ragu1585

So I picked up a 13 z07 recently. Drove perfect 4 hrs home. Next day drove it around, stopped at the store and let it idle for about 30 mins or so while talking. Went and got gas and it started up sloooow. Drove 2 mins to another store. Was in and out in 5 mins and upon about a 10-15 second turn over it finally cranked. Had no tach and threw all the service active handling and traction control codes. I took the car to my cousin who works on these cars daily and he tested everything. Said gm only allows about .5 voltage drop drop. My car was anywhere from .6 to 2+ voltage drop cold and hot, depending on where he checked it from. Obviously it was worse when hot, causing the hard or hesitation at start up. We replaced all of the power (+) wires from the battery, fuse box starter etc. kept the same starter, battery and it seems to have solved my issue.

Pb82 Ronin

Guys, this is a fairly old thread (started back in 2017).

Weak hot starting is a super common problem with these cars. Happens when the starter lug begins to melt (typically on cars with headers) or the battery needs replacing. Always start with the battery (if it's in question) and the next culprit is almost always the starter. The mechanical (no tach issue) is from the slow crank. Fix the starter (or cool the car off) and it goes away.

ragu1585

My opinion, but if you want to band aid the problem and keep replacing starters and batteries, then replace your starter and batteries.... I believe the issue is in the wiring itself. My battery and starter was just replaced a year or so ago. You are correct about the no tach though ... it comes from the hesitation trying to start. Have a mechanic put a meter on the car cold and hot and measure the V drop

gmansbu

I bought a z a few weeks back and had the same issue. I replaced the starter and added a heat shield from lingenfelter this time. Problem gone. Curious how it will hold up over time.

GlennSullivan

So I had the same exact problem 2 years ago. Including difficult to start when warm, no tach, engine misfires, etc etc. Most people I spoke to thought crank position sensor, which made sense, especially because of hard start and no tach), but a few said battery, which did not make much sense but the battery was original and an easy install, Compared to the CPS which is a PITA, so I swapped in a new battery and guess what, all of the issues immediately disappeared.

Change the battery - get a GM battery, most aftermarket units don't fit right. If that doesn't resolve it (I bet it will) at least that question is out of the way.

meanjoe

Get a new one. Don't forget you need one that has the connection for the vent tube. I didn't read this entire thread but good luck with your issue.
One other note about electrical issues on these cars. I always had the same problem that I hear about on here with the electrical gremlins always lighting up the DIC. Every kind of warning you could imagine. I finally installed a new 250 amp alternator, aftermarket, all the issues stopped. Best thing I could have ever done. The OEM unit seems to just not be powerful enough.

PHIL MEMPHIS

i agree

crank position sensor is the problem. Had same issue on my Z06

ZilvisZ

Old thread, same problem.
Engine barely turning when hot. Battery is new, but I found when my power bank (or jumper) is connected, engine starts (not as it should, but starts).
I presume if it would be crank sensor, jumper will jot affect it?
Not enough starting power?

Thanks

ragu1585

can you provide the pn / info on the alternator you got

Farmvette

Had the same issue on mine earlier this year. Was disgnosed as the crank position sensor wire touching a header and melted insulation. Repaired wire and rerouted it, and haven't seen the problem since.

Hirohawa

Just experienced this exact phenomenon. Rough start when warm, No Tach, service Traction, etc. Had car since new and this has never happened before. Hope it just needs battery.

C5 Diag

This is possibly your crank sensor…best to start a NEW thread instead of hijacking this old thread !!…let us know exactly what you’re seeing.

Hirohawa

After it cooled down for awhile it started fine and was running normal. Still had a CEL though.

Didn't start a new thread as I think there is a lot of helpful info here - if anyone needs a comprehensive overview and googles their issue they will find this, as I did.

I'm thinking of replacing the battery - but do you think it might one the crank sensor?

C5 Diag

If the MIL is illuminated what code is stored ??…doubt it’s the battery and a scope is needed to correctly identify a crank sensor !!

GlennSullivan

Put the battery in first, that is easy and if your battery is over 3-4 years old you need a new one anyway. As much as I was convinced it was the crank sensor (I even purchased a new one) decided to try the battery first as installing the crank sensor is a PITA. New battery, no more issues and that was years ago. If you are doing the battery yourself, get a strap handle if you don't have one as there is no room to get your hands around the old battery to pull it out. BTW, the latest replacement Delco battery for the car has a higher CCA rating than the OEM.

Hirohawa

Thanks. Going to try new battery.

gmansbu

Odds are it’s the starter. Especially if you’re claiming after the car cooled down it started up just fine. Do you have aftermarket headers? I did. Starter is literally right next to them and acts like a heat soak. Car won’t restart after it’s piping hot.

I replaced my starter with a new one. And put a lingenfelter heat shield around the new starter. Never had the issue again.

DougHG8

It could be the battery, starter, or voltage drop from a bad connection. C5_Diag was great help on my issue. He advised to measure the voltage drop across the circuits (positive and negative from the battery). Attach a voltmeter between the battery positive and starter positive terminal (not too easy to do, you could also connect to the alternator positive as well I think). There should be no more than 0.5V showing up on the meter during cranking. Also check the ground circuit...attach one side of the VOM to the negative battery terminal and the other anywhere on the block...again voltage should not be great than about 0.5V. What happens to a starter when hot is that the copper wire resistance goes up so for the same voltage applied, less current will flow and the starter will have less torque, causing the slow rotation of the engine. when it's cold, you may have enough voltage (with either a bad battery or voltage drop through the connections) to start just fine, but when it's hot, that same voltage will give less current through the starter so it's slow to turn over.