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Discussion Starter · #1 ·
hi , i have a 2002 merc sable with the 3.o sohc and 110,000 miles. i bought it this febuary, and it ran fine, but since the warm weather hit it has been acting up especially on hot days . i have had an on going problem with the car getting a nasty hesitation at 4krpms and sometimes reacurring at 5krpms. so far i have replaced the fuel filter, new plugs and wires, crank sensor, and the idle air control valve. it shows no codes when plugged in and just today when idling in my drive way the oil pressure gauge was flahing. any ideas? my next step was replacing the coil pack?
 

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take a spray bottle and spray down the coil pack with some water while it is running and see if it changes the idle. wiith the ehsitation being at high rpms i would think it may be an air flow issue. maybe the mass air sensor needs to be cleaned. also this is the season for bad fuel pumps. i would do a pressure check. low voltage can cause problems too. have the alt and battery tested.
 

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Hold the phone.

In your info, you say SOHC vulcan? Vulcan is cam-in-block OHV, the 'tec is DOHC. If you have the DOHC, then it's worth troubleshooting. If you have the OHV vulcan, the engine's plain out of breath at 4k RPM and pushing it beyond that is asking for trouble.

Just my $0.02
 

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Hold the phone.

In your info, you say SOHC vulcan? Vulcan is cam-in-block OHV, the 'tec is DOHC. If you have the DOHC, then it's worth troubleshooting. If you have the OHV vulcan, the engine's plain out of breath at 4k RPM and pushing it beyond that is asking for trouble.

Just my $0.02
my vulcan doesnt hesitate at high rpms.
 

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I have a Vulcan and was having problems under load. Between 3-4,000 rpms it would not be able to pick 3rd or 4th gear. Pulling hills it would also freak out. I bought some CRC Mass Air Flow Sensor cleaner, removed the MAF and hosed it down!! I put my foot down the next day to pass some one and the problem was gone. New MAF is about $150, cleaner is $7. Easy choice and great results. Good luck!!
 

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The CPS can cause this as well, I have the EXACT same problem, I don't have the CPS "Squeak" but the sensor part of the unit can be replaced for 20-30 bucks. I'll be doing that this weekend and I'll let you know what I find.

As far as it being a coil, you would have a steady miss and it wouldn't cut out at just a given RPM range, that's why my first guess would be the Trigger of the coil. It's a simple Magnetic pickup and the magnet can get weak so when the engine is spinning at higher RPM's it will not read as the Tooth goes by the sensor.

There is a Ford TSB out on this..... See the attachment.
 

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Discussion Starter · #7 ·
thanks for the help sorry about the mistype its a vulcan ohv and ive had this motor in this car and a ranger 5spd and they both have run up to 5krpms without problems. today before i left for work i used a spray bottle and mist the coil baack while runninng and appeared to make no difference, i beat the **** out of it on the way to work 20 min drive and it ran perfect. today on the free way after about 1hr of driving i ruggged it getting on the exit and the problem reacurred? seems to happen more the longer i drive it ?im off to get a can of mafs cleaner to try that
 

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A MAF that is weak / Dirty will throw a P0101, P0102 or P0103 - You have no stored codes. It's not a bad Idea to clean the MAF every 15-30K though just as a general maintenance tip. I don't think that the MAF is the culprit here.
 

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A MAF that is weak / Dirty will throw a P0101, P0102 or P0103 - You have no stored codes. It's not a bad Idea to clean the MAF every 15-30K though just as a general maintenance tip. I don't think that the MAF is the culprit here.
you have a good point. the reason i thought it might be is it happens on the hot days. there are other things that could be the cause.
what about the fuel you use? have you tried a different gas station? is it 10% corn? lol...
 

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When I had this problem, I replaced the CPS with no luck - then I did the syncronizer and the thermostat - one of them cured it, don't know which one.

I checked the old thermostat afterwards and found it didn't open fully, so it may be have been that - my theory was heat and fuel pressure. Someone on here had mentioned something about heat and the anti-detonation sensor. Either way, one or the other did the trick.
 

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The thermostat couldn't cause this issue, only the Synchronizer / CPS unit could. If you are going to the trouble of replacing the CPS you might as replace the synchronizer that it's attached to. This is efectively a "Distributor" on the early model vulcans. Personally I would rather have a C.O.P. system - these synchronizer failures are just annoying.
 

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Discussion Starter · #12 ·
so cleaning the mafs did not help i run shell 87octane but when the problem first started occuring a while back i replaced the fuel filter and started running 93 and it did nothing. and i have never tried running e85 or any of that nonsense
 

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By "nasty hesitation" do you mean - like the rev-limiter is kicking in? - motor just seems to cut out? If so, I had the exact same problem, in fact it was my first post on this board. I tried a bunch of things - fuel filter, fuel, plugs and wires, nothing helped.

What I did notice is the problem got worse the more I drove it ( it was worse after an hour than it was after a half-hour ). There is a TSB regarding the syncronizer - so I took a crap shoot and replaced it - along with the thermostat - I'm telling you one of them fixed it.

If it starts out fine when the engine is cold - then gets worse the longer you drive it, then it's likely the same issue(s).

The flashing oil light leads me to believe it's one or the other - mine did the same thing -though it continued after I swapped the parts- only recently did I change out the oil-pressure sensor and that problem went away.

I have 30,000+ miles on the car since I swapped out the syncro/thermostat and now the car runs right up to 5,500 rpm all day long without any issues (167,000 miles now).

As far as "The thermostat couldn't cause this issue"; maybe so, but if it weren't opening all the way, the reduced flow might cause hot spots where it could throw a sensor off, the guage isn't that accurate or responsive so reduced flow might cause a temperature problem to not be picked up by the temperature sensor. If you have access to a live data scanner, I'd bet the fuel trims get richer and richer the more longer you drive it - but that's just a guess.

I'm no expert, and I doubt anyone else is, all I know is what I did and that my car runs fine, in fact it runs better on Shell 87 (27mpg combined) when I can get it.

EDIT - final thought - as far as the syncro I replaced - I couldn't see any problem with it, the gear appears perfect compared to the new one, if it weren't dirty you'd be hard pressed to tell the difference from the new one. Since I had the new one in hand, I couldn't see not replacing it once I went to all the trouble of digging the old one out.

peace
 

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As far as "The thermostat couldn't cause this issue"; maybe so, but if it weren't opening all the way, the reduced flow might cause hot spots where it could throw a sensor off, the guage isn't that accurate or responsive so reduced flow might cause a temperature problem to not be picked up by the temperature sensor. If you have access to a live data scanner, I'd bet the fuel trims get richer and richer the more longer you drive it - but that's just a guess.

EDIT - final thought - as far as the syncro I replaced - I couldn't see any problem with it, the gear appears perfect compared to the new one, if it weren't dirty you'd be hard pressed to tell the difference from the new one. Since I had the new one in hand, I couldn't see not replacing it once I went to all the trouble of digging the old one out.

peace

You see that's the problem, you replaced 2 things to correct an issue so you don't know which one fixed the issue but logically the thermostat could not cause a buck / surge issue.

If the thermostat was not opening all the way creating a flow issue then the vehicle would have an overheat condition. It would be similar to having a bad water pump creating a flow issue, you would be ok on the freeway at speed but in stop and go traffic you would see the temp go up past normal.

As far as the sensor looking normal or undamaged / warn - The simple fact is that this is a magnetic pickup system using permanent magnets that do wear out.

I never claimed to be an "Expert" but it seems 99% more likely for it to be a cam position sensor than a coolant flow / thermostat issue. Given the Taurii's history with failing Crank sensors I would replace that first.

I have seen coolant temp sensors cause a rich condition but the computer in most vehicles has an adaptability to change the fuel curve rich or lean of about 15-17% so this wouldn't be enough to cause a misfire or to even foul a plug. BUT it can cause premature wear of O2 sensors and the catalytic converter - if the cats were clogged then it COULD cause a misfire but the OP has no power issues until the noted RPM in the TSB.

Don't misunderstand me I was not stating that your Idea was bad or that I was discrediting you, because it is a good Idea to keep up on the cooling system anyway especially on a Vulcan. But it is VERY unlikely that the thermostat caused this issue.

Troy. :)
 

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We agree to disagree. And no, I didn't replace 2 things to cure one issue - I did the assembly hoping to solve one problem and the thermostat because I knew it was original and I felt the car was running hot - but you're right, I don't know which solved the cut out problem and I believe I stated so.

Given the opportunity to do it all over again, I'd do the same. However, if I knew one of the two solved the issue for someone, I'd go with the thermostat first because I like simple solutions. Might be costly in the long run, but that's my choice.

I said the syncro looked un warn - I had replaced the sensor months earlier without effect, sorry if that wasn't clear.

And I didn't mean to give you the impression I was calling you out with the "expert" statement, it wasn't directed at you. I've seen the same symptoms reported before and never seen any resolution posted - lot's of people throwing out ideas, coil/plugs/wires, this sensor or that, check the fuel pump and on and on and never seeming to get a resolution. One guy ended up with new cats (under warranty) which didn't solve the problem, as far as I know he never found out what was causing the problem - maybe he found it but he didn't post back.

as far as the rest - I spelled out the symptoms I experienced - like it was hitting the rev limiter, which if the OP's problem isn't the same as what I described then maybe this discussion is moot anyway.
 
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