Barely Runs, Gets Hot quick, too quiet
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Race Director
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Barely Runs, Gets Hot quick, too quiet
1987 Coupe
Background: http://forums.corvetteforum.com/zerothread?id=655746
I got my car to fire tonight finally. I still don't know what caused it, but it runs barely before it warms up, then it will at least idle, if not well. It runs the coolant up to 230 really quick.
The car threw a code 21 (TPS too high) and code 33 (MAF too high). I checked the TPS and it's .63 V to 4.55 V, which is nominal. The MAF has power, but other than that, there aren't many checks. It doesn't run any differently with the MAF disconnected.
The exhaust is really quiet, which it shouldn't be. It's also running REALLY rich. My air/fuel guage is pegged at Rich.
The car is running poorly, but at least its running. Tomorrow I'll probably drop the exhaust behind the headers to see if there is a chance the cat is clogged or collapsed...
Any other ideas based on these new findings?
Thanks!
[Modified by NoWorries, 8:41 PM 9/25/2003]
Background: http://forums.corvetteforum.com/zerothread?id=655746
I got my car to fire tonight finally. I still don't know what caused it, but it runs barely before it warms up, then it will at least idle, if not well. It runs the coolant up to 230 really quick.
The car threw a code 21 (TPS too high) and code 33 (MAF too high). I checked the TPS and it's .63 V to 4.55 V, which is nominal. The MAF has power, but other than that, there aren't many checks. It doesn't run any differently with the MAF disconnected.
The exhaust is really quiet, which it shouldn't be. It's also running REALLY rich. My air/fuel guage is pegged at Rich.
The car is running poorly, but at least its running. Tomorrow I'll probably drop the exhaust behind the headers to see if there is a chance the cat is clogged or collapsed...
Any other ideas based on these new findings?
Thanks!
[Modified by NoWorries, 8:41 PM 9/25/2003]
Le Mans Master
Joined: Oct 2000
Posts: 6,202
Likes: 9
From: St. louis, MO
Re: Barely Runs, Gets Hot quick, too quiet (NoWorries)
1987 Coupe
I got my car to fire tonight finally. I still don't know what caused it, but it runs barely before it warms up, then it will at least idle, if not well. It runs the coolant up to 230 really quick.
I got my car to fire tonight finally. I still don't know what caused it, but it runs barely before it warms up, then it will at least idle, if not well. It runs the coolant up to 230 really quick.
Race Director
Joined: May 2001
Posts: 14,165
Likes: 9
Re: Barely Runs, Gets Hot quick, too quiet (NoWorries)
You said the MAF readings are pegged and it doesn't run any differently without it hooked up?
Sounds like the car thinks that your car is flowing the maximum amount of air that it possibly can, so it's dumping a ton of fuel to compensate. All that raw fuel may well have ruined your cats.
Cats very rarely just go bad, usually something takes them out, running very rich will do it in a heartbeat. If you find that the cats are clogged you'll have to investigate why. If you just put new cats on it you'll have the same problem again down the road. Doesn't take long for that to get expensive.
I would drop the exhaust and see if it runs better in open loop, it probably will. Then as soon as it hits closed loop it will probably go to hell because it's reading from the faulty MAF. If that's the case you can replace the MAF while you've got the exhaust down and see how it works.
Sounds like the car thinks that your car is flowing the maximum amount of air that it possibly can, so it's dumping a ton of fuel to compensate. All that raw fuel may well have ruined your cats.
Cats very rarely just go bad, usually something takes them out, running very rich will do it in a heartbeat. If you find that the cats are clogged you'll have to investigate why. If you just put new cats on it you'll have the same problem again down the road. Doesn't take long for that to get expensive.
I would drop the exhaust and see if it runs better in open loop, it probably will. Then as soon as it hits closed loop it will probably go to hell because it's reading from the faulty MAF. If that's the case you can replace the MAF while you've got the exhaust down and see how it works.
Instructor
Joined: Jun 2003
Posts: 176
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From: Columbia SC
Re: Barely Runs, Gets Hot quick, too quiet (tjwong)
OK, you are running really low on available time. If you have not already checked the IAC, do it. At least ground ALDL and listen for the clicks/counts. This has too much to do with idle. Secondly, you pulled dist, turned 180 and then back again and now it barely runs and heats up quick. Running rich. Is there a chance you could be off by one tooth, thus throwing off timing enough to make it run hotter and have incomplete burn in the cylinder, which in turn dumps raw fuel into exhaust overheating the cats. Watch the timing mark when it goes closed loop - does computer retard or advance, this may help tell you which way to turn dist shaft.Try to move it one tooth(pick up dist enough to turn shaft, don't need to pull out all the way). This might give you more room to adjist timing and level it out some. If the first try doesn't work, pull dist up and go back 2 teeth. Try now. Disconnect bypass before setting timing and leave it off for now - no need for ECM to mess with timing until you kow it's ready.
I really hope this rambling doesn't make me sound too stupid but I started to feel your desperation and am trying to think of anything. :skep:
I really hope this rambling doesn't make me sound too stupid but I started to feel your desperation and am trying to think of anything. :skep:
Team Owner
Joined: May 2002
Posts: 24,337
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From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Re: Barely Runs, Gets Hot quick, too quiet
I had this exact same problem
I'm 99% sure it was a bad IAC. But I changed a few things, so I can't be sure. I really need to reinstall the bad IAC only, and see if that replicates the problem.
I found out afterwards, that it did throw a high TPS code also. TPS never moved. Distributor never moved either.
Lemme find that thread.... At first, I had swapped injectors and suspected them, but my MPG was very bad.. which tells me that the ECM is purposely pulsing the injectors a bunch, and not that they were just putting out more fuel than the ECM intended.
All these problems occurred after an injector swap, new ignition parts, and new fuel pressure reg. ALSO, I should note that I BROKE THE IAC during the install. I put it in anyways, figured it'd be good enough to get to the autoparts store with.
Unplugging the MAF would just kill the engine. The more I think about it, I think it was the IAC. The car ran like it was a tooth off and rich as hell. I even backfired it out the air filter. (YES, with the distributor at 6 deg btdc!)
Here's the original post:
http://forums.corvetteforum.com/zerothread?id=628136
:cheers:
IM me if you need me to clarify anything. I was in a mess at the time I posted all that.
[Modified by CentralCoaster, 12:54 AM 9/26/2003]
I'm 99% sure it was a bad IAC. But I changed a few things, so I can't be sure. I really need to reinstall the bad IAC only, and see if that replicates the problem.
I found out afterwards, that it did throw a high TPS code also. TPS never moved. Distributor never moved either.
Lemme find that thread.... At first, I had swapped injectors and suspected them, but my MPG was very bad.. which tells me that the ECM is purposely pulsing the injectors a bunch, and not that they were just putting out more fuel than the ECM intended.
All these problems occurred after an injector swap, new ignition parts, and new fuel pressure reg. ALSO, I should note that I BROKE THE IAC during the install. I put it in anyways, figured it'd be good enough to get to the autoparts store with.
Unplugging the MAF would just kill the engine. The more I think about it, I think it was the IAC. The car ran like it was a tooth off and rich as hell. I even backfired it out the air filter. (YES, with the distributor at 6 deg btdc!)
Here's the original post:
http://forums.corvetteforum.com/zerothread?id=628136
:cheers:
IM me if you need me to clarify anything. I was in a mess at the time I posted all that.
[Modified by CentralCoaster, 12:54 AM 9/26/2003]
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Team Owner
Joined: May 2002
Posts: 24,337
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From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Re: Barely Runs, Gets Hot quick, too quiet (NoWorries)
Oh, and BTW, I checked your website.. very nice!
I managed to get all my factory speaker covers over my infinity speakers.
In back, 6x9 3 ways, and 5.25" components up front. IM me for more info :yesnod:
I managed to get all my factory speaker covers over my infinity speakers.
In back, 6x9 3 ways, and 5.25" components up front. IM me for more info :yesnod:
Thread Starter
Race Director
Joined: Oct 2000
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From: Enter Post Count Here
Re: Barely Runs, Gets Hot quick, too quiet (CentralCoaster)
It looks like the problem is the cat. :cool: I dropped the exhaust 1/2 way(too much work to drop it all the way, so I'm getting good flow out of half the headers, and it fires right up and idles nicely.
Throttle responce is killer, I blipped the throttle and it was instantly at 4K. :cool: :smash:
Then my mom wanted to kill me 'cuz its 7:30 at night. :lolg:
Anyways, I'm going to run it some more tomorrow after dropping the exhaust completely out of the way and let it run up to temp and see how she runs around the parking lot. If it works, then I'll knock the cat out and run it to town with open pipes to get some mufflers welded on.
Its still a little quiet...but I think thats the fact that half of the exhaust is running through the cat. The cat does have a little bit of a rattle, but nothing compared to what I've heard on other bad cats.
I didn't think a Cat could cause these problems, I thought it'd run fine until it built up back pressure, then it'd slowly die, not just not start.
Glad to be getting this problem solved. :cool: Thanks for all the help! :cool: :seeya
Throttle responce is killer, I blipped the throttle and it was instantly at 4K. :cool: :smash:
Then my mom wanted to kill me 'cuz its 7:30 at night. :lolg:
Anyways, I'm going to run it some more tomorrow after dropping the exhaust completely out of the way and let it run up to temp and see how she runs around the parking lot. If it works, then I'll knock the cat out and run it to town with open pipes to get some mufflers welded on.
Its still a little quiet...but I think thats the fact that half of the exhaust is running through the cat. The cat does have a little bit of a rattle, but nothing compared to what I've heard on other bad cats.
I didn't think a Cat could cause these problems, I thought it'd run fine until it built up back pressure, then it'd slowly die, not just not start.
Glad to be getting this problem solved. :cool: Thanks for all the help! :cool: :seeya
Thread Starter
Race Director
Joined: Oct 2000
Posts: 16,477
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From: Enter Post Count Here
Re: Barely Runs, Gets Hot quick, too quiet (CentralCoaster)
I'm 99% sure it was a bad IAC. But I changed a few things, so I can't be sure. I really need to reinstall the bad IAC only, and see if that replicates the problem.
I think you're problem was a leaking injector, because I saw the exact same thing happen in my buddies 454SS, which only has two injectors, you can see those injectors, because they just sit on top of the throttle body. After we got that fixed, the truck ran fine, so I think you got a bad injector.
Race Director
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Re: Barely Runs, Gets Hot quick, too quiet (NoWorries)
I didn't think a Cat could cause these problems, I thought it'd run fine until it built up back pressure, then it'd slowly die, not just not start.
Then my mom wanted to kill me 'cuz its 7:30 at night. :lolg:
Thread Starter
Race Director
Joined: Oct 2000
Posts: 16,477
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From: Enter Post Count Here
Re: Barely Runs, Gets Hot quick, too quiet (Nathan Plemons)
Ever hear of a potato in the tailpipe?
[qoute]
Oh that's nothing. The 1 a.m. open header trips down the road are the ones that attract the police. Ask me how I know that :)[/QUOTE]
:lol: I remember the story with the Camaro.:lol:
Team Owner
Joined: May 2002
Posts: 24,337
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From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Re: Barely Runs, Gets Hot quick, too quiet (NoWorries)
I think you're problem was a leaking injector, because I saw the exact same thing happen in my buddies 454SS, which only has two injectors, you can see those injectors, because they just sit on top of the throttle body. After we got that fixed, the truck ran fine, so I think you got a bad injector.
Damn. Now I need to track down which one it is. I wonder if it'd leak 100% under all circumstances... that'd be easy to find out.