Taurus Knock/EGR Troubles

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  #1  
Old 07-05-05, 08:53 AM
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Taurus Knock/EGR Troubles

The car: Ď94 taurus w/ 3.0 v-6 and 160k +

I am trying to pinpoint the source of knocking. I have already verified that the EGR valve opens and intake passage is clear. As suggested here I hooked-up a vacuum gauge w/ a tee at the EGR valve and drove the car with hose running in the window and gauge on the dash.

As expected I got no vacuum with throttle closed. I also got no vacuum with hard acceleration. I expected vacuum here, but maybe this is normal, since there will be little vacuum available with throttle nearly wide open. In addition, as expected, I got little or no vacuum when I got the most knocking.

Here is the scenario that yields the most knocking: traveling up a long gentle slope at a constant 35 mph with maybe ľ to 1/3 throttle. Under these conditions the cars sounds like a diesel and the gage registers almost no vacuum.

Additionally, the needle seems to be always moving when vacuum is present. I did not check it on the highway, but I never found a condition where I could sustain a lot of vacuum.

Is this normal? The car does not have a knock-sensor and gets terrible gas mileage. No codes are stored. It has new plugs, cap, rotor and air filter. The timing is set per emmissions label and the car easily passed its emmisions test several months ago.
 
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  #2  
Old 07-05-05, 02:09 PM
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Exactly what are you looking for with a vacuum test? Are you expecting to see retarded timing or sticky valves?

At 35 mph, up a steady incline, in 3rd gear, the engine is at the low end of its power range and that is a likely point for engine knock to be most prevalent, even though it should not occur.

By default, your shift selector is set to 'overdrive on' when you start the car. I'd suggest making the same test drive with 'overdrive off', just to see if you get the same knock results.
 
  #3  
Old 07-05-05, 02:51 PM
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lugnut

Thanks for taking a shot at it.

As my post says, I was measuring vacuum at the EGR valve. I was trying to verify when the ECM is asking for EGR. I was not measuring intake vacuum unless the EGR control soloinoid happened to be wide open and allowing mainfold vacum to the EGR valve and my gauge.

The car has a four speed. If I am in drive and not overdrive it will never shift into fourth. Are you saying that I might be lugging it in fourth (OD) and would maybe ok in third?

I will try this. If your suggestion works, is there a problem with the tranny's gear selection? I read the owners manual years ago and seem to remember that OD was ok for 99% of driving since it is afterall an automatic.
 
  #4  
Old 07-07-05, 03:33 AM
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the ecm should apply vacum to the egr mostly under light throttle or cruising speed it is normal for no vacum at egr when at or near wide open throttle.
the vacum readings will be fluctuating as the solenoid cycles very rapidly.
do you ever have a check engine light come on while drivng and what was your vacum readings while driving the vehicle.
 
  #5  
Old 07-07-05, 09:20 AM
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bejay-trouble codes?

Do I ever get trouble codes? Of course I do.

Taurus ownership is all about trouble codes. I do not believe any currently present have anything to do with this problem, but I am glad you asked.

When I do a KOEO test, I will get a canister purge failure 4 out of 5 times. Everything checks out and the code has never been set while driving.

Another popular one is manual lever out of range, which will set as a KOER code maybe 1 in 5 tries but again never while driving: never recorded as a stored code.

Once a couple months ago I had a stored code: throttle position sensor out of range, but I never saw the dash light while driving. That one has not been repeated.

I also get stored codes about an open in fuel pump circuit. The relay is crap and needs to be hit maybe one in 50 starts or about twice a month, so there is no surprise about that one.

The reason Iím glad you asked is because I remembered trying to check the idle a while back. In search of better fuel economy, now at 14-15 mpg for city driving, I wondered if the idle was too high. After doing the KOER code I disconnect and reconnect the jumper wire within 4 seconds. I think a steady CEL means ok, 1 Hz is too slow, 4 Hz is too fast and 8 Hz is something like throttle position sensor not where it should be so go fish (or fix it first and try again). I can probably tell 4 from 8 if I hand an example of each, but since I donít I guessed I was seeing 8Hz. I tried taking off the throttle position sensor to look at it, but I cannot undo the two small Phillips head screws holding it on. Also, I donít get any codes about idle speed or throttle position other than the one mentioned above. I figured I was at a dead end.

The vacuum was steady at 1 or 2 inches while driving at about 35 mph up a long gentle slope with the car knocking badly. In other driving conditions, it would jump to about 10-12 for an instant and sometimes remain steady at about 6-8 for several seconds.
 
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Old 07-07-05, 10:03 AM
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There is more to vac gauge readings than just the numbers, but your readings sound excessively low to me. Maybe a vacuum leak or a clogged exhaust. You should get a steady 15 to 22 at idle or steady 2000 rpm.
 
  #7  
Old 07-07-05, 11:26 AM
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lugnut-reading is fundamental

AGAIN (3rd time), I was measuring vacuum at the EGR valve. It should be and was found to be zero at idle.

thanks for playing anyway
 
  #8  
Old 07-08-05, 03:46 AM
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if you have a hand vacum pump test the egr to see if it will actually hold a vacum.
check egr sensor hoses for blockage may have 1 or 2 hoses running from egr exhuast tube to sensor depending on what type sensor it has.
if it has a maf sensor remove the 2 screws holding it on and check the 2 wires for debris or buildup it can be cleaned usually by just spraying off with carb cleaner.
if all the above check ok suggest seeing a shop where the vehicle can be driven while scanning the data from the ecm sounds like it is egr system related problem though but by scanning the vehicle while driving it they will be able to check to see the egr sensor voltage output along with other possibles such as the manual lever position sensor out of range which could affect egr operation by not allowing the ecm to know the correct transmission gear it is in.
 
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Old 07-11-05, 09:18 AM
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Thanks bejay

I checked all the simple stuff first, but I will check again. The vacuum pump opened the valve and made the car idle poorly and held vacuum fine. All the hoses appeared connected, leak-free and blockage free.

According to the AutoZone web site, I can buy a neutral safety switch for $25. It sits under the battery and looks easy to change. The tranny has been rebuilt three times. I paid for two, and one was done NC following the second rebuild that only lasted 4 months. Each time they said the price did not include new electronics, so the switch is probably original. I changed the VSS last summer because I was getting a "no data from VSS code.Ē Do you think switching neutral safety switch is worth a shot? I have never had that code set as a memory code but do get it occasionally while running KOER diagnostic.

Since I get such bad gas mileage, I have often wondered if something is mismatched in the tranny or if the tranny is incorrect. The first shop said they switched trannies with a rebuilt one off the shelf. That one lasted for maybe 3 years/ 60K. The second shop said you could not swap them because they are closely matched with ECM and they rebuild all there own trannies. Their rebuild only lasted about 6k, so they did it again and it has bout 5k on it.

While doing a valve job on another family car (same gas, same drivers, same care), I found a lot of carbon build-up in the combustion chamber. The machine shop cleaned the head and I cleaned the piston tops. This car had no egr system and no knocking. It is a completely different car with a different set of problems, but while looking for a head gasket set I read all the stuff on the fel pro web page about carbon build-up causing knocking. This got me thinking about the Taurus. Can excessive carbon build-up be diagnosed without taking the head off?
 
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