All, About two years ago I posted a big write-up about how replacing my ACT and ECT sensors fixed my hot weather related pinging in the 3K to 5K RPM range under 3/4 to full throttle. Well, two years later, my pinging was back! So, what, I say to myself, these sensors only last two years and then they’re bad again? But this time the pinging was there all the time, not just when it was hot outside, so it couldn’t be these sensors. At this point almost all of the sensors on my car have been replaced (including new O2 sensors and, yes, cleaned MAF wires) so I was forced to look elsewhere for a cause. Well, I FOUND IT! It was a vacuum leak at the intake manifold end of the vacuum hose that connects the intake manifold to the fuel pressure regulator! This makes sense, since a leak there actually causes two problems. First, the fuel pressure doesn’t change correctly in proportion to engine load anymore since the FPR vacuum diaphragm isn’t getting the full manifold vacuum signal. Second, an air leak there allows un-metered air into the intake which the MAF never sees and thus incorrectly calculates load as a result. And our fuel/spark tables are what? Load based! This hose is only about a 5 or 6 inch piece of 5/32 inch ID fuel hose. Mine must have been the original piece because it was completely hard as a brick and brittle. Since it was kind of hard to pull off over the flare on the fitting on the manifold side it really didn’t look like it could be leaking there, but it definitely was. It was hard to pull off because the hose was not flexible enough to get past the flare in the fitting. The one-foot piece of fuel line cost me 79 cents. The hardest part was actually finding a 5/32 inch ID fuel line. It seems not to be a common size. I could find 3/16 inch ID fuel line at most car parts places. Though it’s not the best fit, it will work until you can find some 5/32 inch, which is a good tight fit. (Don’t try to use any thin-walled tubing for this, the vacuum will flatten it out and close off the hose. It’s got to be thick-walled fuel line or thick-walled emission control line.) For the past week I’ve gotten all over it with full throttle runs (even with the AC on in upper 80 degree weather). The ping is gone!!! Can I get an “Amen”! I hope this helps someone else with their pinging problem. UNSOLICITED RANT ABOUT 94/95 PCMs: After working on this car for a number of years and reading many posts in this and other forums about how common this pinging issue is with our cars, I have come to believe that the cause is the combination of the “on-the-edge-of-drivability” load-based fuel/spark tables in the stock 94/95 PCM and the poor burn properties of the stock cylinder heads. If any single system or item under the PCM’s purview is just a little bit off, pinging will result. Because that combination puts us on the ragged edge from the get-go, nothing in the system can be allowed to age or deteriorate without causing pinging. Not sensors, not hoses, not EGR, not MAF, not squat! OK, I’m better now!
I agree with you and here is some info to futher support your beliefs and suspicions. Ever notice that the GT's have the ping thing but not the Cobra's The values in the spark table are greater in the GT than the Cobra. The values in the fuel table are greater in the GT than the Cobra. Put the two together and you get more spark and less fuel in the GT file which makes a perfect condition for the ping thing. In the Cobra file, things are just the opposite, which is why you don't see the Cobra boys cry about ping. Glad you found the prob and it turned out to be something simple Later Grady
That would be a great thing for me to check over on my car! I have some pinging issues and it use to be in just 3rd gear but now it seems to happen more in hotter weather and in 1st and 2nd gears when i'm at WOT.
i have an issue with pinging on mine too. just bumped the timing to 14* and it ran just fine till the 80 degree weather hit. now it fall flat on its face at 4000 rpm. i have a new thick walled vacuum line that fits perfectly. i had to because the elbow for the performer intake made it longer than the stock one could reach. every thing is ship shape. im gonna back the timing off tomorrow. 14* was fun while it lasted.
Good write--I stashed it for future reference....this comes up quite often... Mine suffered from day one with that ping...It never did go away after plenty of trial and error...i swapped in someThumpers, 5 yrs later and it went away???....hasn't been heard from since...I also replaced all the vac line at the re-assy... Kevin.... Here is the stock intake....the FPR line is the one hanging in mid-air up top...connects from the nipple to the FPR...
Mine was as hard as a rock too (had to cut it off). It seems to be the SN version of the front plenum hose (to the charcoal cannister) on foxes. they both vulcanize badly.
RIO5.0, Thanks much for posting the picture. (I went out an took one to post, but it's harder to see the hose because its on the car.) Please tell me where the small ID hose from under the intake manifold goes. I can't remember off the top of my head, and I'm not looking at the car right now. Thanks.
you said that you replaced your ACT and ECT sensors a coupl of years ago and this dealt with you "hot weather pinging" I am just wondering did you have a check engine light at the time? What made you replace these sensors...cause that is what I was thinking was the cause of my pinging was the ACT or ECT sensors and my tuner says no cause I would throw a check engine light...
I was not asked but: The ECT and ACT can have gunk on them which affects their calibration. In order to toss a code, usually the sensor has to be pretty far gone. But if the sensor is within absolute specs, but not reading correctly for the situation (out of calibration), that can create issues.
Ain't that the freaking truth! My MAF was on it's way out, but still operating under specs, but it still made the car run like CRAP! So sensors can be "bad", (read not fully broken) and cause a mess of problems.
302fordracer, Here's a link to my post from back in 2003 about ACT and ECT operation and diagnosis. It's long so I didn't want to just copy it here. http://forums.stangnet.com/showthread.php?t=345453 The sensors can still be "working" and still not throw a code. Follow the link for the full story.
Kevin R. I would just call it the fuel pressure regulator vacuum hose. However, even the Ford parts department does not stock that hose as a separate part. (I checked my local dealer.) They will just sell you a foot of 5/32 inch ID fuel line for about 4 times what it will cost you at a chain car parts store. Just go to NAPA or AutoZone, etc. and get a foot of 5/32 inch ID fuel hose. Like I said, 3/16 inch ID will do but its not a really tight fit. A foot should cost less than a buck, and will make two pieces. Share one with a buddy who drives a Stang.
