I have searched over this entire site and found a bunch of help up to this point. A little back story and info. Bought this 91 RS for my son, PO blew up the 305 and his uncle that knew everything about cars dropped in a used 350 truck engine. When he did he reused the original 305 equipment on the 350. So as I have been messing with it a little I have changed the computer, the esc, the injectors to 61# from a guy here on Third Gen. I have been fighting a strange surge at tip in. So if I am stopped and try to just ease away it seems to bog and just flounder. When I let off the throttle the rpm drop to 250 and it tries to die, and sometimes succeeds, other times it will catch itself and come back to idle. I got a meter and checked the TPS which seemed to have some weird things in it so I went ahead and got a new one, it helped a little but it still did the same thing. Last night I read lots and finally found one thread that said to disconnect the coolant temperature sensor and see what happens. Well, it threw a code but ran perfect. We even threw the family in it and drove it to dinner and the autoparts store with it disconnected. Ran flawlessly. I was so excited that I went ahead and changed the sensor before it was even cooled down. (Antifreeze is hot! LOL!!)
Once the new one was in and leak free I took the wife for a ride and it started doing it again. Mostly when I take my foot off the throttle now and not as bad getting back on. I removed the IAC and cleaned it all up before my disconnect experiment. UGH!
This is going to be my sons DD although we will be building another engine for it, I would like to be sure everything works or I might think it was something I did to it during the engine replacement...

Oh the plugs are newer standard plugs, wires are newer and the cap and rotor are good. We checked the timing and it is set to 0* with the wire unplugged.

I haven't checked fuel pressure as it runs fine all the way to 4500 rpm shift points and never faulters. It has the orig pump I assume. So.. Here are my thoughts,
Coil? Seems strange to be having issues only at tip in and throttle closing.
Maybe the IAC is bad?
I have heard there is a difference in the truck EGR valve and the car EGR. How do I know if this thing is working?
Maybe fuel filter, but honestly that seems unlikely as I believe the PO replaced and it runs perfect at higher RPM including at 80 mph.
I am at a loss..Thank you all for your help.
John

 

sounds egr'ish

fwiw, my timing is set to 6 btdc

 

OK well.. I took the EGR off, it is a GM part and the bottom was black but not clogged, I have no idea how hard I should have to push on it! I don't have a vac pump to check it. Is there a way to check the EGR with just an Fluke meter and a vac gauge? I suppose I can invest in another tool, I hate to buy a high dollar egr valve and that not be the prob...
Maybe I will bump the timing a few degrees. Not sure what they were set at in the caprices since that is what the computer came from.

 

disconnect the wire to it.

On my 4th gen the EGR was affecting the idle. I blocked off the egr and then reconnected the sensor/solenoid until I got it tuned out. You just want to see if it's a possible culprit so disconnect it and go for a very quick cruise.

 

I did it! I unhooked the vac line from the EGR valve and it was so much better! It will sometimes dip to 500 rpm as I let off the throttle quick but never seemed to want to die. Maybe that is the culprit. I am still unsure which port on the EGR Solenoid is for the vaccuum and which goes to the EGR valve. I noticed that one of the holes in the solenoid has a restrictor in it, so I am assuming that goes to the valve. Maybe.... Anyone?
So I guess I need to hit the parts store and get a new EGR. I did notice that tonight once I got done getting it warm, (it is tough because it is down to 50 tonight.) I took it down the highway and under cruise I get an intermitten SES. I pulled the codes and I am getting a 13 and a 43 now. I am rather certain the 43 is because the PO was super cheap and reused the 305 knock sensor. Just going to live with that one since it really rarely knocks and this engine is going to a new home this winter/spring when the new engine gets built by my son and me. It will give us something to do when the snow is knee deep.
I will also just get a new O2 sensor since they are cheap and I can reuse it on the new engine too.

Thanks a hell of a lot Torque!

 

you're gonna love this one

I have restored my 3rd gen and had the 305 rebuilt. Anyway, I was getting a code 43 as well. Instead of using 89 octane I filled it with the crap 87 and the problem went away. Apparently, these silly computers want to hear a knock and the 89 was preventing it so my timing was being retarded/advanced and the car would backfire every now and then.

Since I knew nothing was broken having just restored the bugger I got to thinking about maybe these old fashioned ECU's wanted to hear a knock.

After running down the 89 and filling with the crap gas the car ran better with no code 43


absolutely completely opposite of all of my newer vehicles which run better on higher octane and adjust the timing for more performance.

I've come to the conclusion on GM vehicles that if something makes no sense at all, that is exactly how the engineers would have done it. In other words, when you say, "nah, nobody would do it that way" well, think again if it's a GM product.

 

Sounds like more than one issue.

Would grab a used egr before dropping money on a new one. Also would just give the entire engine a good once over. Plugs wires etc check for vacuum leaks, fuel pressure etc etc etc. Think you have a few smurfs messing with things under the Hood, not just one

 

William,
I have checked everything except the fuel pressure. I do know that the PO had run this thing for a long while with the wrong fuel and knock parts. It was always smelling of fuel until I got the computer and esc and injectors right. I drove it again this morning and afternoon with just the vac line to the EGR removed and it runs so nice... No it is not as smooth and comfortable as my 07 Grand Cherokee Limited, but it is running so very nice. William, I also am convinced that the engine has been damaged but all that fuel washing down the cylinders and or the PO may have installed a high mileage engine in it anyway. I have noticed some oil mixed in with the moisture from the exhaust after it has set for a few days. I am not concerned about the long block because this is a project for my son, so we will be buying a good engine for him to rebuild. I just want to be sure everthing other than the long block works before we tear into it!! Where might I get a good EGR? The salvage yards here are not flush with 92 350's...

 

Alright, thank you all for your help. I believe that I just may have found my issue. I went into the local O'Riley Auto Parts to see about the new EGR valve. When he looked it up I was surprised to see a valve that looked different than what I had on the engine. It reminded me of a thread I ready, probably on TGO, where the valve for the Camaro and the one for the truck engines work differently. Seems maybe that they are commanded the opposite way so they are designed to operate differently. If anyone knows for sure I would be interested.
The valve for the truck engine was very hard to push up and IIRC mine should be easier to open. I know mine is not dirty, well not stuck and moves when I push it open, but connecting the hose again makes it stutter, balk, buck, and stall. I guess some how I need to find a used one. Just not sure which engines now and how much to pay. Maybe I can go back to the engine I got my computer and ESC from..... HMM