I had a leaky intake manifold gasket so during the replacement I also replaced the fuel pressure regulator.

When reassembling the motor I put the distributor back in with cylinder #1 at tdc on the compression stroke and lined all of the factory timing marks up. I had to turn the oil pump a little to get the distributor back in.

Once assembled I had to trouble shoot a few things like a leaking fuel line, an unplugged wire connctor on the distributor and a disconnected vac line. Eventually I got it all together and took off on a road trip to California...

On the drive I got pretty regular p0171 and p0174 codes. The blazer ran ok, idle feels a little rough, it has a little trouble starting.

My question; is it possible that I didn't quite get everything lined up when I put the distributor back in and the timing is causing the lean condition to pop up?

Thanks for your help.

 

If the distributor is not timed correctly with the camshaft, P1345 will turn the SES light on. There is an adjustment to the distributor that needs to be checked, and adjusted if necessary, and requires a capable scan tool. The adjustment aligns the camshaft position sensor with the camshaft. The adjustment is called camshaft retard, or CMP retard, depending on the scan tool. Spec is zero degrees, plus or minus 2 degrees. It can be off as much as ~25 degrees and NOT set the DTC. It will not affect ignition timing, which is not adjustable, and fully controlled by the PCM.


Low fuel pressure and or volume will set P0171 & P0174 simultaneously. Might be worth checking: https://blazerforum.com/forum/2nd-ge...eakdown-88305/


Another possibility is a vacuum leak at the oval shape O ring on the fuel metering block. It needs to be oiled before installing the plenum, and the metering block needs to fully seat into the plenum, or it will leak vacuum. If it leaks, it likely to set the DTC's you have, along with unmetered air/air intrusive.

 

Thanks Captain Hook, I am not throwing the p1345 code so I will let that stand for now, I've got a shop that will take a look at the camshaft retard next week. I fogged some break cleaner around the fuel metering block with no effective change in idle, but that is my current hypothesis, I might take the top off and check that gasket, grease it really well, and give it another go.
On my 1500 mile test drive to California and back the heater core kicked the bucket so I am currently banging my head against the wall about that one. I have about 10% of the fasteners removed... for some reason removing the dash makes me more nervous than taking the intake manifold off.

Thanks for the reply.

 

If you need guidance with the fuel delivery tests, let us know when you're ready.


Heater core replacement is far more involved than removing the plenum. If you haven't replaced a core on a 2nd gen S/T body, plan on 8+ hours of work. Each one that I do, I swear it's the last one There is a thread in the How-To section that might help.

 

Well, I put a presure guage onthe service port and got a reading of 65# pump on, 55# pump off but after ten minutes it was down to 45#. Four weeks ago a shop replaced the fuel pump and filter, last week I had the plenum off and replaced the fuel pressure regulator. I am leaning towards the pump being good and the pressure regulator/ gaskets etc. being in question.

 

The link in post #2 explains how to test the fuel pump maximum output pressure and leakdown. With those two numbers, along with the two that you posted, we can determine where the problem is. Without them, all we know is that regulated pressure might be OK, and that the system leakdown is slightly excessive, that's it. That's not enough data to make an accurate diagnosis.