Intermittent Start, Constant Confusion

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c4yrslf12

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Hey Guys,

Just a quick thanks to all those who answered my previous questions. Ya'll are a great help.

But now:

Every time I start my car, it's something different. Sometimes it fires straight away and the RPMs jump to 2k and slowly settle back down. Other times it baaaaarely starts and climbs up to normal RPM ranges. Once in a while, it will even not start on the first crank, but be perfectly normal the next. The only other symptom I have noticed is on the times it starts low RPMs and gets up to normal, there will be an ever so slight smell of gasoline.

So: Airflow/Fuel/Electrical? I can think of something in about every category but I'd be blind testing everything. Fuel filter is new, plugs are new (although I am going to switch back to Iridiums soon), air filter is relatively new. Outside of that, I have only owned this car for approx. 13k miles, personally.

Thoughts :confused: ?

Local guy recomended to me either throttle body is not operating correctly, or air sensor needs replaced. I am kind of doubting the throttle body, only because I can push the accelerator in, and it has no effect on the start.

Any help would be appreciated, and I'll answer as many diagnostic questions as I can.

Thanks again, in advance.


JF
 
c4yrslf12 said:
Local guy recomended to me either throttle body is not operating correctly, or air sensor needs replaced. I am kind of doubting the throttle body, only because I can push the accelerator in, and it has no effect on the start.
Click to expand...

these are fuel injected cars... no benefit will come from doing that...

a dirty MAF sensor would/ could cause some of these but sounds more fuel related..possible leak anywhere?...
 
I see no visible leaks. If there is one, it'd be on the fuel line under the plastic cover or some other place which I'm not seeing. I've already had the valve cover gasket replaced (when I did the plugs and coils) which I forgot to mention last time, by the way.
 
What's a good brand MAF sensor? I'll just buy one and replace it regardless, with new air filter, too.
 
No idea on what other stuff was done on other posts, so...

This is not LS specific, but more a general check. I've found that odd, sometimes conflicting symptoms on a fuel injected engine to be ground related. A flaky ground will make it do weird stuff, and the computer looks at what it's going to do next based off what it did last. It may not be the ground, but it would be something to check.

I've also worked with engines that were particular about their fuel pressure, and low pressure will make them act strange. A failing fuel pump will cause this, and a fuel pressure check will show this. Hope this helps.
 
Since you have a gen I, the IAC (aka Idle Air Bypass Valve) would be good suspect too. If it sticks closed, it will deprive the engine of enough air to start and can cause a gasoline smell due to flooding. Other possibilities exist too.
 
c4yrslf12 said:
What's a good brand MAF sensor? I'll just buy one and replace it regardless, with new air filter, too.
Click to expand...

They're kind of expensive. You might want to be sure about it first. Unplug the MAF and see if the starting problems go away. If they don't then it's not the MAF.
 
joegr said:
Since you have a gen I, the IAC (aka Idle Air Bypass Valve) would be good suspect too. If it sticks closed, it will deprive the engine of enough air to start and can cause a gasoline smell due to flooding. Other possibilities exist too.
Click to expand...

Where's this located? Throttle body?
 
Yup. Cylindrical thing near the throttle blade sticking out pointing to the front of the car with a connector on the end.
 
Pick your brand and go with it. Cardone are all remans.
Both of those items respond well to cleaning and seldom need true replacement. Just be sure to use the right chemicals (MAF cleaner and Intake cleaner). I have seen an IAC (not on a LS) go completely bonkers, but that was after the owner just sprayed cleaner down into it without removing it from the intake - washing all the gunk from the intake down into the mechanism. Lesson learned is to remove the item, clean and blow out (gently) and ensure everything moves freely.
 
I pulled the MAF this weekend and it was absolutely spotless, connections looked perfect. I'll need to replace the air filter, but the filter itself was not really all that shabby (but it's seen better days).

Makes me think I'll end up doing the IAC this weekend. I'll try to clean it first, then I guess I'll buy if that doesn't fix it.

Thanks for the help, I'll keep ya'll posted.
 
Go ahead and clean the MAF anyway. That is a maintenance procedure, even though it's not required all that often. Note that there are multiple sensors in there, so get all the cavities.
 
MAF cleaned thoroughly. No change. Let's play the IAC game!

None of my local stores have it...Plus, from what I can see online, it may be cheaper to do it on my own. Would love a link to the right one to buy! I see a few variations.

Also, any links to a walkthrough? I'm sure it's something I can do if it's right there on top of the engine.
 
Try cleaning the IAC. That often works as well. Use throttle body cleaner.
 
Just finished cleaning the IAC. Seemed to kind of work, and started well a few times. After a test drive, it seemed to revert back. I tried a few warm starts and they were somewhat rocky. The IAC itself looks pretty worn, and there was a lot of carbon on the inside. Thinking maybe I'll get another just for kicks. They aren't that expensive. What else could be the issue? plugs?
 
Sounds like the IAC is a likely culprit. Sometimes they're just too far gone for cleaning to fix it, but the temporary improvement is promising.
One other test is to ever so slightly press down on the throttle while starting. If it regularly starts up fine, then it's definitely the IAC. Once you let off the gas, it may have problems again until the IAC unsticks.
 
oddball said:
...Once you let off the gas, it may have problems again until the IAC unsticks.
Click to expand...

Often, you can lightly tap on the IAC with a hammer to unstick it (for just a little while).
 
I'll give it a try with the accelerator down for a few starts in the next two days. If it seems like improvement, I'll order a new IAC asap. Hoping that's it!
 
Maybe it's the coils. Replace all and put in the correct spark plugs, all set to 1mm gap, no more and no less.
 
Literally just had my car in the shop today for like the same issue, have your fuel injectors checked, one might be leaking down into the cylinder that is what came about with mine, I hope this helps!
 
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