Give me your opinions on exhaust/cat restrictions

JeffP1167

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this is on the 97 firebird I just got my engine in

I did the vacuum test and my vacuum readings were perfect at 2000 rpm it stayed right around 20 inches.

My motor stumbles to the point it shakes the whole car at any RPM and doesn't have snappy throttle response like my excellent running 97 camaro 3.8.

even when you rev it up in neutral the motor is sluggish responding, makes totally different sound, even the exhaust has a much mellower tone then the raspy sound my camaro makes.

Can a converter plug and still allow enough flow to get a good vacuum reading and still choke the motor?

Aside from this I cannot find anything wrong with this engine aside from it detects random misses but will not detect a certain cylinder. I have hear vibration can trigger miss detection.

I know my camaro to be 100% stock and yet this firebird sounds nothing like it. The oddest part is the breathing sound it makes compared to my camaro. I don't think the motor has a balancing issue.

Just nothing I do makes this motor run better, I cant simply unbolt the converter but don't want to just cut it off.

I put new plugs, wires, coil packs, has good fuel pressure, no other codes but p0300, new fuel filter, mass a/f sensor, new air filter.

It also has a fuel odor most of the time

so exhaust or something different?
 
97 and 99 3.8 are the same enines??? if yes, check the ignition module... it's under the coils (at least on the '99 it is).... that thing drove me nutz a few years ago.... crappy idle, random misfire, wouldn't rev past 4000 under load..... sounds about like what you're describing......back then AdvancedAutoparts had the best deal on replacement....
 
97 and 99 3.8 are the same enines??? if yes, check the ignition module... it's under the coils (at least on the '99 it is).... that thing drove me nutz a few years ago.... crappy idle, random misfire, wouldn't rev past 4000 under load..... sounds about like what you're describing......back then AdvancedAutoparts had the best deal on replacement....

95-02 3800 basically the same, yes it has that. I was going to pull the one from my camaro tomorrow to test before throwing money away.

did your vibrate the whole car, when I idle this it shakes the steering wheel and when driven you even feel the vibration in the seat.

This just seems to be bogged down hard compared to my camaro.
 
I tried the ignition coil module from my camaro and it didn't make the vibration go away.

I am wondering if it is a wrong flywheel, I bought it ready to bolt on so I am curious if it is just throwing the engine out of balance and that could be causing the pcm to interpret as missing.

I have had misses in my camaro but it has never done this, I at first thought it could be the harmonic balancer but I replaced it.

I can put my hand on the bellhousing and feel it vibrating as well as the case of the 5 speed.

I'm going to pull the trans tomorrow and see if the trans is the cause and work my way forward.

If need be I will try another flywheel, the trans had to have taken a very brutal pounding when the previous engine split in half so I'm curious if the trans could be the culprit as well.

I put a new clutch assembly in so it probably isn't that. One thing that seemed strange though is the clutch disc looked to be mountable in either way so maybe I picked the wrong way .... really getting to hate cars though that is for sure.
 
97 and 99 3.8 are the same enines??? if yes, check the ignition module... it's under the coils (at least on the '99 it is).... that thing drove me nutz a few years ago.... crappy idle, random misfire, wouldn't rev past 4000 under load..... sounds about like what you're describing......back then AdvancedAutoparts had the best deal on replacement....

95-02 3800 basically the same, yes it has that. I was going to pull the one from my camaro tomorrow to test before throwing money away.

did your vibrate the whole car, when I idle this it shakes the steering wheel and when driven you even feel the vibration in the seat.

This just seems to be bogged down hard compared to my camaro.

it's been 6 or 7 years, but yes..... no power, ran like crap, misfired, vibrated, shook the whole car.....

if you buy this module at Advanced or the Zone they'll take it back and refund your money if it doesn't fix the problem, at least that's what they offered when I bought mine.... that thing is $150 ..... ouch.....

I changed plug, wires, coils before I finally got to the module..... spent at least 250 on parts.... well.... still cheaper than going to a shop..... LOL....
 
I tried the ignition coil module from my camaro and it didn't make the vibration go away.

I am wondering if it is a wrong flywheel, I bought it ready to bolt on so I am curious if it is just throwing the engine out of balance and that could be causing the pcm to interpret as missing.

I have had misses in my camaro but it has never done this, I at first thought it could be the harmonic balancer but I replaced it.

I can put my hand on the bellhousing and feel it vibrating as well as the case of the 5 speed.

I'm going to pull the trans tomorrow and see if the trans is the cause and work my way forward.

If need be I will try another flywheel, the trans had to have taken a very brutal pounding when the previous engine split in half so I'm curious if the trans could be the culprit as well.

I put a new clutch assembly in so it probably isn't that. One thing that seemed strange though is the clutch disc looked to be mountable in either way so maybe I picked the wrong way .... really getting to hate cars though that is for sure.

ok, not ignition related...... only other thing is that stupid crank sensor if I remember right this V6 has one and it can cause some funky stuff......

flywheel? hmmm,maybe..... but the trans shouldn't be the problem as it is pretty much disconnected when you press the clutch.

lots of work but if you run the engine without the trans, clutch and flywheel you'll either know or rule it out....
 
I tried the ignition coil module from my camaro and it didn't make the vibration go away.

I am wondering if it is a wrong flywheel, I bought it ready to bolt on so I am curious if it is just throwing the engine out of balance and that could be causing the pcm to interpret as missing.

I have had misses in my camaro but it has never done this, I at first thought it could be the harmonic balancer but I replaced it.

I can put my hand on the bellhousing and feel it vibrating as well as the case of the 5 speed.

I'm going to pull the trans tomorrow and see if the trans is the cause and work my way forward.

If need be I will try another flywheel, the trans had to have taken a very brutal pounding when the previous engine split in half so I'm curious if the trans could be the culprit as well.

I put a new clutch assembly in so it probably isn't that. One thing that seemed strange though is the clutch disc looked to be mountable in either way so maybe I picked the wrong way .... really getting to hate cars though that is for sure.

ok, not ignition related...... only other thing is that stupid crank sensor if I remember right this V6 has one and it can cause some funky stuff......

flywheel? hmmm,maybe..... but the trans shouldn't be the problem as it is pretty much disconnected when you press the clutch.

lots of work but if you run the engine without the trans, clutch and flywheel you'll either know or rule it out....

How come this flywheel can be mounted in any position? I would have thought it would have alignment holes to correctly install it for balancing or does it just go on any way?
 
How come this flywheel can be mounted in any position? I would have thought it would have alignment holes to correctly install it for balancing or does it just go on any way?

if it's neutral it doesn't matter. Same thing with replacement flywheels, for example when you replace the clutch and the flywheel surface is shot.... just slap a new flywheel on there and go.... now, if they used the flywheel for balancing then it has to be installed in the correct orientation and it should have a dowel or something to locate it....
 
How come this flywheel can be mounted in any position? I would have thought it would have alignment holes to correctly install it for balancing or does it just go on any way?

if it's neutral it doesn't matter. Same thing with replacement flywheels, for example when you replace the clutch and the flywheel surface is shot.... just slap a new flywheel on there and go.... now, if they used the flywheel for balancing then it has to be installed in the correct orientation and it should have a dowel or something to locate it....

basically this flywheel had 8 bolts in a tight pattern and no dowel pin hole nothing. So I guess it is neutral balance. So back to other issues.

when running last night I saw a periodic arc on number 1 cylinder at the spark plug boot. However when I looked towards back of the drivers side block where the wires run I saw streaks of light which seemed to come from within the plug wire/s .... it wasn't a arc it was a glowing pattern and then it kind of went away. I thought that to be strange being no other wires did it.

I used some bosche iridium plugs in it, I have heard these 3.8 engines are picky on plugs.

fuel injectors are another possibility since I used the ones from the replacement engine and not the original ones.

However no matter what I do I still kinda think it is catalytic converter related, since it has the different engine sounds.

the plug wires also concern me so I will replace them as well and run a fuel pressure test but seems like a hell of alot of fuel pressure if you depress the shrader valve.
 
new ICM
New plug wires
cut cat off it looks fine

still no change and motor still vibrates bad still and has fuel odor p0300 random missfires.

the sound of revving up motor alone still doesn't sound like my camaro. Could bad fuel injectors be the culprit or maybe a bad PCM or ground issues?

Can the crank and cam sensor be faulty and the PCM doesn't see it?
 
new ICM
New plug wires
cut cat off it looks fine

still no change and motor still vibrates bad still and has fuel odor p0300 random missfires.

the sound of revving up motor alone still doesn't sound like my camaro. Could bad fuel injectors be the culprit or maybe a bad PCM or ground issues?

Can the crank and cam sensor be faulty and the PCM doesn't see it?

I had a Dodge 318 some years ago with a bad crank/flywheel sensor, notches off the flexplate is what it was looking at.....and the sensor was a magnet with coil around it, wide open...no resistance....but engine would run the way you are describing above....replaced it and ran perfect....

:crutches:
 
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