REBS-TA

Background...New LS-6 motor in 99 Z28 Car.. 1000 miles.. No cats, Showroom car. Has been running like a champ, since I bought it. Recent work...removed plastic parts and painted (hood, bumpers, skirts), only wiring change was replacing the light sockets in the front (sides). Got a new key fob a month ago and programmed it with the car (unplug radio fuse, turn key on/off three times...most know the drill)

Got in the car the other day...Turned the key on, everything lite up like normal and the motor turned over and over and over...but no start... battery and starter operating perfectly. Turned the key off. tried again... repeated this 6 or 7 times... I'm an old school car builder, so if I was in a 69 Camaro, I would go check my points for being stuck or water condensation or check to see if someone had played a joke on me and pulled my coil wire...

Thinking through the main items... fuel, electrical.....I could hear the fuel pump turn on with the key for ~3 seconds then stop.. normal(got pressure, I think)

looked at key to see any abnormal wear on security pin.. locked the car with the key fob, set alarm (no light on dash blinking, didn't before either, but the horn blows like it's set)... unlocked everything with fob...then tried to start again... nothing... motor just turns over like a champ... 15 seconds later on the 4th try, it fires up and runs as smooth as a champ. Drive the car around the block and put her back in the garage...afraid to get stuck on the way to work..not good

2 days later... I decide to take wife on date. We have a two year old and mom needed a break.. Car starts up immediately..We get 15 miles down the road, running down the interstate at 70MPH, then nothing... no throttle response... motor is dead.. no blinking lights, no hesitation, nr sputter...nothing. After 10 minutes on the side of the road, one anxiety attack and 20 failed attemps, she cranks... varroom..off to Red Lobster..as promised. Get to the resturant..eat dinner, come out...car will not crank... turns over perfect..... After trying 6 tries, waiting 2 minutes and talking to the security cop, she fires up and we head home praying...

1 mile from home, climbing a little hill, the motor goes dead again, 100 yards from the crest...fortunately, we were doing 50mph and we made the crest and I was able to coast all the way home and within 10 feet of the garage door...whew!

marriage saved...

So before I go out and disconnect the battery to see if it's something building up in the codes...and before I go yank out the "new" oxygen sensors...I say "new" as that was what I was told...

Help! would like to pass go without going to jail (Old Boardwalk Game)

Ideas....

Thanks,
Robby

1 FMF

iTrader: (1)

first thing to do is get a code scanner and check for DTC's that are stored.
the oxygen sensors would not cause this kind of problem.
if it dieing cleanly, like you turned off the ignition key kind of die, then it's most likely electrical since you put a new motor in.
Have a 2003 jeep with 4L inline-6 which would die on us doing 40mph down the road, turned out to be the wiring harness going to the injectors. the harness as it came from factory was routed around the valve cover in the rear and the valve cover stud wore into the harness after 60k miles shorting wires to ground. The result was it would freak out the engine computer causing it to reset, which shut the engine off and tripped the security light and worst of all stored no DTC's in the computer. It was funny, at first it was random then would happen 5 or 10 minutes after engine was started. Engine would start right up at first after it died, then it would not crank and you would have to wait 10-20 minutes for security light to go out. I had replaced crank sensor and speed sensor per internet advice which was a waste of time & money. To my knowledge there really is nothing sensor-wise that should cause a complete engine shutdown should the sensor fail, prevent engine from starting and throw DTC's yes but not kill engine when running. It would be a complete fail of something important, maybe engine PCM, I don't think the BCM would cause your problem, otherwise best guess you have some important-type wires shorting causing the computer to shut off the engine. I brought the jeep to the dealer to fix it, and they knew what it was after a 1/2 hour diagnostic, but not knowing i would've never found it given the location and everything is black. so look hard and assume nothing.

chrysler kid

iTrader: (14)

I would check fuel pressure.

Next time it dies on you try to prime the pump three times and After the third prime try to start it. Typically turn the ignition to the on position, listen for the door chime to chime 3 times, repeat again twice and after the third prime start on the third chime.

REBS-TA

thanks for the advice. tonight I'll be testing fuel pressure, checking "spark", checking "power/voltage" to the injectors...looking for loose sensor wiring and checking voltage on the crank position sensor.. Don't have a scan tool at the moment.. Might can get one on the weekend from a friend.. wish me luck..

Robby

ucanthangwme

iTrader: (12)

If it wasn't for the "new" engine in the car, I would certainly point to the VATS for the issue. That is exactly what it sounds like. I have read confusing info on knocking the VATS out at the computer. Might need to bypass the VATS at the wiring under the dash.

GMtechmatt

check fuel pressure and intake duct make sure its attatched

LS6427

iTrader: (2)

This is new school.....

Exact symptoms of a failing "Crank Shaft Position" sensor......and I mean EXACT. And you WILL NOT necessarily get a code......so don't drive yourself nuts, change that little SUMBITCH. If thats not it...return it for a refund and keep looking.



.

kSStamp09

iTrader: (4)

this is what i thought, maybe try a re-learn on it before replacing it.

LS6427

iTrader: (2)

You mean an "idle relearn"?

Losing that stuff doesn't cause the engine to shut down on the highway or not let it start......that CSP sensor does exactly that.

.

chrysler kid

iTrader: (14)

No there is a crank relearn process when you tie a new PCM to an engine.

It does sound like a crank sensor though

REBS-TA

Hey guys... yeah I'm an old dude, but I like all fast cars...young and old school. I found the problem by starting with the KISS method...Keep it simple stupid... Start with the easiest. Check as many connectors as I could see, inspect wiring...yady yada yada.. Bought a fuel pressure gauge 19.99..stuck it on there. excellent fuel pressure. Went over to my daughters 99 T/A anniversary, took the Ignition Relay out put it in my Camaro and Bam fired up... just to be sure, it wasn't a fluke, I took it out put the original relay in...no start..put my daughter's in and fired up perfect... Thanks for the edumocation...If 'ole murphy is playing a jokle on me and get half way to work tomorrow and she craps out...I'm looking for a carb and manifold and and MSD box... In my 35 years of restoring old muscle cars (at least 9 of them), I've only had one carb I could not make work and 1 MSD box go out... now that doesn't mean I haven't had my share of points to fail, but a file and a phillips head is all you need.. Just kiddin... These LS motors and setups are pretty damn sweet and to get the same horsepower out of the 'ole school is a whole lot more difficult and gas mileage...that's another story... Thanks Guys

Guess I'll be doing some studying on ODBII readers and programmers....since I've started buying some of these newer cars..

REBS-TA

A had a few lessons learned restoring these bad boys...

For your viewing pleasure and my gratitude for your help..

REBs-Resto and Go

REBS-TA

ps. Spark was next, then Crank sensor...

LS6427

iTrader: (2)

Listen my friend......it takes about 15 minutes to put the front end on ramps and change that CSP sensor.

If thats not it....return it for a refund, tell them it was the wrong part and you never bolted it up. I do that all the time.

Its almost certain to be that sensor....it is just about the ONLY thing that randomly shuts off LSx engine while they are screaming down the road....and gives them hard starts....THEN out of nowhere they start and run PERFECT. CSP sensor........

Other than that....you're probably looking at a dying PCM..........

chrysler kid

iTrader: (14)

Good to hear you figured it out!