OUt of ideas here

[bigtmoney]

Ok, I bought a 92 RCSB from wrecker yard wanted a project and got a deal...or so I thought. Needed a motor so I got a 350 TBI from the junkyard guaranteed to run, while I rebuild the original. Finally got it running and driving but it runs like dog-piss! I can't figure it out, the damn truck will go 80 mph no problem, it just stumbles and bumbles when idling or taking off from a stop.

I have checked and rechecked the timing, set the timing at 0, 2, 4 8 and 12 pulled the power wire off the battery and reconnected the ESC. Won't run right on any at any timimg I set. I'm not getting any trouble codes, I replaced the MAP and CTS sensor to clear 15 and 33 codes. No SES light or anything, just runs like a jalopy?

I need it to run right so I can put a cat on it for emissions test. The muffler shop won't warranty a new cat with it running like crap.

 

[Swims350]

ok just to make sure here, when you do timing you have to unplug the est connector at the firewall, set it, plug it back in then reset the computer by the battery or ecm fuse. Then you say you have no codes? Do you know what the truck had in it stock? 305 350? because I heard the computer and chip must match the motor/injectors. meaning if the truck had a 305 or a 4.3 the plugins would work but it would not run right.

That needs checked,

fuel pressure needs checked.

If those fail maybe you need to make sure the computer can read codes, you can do this by unpluggin the o2 sensor and tape it up out of the way, drive it, wait for it to be up to temp and see if it throws a code.

If the thermostat is the wrong temp it may never reach the proper(195) temp to get the computer in the correct mode, or loop. One is open and the other is closed, one is when it's cold, the other hot, I get them mixed up.

Decode the VIn and see what motor it came with, lmc's website has the vin decoder for engine.



http://www.lmctruck.com/icatalog/cd/full.aspx?Page=10

there's the link.

 

[Mean Green]

Go here to decode the vin, it will give you everything you need to know: www.compnine.com/vid.php

And X2 on everything Chris said, i couldn't of said it better. I'd also check the fuel pressure for sure. Also check out the Distributer and Coil. Coil's can do some really weird things when there on there way out. As can the distributer if the magnet is cracked or the rotor is shot.

 

[bigtmoney]

I ran the VIN and know it came with a 350, I have the old block at the machine shop getting cleaned up right now, I'm gonna call up there and get the number off of it tomorrow. I drove it with the o2 sensor off and the SES light comes on after driving it a while....truck only seems to get to about 150 degrees too.

The computer seems to be reading codes ok, it lights up when i disconnect the EST wire or if pull the connection from the MAP or CTS.

One thing I did do was swap the intake, tbi most of the sensors and dist from the original to the replacement motor. I was having trouble setting the timing so I might have gone back to the junkyard dizzy I can't remember it was on and off soo many times. How can I tell if the distributor is bad or I have a leaky intake gasket?

Funny thing is, I bought this motor so I can use the truck to run the old engine to the machine shop etc. Since I dropped my block and heads off with it Saturday I guess I got my money's worth huh?

 

[Swims350]

well the dist. I think can be checked at your local parts store, and leaky intake gasket, well fuel in the oil or water, vac. leaks etc.

Now that we know the ecm is for a 350 or should be, it's more then likely something else.

check the egr valve, get a hand vac. pump to see if it holds vac. or while it's running reach in and pull up on the inner part, it should change the idle or kill the truck, if not it's bad.

fuel pressure needs checked, that requires a gauge and fitting for tbi.

egr is picky too, if it's bad you have to match the number on it to a replacement, I was told to ONLy use delphi or ac delco if not gm for replacement.

 

[Mean Green]

To check the distributer, the most common reason a TBI distributer goes bad is because of a faulty magnet, in my experience anyways. Anyhow, go pull the cap off the distributer and take a flash light and shine down to the bottom of the distributer and see if you have any visible cracks or rust on the magnet. Also check to make sure the dist hold down bracket is tightened down plenty good.

 

[bigtmoney]

I'll have to go to autozone and get a fuel pressure tester, I may try to swap the distributor with a spare one I have. Anyway i could be off 180 and the think still run and drive?

 

[Mean Green]

It could still run if you where off 180* but it would run like complete ass. You might want to try messing with the timing some more also, it takes a while to get them really dialed in.

 

[DRAGGIN95]

It will run but barely and it will backfire through the intake bad, and just generally run like crap.

 

[bigtmoney]

It does seem to run better the farther I get from 0 degrees with the EST unplugged. But when I tighten the dizzy and plug in the connector it starts acting stupid, idle drops from 1k down to about 500 rpm's.