PaNaRaMuH

Just got done rebuilding my 1995 LT1/4L60E a few days ago. Got it in, started it up but it wont stay running on it's own. If you peddle it, it will stay running. Also, if I unplug the MAF it will idle around 1,500-200 RPM after it comes down from 3,000. I do have a terrible exhaust leak, so I can't really tell if there's any knocking going on. Can't take it for a drive, either. Need to correct my fathers mistake on turning to linkage in the transmission forward one to many.

The guy I bought it from had the PCM tuned to a different cam by PCM4Less that it had when I bought it. Could this be the issue since I swapped cams? The exhaust fumes are reallyyyyyy overwhelming.
There are two plug ins that aren't connected to anything that we don't know of. One of them is blue, on the drivers side in the back and has a very short cord. The second one is red and sits on the passenger side which has a 5-6 inch cord.

Trying to give as much info as I can about this. As it's been a long-term 7 months rebuild and it's frustrating having it not run properly. All info is appreciated.

Mods of importance:
CC503 Cam
Hardened Pushrods
OEM Lifters.

ACE1252

The red plug may be the EVAP purge solenoid. Not sure on the blue could be EGR soleniod...can you get us a good picture of the intake?

What springs are you running? Are you sure the valves are adjusted correctly? Do you have new injectors or stock? What cam was in it with the prior tune? What is the fuel pressure with the key on, engine off?

The CC503 will, generally, "run" on the stock tune with just the injectors tuned(if you changed them...if stock injectors, it will "run" on completely stock tune). So it should not be idling stupid or any nonsense like that.

If the guy that had the PCM before had different injectors and you have stock ones....that could be a major issue right there. Throw your stock computer on it(if you have stock injectors) and see what it does.

ACE1252

Shoebox's site is a treasure trove of 4th Gen F-body information. Have a look at some of these reference pictures.

4th Gen LT1 F-Body Tech Aids

4th Gen LT1 F-Body Tech-Component Location Views

http://shbox.com/1/egr1.jpg

http://shbox.com/1/evap_sol.jpg

http://shbox.com/1/pcv_pipe.jpg

http://shbox.com/1/map_seal.jpg

http://shbox.com/1/map.jpg

http://shbox.com/1/opti_vacuum_conn.jpg

http://shbox.com/1/fp_reg.jpg

bw_hunter

Lots wrong here. Fix the exhaust leak asap.

You have to figure out those connectors. Take pictures and post them

After it runs call the pcmforless guys and get a new tune...

ACE1252

I doubt disconnected EVAP and EGR solenoids would give him the headaches he is having(but I have been wrong before...), but he does need to get them connected to the right spot.

bw_hunter

No, you're right...but he needs to get them connected as they may not actually be the items you mentioned. Anyway, the problem he has is due to a massive exhaust leak confusing the o2's and the PCM that isn't quite right on tune..

mrmint69

What is your exhaust leak from? Having a proper tune is very important and the car will run pourly until fixed. Sounds like you rushed to finish, but need to get those things fixed before even running it. You should make sure you do all the stuff to it before the tune, like if you want to change the gears or delete anything. This way you only pay once right now.

PaNaRaMuH

Thanks alot for all the replies. The previous owner got rid of the EGR, and evap solenoid. Block plates placed and welded. The car has CM612 springs, came with them. The injectors are the same ones that were on the intake when I bought the car. I plan on fixing the exhaust leak as soon as possible but for some reason I don't think that's what is causing these headaches...

Also, I don't know if this is of any help. But if I take off the rest of the cold air up to the MAP sensor and cover it slightly with my hand, it idles right around 1,000RPM. Which is what the previous owner told me he had the PCM idle speed tuned to.

The reference pictures from shoeboxes website help slighty. Particularly http://shbox.com/1/opti_vacuum_conn.jpg <- This one. Could the disconnected "To Optispark" connection cause the issues? Because I thought that was the vent tube and was suppose to be connected to the intake. We just have it hanging around in the engine bay disconnected.

I'll also try to get pictures of the connections tomorrow after work. Thanks again for the help.

ACE1252

Oh, I read the OP incorrectly. I thought there was a second PCM involved. Did the car run correctly before the rebuild?

Unmetered air and vacuum leaks will cause issues. Go over the intake connections with a fine tooth comb.

PaNaRaMuH

Lol, no. The car did not run correctly before the rebuild. As soon as I found a piece of a connecting rod on my trailer when I got it home...I knew it was rebuild time. A new block, all new bearings, oil pump, rings, crank, pistons and seals were all put in. The reason I didn't find a port for this "Vent tube" for the opti spark is because it's capped off on the intake? Why would that be?

ACE1252

I'm not sure why it was capped, but the last thing to do to the optical distributer is to stop the flow of fresh air through it. That will, sooner or later, kill it.

mrmint69

Do you know if the injectors are the same size as the ones the car is tuned for? Very important.

Jesup16

I had a similar issue when I rebuilt my lt1 and did the cam/valve train.

I'm willing to bet it is in the valve train and might even be a vacuum issue.

I swore up and down I adjusted the valves/roller rockers/springs correctly, but it turns out I didn't and it ran like your describe.

PaNaRaMuH

I'd assume they are since we didn't switch them out/change the intake. It was the intake/injectors that came with the car.

Also, got underneath the dash again today to hook up the 2-speed fan switch and found a connector not plugged in. It's small, and I plugged it in already. Could this cause issues?

Here's a picture:

The other connector that I was talking about last night, the red one.

Here's a picture of it:


Took out the plug in the intake for the opti-spark vent tube and hooked it back up, too. Still problematic. :/

ACE1252

I think that first one goes to a small black box in that area. I'm not sure what it does.....I'll have to look it up, unless someone else knows what it does.

The second one goes to the EVAP solenoid.


If you don't mind, get us a good picture of one of your injectors.