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99 escort surge/ miss


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#1 ron1

 
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Posted 04 February 2010 - 02:18 PM

Thanks for reading......

99 Escort 2.0 SPI. Car has on-throttle miss, and "surge" at steady throttle. Power and fuel mileage considerably down.

Compression on all cyl. 188-195 lbs.
MAF showing 3-4 grams @ idle
fuel pressure 30 lbs @ idle, 40 lbs and holds at throttle input & steady throttle.
both upstream and downstream o2, switching correctly.
3 lbs back pressure, no exhaust restrictions.
LT and ST fuel trims roughly 3-6 % +, - respectively.
TPS shows 20% at idle, reads correct with throttle input.
vacuum within limits.
obviously, no CEL, or DTC codes set.
new plugs, wires, ( is not an ignition miss, but needed replaced)
30K volts from all legs on coil.
signal voltage @ Fuel pressure sensor 2.8v @ idle
fuel filter replaced.

concern* FPS shows 8 lbs more fuel pressure than gauge indicates @ idle, 5-6 lbs with engine under load, part throttle.

I have by-passed fuel pump driver module, and pump has approx. 65-75 psi. Volume and flow is good as well. I fabricated a voltage resistance control ( i.e., old radio volume knob) to attempt to "re-set" voltage at FPS. set @ 2.4v, to increase pump output, ( basically fool it to try and match fuel pressure gauge readings) with no positive results. Also checked and verified neutral switch is operational. ( 5 spd)

Car will idle fine, on throttle acceleration produces a "break up" and miss condition. steady throttle will induce a surge as well. As mentioned, power is down significantly, as is mileage. ( 21 mpg)

Any input will be appreciated.


Ron

#2 Karrpilot

 
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Posted 04 February 2010 - 05:10 PM

Try doing an engine running compression test. And see what your readings are then. A sloppy timing belt could case a surge. As well as a sticky VCT unit. But i am not sure if that year and type of Escort has the VCT system. I knew the Escort ZX2 did.

You are not running E-85 gas and aftermarket tune up parts, are you? Like a K & N type of airfilter?

I do remember Escorts of that vintage dropping valve seats from time to time.

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#3 ron1

 
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Posted 04 February 2010 - 06:14 PM

no E85....

soch did not have variable cam timing.

did not try running compression test. Timing belt tensioned properly, and in time. all plugs are white, would suspect one cyl. to read different on bad valvetrain, or stuck tho.

Thanks also for fast response.

#4 greg's garage

 
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Posted 04 February 2010 - 09:23 PM

no E85....

soch did not have variable cam timing.

did not try running compression test. Timing belt tensioned properly, and in time. all plugs are white, would suspect one cyl. to read different on bad valvetrain, or stuck tho.

Thanks also for fast response.

Ron as i understand you have a miss, but no codes like a P0300

If you do have a miss and no codes with ford u can go into mode$6 and check on the miss ref, the highest count # will show witch cylinder is missing but the count is not high enough to switch on the mil, from there you can carrie on your diagnostics,
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#5 ron1

 
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Posted 05 February 2010 - 04:55 PM

The miss is not isolated to one cylinder, but all. The plug readings, for what it's worth, are all the same, and all very lean ( i.e.- white).

With the FPS showing roughly a 20% higher fuel pressure than indicated on gauge is one of my main concerns. Wit readings of 40 psi @ idle, and an actual 31-32 lbs registering, is this an allowable discrepancy? With fuel trim compensation varying on the + side, my only thought is that the FPS is attempting to cut back fuel pressure, due to a possible malfunction. Not being all too familiar with Fords, this is the most logical explanation I have. Granted, I realize a faulty ECU can be the possible culprit here as well.

According to Haynes™, a reading of 50 psi key on, 25-40 psi while running is the norm. Car has 40-42 psi key on, but does have proper at engine run. Flow is excellent, and fuel pressure does not taper off under w.o.t. applications.

I am leaning towards a faulty FPS, or the slim chance of a ECU failure. Does anyone know if that 20% discrepancy is allowable according to Ford? Also, under steady throttle input, the discrepancy is less, @ 4-6 psi, causing a slight stammer, but not as evident as under load throttle input of 8-10 psi discrepancy.

#6 Karrpilot

 
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Posted 05 February 2010 - 05:52 PM

Have you tried a new coil pack? Possibly you have a weak one?

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#7 ron1

 
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Posted 05 February 2010 - 08:01 PM

coil pack shows excellent voltage... all legs jump to 30K+ on tester.

#8 ron1

 
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Posted 07 February 2010 - 03:04 PM

Thanks to all that have replied...

about 99.9% confident source of miss has been found. IAT sensor malfunction.

#9 ron1

 
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Posted 16 February 2010 - 01:36 PM

Back- replaced IAT sensor, resulting in exact same issue. Unplugged, the car runs considerably better, with almost no hint of stutter, except when cold. ( considering pcm has no input on temp, this makes sense). Power is also up, but not entirely where should be. input voltage is 4.61v.

suspect pcm failure.

#10 Karrpilot

 
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Posted 16 February 2010 - 05:25 PM

Years ago i had an Escort like yours in the shop running bad. The check engine light was flashing. I pulled the codes and it was a weird one. I can not remember if it said the RAM or ROM in the PCM had failed. This was the only code outputed.

So i figured, what did i have to lose? I reflashed the PCM. That fixed it. I think. The code erased, the vehicle ran like new, and i never saw it again.

So try that first before you toss a PCM at it. See if it has a reflash available. This may or may no fix it. But if it does, you saved yourself some cash. The last time i priced out a Ford PCM they wanted $350.00. And it was obsolete. Not available from Ford any more.

I wound up going the junkyard route for under $100.00. I did not trust NAPA or CARQUEST.

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#11 ron1

 
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Posted 17 February 2010 - 04:33 PM

Thanks..

the oddity continues. Decided to check voltage @ coolant temp sensor, @ MAF, ect.. to see if i had a wiring issue, or possible drop from bad ground. All checked okay, although 4.61 did seem a tick low. However, upon completion, car has same issues again, only with a hard crank to start now.

C4 might be a viable option at this point.




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