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I’ve become a Eric junkie. I’m hooked. Still working on my 94 Mustang GT 5.0. Running pretty good (well, not perfect, but a LOT better). Was down playing with it a little bit again, and just noticed loud hissing noise when I’m in driver’s seat with driver’s door open. You can hear it like it’s coming through the door hinge area. Sound reminds me of old carburetor car when air filter is off. But I really can’t hear that noise well when I’m under the hood (looking for it). I’m thinking maybe vacuum line to brake booster (?) if that even exists. But again, when under hood no noise in that area. I did have gas vapor line on other side of engine at firewall replaced. Ideas? And would your idea impact performance? Thanks.
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check your PCV and line. spray some carb spray to see if you can
locate the vacuum leak or water in a spray bottle.http://www.ericthecarguy.com/faq/solving-automotive-performance-issues
If you suspect the brake booster, remove the vacuum line and plug it. If the noise goes away, you might have just found the problem.
Good luck and keep us posted.
Since I don’t hear the sound with door closed I’m thinking booster is possibly ok, but I’m wondering about brake booster check valve. Weather should be nice Sunday so I’ll check all this out based on suggestions already posted but if plugging vacuum line makes things better, I may try to replace the brake booster check valve (for $5) before doing something to booster itself.
Still raining – yuck. I also will check the vacuum line that runs to the cruise control or some other part of the cruise control unit since it’s mounted at the front left tire and could be the sound I am hearing when I have the door open on the driver’s side with the engine running. If it was the brake booster, I’m betting I would hear the leaking with the door shut – car is quiet when door is shut. And brakes seem fine.
Break stopped (for a few minutes) so went out and checked the vacuum to brake booster. There is a major vacuum line that runs to a vacuum splitter (tree) on fender well inside engine compartment with one major line going to brake booster and another line that goes into fender well (where the cruise control is!). I can’t get to the cruise control unit (without taking the wheel well material out) so I just plugged the outlet nipple at the tree. The hissing stopped. So there is a major vacuum leak where the cruise control unit is located. I think there are other problems with the cruise control anyway so I’m just leaving that vacuum line disconnected and leaving the plastic rivet plug in the vacuum line nipple on the tree. Took car out again, and it still has a miss but the “scalded dog” is back – she really wanted to go – like a 5.0 should! The “hissing” had become more pronounced lately since other vacuum lines have been replaced. My mechanic mentioned after replacing some lines that the cruise control “might” work. So, he was aware that vacuum pressure was now being sent that way. You may think “he should have found that leak” – well, maybe but my mechanic tries to help me by only doing a few steps at a time to see if problems are solved so as to save me money regarding fixing or replacing stuff that is already ok. Tomorrow I’ll change the oil and I’m going to add some of the “pass emission test” CRC stuff to gas tank to see if that does more than the Chevron Techron has done (hopefully without doing TOO much).
Although my mechanic did some work on the distributor and checked coil, I’m going to try a MSD cap and rotor plus a MSD coil (one of the MSD coils that works well with factory plugs and wires. I’m also running some CRC “Pass Emission” stuff through the gas now with hopes that it helps without hurting anything. Also changed the oil again. “Old” oil was pretty dirty even with less than 1,000 miles on it. I figure oil was not changed adequately with prior owner so engine was probably pretty dirty inside. No smell of gas in oil and no signs of coolant in oil, just dirty. Also, when I drive the car and get on the gas hard, there is no smoke out the back – I figure that is a good sign.
Sounds like you’re making progress. Good job finding the vacuum leak. If you want to fix it at some point perhaps you can pick up a unit in a salvage yard at some point. As for how the engine runs. New parts can’t hurt, but if you don’t locate the cause of the miss you may be throwing good money over bad. In the end, you could have a mechanical issue causing the miss. In fact, I hope to shoot a video soon on checking timing chain slack. It’s something that happens on older engines. The timing chain gets a bit of slack in it and it starts to cause issues with cam timing as well as ignition timing. Not to mention cam lobes getting worn down. My point is that mechanical is always a factor. If you don’t have solid mechanical, then you can replace all the tune up parts you like to no effect. It does seem like you’re making progress though which is a good thing.
Thanks for the updates. Please continue to keep us posted.
Here’s your challenge. Do a “check timing slack” video that could be done by someone that know there way around the car but has no professional training (other than the professional training we get watching your videos). My sister gave me a gift card for my birthday last month to a mustang parts place near Atlanta and I’ll be there this coming Saturday so thinking about blowing the card on the MSD cap, rotor and coil. Still trying to figure out why revs with ease on the road and yet wants to miss when just pulling small hills in higher gear at lower revs. Another vacuum leak somewhere? Electrical? Gas flow and mix? Still getting occasional code for a “miss” – well, I know THAT even without the code. To be continued. 🙂
I always try and make videos that are easy to understand.
That said, Fords of that vintage tend to gum up in the intakes. This can sometimes cause issues. Also, a TPS that’s starting to crap out can cause a hesitation at certain throttle positions. Vacuum leaks can also contribute. Performance diagnosis is a process of elimination. In truth, it’s just practical application of the scientific method.
Good luck and as always keep us posted.
Hmmm. Cleaned TPS – did that way back. Have checked again and still clean and intact. Now trying to figure out if I should use my gift card for new TPS or use it for the cap, rotor, and coil. But then again, we changed the rotor and coil. Just not the cap. Could get the dizz cap and a TPS. Hmmm. Ok, well I’m opting for the TPS and waiting on the cap. Will see if anything changes when I get to play with her again in about a week. Will post results of new TPS here. If does not help, I’ll probably start new topic and just list all that I’ve done so far especially since the Hissing is “fixed.” 🙂
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