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Discussion Starter #1
Hello again,

I'm pulling my hair out with the CEL. I replaced ALL the vacuum lines from the throttlebody to the EVAP system (charcoal canister, thermistor, and solenoid). I replaced both the solenoid and the thermistor. I checked the canister for any cracks or damage and found nothing. The only lines I didn't change was the one on the left side of the wheel well next to 2 other fuel lines and the one after the fuel filter, which both look good.

I have not tried a new gas cap, but will do so next. I'm banging my head against the wall at this point. I have only a few months until emissions testing, and the dang light keeps coming back on. :redmad:
Is there a way to test the canister?

Also, I've been having another issue, which may be connected or not. Every now and then (usually on cold mornings) the car will take longer to start, and when it does, I hear this extremely loud foghorn like noise. It also comes on occasionally on the highway at around 40 - 50, and will only go away when I pulse the gas pedal. If I'm in a parking lot and this noise comes, the moment I put it in drive the car stalls. Even when this noise does not appear, the car idles like crap, going back and forth between 500 and 600 RPM.

I have already replaced the IAC, and all the vacuum lines are brand new. When I try to pinpoint where the noise is coming from, all I can tell is that it's loudest near the passenger headlight.
I'd appreciate it if someone could just point me in the right direction.
 

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I have had the exact same issue(s). Do replace ALL the vacuum lines you haven't already. Our cars are old... The one in the wheel well was shot on mine. Many of mine seemed fine so I replaced all the evac stuff and egr stuff while ignoring some vacuum lines. That was where my mistaked laid in wait for a long time. Even one small seeming perfect vacuum line for the fuel vapor (under passenger side near fuel filter) was adding to the issue. Again, I replaced every component to no avail and it was simply a vacuum line.
The foghorn is likely harmonic resonance due to the IAC. Common issue. I have been through a few of those and I found it was usually due to them not being tightened. Seems simple but pulling them over and over again and cleaning them over and over lead me to that simple discovery.
 

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I get the goose call only in very cold weather for my area, below freezing. It goes away once the engine warms. I've always wondered about this. However, it doesn't affect performance. How are your plugs and wires? I'd check for a loose plug. Just guessing here.
 

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That's the air in the inlet resonating, from the IAC.

Usually it means there's a Vacuum leak, and the IAC is bouncing off one end of travel, instead of being in the middle of the swing.

The fuel vapor canister circuit is where most unfindable leaks are; there are what, 7 sections of tubing less than 4" long?

One is in the passenger fenderwell; that's the hard to find one, lol.

It's worse when it's cold and dry; there's more 02 in the leak, and the IAC is trying to shut off.



The Cigar Test (search) is the best way to find all the leaks; at least someone you know smokes. :)

You can even get one of the really annoying anti-smoking people to help you find the small leaks after you fix the big ones, lol.

:grin2:
 

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Discussion Starter #5
Thanks for the replies guys.
I hear the foghorn even if I'm not on the gas pedal. Coincidentally, I took another look at the vacuum lines in front of and behind the fuel filter, and the one in front was pretty bad. I'm gonna check the one next to fuel tank and in the wheel well next. I'll report back my findings tomorrow once I change the lines and check a few other things too.

My plugs are brand new, but my wires are original. I'm gonna take a look at them along with the coils.
 

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Discussion Starter #6
Well, I bypassed the EVAP system to see if it was the source of the rough idle by blocking the tube coming off the throttle body and blocking the plastic line from the canister. The car ran the same, still going up and down in RPM. Checked the coils, found them to be good. Ran out of fuel line, so I only replaced the line in the wheel well.

I did notice the engine is running rich, and the exhaust has a very strong sulfur like odor. Gonna try cleaning out the EGR next. Haven't scanned the CEL in a while, so I might be getting more then P1443. Got my own scanner coming in, been using parts stores to scan until they stopped loaning them out, jerks.

Maybe a bad oxygen sensor or clogged fuel filter? Another weird thing I noticed, my "check gauges" came on for about 2 minutes when I was on the highway, then went out. Car was low on gas, but my low fuel light never came on. All fluids good.
 

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Have you tried cleaning the MAF? It might not fix everything but it won't hurt. :)

Swapping out the original wires wouldn't be a bad idea either.

Joe
 

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I agree with the above. I clean my MAF sensor once a yr. I have even found a bug splattered on it once, crossing out 3 turns on the wire lol.
Still sounds like a vacuum issue though. The up and down idle is a common sympton. Have you checked the hard line and check valve at the firewall? That was another source of vacuum leak for me.
 

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Discussion Starter #9 (Edited)
Just scanned it. Guess what - the P1443 code is gone. Now it's getting P0402. "EGR FLOW EXCESSIVE". Should I clean/replace the EGR? Did a forum search, just thinking about where to go next.

BTW, I cleaned my MAF about 4 or 5 months ago, but I'll probably clean it again just to be sure.
 

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Test the DPFE and EGR solenoid voltage if you've already cleaned the EGR valve. EGR solenoid filter can be clogged causing lack of vacuum to the EGR valve.
 

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Could be a bad DPFE sensor, check the hoses for it too.

This is for an F150, but it could be the same problem with yours.

Joe
 

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Discussion Starter #12
Alright, so I just finished changing the last EVAP vacuum lines. I took off the EGR and cleaned it, but after doing a couple of tests on it I'm finding it has a rather small leak. Just how bad would the leak have to be to cause a noticeable effect?
 

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I agree with the above. I clean my MAF sensor once a yr. I have even found a bug splattered on it once, crossing out 3 turns on the wire lol.
Sounds excessive. It's okay to check it periodically with a magnifying glass, but don't spray it if it's clean. I know "they say" the electrical cleaner is safe, but I believe if you spray that thing enough times, it will eventually kill it. I have seen them go bad not long after cleaning them.

The bigger question is "how did a bug get past your air filter?"

Al
 

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When my cougar was throwing the EGR codes I didn't notice any performance issues. To fix it I took off the EGR and cleaned it with carb cleaner, put back on with new gasket. Tightened the EGR tube that had come lose over time. Also pulled apart the EGR sensor and cleaned the filter in it (can't recall name of it at moment).
Doing all that and it hasn't thrown an EGR code since over a year now.

I had issues with getting rid of the EVAP codes on mine. I replaced all the vacuum lines, sensor and purge valve, gas cap. I had the same code come back 6 months later. It ended up being my purge valve went bad again. I used BWD brand that fortunately had a 2 year warranty.

Double check for vacuum leaks at your brake booster as well. I had a check valve go bad on my Tbird there. It was leaking slowly at first causing idle issues. Then one day it came apart with no warning causing a massive leak and almost no brakes.
 

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Discussion Starter #15
Well after cleaning the EGR the car's idle improved by 90%. I hear the foghorn noise much less, and the car starts significantly faster now. My CE light has been out for over a week, and it passed emissions. All new vacuum lines, from the throttle body to the fuel tank. Car feels like it has more power and doesn't struggle so much.

Thanks for all the help, looks like this chapter is closed. Now onto greater things, such as my noisy door hinge roller or some interior redecorating (Pics coming soon) :grin2:
 

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On the issue of EGR. I recently got a CEL with a 1407 code. The engine runs flawlessly, but who knows for how long it will with this code. I don't have to go through any emissions testing in my area. I'm tempted to temporarily put a piece of tape over the CEL until I can take the car to a friend's shop for proper diagnoses of the low flow in EGR. Is it a bad idea to put tape over the light?
 

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Where is the DPFE sensor on the 96 4.6? I am having the same issue along with p0402 and 0174.
I've replaced all underhood vacuum lines so far. The ones in the wheelwell and by the fuel filter look good. The evap solenoid (under the passenger side headlight, don't know if that's what it's called) is also new and I've replaced the driver's side o2 sensors.

Car drove much better after that was done. No idle issues or foghorn noises for me, but the codes still remain. Any ideas?
 

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On the 96 4.6L, the DPFE sensor is located behind the intake manifold (up top) just before the firewall. Has two hoses out the bottom. Can't really clean it but it can fill with condensate. You can try unclogging 2 of the 3 orifices through the hoses down towards the EGR tube. GENTLY. And they are small orifices (2-3 mm if I remember correctly).
 
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