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Hello!
Big fan of the youtube videos, had no idea there was a forum until it was mentioned in one.
My car is an ’85 mr2, 4age n/a engine. I rebuilt it myself (scary start, eh?) and it runs great. However, I’m almost certain there’s a vacuum leak I’ve yet to find.
In watching the video “How To Find A Vacuum Leak – EricTheCarGuy” at https://www.youtube.com/watch?v=9CPqbaSgcok Eric mentions a high-pitched sound, or in his words a “high pitched hissing noise”
I’ve got a pretty good ear, but the only vac leaks I’ve ever found it was a sucking sound.
What I’m up against here is not a sucking sound- there may be one, but this other sound is so loud (and painful to my ears) that I can’t hear anything else. Oddly enough, the girl cant hear it- its high pitched.
Since this sound is *only* when the engine is pretty well hot, so I’ll probably start by rigging up a propane tester.
The vac lines are all silicone, so I’m wondering if that might be why the sound is so intense. Due to its pitch, I have a hard time telling where the sound is coming from.Here’s a short video clip of the engine making the sound.
Any and all input welcome! hoping to try and track this down this week.
Other symptoms:
when idle @900rpm or so (fully warmed up) *some* days it will bog down badly right as I hit the gas. Other days, it does not.
Idle bounces around a bit sometimes. I suspect there’s still some air stuck in the coolant on this notoriously hard to bleed engine.
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Honestly cold air intakes can sometimes cause noises like that. I can’t say for sure what the noise is, or verify that it is indeed a vacuum leak, but if you follow the testing for a vacuum leak you might be able to find the source. Also, those vacuum lines are pretty, but they don’t often seal well so make sure you test them at their connections when looking for leaks.
More info here.
http://www.ericthecarguy.com/faq/solving-automotive-performance-issues
http://www.ericthecarguy.com/faq/diagnosing-noises-in-your-car
Good luck and keep us posted.
Thanks.
This old car came from Nevada, and was moved to Maine by me in 2009. The silicone air lines are the only ones available for this car in an easy to install kit, so that’s what I went with- just about all of them were dry rotted and falling to pieces when I tore her apart. That cone filter was an afterthought- the original air box was better, but required a special shaped air hose toyota wanted $200 for- not cool!
I’ll try and find some time for a quick test with propane after work tomorrow, and will update here. That noise is killing me!
Well I got home today and it’s a beautiful afternoon- almost 50F outside, and sunny!
backed into the driveway and the idle was low and steady. No hesitation problems on the way home, but it was making that horrible screeching sound.
I dont know if I mentioned this, but it only does it under no load- if you rev it, it will go away until the rpm levels off- so it’ll make the same sound at 2k rpm, but not when transitioning from 800 to 2000- and it wont do it when driving down the road at any rpm unless my foot is so light on the gas that it’s not accelerating OR decelerating. It might do it a bit when decelerating, but not that I can tell when driving.
Anyhow, I took my small propane torch and stuck it “on” with no flame, and cracked it wide open until I could feel propane coming out- and smell it. Went around all the vac lines, the air filter, the MAF, the intake manifold and everything that connects to it with no change whatsoever. When I put the propane right up to the cone filter (Ensuring propane is getting into the airflow), the idle picks up a bit- but that’s it.
One other symptom that may or may not be related is a shudder. I forget about this one since its very rare- but honestly pretty consistent. The trigger is long highway drives. After about 45 minutes at highway speed, when I’m real light on the throttle (maintaining a little below 65, for example), the thing will kick- almost like a misfire. To me, it feels like its cutting off its own fuel for an instant. Then it kicks right back in.
I had this same problem with another MAF sensor as it was on its way out, right after the rebuild. This sensor is the known working one from my old engine- but might be slowly failing too.
I can’t smell fuel in the exhaust, and I know the cat is bad- I have a new one but wont replace it until I know the engine is running right.When you say the cat is bad, how do you know this? Do you feel it’s bad in a way that causes an exhaust restriction? If so this could contribute to the problem.
Also, I can’t remember but have you done anything to address the ignition system? The miss you describe sounds like it might be an ignition fault to me. More information on all of this in the article I posted for you.
The cat is bad in that the honeycomb inside is half gone- you can see right through the thing. I had it out when replacing another section that rusted through and wasnt worth putting back on after the engine swap, and noted it was junk. Ordered a new one, but never got to installing it…
I have not done anything with ignition yet- the plugs/wires are NGK with less than 10k miles on them, the dizzy was rebuilt with the engine and the cap/rotor replaced with the rebuild as well, all less than 5k ago. The coil was put in used in 2009, its some sort of “performance” coil I picked up cheap on a forum.
I watched the noise-finding video but unfortunately none of these options are working so well for me- the high pitched sound passes through any hearing protection I own, so it’s hard to place where it’s coming from.
What poking around DID do is remind me that the fuel pressure regulator on this thing is effectively a junk yard pull. Mine went bad during the swap so I replaced it with one from a parts car. Napa didn’t have them and the dealer wanted 150+ for one- so I took that chance. Then I wound up having to buy some crazy crush washer from the dealer, and after a five day wait they sent the wrong one. I wound up improvising- and this could very well be the source of this horrible sound.here’s a picture I found online of the factory washer that came off:
http://imagizer.imageshack.us/a/img690/2127/img4335pa.jpg
(crush washer, I tried re-using mine but it didnt hold- never re-use crush washers!)
and here’s one of my “improvised” washer:
http://images.netman86.com/projects/cars/mr2/4age%20rebuild/2013-10-22%2017.08.25.jpgI never have problems with performance or cold starts, so I forgot that I had done this. The only thing it could be doing is potentially limiting the amount of fuel coming through this fitting. I *think* that’s the return line, so that could potentially be causing all sorts of strange issues.
You might try this just for good measure. It might provide some clue as to where the noise is coming from.
I remember when I had this little canister vacuum, tons of suction but the hose was shot. I bought bulk hose, great quality, at the local sew and vac, but I needed to reuse the end fittings. So, I made a project out of it and it turned out great. I attached my new beautiful hand crafted hose, hit the switch and it screamed. I had to throw it away.
So, like Eric said, I suspect the cold air intake. Maybe something acoustic going on there.
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