The Bronx Bull

I think it's a great tool if the engine is cold.

Thus, only when the car is cold. It sounds like your fuel pump is just randomly dying at this point? Intermittent fuel pump that's dying on the highway, but working normally for the most part. We need to narrow it down to whether it's an electrical problem with the pump, or whether the pump is going bad and/or it's clogged with crud.

wrencher

iTrader: (2)

As a mechanic I will tell you there is a lot of shops out there that just throw parts @ cars. They are usually less knowledgeable.
But for the ones that are decent these intermittant failures CAN be hard to find.
That & they might not be a profitable job for them either.
No one likes spend countless hours trying to guess what the cars doing when a failure is intermittant. It will be easier to find will it's occuring.
That's why some people run into issues. Comminication is key here.

Now as for your car. Does the SES light come on in the dash after the no start?
It should be on & stay on when the key is on engine not started.
Is there anything noticable not working when it doesn't start?
Like the cluster, radio, day time lamps anything to help hone in on the issue.
If you get into a habit when you turn the key on (radio fan etc off). You can hear the fuel pump cycle on for 2 seconds. Just key on without cranking the engine.
That will also be helpful to know. All though if you can get a decent shop out there they could current ramp your pump with a DSO & an inductive amp clamp to check it's health.

I have also ran into relay issues. In the shop & on my own vehicle.
Did you have the ignition relay replaced in the underhood relay center?

If it does occur again see if you can do some quick checking to note any abnormalities. It might be difficult to catch it long enough for you to check for spark, fuel pressure etc... I dont know your abilities or equiptment on hand.
A little observance here on your part can go a long way to solving your issue.

Anthony Williams

iTrader: (3)

Check your connections to your ecm, I would even say to disconnect them and clean them with some electrical contact cleaner and re-install and re-torque them. I belive the torque spec is posted on the connector. I've seen codensation build up in the connectors and cause all kind of weird stuff including stalls for no reason.

ccrook19

^I def agree with this!^ i am a auto mechanic also.. only age 20 but im ASE certified in 4 out of the 8 categories, going to be taking the other 4 tests very soon..

DobsZ28

iTrader: (2)

Thanks for your help, sorry for the lag.Little update, dunno if it helps.

The last time the car didn't start, the SES light was on. Today, when I was driving on my way home, I could feel power loss in sixth gear after driving around for about fifteen minutes it felt like, then when I downshifted to go up the hill to my house, the car noticeably lost power, regained it and there was some backfire with the exhaust. I got it home and drove it around the neighborhood to see if it would keep acting up, and it just felt like there was uneven amounts of fuel getting to the engine (but that's just a guess.)

As for other things not working when the car isn't starting, doens't seem to be the case. Radio, dash, lights are usually all on and fine when it doesn't.

I appreciate the help, I put a video camera in the car so the next time it doesn't start I can at least post a vid and hopefully get some help out of that.

That made me think it was the fuel injectors, but I don't think that would explain that the problem doesn't happen that often.

lt1pwr1

iTrader: (1)

At this point, I see everyone has given you some pretty solid advice. However, here is something that is also free that you can try: Next time you are cruising, grab your key and move it up and down (dont turn the ignition off, just push up and down on the key). You may have a failing ignition switch and that can often times get it to act up. Worth a shot at this point.

DobsZ28

iTrader: (2)

Took the car to Seaside Auto Repair (GM dealer's service department) in Miramar.


After three days of not hearing anythign, I t was told that "when we took the car out the first time, it was throwing five codes....when we flashed it and took it out again, it was throwing eight codes."

One of them was engine misfire, the others he said he wasn't even that familiar with. He said based on what he was seeing, he woudl recommend replacing the PCU, which would cost $420. He also said there was a code saying that the MAF wasn't working right, and based on the car throwing so many codes and even more after they took it back out again, that it's more likely a bad "computer" than anything else.

Then he said they also recommended replacing all the spark plugs and wires, which after parts and labor would cost around $400 "because of the labor."

I told him I'd take the weekend to think about it...(they're closed on Saturdays and Sundays)

garygnu

do your own plug change .maybe you can find a PCU(ECM) on this forum for cheaper.clean the MAF and find out if one of the codes was a bad cam sensor.

great421

iTrader: (1)

DobsZ28 -

I can't speak to the "driving down the road and the engine stutters / loses power" but as for the intermittent starting issues, find your VATS relay - behind and to the right of the glove box, and also BEHIND a piece of sheetmetal (!!!) - and find the very small ground BLK/RED ground wire; wiggle this wire (at the relay connector) while trying to start your car. If the ground wire is loose within the body of the relay connector, you may have found your intermittent No-start issue. (Ask me how I know.)

DobsZ28

iTrader: (2)

Thanks for the help -- would this make a difference if i had the VATS removed from the car through a tune? Because that was one of the first things that I had a shop do when the issue started happening...

I assume you had similar problems?

DobsZ28

iTrader: (2)

Just a little update --


The car has been at the shop for aweek now. At first they told me to replace the PCU and sparkplugs/wires. They also recommended a fuel induction cleaning service + MAF cleaning.

Approved the MAF cleaning and the induction service (cars got 72K miles on it, figured it might as well be time to have those cleaned up), got a call back from the shop. They said now that 6 of the 8 codes were no longer on, but there were two new ones, AND the car was driving worse now.

The new code is for an O2 sensor and a misfire on cyllinder 3 and 4. They aagain recommended spark plugs/wires for $400 + $197 for the O2 sensor replacement. I told them no thanks on both, as I'm going to take it to a local place that will do it for half the price, but my question is, if they cleaned the MAF sensor, could that have fucked things up? They're saying my SES light is now constantly on, a problem I never had before...

Also, in terms of the cyllinder misfire, would that cause the car to kind of jerk around during acceleration? And will spark plugs/wires really be a probable solution?

DobsZ28

iTrader: (2)

Also, connections to the fuse blocks were checked and okay'd by their technician.


As for the 8 codes the car WAS throwing, they were:


P0102
P0200
P0300
P0443
P0449
P0645
P0801
P0803

HAZ-Matt

iTrader: (8)

P0102 - Mass Air Flow (MAF) Circuit Low Frequency
P0200 - Injector Control Circuit Malfunction
P0300 - Misfire detected
P0443 - EVAP Purge Solenoid Valve 1 Control CKT
P0449 - EVAP Vent Solenoid Control Circuit
P0645 - A/C Clutch Relay Control Circuit
P0801 - Reverse Inhibit Control Circuit Malfunction
P0803 - 1-4 Upshift Solenoid Control Circuit Malfuncion

Quite a varied amount of stuff there. Might want to double check the PCM connectors as already suggested as well as double check the grounds.

bjamick

iTrader: (31)

First off check all your grounds. To many intermittent issues going on here. If you need the locations of the grounds I can give them to you.

Also make sure the battery terminals are nice and tight and the threads are not stripped in any way.

As I was reading about it losing power, all I can think of would be o2's and fuel pump.

TurboStangJON

iTrader: (27)

It's crazy that these technicians can't figure this out and I wish you were closer because this is textbook easy. All of these DTC's relate directly to each other and shouldn't be hard to figure out. To make a long story short and so I don't end up explaining each circuit individually I will say that the circuits funnel up to three fuses (ENG CTRL, INJ 1, and Ingition 1). The three fuses are all fed by the Ignition 1 Relay Circuit which I believe is the culprit considering it's setting all of these DTC's. This is the cause of the shutting off because it's shutting down an entire bank of fuel injectors. Now in saying that some more diagnosis needs to be done to determine what exactly is happening with the Ignition Relay Circuit. For instance, is it loosing power from the ignition switch, is it loosing the ignition relay ground, etc? Really, if they can't trace this drive to another dealership. If I can diagnose this over the internet they should be able to do it in person.

demonpixel

iTrader: (19)

Not to oversimplify things, but try going back to basics. An engine needs three things to start: fuel, air, spark. The next time it's not starting but turning over, disconnect the fuel line at the fuel rail by your intake manifold. VERIFY that fuel is or is not being pumped.

If fuel is spilling out when you're cranking, verify that you are getting spark. If fuel is not spilling out, then you've narrowed it down to fuel delivery.

My 93 Camaro did this a few months ago. It would turn over and not start. Died in traffic under normal driving conditions. The wire that goes from the fuel pump relay through the body of the car to the fuel pump (the grey wire) had frayed somewhere in the body of the car. I ran a new wire from the fuel pump relay directly to the fuel pump, and now I can drive the car. Once I disconnected the fuel line at the fuel rail and found out that I was not getting fuel, I was able to focus on the fuel system. I tested my fuel pump and verified that it was working. Then I verified that my fuel pump relay itself was working. So the problem lay in between the two.

So verify these three things:

• Fuel
• Spark
• Air

and it will bring you closer to your problem.

remauto1187

iTrader: (1)

Grab a spare computer and have it flashed with your program. Im betting its the computer or the ignition relay like Turbostang said.

Sometimes when you get a intermittent problem like this...the only thing left is to throw parts at it. You cant very well troubleshoot it if it isnt broke, only when it is acting up.

Ive seen where cars/trucks do crazy stuff especially improper transmission operation....its the computer. Alot of times a reflash fixes it. The program gets corrupted and causes havoc.

99Hawk6spd

iTrader: (2)

If it makes you feel any better, I'm having the exact same problem on my Firehawk. I've only gone so far as to swap the relays around and take them apart to make sure they are contacting correctly. Also FYI the relays can go in both ways, they are wired to use opposite corners so either of the 2 ways they fit in will work. My car has yet to leave me "sit," but has cut out on the highway for like 20 seconds, and does the exact same starting issue you have. I replaced the fuel pump recently, so I highly doubt that is the issue for me(it's silent, I never hear it run).

I'm thinking maybe loose ground somewhere. It's slightly frustrating.

Pvincil

ive got a 94 z28 doing the same thing. it gives me trouble. randomly doesnt start. took it to a shop and of course it ran fine for them but when i was driving it home from the shop, it stalled. it has stalled on me a few times before that and when im driving in 4th (auto trans) it gets these random points where it feels like the engine skips a beat. but its all intermittent.

anyway last time i had trouble with it starting, i wiggled the fuses inside the dash and after that it started up no problem. could be an ignition relay, short or even a bad ground somewhere.