you wouldn't think it would cause any problems when driving normally in the city. I have no idea how to put in new computer components, is it pretty easy?

[Blazin]

To swap the ECM just unbolt your glove box hinge, remove it, You will see the ECM a few bolts and a plug it will be out and you can swap in the 350 one. Damaging the motor would take some time. A lean condition will eventually burn up a piston or valves.

[VileZambonie]

It can only enrich the a/f mixture as far as it's capable of according to it's look up table. The 305 isn't mapped for a 350. You NEED to change it. Just make sure if you are just changing the prom you are grounded, they are ESD sensitive. Contact summit or any vendor and get one calibrated for your set up.

[Unofficial]

It can only enrich the a/f mixture as far as it's capable of according to it's look up table. The 305 isn't mapped for a 350. You NEED to change it. Just make sure if you are just changing the prom you are grounded, they are ESD sensitive. Contact summit or any vendor and get one calibrated for your set up.

So after getting the PROM it has to be calibrated too? How is that done? Should I call some junkyards or can I order one?

EDIT: Hey Vile, you showed me this a while ago. http://store.summitracing.com/partdetail.asp?part=MVC-187121&view=32&N=700+4294914956+4294908216+4294925008+4294840140+4294908008 If I buy that, it just slides right into my ECM and I'll be good to go?

[Unofficial]

Ok, I found a guy who had a bunch of GM computers on craigslist, and he has one for my application. This is the whole ECM, not just the PROM, for $50. They are new in the box. Should I take it or buy the chip from summit in the above post? Which is easier, putting in the chip, or swapping the whole ECM?

[VileZambonie]

Easy? It's the same easiness. I would replace the ECM and see how it does. If it's not to your liking have a chip burned.

[DnStClr]

$50 is a great price on a new ecm. Typically they're $150. BTW the throttle position sensor is easy to change. Two bolts on the passenger side of the tbi unit. The heads are torqx bit type.

[Captkaos]

Or just pull the chip out of the 350 ECM and put it in your truck.  They both used the same ECM.

[Unofficial]

Or just pull the chip out of the 350 ECM and put it in your truck.  They both used the same ECM.

Is the chip easily accessed?

[Captkaos]

You have to get the ECM out, but the cover unbolts and you pop it out.  So it is pretty easy.