Having a starting and idling problem - Third Generation F-Body Message Boards

defaced · 06-07-2009, 08:20 PM

Alright, this may be somewhat lengthy, but please stay with me.

I just swapped in a rebuilt 350 bored .030 over. This engine replaced the worn out 305. I reused all of the intake stuff, including the 19lb injectors. I also removed the smog pump. I was having some problems with the car starting so I checked my fuel pressure. Did it 5 times in a row and everything was fine. Just after I did that, I backed the car out of the garage and put it in the street. Went back out a couple minutes later to put it in the driveway and it wouldn't start. Checked the pressure again, and no fuel pressure. Took out the FP fuse to make sure it was ok, ended up being good. I tried starting it after I put the fuse back in and it fired right up. Haven't had any FP problems since.

Now, this problem is what's started to drive me nuts. When I start it on a cold start, it'll crank strong and fire right up. As soon as it starts, the RPMs go up to about 1100 and then it bogs down to about 200-400, and then right back up to about 800-1000. From then on out, it idles kind of smooth. I replaced the TPS, adjusted it according to the Haynes manual. I've also got a new ignition coil, checked the module on the distributor and that was fine. I also just rechecked the timing a couple nights ago, was at about 0 degrees BTDC. Moved it up to 6 degrees BTDC where it's supposed to be.

I put it in the garage tonight and when I started it, it started fine but it idled horribly.

I have some things that I'm going to replace just because they're so old. Those things include the EGR valve and solenoid and the IACV. I have some hook ups at Advance Auto and my buddy is going to swap out my old ones for new ones under warranty so I won't have to pay anything.

This week I am ordering my custom PROM for the ECM to run my LT1 injectors and disable the smog crap.

One more thing I forgot to mention, I explained what it does on cold starts, this is what it does on warm starts. After driving for a while, if I park it and go to start it about 10-15 minutes later, it's really hard to start. Once it does fire, it doesn't bog or anything but still kind of has a rough idle and the tach needle seems to be all over the place within a couple of hundred RPMs.

It's not the FP because I check it every once in a while and it still has normal pressures and I can hear it turn on all the time. I'm still thinking about replacing it though with a Bosch pump just because this one has 130,000 miles on it.

If any of you guys can think of anything else I should check or replace that I haven't already listed please give me some input. This crap is driving me absolutely nuts. I still drive the car because it hasn't left me stranded yet and I trust it to start, it just starts too hard. I'm very anal about very little things and this is just another one of those things. I would literally be pulling my hair out if I didn't shave my head.

Edit: Thought of one more thing. It also seems to be running pretty lean. The cap and rotor have less than 1000 miles on them and the spark plug have about 2000 miles, same as engine.

formula_novice · 06-08-2009, 02:43 PM

A 355 with 19lb injectors... I guess it would run lean. Those injectors are too small.

defaced · 06-08-2009, 05:14 PM

Quote:

Originally Posted by formula_novice

A 355 with 19lb injectors... I guess it would run lean. Those injectors are too small.

Oh I know, that's why I'm in the process of ordering my PROM chip from TPI Parts on ebay.

Well, I think I've narrowed the problem down to actually being the fuel pump, considering the fact that the FP just failed on me last night, haha. Oh well, it has 130,000 miles on it so I guess it was time for a new one anyway.