Cat converter issue? She's misfiring still....

[misledxcracker]

So since I sorta got out of working for awhile I've been messing with the car. '86 SPFI 3AT coupe.

 

The idle isnt necessarily what bothers me anymore, I cleaned the MAF up with CRC, I replaced the IAC altogether today, tuned in the "new" TPS correctly with feeler gauges, screwed out the idle screw some, sprayed carb cleaner all around to reveal no leaks, ran a D-Check and all I'm getting is a 31, which SHOULD be irrelevant to the problem... Oh yeah, I've Seafoamed it a couple months back and I cant think of one tuneup part on my car that arent more than 3,000 miles old. My timing is dead on, the pulleys are on correctly, I just replaced the belts, actually. Havent done the reseal yet :-\

 

Anyway, the car shakes and misfires. It wont stop. I cant stand it. Why why why why does it have to shake and misfire so much?!?!

 

Anyway, while I was under the car trying to clean off all the grime in front of the engine, I noticed my cat converter has a small hole in it, and it tends to make a vibrating noise in the morning. There's no heat shield on it, so that cant be the case... Can the cat converter cause this puh-puh-puh out the exhaust and the shaking?

 

Or if it aint that, what could it be?! I've replaced so much, I cant figure out why it would still act like this... It's been almost 6 months, this car hasnt rode smooth since ownership... I'd love for it to do so sometime soon! :cool:

[DaveT]

Anyway, the car shakes and misfires. It wont stop. I cant stand it. Why why why why does it have to shake and misfire so much?!?!

 

(assuming you checked the plugs & wires, including checking that 1-1, 2-2, 3-3, 4-4)

 

If a piece of the catalyst broke off, turned sideways, and stuck in the outlet, it would make it run very bad. No power, pinging. Mine didn't shake when that happend. My test for plugged exhaust is to drop the Y pipe 3/4" from the engine and hook a vacuum cleaner to the tail pipe. There shouild be a small change in vacuum cleaner RPM with exhaust VS without. A large change indicates blockage.

 

Try not to bang the exhaust around while preparing the test - you don't want to dislodge the blockage.

[Tom63050]

I just replaced the belts, actually.

 

Can the cat converter cause this puh-puh-puh out the exhaust and the shaking?

The hole in the cat might well cause the puh X 3 sound, but I can't imagine that would have anything to do with the shaking. I would think that a plugged-up exhaust would just make the car underpowered or not run at all, if sufficiently plugged. But Board members with more experience might think otherwise...

 

Are you absolutely sure the belt on the driver's side isn't a tooth or two off? That would of course affect ignition timing. The passenger side belt might cause shaking if it's off a bit too.

[misledxcracker]

It doesnt seem to run bad... it can still do 85+ without THAT much issue... tuning the TPS to specs sure made a difference.

 

It mainly shakes at a stop... only seems to misfire at low RPMs...

 

Timing is perfect.

[Zebisko]

You could just chop the cat off, although after that it will be quite loud.

[misledxcracker]

And quite the recipe for a ticket. :-\

[daeron]

i'm assuming welded joints in the exhaust? I have flanges so its easy to just, take the cat off and see. idling isnt THAT loud.. resisting the temptation to gun it once or twice once you actually hear the IDLE with no exhaust, is kind of difficult

 

it doesnt really sound like the kind of problem that would arise from a clogged cat, but it never hurts to check. The "smoking gun" to me on my last clogged cat diagnosis was the fact that the exhaust immediately behind the cat cooled off in no time flat, while the cat was still burning hot for 30-45 minutes. The cat SHOULD be hotter than the exhaust.. but not THAT much hotter.

 

Have you inspected your pitch stopper and motor mounts? these engines arent the smoothest in the world, in the sense of normal operational vibrations, and a worn mount or bushing could easily cause the shaking. As for the idle miss, have you put in a new O2 sensor?? couldnt hurt, only about twenty bucks, file it for future doing.. you COULD try testing the output of the O2 sensor, it should read about 0.5 volts DC across the wire and the body of the O2 sensor when the engine is running, and idling at the right ratio, and the O2 sensor is hot. (HOT, no ride to the corner store, get it good and hot!) You can actually use the multimeter on the O2 sensor to tune in the idle bypass screw (NOT an idle mixture adjustment) properly; a good, new O2 sensor will read about 0.5 volts at stoich, and higher voltage up to about 1.0 for lean (i think) and down to minimal for rich.

[misledxcracker]

My pretty much new exhaust (minus y-pipe and cat converter) is completely welded. No bolts or flanges unless I want to drop the whole thing it's gonna be TONS of FUN when i have to drop it to swap the transmission

 

Never even thought of the O2 sensor, I'll check it out.

[Tom63050]

My pretty much new exhaust (minus y-pipe and cat converter) is completely welded. No bolts or flanges unless I want to drop the whole thing it's gonna be TONS of FUN when i have to drop it to swap the transmission

 

Actually it won't be a problem. When Gloyale and I (OK, mostly him) put a clutch in my Loyale, he just had to undo the eexhaust flange nuts, and a 14mm nut a foot or two behind the cat. The exhaust just hung down. You might have to cut your O2 sensor wire, or pull the sensor, if the wire's too short. Mine was long enough because I had just spliced in a new sensor and had more wire than stock.

[misledxcracker]

Actually it won't be a problem. When Gloyale and I (OK, mostly him) put a clutch in my Loyale, he just had to undo the eexhaust flange nuts, and a 14mm nut a foot or two behind the cat. The exhaust just hung down. You might have to cut your O2 sensor wire, or pull the sensor, if the wire's too short. Mine was long enough because I had just spliced in a new sensor and had more wire than stock.

I dont have any flanges behind the cat... no flanges at all. Either the whole exhaust comes off complete, or it wont drop. I'd have to unbolt the Y pipe and carefully drop the whole thing

[Cougar]

As DaveT hinted, are you sure the firing order is correct. 1-3-4-2, I think and the rotor goes CCW.

[misledxcracker]

Firing order is 1-3-4-2 CCW. Maybe the rotor is pointing at the wrong one, or would it matter?

[86BRATMAN]

It could be slightly off. Maybe too advanced, or retarded. Causing missfiring low down, but still running decent up in the rpm range.

[misledxcracker]

It's supposed to line up with the #1 plug wire when the flywheel is showing those three lines, right? Like when you line up the cams?

 

Or is it supposed to line up with #1 when the flywheel is set at 0 degrees? Right now, lined up with 0, it points at #2 wire

[Tom63050]

I dont have any flanges behind the cat... no flanges at all. Either the whole exhaust comes off complete, or it wont drop. I'd have to unbolt the Y pipe and carefully drop the whole thing

 

Yeah, that's what I was talking about--the exhaust flanges where they attach to the motor. Plus that other bolt, then the exhaust is only held up by the rubber donuts farther back, which is fine.

 

I also don't have any flanges behind the cat. I cut the pipe there in order to inspect the cat, then reconnected the pipe with a short connector piece and two u-bolts. But I didn't need to take the pipe apart to do the clutch.

[Cougar]

It's supposed to line up with the #1 plug wire when the flywheel is showing those three lines, right? Like when you line up the cams?

 

Or is it supposed to line up with #1 when the flywheel is set at 0 degrees? Right now, lined up with 0, it points at #2 wire

 

This doesn't sound correct to me. Are you sure you are on the compression stroke of #1 and not 180 degrees out? If the stroke is correct then the rotor should be close to #1 wire position. So either the disty is way out of alignment or all the wires need to move back one position in the cap.

[misledxcracker]

I sorted out the plug wires, and noticed the coil red/black wires are kinda corroded.

 

So I cleaned them some, and it seems to be a bit smoother, but it's still misfiring a little bit. Cold or warm it misfires. The shaking went down a little bit, but it's still there. Spark looks a tad fatter after cleaning the coil contacts and wire connectors.

 

Hm, maybe I should just assume since it's 21 years old, it's going to shake and there's nothing i can do about it. :-\

[86BRATMAN]

At 0 i believe it should be pointing at #1.

[Gloyale]

It's supposed to line up with the #1 plug wire when the flywheel is showing those three lines, right? Like when you line up the cams?

 

Or is it supposed to line up with #1 when the flywheel is set at 0 degrees? Right now, lined up with 0, it points at #2 wire

 

 

That is a likely problem. The 3 little lines are only for belt alingment. When the Flywheel is at 0 TDC, the rotor should be somewhere near #1. That's the starting point, then you time it with a light so #1 fires at 20 degrees.

[Gloyale]

I dont have any flanges behind the cat... no flanges at all. Either the whole exhaust comes off complete, or it wont drop. I'd have to unbolt the Y pipe and carefully drop the whole thing

 

 

It can be unbolted from the engine and the one bolt at the back of the trans, then slip it off the rubber hanger near the rear diff. Now it should hang down and swing to the side, out of the way enought to remove the trans. We didn't have to unbolt any of the sections of Toms to drop it down and slide it to the side(IIRC his is all welded up too).

[misledxcracker]

It points at the #1 wire, when the flywheel's at 20 degrees. So, is it right, or completely wrong? I tried swapping the wires so #1 could be first, and the car wouldnt run. Wont run any other way, actually.

[86BRATMAN]

It should be dead on zero if memory serves, and timing adjustments made at the disty itself. And by the advance system in it.

[misledxcracker]

At 20 degrees on the flywheel (or flexplate i guess) the rotor points towards #1 (towards the MC) but at 0, it sits the complete opposite way towards #2.

 

 

I've driven the car like this since I've had it, wouldnt it be pretty thrashed if it were THAT much off?

[86BRATMAN]

The car should be firing at 20 degrees without the green connectors plugged, I believe. And 8 with them plugged. The rotor button should point at cyl #1 wire at tdc.

 

I goofed one by a couple teeth on an ea81, it would run like a dog at idle and not make any power till about 3k.

[misledxcracker]

I've timed it before... perfect 20 degrees...

 

And at TDC it points at number 2