1997 Riviera SC HARD START problemo!

Hello all!

Here's what is THE problem;

The car runs very fine and works otherwise very well (except failing tranny), but has developped annoying hard start problem. When we measured emissions, it seems it has too much fuel in starting condition (too much Hc value) and engine seems to choke. I even smell gas from exhaust when that occures. Interestingly, when I turn engine off for a minute or so, it fires up right away, but if let sitting for, say 10 minutes, it gives this rich condition. And ther's no DTC codes. Very very odd!

The NEW parts I already swapped;

-fuel injectors
-fuel pressure regulator
-spark plugs
-crankshaft sensor
-coolant sensor
-ignition module
-IAC (idle air control) motor
-new (even bigger) battery

Sooo, where one should go next, you think?

BTW, Our car ---->

https://rivperformance.editboard.com/t9952-finnish-ok-canadian-originally-97-riviera-resurrection

I'm thinking, is it anyhow possible that ignition system isn't having full voltage due corroded ground points? But then again, it would affect whole performance, not only starting, yes? Or can starter motor eat up enough current, so PCM not having enough when cranking? Just my hopeless thoughts...

You mention putting in a bigger battery. Why? Is it cranking slow?

Abaddon wrote:

You mention putting in a bigger battery. Why? Is it cranking slow?

Actually no. I was suspecting low voltage condition at ignition circuit when cranking.

Can you connect a scanner to the OBD-II port and see what the coolant temp sensor is reading when this happens? I'm wondering if you have a bad wire to that. The wiring harness can get brittle, and especially hot down where that coolant sensor is. Possible wires melting?

deekster_caddy wrote:

Can you connect a scanner to the OBD-II port and see what the coolant temp sensor is reading when this happens? I'm wondering if you have a bad wire to that. The wiring harness can get brittle, and especially hot down where that coolant sensor is. Possible wires melting?

Actually this is not bad idea. I had OBD scanner onboard, but didn't notice any deviation from normal values. Now I'll try and disconnect IAT sensor, and drive around tomorrow, in hope to find the culprit.

Well, no luck. I even changed new fuel pump unit, because had wild idea of bad drainback valve in the pump. I think I have built "new" Riviera with all these new replacement parts!  But seriously, new ideas are very welcome. Next part I'll be replacing is MAF sensor, or should that be camshaft sensor?

And to think of it really, car start right away if shut down and started immediately, but if let it sit for a while (like getting a beer from supermarket) then hard start thing!?! Drieves me REALLY crazy.  

Feels a little stupid to replace all these parts for nothing, even when I managed to succesfully install fuel injected 1995 LT-1/4L60e in oldskool '80 T/A which I think  was little more complicated s**t compared to this troubleshooting dilemma )

You probably had multiple things go at once, not a big surprise on a car engineered for a more or less finite lifetime.

maybe the FPR was bad new... (happens if you don't get a Bosch or a Delco/Delphi)

maybe the CRANK sensor is having issues (they will go bad warm). You have to install a good one, I would use a Delphi. The replacement low price ones fit but are really made differently, and don't last.

maybe something is wrong in the vapor recovery system that is causing the fuel supply to over-pressurize?

Hi!

Thank you for ideas. It came to my mind, that it's possible to have Vapor Recovery System to cause this kind of malfunction.. It would make sense. Now, is it possible simply bypass it? Should I simply disconnect purge solenoid connector?