1995 Ford Taurus Rough idle various times, poor acceleratio

JGOVONI

MEMBER
1995 FORD TAURUS
6 CYL
FWD
AUTOMATIC
130,000 MILES

My Taurus has been acting up. Poor idle at various times then smooths out, misses and bogs down on acceleration and backfires cold through the carb then goes away not all the time on either and intermittent check engine light (comes and goes) no codes.
I have changed the plugs, wires, cap, rotor, coil and fuel filter. Checked and cleaned EGR valve, ECT, ACT, IAC, MAF, PTKFE and fuel pressure regulator. I also checked Evap and emission system, intake manifold and vac hoses and brake booster for vacuum leaks and obstructions nothing noticeable.I also put a spark window on the coil (nothing noticeable), vaccuum gauge(steady at hot idle 15-20) and checked fuel pressure(steady) drops to 32psi (fpr disconnected) at injectors normally 39 psi. What do you think?

3 Replies

JGAROFALO

MECHANIC
489 POSTS

Sounds like it could be a problem with the throttle position sensor. The computer relies on this sensor to determine engine load. Bad information to the computer means that it gives the wrong amount of fuel, and the engine runs erratically.

You said there were no codes, but did you check the keep-alive memory? Any problem that causes the "check engine" light to illuminate will store a code in the keep-alive memory. These codes remain in memory until a sufficient number of drive cycles are completed WITHOUT the problem recurring. Sounds like the test was not carried to completion.

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Friday, January 2nd, 2009 AT 7:47 AM

JGOVONI

MEMBER
2 POSTS

Checked sweep of tps sensor with my fluke 88 nothing found( smooth). Checked fuel pressure again and the way the engine misses wondering If I have a bad/dirty injector. The problem comes and goes. The only code I got recently was for ECT/Emisions probably because of misfire. Thanx for any help you can give.

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Saturday, January 3rd, 2009 AT 3:02 PM

JGAROFALO

MECHANIC
489 POSTS

Diagnosis of an intermittent problem is unusually difficult. In order to get a handle on it, you need to be able to check things while the problem is presenting itself.

Some things to check would be cap and rotor, spark plug wires, air leaks around the mass air flow sensor, and connectors.

Taking notes about when and under what conditions the problem occurs may also be of some help. What was the engine loading? Was the weather warm or cold? Dry or damp/wet? Going up or down a particular hill or section of road? Accompanying symptoms?

There are a number of malfunctions that will not set codes in the system. I might also suggest unplugging the processor connector and plugging it back in. Do the same for the ignition module and coil connector. Just that much disturbance could remove a small bit of corrosion or resistance in a connector pin.

Hope some of this will help.

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Saturday, January 3rd, 2009 AT 8:03 PM