I have a 98 k1500 Suburban with the 5.7.

Occasionally, but not every time, in the morning or after sitting for a few days I have a hard start issue. It cranks, but it won't start until I try to crank it a few times. Then, it will just barely catch and it coughs and sputters while I have the key turned and the gas pedal on the floor until the odometer eventually gets past 1000 and it evens out. If I am not holding the key and gas pedal down it will not start.

Then, it will start with no issues for the rest of the day. This only occurs in the morning after sitting all night or after sitting over the weekend.

At first, the hard start thing only happened once every couple of weeks, but it is more frequent now.

I have recently replaced the starter and the ignition control module. Fuel Pressure is 58 key on engine off and 52-54 when running. It is currently throwing a code P0420: Catalyst System Efficiency Below Threshold Bank 1, which I think is a bad 02 sensor.

Other issues that may have bearing but don't seem related to me, it has a coolant leak somewhere but it doesn't overheat and coolant isn't getting in the oil. Power steering seems to be intermittant also as sometimes at low speeds it is very hard to turn. It is throwing a little bit of oil when running somewhere under the engine, but the amount it leaks while sitting is miniscule. If you don't think these issues are related to the hard start, let's not address them with this post.

I don't know squat about fixing vehicles and am not particularly mechanically inclined. I basically youtube or get help from a buddy, so please address your responses to the lowest possible mechanical intelligence.

How would you go about diagnosing this issue?

 

flooring the pedal while cranking does the complete opposite of what you think. it kicks the ecm into "clear floor mode" which limits the fuel being sprayed, by it starting under these conditions i would think it is a fuel issue where the ecm is dumping fuel when it shouldnt. i would check the CTS and check/clean all your ground connections
you can find the ohm specs for the CTS on this link
Troubleshooting sensors and how to test

 

Thanks, Irish.

 

Curious.
You state your fuel pressure. After sitting for a day or two how long does it take to achieve this fuel pressure.
When you turn the key to the "on" position it cycles the fuel pump for 2 seconds. Does yours come to fuel pressure on the first cycle? Second? What's the fuel pressure doing while cranking after sitting for whatever length of time?
How long does it take for the fuel pressure to bleed off after shutting it down?
Any fuel in your oil?

As for your coolant leak which could have some connection to your starting issue.
Verify you have the Vortec 5.7L for me and this will apply:
You probably have blown intake gaskets causing part of your hard starting issue and your coolant leak.
Hard to see on the passenger side because of the heater hose fiasco going on over there but this is where I found my coolant leak, and blown intake gaskets on both sides.
Which I believe I posted pics of the 4 bent valves I found as well because of the blown intake gaskets.
It could also be the upper plastic intake manifold has warped.

As for the power steering and oil issues. The joys of owning a real truck :-)

Get a good shop manual BEFORE attempting any repairs... Please

 

I'm having the exact issues with my 97 K 1500 5.7 Vortec.. oops sorry replied to wrong thread.