99 Tahoe start then cuts off and on

[chris peter]

Today my 99 Tahoe 5.7 150K miles starts fine after 2 minutes it starts to shut off and back on then runs smooth and then cuts out again. It almost seems like the engine stops all the dash light go on then kicks in again. I all so notice the tach moves all over the place (0-1200 rpms). Fuel psi 62 checked the MAF, Coil, ICM and new Distributor 2 months ago. Looking for ideas here this one is a head scratcher and it all started as I was driving home.

[j cAT]

Originally Posted by chris peter

Today my 99 Tahoe 5.7 150K miles starts fine after 2 minutes it starts to shut off and back on then runs smooth and then cuts out again. It almost seems like the engine stops all the dash light go on then kicks in again. I all so notice the tach moves all over the place (0-1200 rpms). Fuel psi 62 checked the MAF, Coil, ICM and new Distributor 2 months ago. Looking for ideas here this one is a head scratcher and it all started as I was driving home.

if your dash lights go out as the engine dies then you too may have a bad ignition switch.

[chris peter]

Thanks j Cat you have helped me out in the past. I will check that tonight. I did notice that the Tach bounces violently up and down as the engines seem to turn off and on. The Tach does not move the same as if you had a rough idle or misfire. The more I think about it all the warning lights come on as it almost stalls.

[j cAT]

Originally Posted by chris peter

Thanks j Cat you have helped me out in the past. I will check that tonight. I did notice that the Tach bounces violently up and down as the engines seem to turn off and on. The Tach does not move the same as if you had a rough idle or misfire. The more I think about it all the warning lights come on as it almost stalls.

if you do use the ignition switch a lot with much short trip driving and start ups every day this will wear out the switch. normal at 220,000 these fail..but I have seen 170,000 miles also. this is with your old body style..5.7L

[chris peter]

Update on problem I watched my dash lights and radio to see if the lights went out and they stayed on so I was puzzled maybe not the ignition switch. Next I rechecked all my voltages (ignition, maf, coil ) all checked good including the grounds. Finally I let the truck run until it shut off its self and this time it set a code P0339 crank sensor intermittent signal. Replaced the sensor problem solved. This crank sensor was only 2 years old so I did not suspect it to be bad. I purchased the sensor at AutoZone so the duralast warranty paid for the new one but now I think I should purchased a OEM sensor instead. Time will tell.

[j cAT]

Originally Posted by chris peter

Update on problem I watched my dash lights and radio to see if the lights went out and they stayed on so I was puzzled maybe not the ignition switch. Next I rechecked all my voltages (ignition, maf, coil ) all checked good including the grounds. Finally I let the truck run until it shut off its self and this time it set a code P0339 crank sensor intermittent signal. Replaced the sensor problem solved. This crank sensor was only 2 years old so I did not suspect it to be bad. I purchased the sensor at AutoZone so the duralast warranty paid for the new one but now I think I should purchased a OEM sensor instead. Time will tell.

crank sensor on the 5.7 L may be in the mounting of it..some have had mounting issues. make sure it sets securely. also the connector/wiring is good and clean protect the wires with some tape or loom material. just could be a bad sensor..

I have had trouble with these usually after they heat up they then internally open and the engine will just stop. then after a few hours it start up fine..

good to report back ..this being intermittent you got lucky..