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I got an 87 Taurus LX 3.0 Vulcan. I had a new tranny put in a month ago. Now i have a new problem. When the tranny was done we had all new sensors put Except the MAP sensor and the HEGO sensor. Lately I've been experiencing weird noises and it has been running weird also Related not sure thats why im here. Well whenever i give it gas i hear a rattling noise from the engine but i will not do it all the time and the weird thing is that when i go on a moderate trip the engine starts popping like it is backfiring BUt i got new plugs wires New distributor new TFI module IAC IAT coolant temp sensor ETC whats really weird id that the car doesn't have a EGR Valve. this car is in near mint shape very clean engine has 110k miles promised gma to keep it running so here i am trying to hold my word. PLEASE HELP IM RUnning out of ideas
 

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I really don't mean to rain on your parade here, but the MAF sensor and the HEGO sensors are both VERY important. I'd even be willing to bet that you have a "Check Engine" light on. The MAF stands for Mass Air-Flow sensor. This tells the computer how much air is being sucked into the engine. The HEGO stands for Heated Exhaust Gas Oxygen sensor. This tells the computer how much oxygen and hydrocarbons are left in the exhaust. Basically by disconnecting the BOTH of them, the engine now has no way how to determine fuel mix ratios other than by the TPS sensor, and that is really a bad measure. It's only a guess for the engine. The sensors are to nail it down. The TPS (throttle position sensor) is only a ballpark guess for it. Get those reconnected pronto buddy.

-mobiuslogic
 

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Discussion Starter #3
I don't have a MAF sensor but i do have the HEGO sensor and i was gonna change it cause it the only thing i got left to change but it looks impossible to change. I tried to get the Check engine light to come on on purpose but i will not come on. It turns on when i start it but never returns I got the 87 LX so i have the digital dash and all i have is the service light is this the same cause if it is that will not set a code either but turns on when started This engine is as basic as is gets and i don't get it at all. Other then that when it starts the IDLE LOOPS also i got the timing perfect and i got the bosch platnium 2 in there
 

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I'd check the heat shields on the cats for the rattle. Very common.

The backfiring doesn't sound good. I think it's a bit strange to replace every sensor on the engine except MAP and O2. These are the most commonly replaced sensors. What made you decide to replace everything but these two?
 

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Discussion Starter #5
Wel i would have had changed the o2 sensor but i cant get to it i dont think i can get to it unless i remove the header pipe is there a trick to replaceing this o2 sensor?


I unplug the MAP sensor and the car continues to run normal with no changes? Ive heard that the car usually will not run with this unplugged how do you know when this sensor goes bad

I hooked the car up to a scanner and there is no codes in the system. Theres no data to read also so i cant check the sensors at all except for my ohn meter i have no idea how to check the MAP sensor i think you need a special tester for this?
 

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Discussion Starter #6
Also it will not start without pressing the gas
 

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My grandmas '98 vulcan had something put in the gas tank that detiorated the lining and created gook, this clogged the gas tanks sock, and the fuel filter. The car lost lots of power, and would back fire alot because of the lack of fuel delivery. This happened to us on a trip. I would change your fuel filter, specially if you have never done so, most say to change it every 10k, my 96 had its original one with 130k on it. If that doesnt solve the problem I'd have your tank checked, or you may have a bad fuel injector. Have you tried running fuel injection cleaner? Our '93 Vulcan had a similar problem but it didnt involve backfiring, the engine just stutered from 1,000-3,000 rpm's, but we traded it in...I think it just needed a tune up. I would rule the problem to fuel delivery from experience, you may also just have water in your tank, buy some water remover solution, or isoprpyl alcohol from the auto store(usually 39cents a bottle), use a bottle or 2 every time you fill up. See if you get any results. If you dont, start pulling sensors...thats my 2 cents.
 
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I would start with the basics to solve the backfiring issue:

Check timing
Check compression
Check all vacuum hoses

For the MAP sensor, it can be tested. You'll need a volt meter. Check the votage with the car off, then with it running. When vacuum's applied (car running) there should be a voltage change. If not, I'd replace it. The fact that the car doesn't run any differently with it disconnected, and that you need to hold the gas peda when starting, leads me to think that it's bad.

As with anything, proper diagnosis is very important.
 
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