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Lt1 exhaust manifolds glowing red and hesitation and missing only when warmed up .

14K views 16 replies 10 participants last post by  Rooster438 
#1 ·
Here is the run down.

200k 1995 Impala SS
BONE STOCK LT1
I decided to put a cold air intake on this car and goofed and installed the maf backwards. I drove it for a good 2hours and then the car seemed to start missing a lil and at low rpm has some hesitation and pinging noise. I looked under the hood and found by manifolds where glowing beat red. I went home removed the intake and discovered the maf backwards . Reinstalled the stock air intake setup and correct way for the maf. And I still have the issue. It only does it when it warms up runs fine cold.

Car has no codes nore a engine light on.

I replaced the spark plugs . But when it warms up same issue.

I had a appointment be for the issue for a new exhaust so while I was there I had them check the cat and they tested fine.

I could not get the 02's out . There gonna need some heat or cut out so Im going to call around today about that.

Also going to the hardware store and going to by some maf cleaner. Might jus buy a maf.

Any inputs or suggestions greatly appreciated.
 
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#2 ·
When cold it's in open loop , Not looking at the O2 sensors , Then after warm up it changes into closed loop , looks at the O2 sensors . So I would start with those. You may have cooked them or the wiring going to them or any wiring that was any where close to the manifolds. I would suggest having a leak down test done on the engine to see if it did any piston or valve damage.
Hope this helps.
 
#3 ·
Davi☠Rotten said:
Here is the run down.

200k 1995 Impala SS
BONE STOCK LT1
I decided to put a cold air intake on this car and goofed and installed the maf backwards. I drove it for a good 2hours and then the car seemed to start missing a lil and at low rpm has some hesitation and pinging noise. I looked under the hood and found by manifolds where glowing beat red. I went home removed the intake and discovered the maf backwards . Reinstalled the stock air intake setup and correct way for the maf. And I still have the issue. It only does it when it warms up runs fine cold.

Car has no codes nore a engine light on.

I replaced the spark plugs . But when it warms up same issue.

I had a appointment be for the issue for a new exhaust so while I was there I had them check the cat and they tested fine.

I could not get the 02's out . There gonna need some heat or cut out so Im going to call around today about that.

Also going to the hardware store and going to by some maf cleaner. Might jus buy a maf.

Any inputs or suggestions greatly appreciated.
It's running lean when it gets out of warm-up mode (choke). At that point as stated by ayers1981 it goes into closed loop and the mixture leans down for normal operation.

This is telling you that if the sensors are operating the mixture error is greater than the system can fix. If the O2 were dysfunctional you'd get a code as OBD II systems are right on top of things like that.

I would suspect a vacuum leak is upsetting the mixture. Also low speed ping is an indicator of a lean mix, this could be affected by EGR the lack of which results in a lean mixture.

Retarded timing whether ignition and or camshaft has the same look and feel as a lean mixture.

But all of these should be failures that are throwing codes on the OBD II system.

Bogie
 
#5 ·
Even though the codes should have illuminated the SAS/MIL on the dash- check the ECM for codes w/a reader, scanner, etc., anyway- if you haven't already.

Many things have already been mentioned that will cause a lean A/F mixture or the symptoms of it. To those add the knock sensor(s)- they will dump ignition timing, don't know if it alters fuel map or no.
 
#7 ·
Alright folks, I seem to be having the same issues, Thank you Google for sending me here. I've got a 1995 Chevrolet Caprice, with a stock LT1. It developed an exhaust leak and I replaced the passenger side manifold and the driver side gasket. Fixed the leak, but now they glow a beautiful red after running it for a bit. I'm just wondering, did the O2 sensors fix the issue you were having?
 
#8 ·
You are going to need a good scan tool. Look at the live data like MAF reading and look at the fuel trims.If the MAF looks normal and the trims are subtracting , then unmetered fuel is getting into the engine. No codes usually means a mechanical problem . Even if you get a code you need to understand the condition it is describing.
Maybe look at the fuel pressure regulator for leaking into the intake through the vacuum hose.
The condition you are describing is due to excess fueling from somewhere.Could also be a vapor canister getting raw fuel into it sucking it into the engine in closed loop. The evap only runs in closed loop
 
#9 ·
I haven't been able to get ahold of a scan tool just yet, but I was able to check the fuel pressure. Specs call for 41-47psi off the test port, but I was only getting about 36psi. When I removed the vacuum hose to test the pressure regulator the pressure spiked about 5psi. Any suggestions from here?
 
#11 ·
classicchevyman said:
where can i find the manual on a 283 motor i need to replace the bearings and rings any suggetions
In order for your question to get the attention of the membership, the best suggestion would be to start a new thread by clicking on "Bulletin Board" at the top of the page. When the page opens, you'll see all the forums listed.

I'd say to post your engine question in either the Hotrodding Basics forum: This forum is for beginner hotrodders or basic hotrodding questions. Or the Engine forum: This forum covers all engine questions, including intake and exhaust discussions.

Click on the forum you decide would best suit the question, then at the top left of the page you'll see an icon "New Thread". Click on that, and give a title (not "Help!", something like "283 SBC Service Manual", then add the post in the text field.

Do a spell check and if you're happy w/the post, submit it. You can edit your post for 30 minutes, after that the edit function is locked out.

And, welcome aboard!
 
#12 ·
If you had an oiled type air filter (k&n ect) it is possible that the MAF got oil on it and after it goes into closed loop it is not seeing the correct amount of air entering and there for the A/F ratio is off and running way to lean.

Take the MAF out and clean it with MAF cleaner or brake clean and let it dry then retry.
 
#13 ·
Davi☠Rotten said:
Here is the run down.

200k 1995 Impala SS
BONE STOCK LT1
I decided to put a cold air intake on this car and goofed and installed the maf backwards. I drove it for a good 2hours and then the car seemed to start missing a lil and at low rpm has some hesitation and pinging noise. I looked under the hood and found by manifolds where glowing beat red. I went home removed the intake and discovered the maf backwards . Reinstalled the stock air intake setup and correct way for the maf. And I still have the issue. It only does it when it warms up runs fine cold.

Car has no codes nore a engine light on.

I replaced the spark plugs . But when it warms up same issue.

I had a appointment be for the issue for a new exhaust so while I was there I had them check the cat and they tested fine.

I could not get the 02's out . There gonna need some heat or cut out so Im going to call around today about that.

Also going to the hardware store and going to by some maf cleaner. Might jus buy a maf.

Any inputs or suggestions greatly appreciated.
Either the mixture has gone quite lean or the timing has become retarded, which could be caused by the cam out of synch with the crank as well as the ignition falling behind. I'm highly surprised that this isn't showing the check engine light, these kind of things usually cause the computer to display codes. They may not be correct as to cause but rather indicating a symptom affecting something, but not to see the Check Engine Light is quite unusual. I'd plug in the reader and see what pops up rather than wait for what might be a burnt out bulb in the CEL.

Hesitation with pinging points to a lean mixture along with the glowing hot exhausts. This could be as simple as plugged fuel filters or as complicated that the backwards MAF took something out.

O2 sensors are hardly ever removable intact. If they have failed you should see the CEL lit and codes being set. But it they are there to trim the mixture, without their input the computer resorts essentially to start up mode which is open loop operation that will tend to be cold start rich, but since exhaust manifolds don't glow from the extra fuel on cold start, it's not likely they will if that mode is invoked when the engine is warmed up.

Bogie
 
#14 · (Edited)
Blythe is correct about the K+ N filter. They will contaminate the MAF. But it will cause a lean condition. Your problem is fuel burning in the exhaust manifolds.
Now that you have a code 43 that is a good direction to go. Oldbogie is correct about cam/crank syncronization it can cause a problem as this as the injectors would switch back to batch fire instead of spraying in a sequencial order.This would cause too much fuel to be injected a loss in performance and quite probably red hot manifolds .
Lean conditions wont cause an exhaust to get red hot. Lack of fuel doesnt make extra heat in the exhaust but extra fuel will.
By the way 1995 LT1 5.7 SS impala code 43 is for the knock sensor circuit/malfunction , that does have effect on timing if there is a cicuit problem. It does not mean est circuit problem
 
#17 ·
I found my problem to be a vacuum leak. Plugged a cheap vacuum gauge into the intake and it read 19-21 in closed loop, when it went into open loop the O2 sensors we're seeing non metered air and telling the ECM to send all available fuel causing it to run rich and burn excess exhaust in the header. Exhaust had a slight gray tint when a bright flashlight was shined across the exhaust tip. Sprayed brake cleaner down both side of the intake and found the line going to the brake booster sucking air. Repaired the leak and problem went away
 
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