92PurpleHazeRS

Hey Everyone...been awhile since I posted.I recently installed a new 3.1L V6 in my 92 RS.As of late its been giving me a hard time starting once in awhile after running for about 4-5 miles.When it does I have to force it with starting fluid.I've been told it could be one of two things. 1)The catalytic conv.is bad... 2) The coil is going or is bad.The engine is brand new and dosent even have 3000 miles on it ,although the convertor and the coil are still original parts and the old engine had 219,000 miles on it.When it gets to the point of not starting and I just decide to let it sit and not use the starting fluid it fires right up the next morning.But sometimes when I use the fluid it tends to run real rough.While taching it up once after a fluid start it popped some s**t outta the exhaust that loohed like a honeycomb and turned to dust in my hand when I crushed it.The engine tached up to a certain point and then sounded like it was bogging down.

Any ideas/suggestions will be GREATLY appreciated.

~Bob

2_point8_boy

Could also be a bad ECT(Coolant temp sensor). It's located under the plenum on the drivers-side front of the engine. It's a 2 wire sensor. It'll give you wierd starting problems like this. i dob't it's the cat because the car would run then, it just won't rev much over idle.

Coil could be crap, but it would run like crap after it warmed up. You would get misfiring REAL bad.

I would check out the ECT and make sure that you have a good connection, then you can check the voltage if you have a Digital voltmeter and a couple of paper clips.

Maverick H1L

iTrader: (8)

Sounds like you need a new catalytic convertor. That honeycomb stuff is what fills up the cat.

Chances are, you need both the cat and coil, since these cars tend to also eat ignition components. Proof? I've gone through two coils, one ign module, two caps and rotors, one full set of plugs, and two sets of wires in about a year and a half...

2_point8_boy

The cat is not the starting problem, it might be another problem that he'll have to look into later, but it's not the starting problem. If the cat were clogged enough that it prevents the car from starting, it wouldn't start, period. Not even cold. That's not the kind of thing that gets worse as the car warms and cools. The cat doesn't even start to melt until well into the 1000's of degrees. At that point it's on fire, not just melting.

BTW...you have a lot of other issues if you have gone through that much in a year and a half. There is something going on there. That's not normal.

I say, start with the coil, it's a good bet that it's toast. A lot of people say that the stock coil location sucks, but the thing that they don't take into account is that most people are running coils that are 7+ years old. True, heat does kill them early, but people overlook the fact that they are already running an old coil and leave it out of the whole maintinence thing until it dies, then they blame the location.

I've benn running mine in the stock location for the last 3 years and never had an issue once I got a good coil from the store. The first one on the car was an original AC DELCO coil, it dies soon after I got the car, then I got a defective coil "brand new." After I took that one back and got a good one, it's been on there for 3 years, never to bother me again.

wildponies3

2_point8_boy is a certified emmissions guy, listen to him he knows what he is talking about, just ask around the board
(your welcome jeff)

2_point8_boy

TY. I never knew I was known for it, but Wooohoo Me! lol

Anyway. I have seen my share of broken cars, and gone through A LOT of training. The only warning I have is that I am only guessing. They are VERY educated guesses, but without actually having the car in front of me and knowing exactly how it's acting, I have limited info to base my suggestions on. I try very hard to give you the best advice that I can so that you don't go out spending a crapload of money on parts that you don't need.

I still suspect something with the ECT or the coil.

The computer uses the ECT to get a base pulse width for starting the car depending on the temperature of the coolant. The colder the engine, the more fuel it needs to start. Here's how the ECT works.

The computer supplies it a 5V signal voltage and the and uses the Reference Wire as the Signal wire also. The Sensor itself is what they call a negative co-efficient thermistor, meaning the the resistance of the sensor goes down as the temperature increases. What the computer looks at is the amount of voltage the Sensor consumes of the 5V signal provided.

When the car is cold, the resistance is high, which means it uses a good portion of the voltage. As the car warms up, the resistance goes down, and hence the signal voltage goes down because it is using less voltage across the sensor. (Kind of hard to understand, I know.) Now, when the sonsor is, say, shorted to ground, it draws all 5V to ground and the computer sees a 0V drop across the sensor, meaning it's VERY warm and it makes the pulse width as short as possible. Once the car is started, the only thing the ECT is used for is to determine WOT pulse width and when it's time to go into closed loop. It becomes a very small part of the overall running of the car.

Most things electrical tend to short to ground and have a VERY low resistance when they get hot, this means that if this is what's happening to your ECT, it'll cause a very short cranking pulsewidth, but once the car is running in closed loop, it runs better. If you want, i can look up the values for the ECT at a given temperature and can even take a picture of how to hook up to it for you. Let me know.

wildponies3

lol. knowing karl and some of the other cali guys, i guess i learned to trust you on that stuff.
p.s even on educated guesses he's about 80% accurate from my experiences.

Maverick H1L

iTrader: (8)

A little off topic:

The ICM (Wells reman from AutoZone) was bad when I bought the car, but it was good enough that the engine ran. The original coil was bad. The wireset that was on the car when I bought it was bad, except for about three plug wires. The cap and rotor were bad (and who knows how long they were on the car) and I use that cap for dizzy alignment. The first wireset I bought became toast after a while and killed my replacement coil, so I had to go out and get a new one. The Accel coil I have now has been relocated to the outside of the A/C heater box so as to keep it cooler (being bolted to a bracket that is rather heavy gauge steel and bolted to the exhause manifold kills them quick), so hopefully I don't have to replace it in another year...

Now on topic: I'd still get the cat, since it seems like it's disintegrating and it may eventually clog the muffler or something. It also helps the environment, which could use all the help it can get ...

92PurpleHazeRS

Hey guys....thanx for all the advice.Jeff,I changed out the coil in my RS and so far she seems to be running real good.I figured I'd start with the cheaper parts and work my way up.

So far with the new coil (only $17)shes doin ok.

Once again guys thanx for all your advice and input.

I'm on the road again!!!



~Bob

KED85

Western NY ...
Hmmm...
How do you spell humidity? All Day LONG!
Yeah you sounded like coil troubles.
I also say new cat is due soon.
BUT to really find out... don't laugh, pull the muffler off and see what's at inlet of muffler... you may find the broken down cat. I know I did when I had removed my muffler! New muffler sure helped and then I did replace the Cat Convertor.
I used a Magnoflow #23494 for a 3.4 1995 F Body 2 1/2" in & out & it was a direct fit (even on my 1985 set up!) & cost me $113 including shiping from Summit.

92PurpleHazeRS

Thanx...just put a new exhaust on it over last winter...from the CAT Conv.back.Unfortunately I didnt replace the Cat and the muffler is welded on.Guess I can take it back to the same guy and have him check everything out for me.The guy has reasonable prices so it shouldnt hurt too bad.

Thanx again


~Bob

monsterj1j1

This sounds kind of like what my problem is.. I have a 91 firebird with a 3.1l. The car was running a little boggy when I first got it so I replaced all of the plugs. It was running even worse after I changed them and now my car doesn't even want to start