bp71k5
3/4 ton status
Fuel pressure is ~48psi. Starts up and runs fine if you step on the gas, idle just drops to 400rpm and then dies.
Any ideas?
Any ideas?
CK5
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2000 suburban won’t idle
- Thread starter bp71k5
- Start date
Iac valve?
bp71k5
3/4 ton status
Any secret tips to check it other than what a chiltons Manuel would tell me?
IAC motor is a prime suspect but--.
Could be lots of things--big vacuum leak,or a sticking EGR valve,if it smells like raw gas and starts loping before it stalls,and has to be cranked a long time with the throttle applied to re-start it,it may be the fuel pressure regulator..
Could be lots of things--big vacuum leak,or a sticking EGR valve,if it smells like raw gas and starts loping before it stalls,and has to be cranked a long time with the throttle applied to re-start it,it may be the fuel pressure regulator..
No CEL?
bp71k5
3/4 ton status
No cel.
I did remove and clean the iac valve. Wasn’t very dirty, but the motor idles ok with the iac valve unplugged, but a little higher rpm than normal. Guessing a new one might be the ticket?
96-up gm if i recall is mid to high 50psi range not 48 psi . so check that also for fuel pressure .
years ago we had a s-10 come in on the hook and it would fire and run but no power to move its self . turned out the fuel pressure was around 10psi below spec from a failing pump . installed new pump and like new truck .
not saying its your problem but better make sure .
years ago we had a s-10 come in on the hook and it would fire and run but no power to move its self . turned out the fuel pressure was around 10psi below spec from a failing pump . installed new pump and like new truck .
not saying its your problem but better make sure .
Thought it should be closer to 58psi
bp71k5
3/4 ton status
Hmm, looks like you might be right. Will try a regulator and filter first.
Prob the pump
bp71k5
3/4 ton status
After replacing the filter (it was kinda dirty) and the regulator, the pressure is now a steady 46psi at idle, goes up to 48 at about 1500 and drips back to 46 at any rpm above that. It’s strange that the thing drives fine at high speed, but the problem is at idle isn’t it?
Does now look like the fuel pump though.
old vortec 350 is 60-65 psi
newer ls vortec is a bit less 48-53ish i found on line.
newer ls vortec is a bit less 48-53ish i found on line.
bp71k5
3/4 ton status
It is the newer LS. Where did you find that and is it “official”. I can’t seem to find a definite specification, but lots of different places says over 55psi.
black dawg
1/2 ton status
I have seen lots of very dirty throttle bodies on those, usually just low idle and stall when warmed up, but probably worth a look.
bp71k5
3/4 ton status
It’s at a mechanic I trust now. I’ve done everything I can do.
I was going to say clean the throttle body and the mass air sensor if it has one(been working on Fords too long and can't remember). I had an F150 here at work that would throw no codes and supposedly die when put in gear if the engine was warmed up and at low idle. It wouldn't do it when the engine was cold at high idle though. I cleaned the mass air sensor and it ran way smoother and no more issues.
bp71k5
3/4 ton status
Of course, the mechanic can’t find anything wrong with it. Starts up every hour and idles just fine.
Of course, the mechanic can’t find anything wrong with it. Starts up every hour and idles just fine.
my first failed fuel pump did that
idles and load are 2 different things to a fuel system .Of course, the mechanic can’t find anything wrong with it. Starts up every hour and idles just fine.
bp71k5
3/4 ton status
When the problem is happening, the only thing affected is the idle. It has normal power on hard acceleration. Just doesn’t idle. Wouldn’t low fuel pressure show up on hard acceleration rather than only idle? Mechanic did say the spec for fuel pressure was 66psi, since it was working fine he wasn’t ready to blame the fuel pump itself, thought maybe the check valve was faulty which would make the problem tend to happen only when first starting it up.
Strangely enough, if I unplug the new IAC connector, it’ll idle fine at about 1000rpm. I assume because it’s bypassed.
Mechanic mentioned a possible intake vacuum leak, but tested with smoke and didn’t find anything. Checked the MAF sensor and no problem. Will check the coolant temp sensor tomorrow after it cools off to see if that’s flaky. If all that doesn’t find anything, I may just go ahead and ask him to replace the pump.
Strangely enough, if I unplug the new IAC connector, it’ll idle fine at about 1000rpm. I assume because it’s bypassed.
Mechanic mentioned a possible intake vacuum leak, but tested with smoke and didn’t find anything. Checked the MAF sensor and no problem. Will check the coolant temp sensor tomorrow after it cools off to see if that’s flaky. If all that doesn’t find anything, I may just go ahead and ask him to replace the pump.
