Ok, car is a mutt. 84 Z28 body with an 85 305 TPI. Was a project that I started about 5 years ago. Dropped in motor and it ran well for the 6 months or so that I drove it. Parked it and now getting back to the project. Since I started working on it again, car is hard to start (IE takes a couple tries to start, you can hear fuel pump when you turn key forward before cranking so relay is working, starts perfectly once engine is warm). Car is running rich (can easily smell gas and have had more than one person driving behind me comment that it smells), loping at idle, and sometimes will die at idle before it warms up. I have a leak at valve cover (have new valve covers, gaskets and pvc valves just havent had time to install) and am loosing coolant somewhere (I cant seem to pinpoint at the leak so I may have a blown head gasket but thats a whole other ball of wax).

Im thinking I have a bad injector or something but not really sure where I should start and am a little hesitant to drop 2+ bills on injectors without testing. I know I have a couple loose pins at computer which I also have to replace but the engine runs way worse if they are loose so I dont think thats the issue. To give a little more info, engine is stock 85 305 tpi, emissions has been nixed, exhaust is thunder series flowmaster with no cat/O2 (welded in pipe in its place of course). Havent had the check engine light come on once (which surprises me with the smog and O2 gone). If someone could give a couple things to check that would be awsome. Im not a moron but not a mechanic either so if you dumb it down to my level that would be great!

 

Ohm the injecters. I can't remember right off the top of my head what they are supposed to be but thats and easy way to tell if you have a bad one or not. Also check the tps for proper voltage and adjust the iac. do a search for these things and you can find the info on the correct ohms, voltage and how to adjust the iac.
Thats where I would start. And the missing o2 could be a problem also. I know a dodge will smoke like crazy and runs very rich with a bad o2, may be similar on a thirdgen.

 

Injectors should test 12 ohms each. Also, check your coolant temp sensor. The one thats right by the thermostat. It should read 3,400 ohms at 70 degrees and 180 ohms at 220 degrees. Fix the coolant leak and make sure the engine is full of coolant.

 

Thanks for a place to start. As far as the O2, I was having this issue prior to installing flow masters and getting rid of the cat/O2. Engine hasnt seemed to behave any differently without it.

 

If your O2 sensor is unhooked, then your CEL should light up to indicate error codes, if the light still works. If your CEL light is unhooked or bypassed, then you'll need to plug in some sort of scanner or datalogger into your ALDL port to retrieve the error codes.

Without the O2 sensor the car will run in open-loop mode all of the time, which is generally much too rich when the engine is warmed up.
If you want to continue to run as is in open-loop mode without the O2 sensor then you need to find a tuner in your area to make you a custom tune for open-loop only mode.
That would be the quickest and easiest way to address that situation.
You may find at that point that your engine doesn't have any other problems.

 

I respect and value 305SBC's input. However, I generally find, with all else as it should be, that an engine runs reasonably well in open loop. In open loop, the system operates on its base fuel or VE map, without any secondary fuel correction(BLM ,Integrator). The base map is programmed for the engine and generally runs the engine fairly well. Of course as parts of the system wear, precise fuel delivery may change somewhat. This is what BLM and Integrator are for.

Still, your issue sounds like alot more than just a problem of normal wear. It sounds like a serious fault in part of the basic fuel management system. This system includes the MAF sensor, coolant temp sensor and TPS. thwe system also relies on correct fuel pressure of approx. 43 psi. I am not saying that you shouldn't check out the O2 circuit. I would recommend that you check it for a short to ground. This would also cause your symptoms. I would also love to see you connect a scan tool to look at codes and to view data, looking for any of the above mentioned sensors to read abnormally.

 

Ok, all of my issues went away with one simple solution. I installed an inline check valve at the fuel filter. A little background; Motor is an 85 305 TPI dropped in an 84 body which was a 305 HO. The consequence is that the fuel lines did not match up well. 84 comes out on the passanger side of the engine bay where as the 85 is on the driver side. I had lines fabbed to get from the engine bay to the motor and also dropped the tank and fuel pump out of the 85 so I thought I had all my bases covered. Either the check valve in the pump is broken or it is missing somehow. The pump would pressurize the fuel line and then would drain right back out so the motor was constantly surging as it got gas then got starved before the pump kicked on again. Adding an inline check valve solved the hard start issue, loping at idle, and the motor no longer smells like its running rich as hell. It is also much more responsive; at low speeds it would sputter if I matted it because it didn't has gas for a split second. Still want to hook it up to a scan tool and see if there is anything else going on but my major running problems have fortunately gone away. Now I can move to the 500 other things in gonna do to this car before it is finished. Thanks to everyone for their input.

 

I have an '87 IROC with a VIN "F" TPI 305 in it that is doing the same exact thing that the OP describes. I was trying to find a chart with ohms readings for different temps. I suspect I have a bad coolant temp sensor.

I also can't imagine an inline check valve solving the problem....that just doesn't make any sense.