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Discussion Starter #1
I drove to church this morning, car seemed to run fine. Came out, pulled out the parking lot onto the road, and car would not rev over 1000. Puttered along to the next place to pull over, it took off a couple of times and jumped to 2000-2500, but just for an instant. After pulling over, it idle roughly a bit, then died.

It will now restart for a few seconds, after some cranking, and then idle roughly at under 500, will rev in park to 1000 or less, and dies after several (or a few) seconds. My first thought was no fuel, but it gave a healthy squirt out of the valve on the rail when depressed.

Car is not yet at home, I am waiting on it to be towed, so I haven't been able to do any real testing yet.

I really don't know where to go with diagnosis on this. My first thoughts are to get a confirmation on fuel pressure, check the MAF for obstruction, and maybe the crank sensor? Some direction would be greatly appreciated!
 

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If you unplug the MAF and it runs better there's your problem. A simple quick test.
Your symptoms are exactly the same as my car exhibited when the MAF went bad.
It had to be towed home and it did not set a code.
 

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I once had a seemingly electrical problem with the IAC. The darn thing just went wide-open and it jacked up the idle. Turned out, there was nothing wrong with it, it was just a glitch that was resolved by resetting the PCM with the fuse-pull-cranking procedure. Just something else to consider.
 

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Discussion Starter #4
UPDATE: I tried both things suggested, thanks guys! Unfortunately neither helped. I do have some more information, but I'm unsure what it means....

I swapped the cam position sensor, mostly because it is a cheap and easy thing to eliminate. No change.

I tried a shot of brake cleaner into the IAC, hoping to free it up if it was sticking. After that, it started up and idled normally. But if I touch the throttle, even a little, it immediately stumbles, sputters, and will run roughly and rev up to 2500 or so, and generally bounce all over the place between 300 and 2000. Letting off the throttle, it return to a nice idle.

If I shut it off, it will not restart and idle without another shot of brake cleaner into the IAC. I assume this is just acting as starting fluid somehow.

Unplugging the TPS or IAC while it is idling causes it to die.

I am leaning towards a problem with the IAC.....but my past experience with IAC problems has been that the vehicle will not idle normally, but once it is given some throttle, it runs ok....what I am experiencing here is the exact opposite.

Suggestions appreciated.....I would prefer not to spend $50 on an IAC without a bit more confidence that this is the problem....
 

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First hook up a voltmeter to the TPS, and check to see that the voltage increases with increased throttle position. The engine can be off, just the ignition needs to have power. It should start out at ~0.8VDC and top out around 4.5VDC. If the voltage jumps all over the place, then it might be a TPS issue.

You can also check the maf signal on the tn/lb for the 0-5V signal, and the bk wire for ground. It might be the lb/rd, but I'm pretty sure it's the tn/lb wire. When you first start the car, especially when it's cold, you should see around ~1.0VDC ± a couple tenths of a volt in neutral. Once the idle timers die out, and the RPMs drop a little, you should see around 0.8VDC. In gear, the voltage should jump back up to ~1V or a little higher. As you give it throttle, the voltage should smoothly increase with no discontinuities. The voltage increase is not linear, but none the less it is always increasing in a properly working maf.

 

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i'm thinking fuel pump and or bad inertia switch. just because fuel squirts out of the fuel rail doesent mean the pump is working properly... also,it could be a bad inertia switch (it shuts off power to the pump in the event of an accident or for security purposes) located in the left side of the trunk behind the trunk carpet, it has a red button on it. i'd change out the switch first, then the pump
 

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Inertia switch wouldnt cause the engine to only rev to a limited number of RPM, thats not the problem.

Bad crank sensor would cause it to not start at all, not a revving problem.

Check fuel pressure. Check the MAF. Most likely has something to do with air/fuel .. or the cats are plugged up really bad. Even a misfiring engine should still rev up higher than that.

I once had a similar problem on a 94 Tbird, turned out the wire for the transmission shorted somewhere and no power to the trans put the PCM into some kind of safe mode where it wouldnt rev much at all.

Any Check engine light codes ?
 

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Pull the #8 spark plug wire, and see if there's coolant there.

I had a "degraded run, no idle" problem that was bad wires and a leaky intake gasket.

Replacing wires is an expensive temporary fix, if there's coolant. You have to fix the coolant leak, or it will recur regularly.
 

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Discussion Starter #9
No check engine light/codes. I had considered plugged cats, but this problem appeared out of nowhere....ran fine first thing this morning, sat for 2 hours, than ran like crap.

I just did the test on the TPS. I have only a digital meter, not an analog, so it is a bit harder to watch, but as best I can tell, it is putting out a normal signal. I will check the MAF tomorrow, just to be sure.

I'm really starting to think it isn't getting adequate fuel for some reason....based on the fact that it takes a shot of brake cleaner to get it to start up and idle at all normally, and that any load whatsoever kills it, or at least makes it go all whacky.

The way it's acting kind of reminds me of when you are running out of gas, and the spit/sputter/die/restart stuff that happens when you are trying to coax it that last mile to the gas station on fumes and prayers. :D

I'm planning on checking out the fuel pressure with a proper gauge tomorrow, and I"ll go from there. A new filter will be installed for sure, to eliminate it as thebproblem and good basic maintenance anyway.

Will check #8 plug well as suggested also.

Thanks for the help!
 

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Discussion Starter #10
I did some testing this evening with a proper fuel pressure gauge.....found I am getting about 10 pounds of pressure max, and as soon as the pump shuts off, it drops to zero, rather than holding pressure for a period of time. Even when the pump primes at key on, it runs up to only about 10 lbs, then drops within a couple seconds after the pump shuts off. Pulling the vac line off the regulator makes no difference.

I now need to know whether it is the regulator, or the pump....how can I make the determination?? I hope its the regulator....half the cost and a whole lot easier to change..but it is what is I guess.

I tested the gauge (its a loaner) on my truck, got about 35 lbs, so I am confident the gauge is reasonably accurate.

I changed the fuel filter before testing.

SO......weak pump or bad regulator????? :confused:
 

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There's been a rash of Fuel Pump threads lately; yours sounds dead.

At 10 psi, it's either a dead pump, or fuel pouring out somewhere; I think you'd notice the fuel spraying everywhere. :)



BTW; Did you shake the car to make sure there's gas in it?

It's common for gauges to go bad, and the tank empties before you realize it.

Don't be tempted to add gas at this point; you have to drop the tank to swap the pump. :)
 

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if the fuel pressure regulator was working properly, it would hold those 10psi after you shut off the engine, as low as it is.
There is a one way check valve on the Fuel pump itself .. if that check valve isnt seating, it will bleed off the pressure.

Test the regulator by pinching the return line - if it holds pressure, bad regulator .. pressure drops = bad check valve on pump.
 

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Discussion Starter #14
Fixed! :cool:

Based on pinching off the return line not making a difference, I decided the problem was the pump, not the regulator. Swapped out the pump tonight, what a pain that was! Anyway, it runs great now!

Thanks for all the help guys, it is hugely appreciated!! :)
 
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