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Red hot exhaust manifold?

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Old 04-20-2009, 12:41 AM   #1
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Red hot exhaust manifold?

So I replaced my fuel pressure reg while back and after about 10 minutes it would be glowing red hot. I went to put the old one back in and now it wont stop leaking when it gets pressurized. AH! Then I put the new one back in and its leaking too. This is ridiculous... Thanks for the help guys
Old 04-22-2009, 02:56 AM   #2
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Re: Red hot exhaust manifold?

the red hot manifold is more than likely a clogged cat/exhaust
Old 04-22-2009, 07:15 AM   #3
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Re: Red hot exhaust manifold?

replace your cat.it is cloged up.

Last edited by garvos; 04-22-2009 at 07:16 AM.
Old 04-22-2009, 09:15 AM   #4
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Re: Red hot exhaust manifold?

yea you probably just didn't notice it until you were under the hood replacing the pressure reg...natural reaction is to blame whatever you replaced.
Old 04-22-2009, 05:07 PM   #5
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Re: Red hot exhaust manifold?

Nah, the cat is new. And I had watched it uner the hood while doing other things plenty of times after the cat was replaced and it wasnt red hot. It only happened after the fuel pressure regulator. I can guarantee it isnt the cat. Oh and what I meant by leaking was out the side of the cover.
Old 04-22-2009, 08:50 PM   #6
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Re: Red hot exhaust manifold?

correct me if i'm wrong, but wouldn't it also be a sign of running extraordinarily lean?
Old 04-22-2009, 09:39 PM   #7
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Re: Red hot exhaust manifold?

Quote: Originally Posted by 93v6banger
correct me if i'm wrong, but wouldn't it also be a sign of running extraordinarily lean?
Ding Ding Ding, Lean burn will cause red exhaust manifold as lean is hotter combustion, rich will cause cat to overheat as it burns off the raw excess fuel, have you tried a new O2 sensor? Ran some cleaner thru the fuel system? Changed the fuel filter? Checked fuel pressure?
Old 04-24-2009, 09:13 PM   #8
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Re: Red hot exhaust manifold?

Yeah I have a new O2 sensor which was replaced not too long ago. Filter is fine and so is the pressure. I've ran cleaner through. But could this be related to the fuel pressure reg? Or maybe I was given the wrong O2 sensor? Would a different O2 sensor even make a difference? I'll grab the numbers from it and see if it's the right one. I still have the part number on the box here somewhere...
Old 04-25-2009, 10:38 AM   #9
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Re: Red hot exhaust manifold?

Do you have any exhaust leaks near the O2 sensor?
Old 04-25-2009, 12:15 PM   #10
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Re: Red hot exhaust manifold?

I did with the old manifold, but then I got a new one. I havent been able to fire it up cause of my fuel pr. reg.
Old 04-26-2009, 12:30 AM   #11
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Re: Red hot exhaust manifold?

Alright I figured it out, for some reason the pressure reg. I had wasn't right. It looked exactly like the old one tho. But I took it back got a new one and both problems are taken care of. Now I just have to figure out why it has no power when it warms up... When it's cold it runs fine. But after it warms up it loses power when trying to accelerate. Seems like a sensor problem but there's no codes.
Old 04-26-2009, 11:03 AM   #12
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Re: Red hot exhaust manifold?

Well, the ECM ignores the O2 sensor untill it warms up...... Might pull it and clean it, might also pull and clean the EGR. If the manifold was running that hot it may have damaged the O2?
Old 04-27-2009, 02:00 PM   #13
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Re: Red hot exhaust manifold?

Alright cool. I'll see if that's the case. I really hope it is. This engine has been nothing but trouble for the past 3 months. If I get sick of it I'll just give in and buy the gasket kit for the '89 4.3l im building and throw it in lol
Old 04-30-2009, 10:18 PM   #14
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Re: Red hot exhaust manifold?

Ok, the O2 sensor is fine. I cleaned the EGR, and I noticed in the chiltons manual that it says if you compress the valve and put your finger over the vacuum line hole that it should take up to 20 seconds to fully refill itself (move back to uncompressed) Well when I tested this it doesn't move at all. Could this be a problem?
Old 05-01-2009, 10:02 AM   #15
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Re: Red hot exhaust manifold?

Quote: Originally Posted by chsdrummer07
Ok, the O2 sensor is fine. I cleaned the EGR, and I noticed in the chiltons manual that it says if you compress the valve and put your finger over the vacuum line hole that it should take up to 20 seconds to fully refill itself (move back to uncompressed) Well when I tested this it doesn't move at all. Could this be a problem?
=============================
cd07--

First, determine (using the part number on it) if it is a Stock OE EGR valve. An AC-Delco/Delphi part, a "real" one. Then, if it is, determine, again using the part number, if it is the "correct" one for your rig. AC-Delco makes two, one for the manual transmission-ed rigs and one for the automatic transmission-ed rigs. A previous Owner may have stuck the *wrong* one on there, being sold a bill of goods by an unknowing (ignorant) Parts Geek. If it is the correct part, an AC-Delco, but for the wrong application, then it will never "work" right.

The Aftermarket EGR valves often do not work, brand new, right out of the box. The "normal" state of operation on these valves is closed. The EGR valves made over-seas do not have an adequate (strong enough) internal spring to keep them closed at idle. It is a catch22, it is good but not good. Being open a bit at idle causes all sorts of goofy idle speed problems as well as adding black, gooey, carbon to the insides of the intake tract. This, in turn. blackens the temperature sensor (IAT) and fouls ITS' readings, compounding the problem. A bad situation, getting worse by the minute.

I would not trust the Chilton's Book to tell me how to test the OE EGR valve. It is a "bass-ackwards" application, being a negative backpressure valve, which is exactly OPPOSITE of how 99% of EGR valves work. I have yet to learn how it is tested, "on the vehicle" as even my GM, S10 Service Manual is un-clear on how it is done. It is kinda one of those things where, if suspected of being bad, it is simply changed out.

I cannot figure out "how" this system works...does the EGR valve solenoid fire all the time (pulses), or just when the road speed is constant above 40 MPH?? At a constant road speed of above 40 is when the system is "tested" by the OBD1 brainbox. It calls for EGR valve solenoid vacuum to be applied, to open the EGR valve. The O2 sensor then "looks for" a lean-out condition and if none is found, the SES light comes on, and it sets a trouble code.

The whole of the issue is a PITA....
Old 05-01-2009, 10:35 AM   #16
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Re: Red hot exhaust manifold?

One (or two) other things.

If a S10 truck is worth, say, $400, how can you justify spending over 1/4 of what the rig is worth, just to buy an AC-Delco part (the EGR valve) to make it run "right"??

Also, the Chevy small and big block V-8 Guys spend thousands of dollars looking for more performance. A 7% boost would be a wonderful thing. Guess what?? The S10 EGR valve adds 7% of the swept volume of each cylinder, in the form of non-combustible exhaust gas, to all cylinders. The little engine is eating 7% of its' own dung, (I suspect) all of the time.

If you add to the mix, an Aftermarket EGR valve, that is hanging open, then performance and driveability problems raise their ugly heads. The goofy up and down idle has to whack the hell out of any hoped for fuel economy AND performance.
Old 05-01-2009, 06:02 PM   #17
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Re: Red hot exhaust manifold?

Well I just looked at it and it's OE. It has the GM symbol on it and everything. I looked it up. I did notice though that there was some carbon build up on the intake of the EGR.

Also when i tested it, it wasn't on the truck it was removed.
Old 05-01-2009, 07:13 PM   #18
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Re: Red hot exhaust manifold?

You could use a handheld vac pump to test it.
Old 05-01-2009, 08:21 PM   #19
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Re: Red hot exhaust manifold?

How would I test it with that? Man, if it's this stupid little EGR valve I'm gonna destroy that little mother lol.
Old 05-01-2009, 08:31 PM   #20
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Re: Red hot exhaust manifold?

If I do need to replace it would this be a good choice? I can't find an AC Delco EGR but I did find this delphi. Let me know.


http://www.autopartswarehouse.com/de...3-1614078.html
Old 05-01-2009, 10:02 PM   #21
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Re: Red hot exhaust manifold?

Have you ever bothered to check your ignition timing?
Old 05-01-2009, 10:26 PM   #22
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Re: Red hot exhaust manifold?

Quote: Originally Posted by chsdrummer07
If I do need to replace it would this be a good choice? I can't find an AC Delco EGR but I did find this delphi. Let me know.


http://www.autopartswarehouse.com/de...3-1614078.html
They dont say wheather that little mother huncher is for MT or AT, pull the vac line off the egr and plug it. Start and idle truck. Pump HHVac to open EGR slightly, let vac bleed off. Idle should go to hell and back to good as vac bleeds off. Vac solenoid could also be sticking open, plugging vac line to egr would let EGR stay shut indicating it is ok.
Old 05-01-2009, 10:28 PM   #23
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Re: Red hot exhaust manifold?

Quote: Originally Posted by MadMikeZ28
Have you ever bothered to check your ignition timing?
Just for shits and giggles throw a timing light on there and see how far advanced your timing is (must jumper upper right 2 terminals on ALDL under column to put to base time.) Should be at 8* default.
Old 05-02-2009, 11:54 AM   #24
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Re: Red hot exhaust manifold?

The timing is fine, it was one of the first things I checked. I've checked again and again through this process just making sure. I'll check the EGR in a bit here. It's supposed to rain all day and I can't pull it in the garage (cause of my '72 c10) lol
Old 05-08-2009, 07:24 PM   #25
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Re: Red hot exhaust manifold?

Ah, so I've been pretty busy lately. But I cleaned and checked out my EGR, seems to be work fine (the valve itself) BUT I checked the vacuum line to it, and there is no vac... at all. This has to be a problem. How do I fix this?
Old 05-08-2009, 11:11 PM   #26
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Re: Red hot exhaust manifold?

There should be a little black box (vac modulator valve) that the hose hooks to, pull the line off the other side, is there vac there? If no vac, pull TBI and clean all the ports of cabon. If it has vac, might check if there is a signal to the modulator valve, if so replace the mod valve.
Old 05-09-2009, 11:16 PM   #27
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Re: Red hot exhaust manifold?

So, there wasn't any vacuum coming from the line that connects to the throttle body. I took the little plate (that all of the vac lines connect to) off and cleaned behind it. There was a little bit of carbon, but there's still no vacuum. Do I need to take the whole TBI off an clean?
Old 05-10-2009, 01:06 AM   #28
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Re: Red hot exhaust manifold?

I would, my model 700 TBI had no vacume on the PCV line and another vac line, ended up there was 2" of carbon up under the TBI to base gasket that was much easier to get to with it off.

Good luck, might also clean the IAC valve and the EGR valves while you have it torn down and are in a carbon killing mood. :-)
Old 05-12-2009, 08:40 PM   #29
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Re: Red hot exhaust manifold?

I took the TBI off and there wasn't any carbon there at all. Then I checked all of my vac lines just to make sure they weren't plugged or cracked. I also cleaned my EGR and IAC valves. But I had cleaned my EGR not too long ago I figured, why not? Just for kicks, I might as well. Any way, whats next? This doesn't make any sense to me. Nothing blocking the line, yet there's no vacuum?

Thanks for helping guys
Old 05-13-2009, 11:15 PM   #30
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Re: Red hot exhaust manifold?

This is 1992 right? Should have vacume on the modulator on the TBI side IIRC. (engine running)
Old 05-13-2009, 11:29 PM   #31
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Re: Red hot exhaust manifold?

The little square-ish looking vacuum supply block has different diameter supply tube sizes on it. If you get the wrong tube on the wrong supply, you may not have the correct volume of vacuum to make that particular "thingy" work right.

Just a thought. You may need a vacuum map...
Old 05-16-2009, 03:24 PM   #32
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Re: Red hot exhaust manifold?

Well lesterl I should have read your posting more carefully
Quote: Originally Posted by lesterl
There should be a little black box (vac modulator valve) that the hose hooks to, pull the line off the other side, is there vac there? If no vac, pull TBI and clean all the ports of cabon. If it has vac, might check if there is a signal to the modulator valve, if so replace the mod valve.
I found out why I have no vacuum. The vac mod valve has no signal to it. That wouldn't set a code would it? Cause I don't have any lol. But there's no signal from the plug that connects to it. So I'm gonna hunt down the crack in the wire or wherever it's split and fix it.


All of the vac lines are the correct size, thanks for mentioning that! Always a good thing to check. Thanks Eddie!
Old 05-16-2009, 04:32 PM   #33
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Re: Red hot exhaust manifold?

Wow... Ok, I'm an idiot. There wasn't any signal because the key wasn't in the on position. I re-tested and there was signal. Although because it seems that my power drops dramatically once it's warmed up I'm gonna test the signal to all of the temperature driven items, i.e. thermostat, O2... I'm gonna check everything in the end, but those first. I'll write down everything I get back, cause maybe some of them aren't putting out the signal they should be?
Old 05-16-2009, 08:29 PM   #34
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Re: Red hot exhaust manifold?

Quote: Originally Posted by chsdrummer07
Wow... Ok, I'm an idiot. There wasn't any signal because the key wasn't in the on position. I re-tested and there was signal. Although because it seems that my power drops dramatically once it's warmed up I'm gonna test the signal to all of the temperature driven items, i.e. thermostat, O2... I'm gonna check everything in the end, but those first. I'll write down everything I get back, cause maybe some of them aren't putting out the signal they should be?
I swear this is the last time im posting on this today
Alright, I made it sound confusing earlier. I know that the vac is supplied by the TBI unit. Ignore what I said about the mod valve. But why would I not have vacuum if there's nothing blocking this line? I checked and made sure everything is clear from the TBI all the way to the EGR. Does it only supply vac when it is above idle? Sorry for all of this random posting today guys. Thanks for putting up with this stupid problem, or at least helping me with it haha
Old 05-17-2009, 12:06 AM   #35
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Re: Red hot exhaust manifold?

Did you see (and clean out) those little holes in the TBI, that live down in the "neck hole" of the TBI, near the throttle butterfly?? These must be open and mine were jammed full of black, bear-shit carbon. They are what the Rochester Engineers call "ported" vacuum supplies. Your hunch is correct.

They do not have vacuum on them 100% of the time.

Your comment about your truck, running funny when warm, reminds me that the timing advance/retard is solely based on temperature. Temperature of the coolant and temperature of the incoming air/fuel charge in the intake manifold.

A screwed up temperature sensor will cause all sorts of problems.

Last edited by Steady Eddie; 05-17-2009 at 12:08 AM.
Old 05-17-2009, 12:22 AM   #36
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Re: Red hot exhaust manifold?

Yeah I cleaned out those holes, I had the TBI off and made sure it was clean all the way through. If the temp sensor was bad wouldn't I get a code? Or could something cause it to not set one?
Old 05-17-2009, 01:07 AM   #37
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Re: Red hot exhaust manifold?

Most times, these old OBD1 brainboxes have to see a totally failed sensor to set the SES light and a code. If a sensor is showing a signal, to the brainbox, even though it is way off scale, no codes or light will be shown. In the for instance of a temperature sensor, it could be telling the brains that your coolant is at 210* F. when it is cold. The reading is within spec and the PCM is too stupid to know that you just started a cold engine. So, the SES light remains off, and no trouble code is set. Do not "ass"ume for one second, that all of your sensors are functioning perfectly because you do not have a SES light or a code.
Old 05-17-2009, 10:17 AM   #38
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Re: Red hot exhaust manifold?

Yeah Eddie X2, the temp sensors usually read colder than normal, the chart in my Signature will give you a resistance value for temperature (must disconnect wires from sensor and measure pins on sensor).

NOTE: This reading will be accomplished with an OHMMETER or a DMM on an Ohms Scale.
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