lacseville Posted February 21, 2004 Report Share Posted February 21, 2004 My last 2 Cadillacs have had a ching sounding rattle that occurs usually during acceleration when I am going about 42-44 just after the trans shifts into o/d and there I am giving the car normal amount of gas. (still accelerating) My 93 DeVille had 186xxx mi on it, so I didn't worry about it... local caddy man said it was the cat. Got a '91 seville now and it had the same chingy rattle noise. I assumed again that it was the cat, so when I had my exhaust put on I had them cut off the cat instead of buying one. (no emission tests here in AR!) STILL THERE! I'm sure this is a common problem, as I've heard it on other lacs of the same year around town. Link to comment Share on other sites More sharing options...
KevinW Posted February 21, 2004 Report Share Posted February 21, 2004 The rattle or "pinging" is likely detonation (unstable combustion) resulting from insufficient EGR flow. You should try cleaning the EGR feed tubes, visible directly under the throttle plates. BTW, are there any diagnostic trouble codes? ___________________________________________________ Link to comment Share on other sites More sharing options...
lacseville Posted February 21, 2004 Author Report Share Posted February 21, 2004 bump.... oh yeah, and I always use 93 octane. Link to comment Share on other sites More sharing options...
lacseville Posted February 21, 2004 Author Report Share Posted February 21, 2004 The rattle or "pinging" is likely detonation (unstable combustion) resulting from insufficient EGR flow. You should try cleaning the EGR feed tubes, visible directly under the throttle plates. BTW, are there any diagnostic trouble codes? sorry, you posted same time I bumped I think! Anyhow, no codes... How do I clean the EGR feed tubes... where exactly are the throttle plates so I can locate these bad boys. BTW what does the EGR do and why does it cause this sound? Thank you for your help so far! Link to comment Share on other sites More sharing options...
KevinW Posted February 21, 2004 Report Share Posted February 21, 2004 Anyhow, no codes... How do I clean the EGR feed tubes... where exactly are the throttle plates so I can locate these bad boys. BTW what does the EGR do and why does it cause this sound? Thank you for your help so far! First, unfasten the 4 wing bolts around the air filter. Follow the ducting towards the passenger side; you'll find a ~1 inch diameter black nut which you can unscrew with your fingers. Pull the PCV feed hose off (rear, closer to windshield), then you should be able to remove the whole air intake assembly. While the throttle is open (helper inside the car holding the accelerator down or jam something ahead of the ISC plunger), scrape the black crud out of the feed tubes with an old screwdriver, stiff piece of wire or equivalent. Be careful not to damage the edge of the throttles, as this would affect the seal near the closed position. It's OK to let the crud fall down into the EGR passage. This is an opportune time to clean around the throttle plates (where they would rest when closed) using a rag and some solvent like GM combustion chamber cleaner. Afterwards, it may help to perform the idle learn procedure so the PCM can relearn what throttle angle corresponds to the desired idle speed, but driving around a bit will eventually accomplish the same thing. ___________________________________________________ Link to comment Share on other sites More sharing options...
lacseville Posted February 21, 2004 Author Report Share Posted February 21, 2004 what else could I use instead of gm solvent cleaner?? carb cleaner and rag?? does it matter if lots of this stuff get down in there? Link to comment Share on other sites More sharing options...
Ranger Posted February 21, 2004 Report Share Posted February 21, 2004 Carb cleaner and a rag will work fine. Carb cleaner getting in the manifold should hurt nothing. What doesn't evaporate, will burn off. Link to comment Share on other sites More sharing options...
KevinW Posted February 22, 2004 Report Share Posted February 22, 2004 Make certain that the cleaner you're using does not contain anything (like silicon) that could poison the oxygen sensors or exhaust catalyst. ___________________________________________________ Link to comment Share on other sites More sharing options...
lacseville Posted February 23, 2004 Author Report Share Posted February 23, 2004 I cleaned the TB... runs about the same, although I had to "relearn" the idle. It still makes the same noise... This is so frustrating. I looked under the car at all the exhaust hangers and pipe clearance, but that's not what it sounds like anyhow. I just got back from the Cadillac place. they can't get the car in until Thurs morning, but he quickly said, "it may be the trans or motor mount grounding out". does this seem likely? i think it does, since that's the area it's coming from. what are some give aways that either of these mounts are shot? Link to comment Share on other sites More sharing options...
JasonA Posted February 23, 2004 Report Share Posted February 23, 2004 Boy, that sure sounds like spark knock to me (like KevinW was describing). Part throttle pinging is almost always due (on older GM cars) to the EGR tubes/ports in the intake manifolds. Same problem and symptoms on V8s all across the board from the era. I had to remove the carburetor on my '84 Cutlass (Olds 307 V8) to gain access to the very same EGR tubes that plug on the 4.1/5/9 engines. My bet is on your EGR system. If you haven't done it yet, clean those EGR tubes (may require a drill bit) and clean the EGR valve itself. Check the electrical or vacuum circuits to the EGR valve to make sure the valve is operating. Here's a quick test -- when the engine is cold, start it and place your hand under the EGR valve. Gently lift up on the diagram to manually open the valve (if your valve is designed so that can be done). With good EGR flow, your engine should stumble or even die. If the idle is not affected very much, you know that's your problem -- clogged passages somewhere. Good luck! Jason(2001 STS, White Diamond) "When you turn your car on...does it return the favor?" Link to comment Share on other sites More sharing options...
lacseville Posted February 24, 2004 Author Report Share Posted February 24, 2004 okay, cool i'll try it later tonight, after she cools down. I cleaned the egr tubes. (the were gunked up, but now they are almost shiny! I rolled up the end of a rag and stuffed it down in there and twisted around. they look like new), so it may be the EGR valve itself. I haven't looked yet, but where is that? What does it look like? If this helps: To try to locate the rattling, I put the car in drive, and slowly power braked it until I heard it. I was probably @ 2000-2400 rpms. Link to comment Share on other sites More sharing options...
lacseville Posted February 24, 2004 Author Report Share Posted February 24, 2004 bump... where's the egr valve, what does it look like? Link to comment Share on other sites More sharing options...
Ranger Posted February 24, 2004 Report Share Posted February 24, 2004 4.9? If I remember correctly it is on the passenger side next to the throttle body. It looks somewhat like a mushroom, about 3' in diameter and has a vacuum hose attatched to it. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.