green.Z

Camaro is often slow to start. It requires extended cranking then when it does start, it stumbles to life for the first 2-3 seconds. The extended cranking occurs when the engine is hot or cold but is more likely to occur when the engine is hot. The stumbling happens regardless of engine temperature. Sometimes, I turn the key off and back on to start just so the starter isn't engaged for too long. No other engine performance issues other than the starting. It has plenty of power and idles fine.

I cleaned all battery cable and starter connections. No change on the starting condition but it did help the starter turn over faster.

I replaced the fuel injectors and fuel pressure regulator, both are factory Delphi/AC units. No change for the starting condition but does seem to have more power.

I removed the ICM and put a fresh layer of thermo grease behind it. I used the stuff you can get at Radio Shack. No change.

I checked fuel pressure today with these results: key on = 42psi and holds 40 psi for at least 2-3 minutes, idle with vacuum attached to regulator = 35 psi, engine running and blip throttle = 40psi. According to Haynes, these are acceptable numbers.

I've read a lot on this forum about this subject but not sure what to do next. Is there a way to figure this out without a scanner?

Injuneer

What happens to the fuel pressure if you wait more than 2 minutes for it to drop? What is the pressure after 10 minutes?

Will it start faster if you cycle the ignition key several times before turning it to "start"?

green.Z

I'm not sure what happens after 10 minutes. I didn't watch the clock too closely after the first 2 minutes but I would estimate it was more like 5+ minutes with good pressure.

It didn't make any difference when I cycled the ignition key several times. It still turned over for an extended period. I tried that before I got the gage - from reading this forum.

I cleaned the air filter (K&N) and MAF late yesterday. It's too early to be sure, but I don't think this has helped either. It also has a fuel filter on it with less than 5K miles.

Shoebox has the resistance values for the coolant sensor in the W/P and I read this is important for starting. I gave up on getting a good contact on the pins while it's in the car, but I may investigate this more or just replace it. I can't remember how old mine is either.

Do you think it would be worthwhile to watch the pressure for an extended period? If so, I can stop by the parts store sometime this week and rent the gage again. Anything else? I'm using the car as my daily driver at the moment, 140 miles per day, so I've got plenty of observation time available.

Injuneer

The factory manual has a spec for pressure loss after either 10 or 15 minutes. But if cycling the key doesn't help, not likely its a pressure bleed-down problem. Since injectors and FPR are new, not likely it's a flooding problen. But as you already figured out, could be the CLT sensor providing a low temp reading.

Try putting the accel pedal on the floor before trying to start, and hold it there until it starts. That would minimize the extra fuel provided by cold start enrichment.

green.Z

Holding accel pedal to floor while starting helped a little.

Wednesday night, I installed a new CLT sensor in the w/p. The stumbling I was getting on start-up is now gone. It now starts with a "vroom", about like it used to when the car was newer. It runs smoother than before also. MPG went up a little too. From 21-22MPG to 23MPG on the first tank since the new sensor was installed. I used to get 26-27MPG before the Crane 227 cam went in. I haven't given up on getting this mostly highway MPG number back. Not yet, anyway.

It does still sometimes crank over slowly, especially when it's really cold outside and the engine is hot. I can deal with this for now. I will eventually take my starter and battery to get tested. The starter is 8 years old, with the Autozone lifetime warranty. I suspect the issue is the starter. Still OK, but on it's way out.

Anyway, I say "case closed" on this starting issue. Thanks!