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Discussion Starter #1 (Edited)
I have had an intermitent / random rough start on my 99 Duratec.

This has been going on for close to a year. It was happening maybe once every couple weeks, but recently has happened more often (although only once in the past 10 days or so).

Over the past year, I have "thrown" various parts at it... IACV, EGR, EGR DP Sensor, Fuel Pressure regulator...

I have had the left/right bank lean codes for about 6 months. FINALLY resolved those codes this weekend. replaced the rubber hose at manifold end of the crank case breather tube from the pcv (that assembly wasn't avail at local dealers or parts stores, so I used a piece of 19/32 rubber hose and clamp along w/ some marine sealant stuff intended for hoses and gaskets). I think my vac leak was the small 90 degree elbow that has two plastic vac lines coming from it. It fit really loose onto the nipple behind the throttle body towards the firewall. That part also was not available, so I used a hose clamp on it along w/ some of the marine sealant (might have to revisit this again). But, the check engine light has not returned, so that problem is gone.

I was "hoping" that this some how was related to the random rough start, but after a long test drive, I stopped at the store to get the kids some snacks and when I left the store, it had the rough start issue a couple times, then finally started normal and I drove home.

OK, on to the real issue. My car usually starts just fine when cold. The rough start seems to be after it has been parked for about half an hour then restarted.

It will start, but idles REALLY low, coughing, stumbling, wheezing... it will not respond to the gas pedal except for occassional back fire (out intake I think). Turn the key off wait a second, try again and it might start and run OK, or it might do that a few times.

The battery is strong. It has no issue cranking.

A couple weeks ago, it failed to start at all. Cranked it over for a period of about half an hour. Seemed as if there was no spark or no fuel at at that point. I called a tow truck, went into the store to get a drink while waiting on the tow truck. Came back out and it started fine. That is the only time it failed to actually start after a try or two.

When it finally does start, it might run a little rough while driving for a minute then runs fine.

Normally, there is NO hesitation under acceleration, no misfires, runs fine. This starting issue almost seems as if the timing is WAY off, but once it starts, then it runs great.

A lot of posts seem to point to the fuel pump, but I am hesitant to replacing it again on a whim. I have already thrown a bunch of parts at it. I replace the fuel pump maybe 5 years ago.

The car has about 260,000 miles on it. No major problems other than this.

Thanks in advanced for the help.

Ken
 

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Have you ever checked the fuel pressure. If not, that's where you need to start. You can also try priming the pump before starting(turning the key to run a few times before starting it) to see if that helps. If so...... time for a fuel pump.
 

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I have no issues throwing parts at my '95 GL 3.0L. I got the car w/30,000 miles and no one has wrenched on it but me (minus alignments). I know if the parts are original or not. If you haven't thrown these at it, consider the Air Charge Temp Sensor and Coolant Temp Sensors. I removed the ACTS from my '95 and it was BLACK and sooted up. That was at 152K and it had never been removed or replaced. Clean the throttle body/butterfly with the correct cleaner. Clean the MAF, there's a different cleaner for that. The MAF sensors are delicate, be careful. For fun, ohm out the spark plug wires, should be around 5000 ohms per foot.

I threw a fuel pump at an issue for fun recently, Didn't fix anything, but I know how to get my tank on and off correctly. I ran my car to 135,000 miles before replacing the O2's. Never got a code. But talk about a difference in performance when I replaced them. Go figure.

I suspect that cleaning the MAF and throttle body/butterfly will improve the performance of your engine. Apologies if I'm rehashing some of your work here.
 

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During a heat soak as decribed loss of fuel pressure or an electrical problem are most likely.
Fuel pump, clogged filter and bad relay are possible. (Cycle the key as suggested)

Ignition sensors (crank and cam pick ups) along with PCM are also possibilities.
They control spark and injector opening. Check for spark and injector clicking during no start.
 

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Discussion Starter #7
phantom57 Thanks for the tips.

Over the past few years (about 3) I have replace the fuel filter, air filter, plugs, wires (all just regular tune up precautions). Then, more recently (past 9 months) I have replaced IACV, EGR valve, cleaned TBI, cleaned MAF (that did seem to make it run stronger initially), and this past weekend the DPMS and hoses associated w/ the PCV valve.

I have a replacement Fuel Pump assembly on order right now. I replaced it before, but I cannot remember how long ago (also did that job in past 5 years on my truck, so can't remember which vehicle was when). I don't remember if I did just the pump, or if I replaced it as a whole assembly (hoses, fuel level sender etc.) This time, I am replacing the whole unit in the tank. Prices are SO much better on Rock Auto than at local part stores. Denso assembly is $129 on Rock Auto, and locally was $189.

I have not checked for spark, but since the car will start (it just runs really rough as if timing was way off) I assume there is spark.

Pretty sure I have replaced O2 sensors, but cannot remember when. I have had car since new. Guess I should put them on the 2 Do List.

Thanks again to everyone for the pointers.
 

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Discussion Starter #9
Oh boy a replaced IAC valve and bad idle. I bet not motorcraft brand
99% of the time the car starts just fine. The idle is steady right around 700 RPM, with the AC running or not. IAC valve is working.

About once a week, when I start the car something happens that causes it to run REALLY rough for a minute or two. Then, it begins to run just fine.

There is a random starting issue, not an idle issue.
 

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Discussion Starter #10
Replaced my fuel pump 6 days ago. Problem has gone away. Guess the fuel pump was getting degraded. Pumped enough to make car run most of the time, but something caused it to not work when engine was warm?

Not really sure in what way it was failing, but it is running MUCH better.

I thought the electric fuel pumps either worked or didn't. Didn't think they would become "weak".
 

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Replaced my fuel pump 6 days ago. Problem has gone away. Guess the fuel pump was getting degraded. Pumped enough to make car run most of the time, but something caused it to not work when engine was warm?

Not really sure in what way it was failing, but it is running MUCH better.

I thought the electric fuel pumps either worked or didn't. Didn't think they would become "weak".
I have had 2 fp fail, '92 and '93, both got noisy but ran OK. Of course the noise gets worse quickly. Then '95 that would not pump when weather was really hot and car hot. After an hour, it would then pump. All those new pumps and then OK.

'03 failed last year, just failed to pump cold. Started and ran a few seconds and choked down. However, later after a few key on and no noise, it did pump and started and I drove it to a shop. New pump OK. Then realized I had noted surging at road speed just before. No more with new pump. Now, my other '03, intermittent, no pump with key on. It is going to the shop in the morning if it starts.

Appreciate your input. Seems pumps are a wear item, but how long they last is quite different. However, '02 and later have FPM that modulates the volts to the pump and thus the pressure. If it draws too much current it shuts down and gives a CEL. The code is: your pump is not running, or you are out of gas. It does not know which. :D

-chart-
 

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Discussion Starter #12
I think my issue might have been aggrevated by my "need" to drive as far as possible between fuel stops. I think extended slow city drives w/ the low fuel light on might have shortened the life of my pumps. Going to try and change my driving habits to start topping off right after it drops to 1/4 tank for my normal around town driving. Now, for the occassional road trip, I might push it the extra few miles so I am not refueling w/ 5 gallons still in the tank.
 
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