Car Starts Weakly, After Time Doesn't Start at All

[Brandybuck]

My car starts "weakly." It is difficult to describe, but the symptoms seem fairly consistent. When I turn the key/start the car, I can hear the motor turning over quickly and very well. But it takes a second or two for the vehicle to catch on and start. I get the impression it's having a hard time getting something - fuel or air, perhaps.

When it does "catch on" and start, it is a very quiet, low key idle - consistent, but low powered. I noticed because my family's red 2000 Grand Prix GT (non-super charged, 3800 engine) starts very powerfully, and catches on a little bit quicker then mine. It's idle is louder/more powerful as well.

Here's something else that might help. The symptom described above occurs if I'd driven the vehicle less than a day or two before. If I don't start it for several days, it will not start at all. What happens then is the following: I turn the key, the motor turns over quickly and great like normal, but the car doesn't "catch on"/start at all. I have to give the car some gas with the accelerator to get it started. Then it starts normally and idles great (but still relatively low-key compared to my family's GT).

[rickisrad]

clean out your throttle body very well, also a fuel system/intake cleaning should do the trick. make sure your air filter is clean, clean off the iac and maf sensor with special Maf cleaner. replace the fuel filter with a quality brand filter. make sure you use a quality fuel like shell or sunoco (they contain 0% ethanol).

[Brandybuck]

clean out your throttle body very well, also a fuel system/intake cleaning should do the trick.

I believe the dealership performed this at our request before I bought the car. "BG Fuel service" is what they called it. Is this the same thing?

Air filter is in good shape.

What brand is a "quality brand" fuel filter?

How do I clean the IAC and MAF?

[olopezm]

Check the Fuel Pressure Regulator; it has a vacuum hose on top of it. Remove it and look for fuel coming out of it or move the key to the run position while the hose is removed and see if any fuel comes out of it.

A bad FPR or a weak fuel pump can cause hard starting and roug idle. To check the pump try cycling the key from off to run several times before you crank the engine to build up some pressure and see if it helps. You can rent a fuel pressure gauge tester from autozone to make sure it's within specs.

Oscar.

[rickisrad]

you just take off the maf and IAC and spray it with the special MAF cleaner sold at the autoparts store usually has a green sticker. Do not touch the wires on the MAF. check the throttle body anyways, their version of a fuel system cleaner might just be the fuel injection cleaning machine or even worse an additive to the tank, which does not clean the throttle body. below are from when I put my throttle body spacer on. It is the most thoroughly cleaned if you have it off, but you can get it well with just the intake tube removed. When on the car I use a very soft babies tooth brush to get into the throttle body deep and wipe clean with a microfiber cloth (top and bottom of the butterfly plate). I also use the seafoam spray lube and cleaner to clean the throttle body out, it seems to get the carbon off quicker.

[Brandybuck]

I have the honeycomb on my throttle body, so I'm not going to be sticking any toothbrush in there without taking the whole throttle body off. Should I use throttle body cleaner (Is the CRC brand good?) to clean the throttle body? If so, should I spray straight through the honeycomb? It seems to me this would get on the MAF sensor and cause problems.

Also, I believe my IAC and MAF sensor are two separate things; this picture shows my setup exactly.



Should I take off both the IAC and the MAF sensor, and spray both with the same MAF cleaner?

[Brandybuck]

Update: I tried Oscar's suggestion of turning the key from off to run several times before cranking. Following are the results:

Initial Conditions: Had not started car for about 32 hours. (I didn't try to start it until after turning the key from off to run five times for the first time.)

turned key from off to run five times, then turned to start. Car started immediately without hesitation, and seemed to have fair power.

turned off car. turned key from off to run five times, then turned to start. Car cranked/turned over, but didn't even come close to starting.

repeated this procedure twice, with identical results.

So it was only after the first cycle of turning the key from off to run that the car started; after that, it was ineffective.

(It could very well be, by the way, that the car would have started the first time, after only turning the key once, but I didn't try this.)

Can anyone interpret these results for me?

(I wanted to clarify that my engine does not run rough or idle inconsistently; it is just that the idle sounds very low-powered compared to the other Grand Prix. It also does one of three things when I try to start it: crank but not start at all, crank but start only after a couple of seconds, or crank and start immediately, albeit with low power. I am getting the impression that it only starts immediately when I have been running the car for a while soon before starting it again.)

Thanks!

[rkvons]

Originally Posted by Brandybuck

Update: I tried Oscar's suggestion of turning the key from off to run several times before cranking. Following are the results:

Initial Conditions: Had not started car for about 32 hours. (I didn't try to start it until after turning the key from off to run five times for the first time.)

turned key from off to run five times, then turned to start. Car started immediately without hesitation, and seemed to have fair power.

turned off car. turned key from off to run five times, then turned to start. Car cranked/turned over, but didn't even come close to starting.

repeated this procedure twice, with identical results.

So it was only after the first cycle of turning the key from off to run that the car started; after that, it was ineffective.

(It could very well be, by the way, that the car would have started the first time, after only turning the key once, but I didn't try this.)

Can anyone interpret these results for me?

(I wanted to clarify that my engine does not run rough or idle inconsistently; it is just that the idle sounds very low-powered compared to the other Grand Prix. It also does one of three things when I try to start it: crank but not start at all, crank but start only after a couple of seconds, or crank and start immediately, albeit with low power. I am getting the impression that it only starts immediately when I have been running the car for a while soon before starting it again.)

Thanks!

Put a fuel pressure gauge on it and see if it is within specs. When you turn the key to on, the pressure should "bang" up to 50psi, or so (others can be more precise). After you start it, it should be at a lower level and vary by how much you press on the accelerator. You may have a fuel pump resistor that is going out. Your pump has the full 12V when you first turn the key to on, and after the engine starts, it is reduced through a resistor.

[rickisrad]

you can take the honeycomb out and then put it back in if you wish. I got rid of the piece in all four of my grand prixs, it helps with air flow performance when you are at that point. I have extras if you need or want one. use a curved pick and pry around the edges to get it out. if it is still there I can almost gaurantee you that it has never been cleaned. If it is not the main issue it definately will not hurt to clean it. It only takes a few minutes. Yes the CRC throttle body cleaner will work fine. Personally, I use it for the Maf and iac also.

(if the throttle plate is getting resistance or there is carbon build up at the plate you will not have enough air to start the car at idle)

[olopezm]

Did you actually check the Fuel Pressure Regulator?

Since the car is not starting I don't think it can be your problem, but it doesn't hurts to check.

Oscar.

[rickisrad]

yeah definately check the fuel pressure regulator like Oscar said, it could be the primary and most likely cause. You have the possible symptoms of a bad regulator. Also, do yourself a favor though and clean the throttle body while you are at it. It won't hurt and can only help.

[Brandybuck]

Oscar,

I removed the vacuum hose from the fuel pressure regulator for exactly five minutes while the car was idling. No fuel came out, so I'm assuming that my FPR is operating correctly. Is this reasonable, or is there another test for a bad FPR?

I wanted to clarify the way it starts. I think my first description was accurate as well, but most of the time it behaves like the following: I turn the key to the start position, the car cranks for a second or two and then starts, but as soon as I release the key to "Run," it dies. I have to give it gas with the pedal while holding the key in the start position to get it started.

Any suggestions? (I plan on cleaning the MAF and throttle body, but I'm thinking there's something else the matter.)

[doctorhrdware]

Yes that is a good thing, you do not want any fuel comming out into the vaccum line.

[olopezm]

In that case, cleaning the MAF and throttle body (TB) would be the first step, like Rick said.

What happens if you floor (and hold) the gas pedal before actually starting the car, have you seen any smoke coming out form the tail pipe?. Flooring the gas will prevent the injectors from firing which would clear a flooded engine. In your case a leaky injector could cause it to slightly flood overnight. This is just a theory.

Another thing could be a bad TPS. When mine failed it would cause the car to sputter during a coldstart. When I unplugged it the car started perfectly and that's how I found out it was the problem (when I connected my low end scanner it would read the TPS as good, if you have a high end scanner you can graph it and see if it has any dead spots).

You can try unplugging the MAF, ECT and IAT sensors, one by one, to see if any helps your no start condition. Specially ECT and IAT sensors are used during open loop mode (when you start your car or drive at Wide Open Throttle-WOT).

Oscar.

[Brandybuck]

rkvons: Thanks! I found that when I turn the key to "Run," the fuel pressure jumps immediately to 50psi. When I start the car, it drops to 45psi and stays there. (I've thus ruled out fuel pressure for the problem.)

rickisrad and olopezm: I took off my air duct, MAF sensor, and honeycomb. The MAF sensor is extremely clean. So is the inside of the throttle body - it looks almost new. I checked behind the butterfly valve, and it appears to be clear. I didn't bother cleaning the TB and the MAF.

I unplugged the MAF, ECT, and IAC sensors, and it made no significant difference in the starting issue.

I believe I've now isolated the problem, however. I've always noticed that my car starts and runs a lot more quietly than my family's Grand Prix. Today I turned them both on at the same time and compared them. I noticed that my family's red Grand Prix has a much louder "rumble" than mine. It can especially be noticed near the rear of the cars. I deduced that perhaps I wasn't getting enough air. So I partially removed the air duct from the TB on each car, so that I could pull it back and hear the air going through. Sure enough, there was a loud air noise on the red car, while on mine it was much softer.

Am I correct to assume that I'm not getting enough air into my engine? I know that it's not my air filter - that's relatively clean. What are the remaining possible causes of low air flow?