1993 Lumina Z34 help?

[NickAbate]

I have a 1993 Lumina Z34 with the 3.4L DOHC and I have two separate issues that I need help diagnosing. The first problem is that my car will turn over but won't start for a few tries. When I first start it up in the morning, it'll start fine. it only does it when the engine has been warmed up. I have changed the fuel filter and put some fuel injector cleaner in the tank and neither has helped. my fuel pressure is at 40 but the car wasn't having the issue when I tested it. Any ideas? My second issue only occurs when the weather is colder (50 degrees or under) and basically what it does is idle very high when I start it in the morning. There were times it went up to 4000rpms and kept revving itself. I have changed the IAC and TPS sensors and it has helped, but its still idling too high. Thanks your time!

[Psych0matt]

your first issue:

 

does it crank at all? As in, does it crank and not start, or not crank? I used to have the issue where when hot it wouldn't crank. Sometimes when cold too, but that car also had electrical issues.

 

 

2nd issue:

 

Sounds like a vacuum leak, quite possibly intake gaskets. My GTP had the same issue, and after checking all the vac lines and whatnot it ended up being the LIM gaskets. Replaced those and it's been fine since.

 

[NickAbate]

Yeah it cranks fine, it just doesn't want to start when its warmed up. I'm going to check the fuel pressure when the problem occurs. I'm almost hoping it is the fuel pump because I definitely don't want it to be fuel injectors. how would I go about checking the vaccum lines? Is it a tough job changing the gaskets?

[Psych0matt]

to check all the lines you could get a small mist bottle of water and squirt lines here and there to see if it changes the rpms. For the gaskets, they're not too difficult if you're comfortable tearing apart the top of the engine. It's basically just pulling the whole top half off, slapping some new gaskets on, and reassembling. Check all your lines first just to rule that out, but that sounds exactly like what mine did.

 

Also, for your starting issue, check your schrader valve to make sure you have pressure. Also, when you first turn your key on (before trying to crank it) listen for the fuel pump.

[Schurkey]

to check all the lines you could get a small mist bottle of water and squirt lines here and there to see if it changes the rpms.

Cancel the "water". Use aerosol carb spray. Some folks use propane. Point being, use a fuel that will burn. Water won't do squat.

 

For the gaskets, they're not too difficult if you're comfortable tearing apart the top of the engine. It's basically just pulling the whole top half off, slapping some new gaskets on, and reassembling. Check all your lines first just to rule that out, but that sounds exactly like what mine did.

"Top of the engine" to me includes cylinder heads. In this case, there's no need to pop the heads off to change intake gaskets. Overall, very simple job.

 

Also, for your starting issue, check your schrader valve to make sure you have pressure. Also, when you first turn your key on (before trying to crank it) listen for the fuel pump.

my fuel pressure is at 40

40 is below spec.

[NickAbate]

Thanks! Do you know what the fuel pressure should be at for my particular car? I really need to get a repair manual to learn this stuff.

[OneBadCutt]

Thanks! Do you know what the fuel pressure should be at for my particular car? I really need to get a repair manual to learn this stuff.

 

Prime psi- 40.5 -47

 

idle-run-psi- 30.5 - 44

 

pressure with return line restricted. 47.

[NickAbate]

Thanks. That makes me wonder if something else is bad because it looks like 40psi is around the average.