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| Mekanic | Weird Issue | ||
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Dunno if this is normal, but I have a strange issue I wanted to ask about.
It seems like my LT4 runs MUCH stronger before it gets all the way warmed up. I was thinking it was heat soak in the intake, or maybe underhood temps, but maybe its something else  Opinions? thoughts. Another problem I've been noticing, is my footwell has been getting real hot lately, just on the drivers side, I had my girlfriend feel down there and she said it felt hot too. I'm wondering if my drivers cat is starting to go, would I get a CEL from the 02 sensor if it were? Thanks guys, always appreciate the help. |
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Posted on: 2008/7/2 15:00
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~Rich Polo LT4 Yea tho I walk through the valley in the shadow of rice, I shall fear no turbo, for torque art with me. |
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| CSS996 | Re: Weird Issue | ||
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Mega Guru
 
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I don't know squat, but sounds like a cat to me. Maybe drive it, park it in the garage, and see if she glows!
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Posted on: 2008/7/2 15:29
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Currently "Between Vettes". 
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| Mekanic | Re: Weird Issue | ||
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checked that, no glowing that I could see, I'll check again on friday
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Posted on: 2008/7/2 15:30
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~Rich Polo LT4 Yea tho I walk through the valley in the shadow of rice, I shall fear no turbo, for torque art with me. |
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| Matatk | Re: Weird Issue | ||
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Webmaster
 
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I agree. I remember someone else having a problem with his cat and it didn't glow. He unhooked the exhaust at the manifold to see if it was the problem, and it ran better unhooked. Just a thought. Matthew |
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Posted on: 2008/7/2 18:44
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2002 EBM convertible, Magnusson supercharger, cam, headers, etc. 1989 Corvette...RIP |
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| 81c3 | Re: Weird Issue | ||
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sorry man, I couldnt resist! makes for a great sig. |
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Posted on: 2008/7/3 13:41
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| CSS996 | Re: Weird Issue | ||
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Dang, how did I miss that?
 Anyway, just to keep this on the technical side, the blockage could be somewhere other than the cat, right? And if it is not IN the cat, maybe the cat wouldn't glow? |
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Posted on: 2008/7/3 14:26
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Currently "Between Vettes".
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| red_johnny | Re: Weird Issue | ||
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On Sabbatical
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Thats funny, but yeah sounds like a cat |
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Posted on: 2008/7/3 14:33
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| bogus | Re: Weird Issue | ||
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Grand Imperial Pooh-Bah
 
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I would start at the cat, no question.
Things like that take a while to expand. Case in point: Some of you may remember the problem I had with my Corsa exhaust a couple of years ago. For the longest time, I could not cruise in 6th gear. The din was just awful. There was a resonance that was deafening. I blamed it on the aluminum flywheel (I mean, what else could it be?). I dropped the exhaust one day and found that the resonator had broken. The tangs that support the outer pipe to the inner pipe had broken. Clean through! The resonator was leaking exhaust and was vibrating, I am sure. Had been for a couple of years. Well, Corsa handled it PERFECTLY - 100% fast and wonderful. No complaints, just recommendations. EXCELLENT customer service. The side note to this: When the engine was cold, it was quite as quite gets. It wasn't until the exhaust heated up that the noise got unbearable. That might give you a hint. As for the downstream O2 not coding, perhaps the cat is still cleaning exhaust, just not enough of it. |
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Posted on: 2008/7/3 14:42
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The single biggest problem with communication is the illusion that it has taken place. - George Bernard Shaw Education is the best tool to overcome irrational fear. - me |
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| pappyfreebird | Re: Weird Issue | ||
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round here any muff shops will test it free...
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Posted on: 2008/7/3 16:23
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| Mekanic | Re: Weird Issue | ||
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I dunno what other places the blockage would be, I have no resonator or mufflers. The exhaust note stays the same throughout the temperature range, but the car just feels stronger when its cold. I'll see if someplace around here could test them for free, I'm also trying to hunt down an OBDII scanner that will show me real time A/F of all my O2 sensors to check that out too. This is a pic of my exhaust system.  |
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Posted on: 2008/7/4 1:20
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~Rich Polo LT4 Yea tho I walk through the valley in the shadow of rice, I shall fear no turbo, for torque art with me. |
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| bogus | Re: Weird Issue | ||
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Grand Imperial Pooh-Bah
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I am now worried.
You may want to do a leak down test. |
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Posted on: 2008/7/5 6:31
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The single biggest problem with communication is the illusion that it has taken place. - George Bernard Shaw Education is the best tool to overcome irrational fear. - me |
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| Mekanic | Re: Weird Issue | ||
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whaaa? why do you say that? I'm not saying it falls on its face when warm, it just feels a bit stronger cold |
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Posted on: 2008/7/5 6:39
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~Rich Polo LT4 Yea tho I walk through the valley in the shadow of rice, I shall fear no turbo, for torque art with me. |
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| bogus | Re: Weird Issue | ||
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Grand Imperial Pooh-Bah
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my concern is a warped head... it gets hot and changes properties. That's all I can think of.
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Posted on: 2008/7/5 7:19
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The single biggest problem with communication is the illusion that it has taken place. - George Bernard Shaw Education is the best tool to overcome irrational fear. - me |
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| Mekanic | Re: Weird Issue | ||
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hmm, that is a thought.
Although its never overheated the whole time i've had it, and does not loose a drop of coolant. |
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Posted on: 2008/7/5 8:38
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~Rich Polo LT4 Yea tho I walk through the valley in the shadow of rice, I shall fear no turbo, for torque art with me. |
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| BillH | Re: Weird Issue | ||
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The Stig Moderator
 
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That's the same exhaust I have on my LT1.
Really like the sound. |
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Posted on: 2008/7/5 14:53
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Every man dies but not every man lives. |
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| Midnight85 | Re: Weird Issue | ||
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I don't know of any car that won't run a bit stronger when it's cold. Is it a severe difference or just noticeable? If it's just noticeable then I would say it's normal.
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Posted on: 2008/7/5 15:57
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HORSEPOWER! Some is good, more is better, too much is just right. |
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| Mekanic | Re: Weird Issue | ||
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I get tons of compliments on it.
I'm just a little nervous that catless it will be a little too loud. |
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Posted on: 2008/7/5 16:08
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~Rich Polo LT4 Yea tho I walk through the valley in the shadow of rice, I shall fear no turbo, for torque art with me. |
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| Mekanic | Re: Weird Issue | ||
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I think sever would be a bad choice of words now that I'm thinking more about it. Its just quite noticeable. the butt dyno would guess about 15-20hpish. But my butt dyno is not calibrated very well lol. But what else could explain the heat in the drivers footwell? |
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Posted on: 2008/7/5 16:11
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~Rich Polo LT4 Yea tho I walk through the valley in the shadow of rice, I shall fear no turbo, for torque art with me. |
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| bogus | Re: Weird Issue | ||
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Grand Imperial Pooh-Bah
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no cats and heat in the footwell? odd...
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Posted on: 2008/7/5 18:42
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The single biggest problem with communication is the illusion that it has taken place. - George Bernard Shaw Education is the best tool to overcome irrational fear. - me |
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| Mekanic | Re: Weird Issue | ||
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I have cats now.
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Posted on: 2008/7/5 19:07
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~Rich Polo LT4 Yea tho I walk through the valley in the shadow of rice, I shall fear no turbo, for torque art with me. |
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| Midnight85 | Re: Weird Issue | ||
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Guru
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Without the benefit of the sop feeling I would say the drop in performance is normal when the engine heats up. As far as the heat in the footwell goes I would be looking for a change in the position of the exhaust in that area, possibly a small hole leaking exhaust in that direction? |
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Posted on: 2008/7/5 19:20
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HORSEPOWER! Some is good, more is better, too much is just right. |
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| Mekanic | Re: Weird Issue | ||
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possible, I need to get it on a lift to check it all out. I'll call Bob at precision and see what I can get going soon. |
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Posted on: 2008/7/5 20:55
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~Rich Polo LT4 Yea tho I walk through the valley in the shadow of rice, I shall fear no turbo, for torque art with me. |
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| Mekanic | Re: Weird Issue | ||
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new developments.
idled around a parking lot, sat at a stop light, as soon as I was about to leave the light, SES light came on. Engine temps and all gauges looked perfect. interior and underhood temps were very hot. idle was smooth and quiet, I got on it a bit and it felt very strong, slightly stronger than normal I would say. Looked at the cats, no glowing. |
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Posted on: 2008/7/6 2:23
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~Rich Polo LT4 Yea tho I walk through the valley in the shadow of rice, I shall fear no turbo, for torque art with me. |
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| Mekanic | Re: Weird Issue | ||
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just got it scanned. 2 codes. Reading a lean condition in both banks.
I'm letting it cool off now to check fuel pressure, then gonna reset the ECM and let it re-learn, and I'm calling my mechanic who has HP Tuners to see what he would charge me to do some data logging on it to see what the 02 sensors see. |
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Posted on: 2008/7/7 19:44
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~Rich Polo LT4 Yea tho I walk through the valley in the shadow of rice, I shall fear no turbo, for torque art with me. |
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| Mekanic | Re: Weird Issue | ||
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just tested fuel pressure and it was fine, waiting for it to cool to go to open loop so I can make the ECM relearn
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Posted on: 2008/7/7 21:07
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~Rich Polo LT4 Yea tho I walk through the valley in the shadow of rice, I shall fear no turbo, for torque art with me. |
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| CentralCoaster | Re: Weird Issue | ||
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Senior Guru
 
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I've read that the tunnel design on the C4 doesn't allow much air circulation in there and can build up heat from the engine.
Mine gets toasty on the radio panels and center console on a hot day, to where you can't touch the plastic very long some times. Makes it hard to keep drinks cold in the cup holder. I have a carsound cat. It has a small built in heat shield, I removed the factory heat shield. |
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Posted on: 2008/7/7 22:29
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1985 Z51, ZF6 |
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| Mekanic | Re: Weird Issue | ||
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just finished the ECM reset. SES went off, and the car ran strong.
I also didn't get the heat like normal, but its hard to tell on such a short drive (in the rain) I think I'm still gonna do the datalog on Thursday. |
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Posted on: 2008/7/8 0:01
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~Rich Polo LT4 Yea tho I walk through the valley in the shadow of rice, I shall fear no turbo, for torque art with me. |
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| Mekanic | Re: Weird Issue | ||
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Didnt do the datalog.
SES came on Saturday night. Checked it Sunday, Lean Bank 2. Had it cleared. Came back on Sunday night, dunno what the code is yet, didn't get to get the code read. Scrapping some money together to buy a used Autotap, since its only $25 more than getting it scanned at a shop |
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Posted on: 2008/7/21 12:01
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~Rich Polo LT4 Yea tho I walk through the valley in the shadow of rice, I shall fear no turbo, for torque art with me. |
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| anesthes | Re: Weird Issue | ||
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Master Guru
 
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Must be the ethanol.
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Posted on: 2008/7/21 13:59
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'79 Z28. 412 CID, NP 833 transmission, 3.73 10.5" rear end. |
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| Mekanic | Re: Weird Issue | ||
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It may be, but I would assume the o2 would pick up on it and adjust fuel trims accordingly. |
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Posted on: 2008/7/22 1:48
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~Rich Polo LT4 Yea tho I walk through the valley in the shadow of rice, I shall fear no turbo, for torque art with me. |
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| anesthes | Re: Weird Issue | ||
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I was actually just busting your chops for the other thread. I think it's your MAT correction tables in the prom adjusting your AFR when things heat up. Mine was driving me nuts with the blower so I disabled them and that cured it for me. Obviously your MAT swing won't be as serious as mine naturally aspirated, but a failing or improperly reporting sensor could be causing your issue. You really need to get an idea of what the ECM thinks the difference is between cold and hot, and what it is doing differently. (reducing spark? Adding fuel? I saw both with the higher MAT for no good reason). You also have some code issues which need some attention. I'm trying to think of who I know in your area that does proms that could give you a hand. -- Joe |
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Posted on: 2008/7/22 12:23
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