hard start/rough idle/low power/glowing manifold
09-06-12, 09:29 AM
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hard start/rough idle/low power/glowing manifold
Just finished my first rebuild and I have some problems to sort out:
The car only starts on starter fluid. The engine still has very little miles on it. It has only started once on its own. Once it starts, it idles very rough. It can hold an idle at ~800rpm, but i set the idle higher because of how rough it runs below 1100/1200rpm (vacuum about 12-14in). It idles smooth at those ranges or higher.
When driving, it's very underpowered. I have to floor the throttle to even accelerate. And when I do, it can't go over 5-6PSI of boost. Once it hits 3800/4000rpm, the boost begins to bounce rapidly from 5/6PSI - 8/9PSI. Then goes back to 5PSI to redline. The acceleration is very poor until it hits about 6000rpm and then the car begins to pull significantly stronger, but still only boosts 5/6PSI.
While accelerating 4000rpm+ the car begins to sputter (I'm not sure if that's the best way to explain it. It sounds like rapid bits of air shooting out of the exhaust).
After doing a few WOT pulls, the dash light for overheating exhaust came on, so i pulled over and let it cool down. It was dark out, so when I looked under the car I saw some glowing from the muffler (very little) and a bright red glow from what looked like the exhaust manifold. It took a long time to cool down with the engine running, so I shut it off after about 5-7 minutes.
Also, there is no sputter during a high rpm rev in neutral. Only in gear with a load.
My car:
Nearly stock 1996 JDM, Koyo radiator, stock exhaust (JDM downpipe), rebuilt engine with used housings/rotars.
Any guidance would be greatly appreciated.
The car only starts on starter fluid. The engine still has very little miles on it. It has only started once on its own. Once it starts, it idles very rough. It can hold an idle at ~800rpm, but i set the idle higher because of how rough it runs below 1100/1200rpm (vacuum about 12-14in). It idles smooth at those ranges or higher.
When driving, it's very underpowered. I have to floor the throttle to even accelerate. And when I do, it can't go over 5-6PSI of boost. Once it hits 3800/4000rpm, the boost begins to bounce rapidly from 5/6PSI - 8/9PSI. Then goes back to 5PSI to redline. The acceleration is very poor until it hits about 6000rpm and then the car begins to pull significantly stronger, but still only boosts 5/6PSI.
While accelerating 4000rpm+ the car begins to sputter (I'm not sure if that's the best way to explain it. It sounds like rapid bits of air shooting out of the exhaust).
After doing a few WOT pulls, the dash light for overheating exhaust came on, so i pulled over and let it cool down. It was dark out, so when I looked under the car I saw some glowing from the muffler (very little) and a bright red glow from what looked like the exhaust manifold. It took a long time to cool down with the engine running, so I shut it off after about 5-7 minutes.
Also, there is no sputter during a high rpm rev in neutral. Only in gear with a load.
My car:
Nearly stock 1996 JDM, Koyo radiator, stock exhaust (JDM downpipe), rebuilt engine with used housings/rotars.
Any guidance would be greatly appreciated.
09-06-12, 09:37 AM
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Will do. I was told that didn't matter, but timing definitely could be my problem. There's nothing else i can do with timing on this car without special tools, right?
09-06-12, 11:44 AM
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09-06-12, 12:14 PM
#7
or leading coils not firing. the connector clips can break very easily and it may not be solidly connected to the center coil or the coil itself may have went on vacation while the engine was being rebuilt.
if the crank triggers are wired up fine and the leading ignition firing properly then you may want to compression test the engine regardless of how short it has been run to see if the compression strokes are even. a rebuild may have low compression but it should still have even compression, that vacuum range is rather low and is likely related to:
retarded timing(leading ignition faulty)
crank trigger fault
map sensor unplugged
fouled leading spark plugs
low/uneven engine compression
aggressive porting requiring a retune
plugged up exhaust
leaky/improper injectors(not likely leaky injectors since it starts on starting fluid, but are the injectors now larger than they were?same impedence?)
if the crank triggers are wired up fine and the leading ignition firing properly then you may want to compression test the engine regardless of how short it has been run to see if the compression strokes are even. a rebuild may have low compression but it should still have even compression, that vacuum range is rather low and is likely related to:
retarded timing(leading ignition faulty)
crank trigger fault
map sensor unplugged
fouled leading spark plugs
low/uneven engine compression
aggressive porting requiring a retune
plugged up exhaust
leaky/improper injectors(not likely leaky injectors since it starts on starting fluid, but are the injectors now larger than they were?same impedence?)
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09-06-12, 12:15 PM
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09-06-12, 12:18 PM
#9
you also shouldn't be pushing a laboring engine on a fresh rebuild unless you like redoing all that work again with additional parts cost when it pops.
first 30 mins of run time the rebuilds usually labor to break in the seals, glowing exhaust isn't uncommon for the first run cycle. but trying to beat it out of the engine isn't going to be favorable. some engines break in much faster than others, recheck everything mentioned and drive it reasonably for an hour or 2 and see if it gets better, if not then something on that list is being a problem.
first 30 mins of run time the rebuilds usually labor to break in the seals, glowing exhaust isn't uncommon for the first run cycle. but trying to beat it out of the engine isn't going to be favorable. some engines break in much faster than others, recheck everything mentioned and drive it reasonably for an hour or 2 and see if it gets better, if not then something on that list is being a problem.
Last edited by RotaryEvolution; 09-06-12 at 12:21 PM.
09-06-12, 12:25 PM
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or leading coils not firing. the connector clips can break very easily and it may not be solidly connected to the center coil or the coil itself may have went on vacation while the engine was being rebuilt.
if the crank triggers are wired up fine and the leading ignition firing properly then you may want to compression test the engine regardless of how short it has been run to see if the compression strokes are even. a rebuild may have low compression but it should still have even compression, that vacuum range is rather low and is likely related to:
retarded timing(leading ignition faulty)
crank trigger fault
map sensor unplugged
fouled leading spark plugs
low/uneven engine compression
aggressive porting requiring a retune
plugged up exhaust
leaky/improper injectors(not likely leaky injectors since it starts on starting fluid, but are the injectors now larger than they were?)
if the crank triggers are wired up fine and the leading ignition firing properly then you may want to compression test the engine regardless of how short it has been run to see if the compression strokes are even. a rebuild may have low compression but it should still have even compression, that vacuum range is rather low and is likely related to:
retarded timing(leading ignition faulty)
crank trigger fault
map sensor unplugged
fouled leading spark plugs
low/uneven engine compression
aggressive porting requiring a retune
plugged up exhaust
leaky/improper injectors(not likely leaky injectors since it starts on starting fluid, but are the injectors now larger than they were?)
What would be the easiest way to check the leading coil?
Also, thanks for the detailed response! I see you post in so many topics with a lot of great information. I really appreciate the help!
09-07-12, 11:19 AM
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The dash light for overheating exhaust came on. I've never seen that come on before.
I'm thinking the easiest way to check for a clogged cat is disconnect the dp from the mp. And see if it runs better. My neighbors are going to hate me though
I'm thinking the easiest way to check for a clogged cat is disconnect the dp from the mp. And see if it runs better. My neighbors are going to hate me though
09-08-12, 12:30 PM
#17
never, the car usually has to be on fire before it comes on.
that light ranks on the same level as the sub zero assist system that mazda used for about 20 years before realizing it was completely useless. except the exhaust light has been around longer.
that light ranks on the same level as the sub zero assist system that mazda used for about 20 years before realizing it was completely useless. except the exhaust light has been around longer.
09-08-12, 05:27 PM
#19
Vintage sportcars
So I was there too and did a test run after we finished working on it.
The catalytic converter was completly destroyed inside. Material shattered to pieces.
We did remove all of the remaining material out of the cat (replacement pending) so we can do further tests. So it basically has now a straight pipe from exhaust turbine to tailpipe
Engine compression is fine, around 80 psi evenly on all 6 faces. about 150 psi max when not pushing the valve on the tester. I think thats pretty good on a new rebuild, new seals are probably not broken in yet.
The leading plugs have been cleaned, they should be good to get the job done, but a new set wont hurt soon as they are almost halfway done.
On a test drive the car does start after a few tries
but does not have a lot of power. It does make boost up to 7 psi and starts to sputter (boost bouncing around), its like "wosh wosh wosh wosh woosch bang wosh"
After a short drive the exhaust temp light comes on and we stopped there, letting the car idle for about 5 minutes and shut it down. The inside of the tailpipe was glowing red and so was all the exhaust system. Although I was going easy on it since its new rebuild.
Seeing the glowing exhaust I am pretty sure that this thing is running lean.
I recommended to tmenzz that he should change his fuel filter (which was probably never changed in its life) and check the fuel pump voltage to see if it gets full power.
Also checking the FPRs MAP reference could not be a bad idea too. Besides of that I am pretty sure the injectors and rails are seated fine.
Steven
The catalytic converter was completly destroyed inside. Material shattered to pieces.
We did remove all of the remaining material out of the cat (replacement pending) so we can do further tests. So it basically has now a straight pipe from exhaust turbine to tailpipe
Engine compression is fine, around 80 psi evenly on all 6 faces. about 150 psi max when not pushing the valve on the tester. I think thats pretty good on a new rebuild, new seals are probably not broken in yet.
The leading plugs have been cleaned, they should be good to get the job done, but a new set wont hurt soon as they are almost halfway done.
On a test drive the car does start after a few tries
but does not have a lot of power. It does make boost up to 7 psi and starts to sputter (boost bouncing around), its like "wosh wosh wosh wosh woosch bang wosh" After a short drive the exhaust temp light comes on and we stopped there, letting the car idle for about 5 minutes and shut it down. The inside of the tailpipe was glowing red and so was all the exhaust system. Although I was going easy on it since its new rebuild.
Seeing the glowing exhaust I am pretty sure that this thing is running lean.
I recommended to tmenzz that he should change his fuel filter (which was probably never changed in its life) and check the fuel pump voltage to see if it gets full power.
Also checking the FPRs MAP reference could not be a bad idea too. Besides of that I am pretty sure the injectors and rails are seated fine.
Steven
09-08-12, 08:13 PM
#23
+1
Not sure why people always think its a great idea to put load or even boost a sketchy motor. Especially a rotary. Fix the problem and break it in before you get on it.
If your cat melted to pieces then you most likely have either a stuck open injector or faulty ignition components. Too much excess unburned fuel kills cats.
Matt
Not sure why people always think its a great idea to put load or even boost a sketchy motor. Especially a rotary. Fix the problem and break it in before you get on it.
If your cat melted to pieces then you most likely have either a stuck open injector or faulty ignition components. Too much excess unburned fuel kills cats.
Matt
09-09-12, 12:31 AM
#25
double check your injector clips and make sure they are secure, check the map sensor hose and electrical clip to it, change the fuel filter and spark plugs, check that the leading coil pack is firing the leading plugs and drive the car normally for at least a few hours before trying to give it an enema.