Hard start when warm 97 5.7L

[denhamt1983]

I'm at my wits end here. 1997 Suburban K1500 5.7L. Newish fuel pump, new plugs, wires, cap, rotor, ICM, TPS, IAC, EGR, spider injector, exhaust completely all new. When the truck has been sitting between 15 mins and 45 mins hot will not start for anything, and once it does start it idles super rough. Let it sit over an hour starts no problem. Also starts perfect cold. Also intermittently surges and stalls after hard, hot driving. Seems related. Only codes stored were for the O2 sensor from before I replaced them all. Any help is appreciated, thanks

 

[stutaeng]

Well darn, that's a lot of new parts! Everything was swapped in an attempt to fix the problem? What's the history on the truck? Ran fine before? Or did you just buy it?

What about lower intake gaskets? No leaks? You can check for vacuum leaks with an inexpensive gauge. "No-start when warm" are usually leaking injectors and/or fuel pressure regulator. I know you said injectors were replaced, but I would check with fuel pressure gauge. Even new parts fail.

I'm assuming you have checked for spark? Spray carb cleaner in the intake? At this point you either need to get yourself a good diagnostic scanner and do more research on what could be causing or just take it to a mechanic to diagnose. Some places will charge you to diagnose and you pay them just for that. You can then do your own mechanical work.

 

[east302]

Check coolant temperature with a scanner the next time it does it. See if temperature reading is reasonable - between ambient and thermostat setpoint. Try holding gas to floor when it does it again. That puts it in clear flood mode and stops injector flow.

 

[denhamt1983]

This is all great advice, thanks! I have been worried about crank sensor. I did buy the truck in March, think it was probably this way for PO too. Am worried about crank sensor, havent replaced but when I got the truck had a very bad, long term coolant leak from water pump, replaced that too. Think fouling from tons of coolant (it stained the whole front of engine gummy orange) could have fouled it?

 

[Anim8r]

I've had the same symptoms about a month ago. It turned out to be the coolant temperature sensor. I'm pretty sure it threw a code. I was able to replace it without draining the radiator, a little may come out. It is on the top front of the engine near the thermostat housing.

Here is a youtube link of the install I found.

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This fixed it for me. Running perfect since.

Tom

 

[The Blue Ox]

I'm at my wits end here. 1997 Suburban K1500 5.7L. Newish fuel pump, new plugs, wires, cap, rotor, ICM, TPS, IAC, EGR, spider injector, exhaust completely all new. When the truck has been sitting between 15 mins and 45 mins hot will not start for anything, and once it does start it idles super rough. Let it sit over an hour starts no problem. Also starts perfect cold. Also intermittently surges and stalls after hard, hot driving. Seems related. Only codes stored were for the O2 sensor from before I replaced them all. Any help is appreciated, thanks

Check Distributor cap and rotor again, when replacing,always use one with the copper contacts on the cap! I think borg Warner makes one,it’s a whole lot better than Delco! Mine was doing same symptoms as yours and that’s what it was on mine!

 

[badco]

Since everyone else covered the temp sensor and other stuff ill ask if it still has all the evap system? Could be its not purging properly and building pressure.. you could try taking gasket off cap or leaving it loose to rule that out.

When mine did same thing ( dont have evap) it was my "spider" injection had a cracked line and would leak into manifold and start hard when hot but run great all other times

 

[denhamt1983]

Thanks everybody! I replaced the crank sensor and the temp sensor (one on thermostat housing) and now it starts when hot, but still runs kinda crappy once it does. Next step is the evap vacuum solenoid, just got here today and will get it on soon