Okay guys, been chasing this one for months, hope someone can help.

I have a '92 350 TPI T/A, auto. Car has over 200K on it, but the engine and tranny have less than 10k. Mods include edelbrock headers into factory dual cats (which to seem to be working fine), Flowmaster muffler, ported intake plenum, bypassed TB heater, Holley fuel pump, BBK AFPR (set presently at 45psi), all new tune up stuff (plugs, wires, cap rotor), Accel coil, mild stall. I plan to install a home fabbed air cleaner/ intake tract soon. I have also installed a newer distributor off of another car, that was in perfect running condition before removal (this has yielded no result). Also has new egr solenoid. Stock injectors have been reconditioned and flowed. New stock computer. New 190 high quality thermostat. Timing currently set to 8 degrees.
So here are the problems. 1) The car is difficult to start in the a.m., taking 5 to 10 seconds of solid cranking to start. When it does start, it runs rough for several minutes, and is very rich. It does smooth out, though it has a slight miss/ surge at part throttle cruise rpm ( this is barely noticeable to passengers, if at all, but I've been building small blocks with carbs for many years, and can feel a miss). It leans out a little once it warms up, but seems a little rich all the time, though I get about 23 mpg on the hiway and around 10 to 12 in town. 2) I occasionally get a raw fuel smell out of the car, like spilled gas. The fuel cap is fine, and I can't find any leaks. While I have not checked the actual fuel pressure after the car has been sitting for a while, but it seems to hold pressure because I can hook up the gauge after it has been sitting for over an hour and get fuel spray all over.
3) Once the car warms up, I can shut it off and it will start easily if I restart it within a few minutes. However, if it sits for anything much over 15 minutes, it exhibits hard start again.
4) Car idles poorly, even after adjustments; seems to want to idle too low, and will sometimes slightly surge (50-100 rpm fluctuation). Occasionally dies at stoplights randomly. It did it a couple of days ago as I was trying to pull away from a stop sign.
I just changed the oil today, and while not excessive, the old stuff does smell a little fuelly. My concern is that I may be washing down the cylinders.
I have set the idle by the book several times, the TPS shows proper voltage across the board, the timing has been set anywhere from 6 to 12 degrees with no change. I have adjusted the fuel pressure from 38 to 53 psi with no real change.
On the positive side, the car has tons of power ( for a basically stock TPI), and lights the tires at will. It is throwing no codes.
Sorry this one has been such a long post, just trying to eliminate some possibilities, and am tired of throwing money at this car. Thanks!!

 

on the fuel smell, an intermittent leaking FPR is a possibility, check inside the vacuum hose for fuel signs just before you start it after sitting over night. leave the vacuum hose off when you start it & check the FPR for any fuel when you start it. the FPR may also be sticking at times & cause a higher
than normal pressure.
check the charcoal canister & the hoses for raw fuel, there is a filter on the bottom of most canisters that gets dirty & can cause raw fuel to get drawn into the canister.
the injectors may be leaking intermittently. the only way to know for sure is to pull the fuel rail up, pressure the system up & put some clean paper towels under them and let it sit over night & check the paper towels for any signs of fuel. pressure the system back up a second time & check the injectors again for any signs of fuel leakage before you put it back together.

if you can, scan the ECM. look for the air & coolant temp sensors readings to be pretty close after sitting over night. see what the block learn & integrator are running at. check the MAP & TPS readings. the O2 sensor may not be working right, they can shift & cause you to run rich & not set a code.

 

Thanks, I'll check the canister...I had a suspicion about that, but didnt want to say so and skew anyone's ideas. Also didnt realize an o2 sensor could change and not throw a code... I'll just replace it anyway, who knows how old that is.
Any suggestions on which one to use? So far I have been going with GM sensors, or high quality aftermarket stuff (NAPA, etc).

 

For the long crank on a cold start. Check that the fuel pump runs for 2 seconds at key-on, engine-off. It should, if not then the engine needs to build oil pressure before the fuel pump comes on (lots of cranking).

Using a scan tool verify that the CTS & MAT are reading correctly. A bad sensor will throw the fueling way off.

Then check the resistance of the injectors. Measure across each injector's terminals. Each one needs to be above 12 ohms. Doing this while the engine is hot is recommended. The stock Multec injectors short the coil windings and cause all kinds of problems.

RBob.

 

Thanks, rbob. I just checked the fuel pump on your advice. Interesting results. Pump runs for a second or so, then shuts off. Normally, I just climb in and start winding the starter. This time, after listening for the fuel pump a couple of times without starting the engine, then turning over the starter, it fired quickly (pluh-pluh-pluh) and died. Then after only a couple second of cranking, fired right up. Still ran crappy, but started easier. Strange.
Wouldnt a CTS or MAP sensor failure throw a code? I'm not getting any. Thanks, and I'll check those injectors shortly.

 

The MAP sensor is such a dynamic reading that it typically throws a code when bad. They also rarely go bad.

The CTS can be bad and not throw a code. This happens quite often. There is no way for the ECM to double check the reading. If the sensor is dead shorted or open, that the ECM can tell.

If the reading is way off, the ECM doesn't know that. What usually happens is that the CTS connector gets a little corrosion on it and drives up the resistance. The ECM sees this as the engine being colder then it really is, and adds fuel.

RBob.

 

i recommend using A/C Delco on the o2 sensor, i have had too many problems with other brands.


it sounds like your pump takes some time to build up pressure.
my pressure will bleed down to 0 rather quickly, but seldom ever takes more than 2~3 seconds of cranking to start, even after sitting for 2 or 3 days.
hang a pressure gage on it for the next cold start & see how long it takes to build the pressure up.

 

Thanks for the help guys. I just found out I will be driving this car to Vallejo Ca from my home in Vancouver, WA. I'll give this stuff a try and let you know how it goes!

 

Ok so my 88 camaro v6 does the same thing. But it doesnt start acting up until its warmed up. And then it start to idle low at stoplights and it starts to smoke nonstop out of the pipes. And when i turn it off to go into the store and come back out it wont start so then i have to wait for it to cool down sometimes 15 to 30 min. And then when it starts up its still acting up. It has a new fuel pump and injectors., plugs and wires and distributor cap. Any help would be awesome. Thanks

 

Sounds like what I mentioned about the CTS in post #6. Next time it is warm and won't start hold the go-pedal on the floor when cranking. That is a clear flood mode.

Leaking injectors will also cause this issue.

RBob.