Pass side miss,huff,chug

[wcamaddox]

OK I am at my wits end. Tried searching but had no luck in finding an answer so here goes. I have a miss on my passenger side.
96 RMS. Pulled engine & tranny because tranny had bad reverse and engine had a couple small oil leaks. all new gaskets except head gaskets. Oil pump. New plugs(ngk g-power .050) wires(ac delco). replaced wires when engine was out so I wouldnt cross the wires up.

Po3o4 Cyl#4 misfire
No vacuum leaks.
Fuel pressure : 37lb key on, 40lb idle, 48-49lb under acceleration or vac line removed.
idle 600-630 rpm
MAF 1.20 lb/min
MAP 13.3 Hg
coolant 190
Ign Adv -18 - -21
ST FTRM1 2.3%
LT FTRM1 -1.6%
ST FTRM2 -50%
LT FTRM2 -15.6%
O2 S11 .135 - .705v
O2 S12 .010v
O2 S21 .720 - .730v
O2 S22 .155v

I am wondering if this could be caused by my opti? 160,000 miles and never been replaced. O2 sensor bad? Fuel injectors stuck/dirty making it rich?

Any ideas would be greatly appreciated!😀
Bill

 

[paart]

Just a couple of questions and ideas. Have you checked the "bad cylinder" for compression or with a "leakdown" test"? When you had the engine out, did you have the intake off? Doing so would have made visual inspection of the cam condition easier. You can still do that, by measuring the lift at the valves, by removing a valve cover. Compare the bad cylinder with one of the others. If you didn't remove the intake, these engines are known for intake gasket leaks, and that can cause this sort of issue.
This can be checked by spraying "starting ether" along the intake gasket surfaces on an idling engine. If the RPM increases, ether is being draw into the port because of a leaky gasket. (BE CAREFUL with ether-very flammable).

OPTI's are not easy to troubleshoot, but are generally pretty reliable. Pull a plug wire off the bad cylinder, insert a plug, ground the plug body, and observe the spark with the engine idling. Compare the spark with another plug wire under the same conditions. Not a great test, but could be helpful. Anything more will require a "scope". Most OPTI issues can be resolved by replacing the the cap and rotor, but unfortunately that requires OPTI removal.

You can check out the injectors by moving the injector on the bad cylinder to another cylinder, and see if the problem "follows" the injector.

 

[wcamaddox]

Yep. Replaced the intake gasket. lifters/cam all looked good when i turned it over on the stand. I was so distracted by it running rich I forgot that one basic check, compression. Will do that tomorrow as well as get my spark checker out. The reason I believe this to be more O2 sensor, injector, broken manifold is it only does it in closed loop. open loop idles fine, above idle rpm it comes alive, and if I shut it off wait a couple seconds and restart it goes away until the computer realizes the engine is warm...... I will also try to check and make sure I didnt pinch the #4 wire when I put the ac compressor on, I dont think I did but its cheaper to check than to just throw parts at it!
Bill

 

[buickwagon]

I gather from your numbers that you have a scan tool to verify exactly when the system goes into closed loop?

That short term fuel trim 2 reading -- that is in closed loop, I assume? "-50%" means the system is leaning the hell out of that bank for some reason. The long term follows suit. The PCM thinks the system is running too rich.

That could be due to a faulty O2 sensor. The system just looks at the voltage coming back. High voltage = low O2 = rich, so the system compensates by leaning out the mixture. But O2 sensor poisioning and connector corrosion usually lead to low voltage, not high. So I would suspect one or more cylinders just aren't firing, dumping unburned fuel and extra O2 into the exhaust stream.

You might be able to figure out which cylinder is the culprit. With the engine stone cold, start it and immediately monitor the exhaust manifold temperatures at at the head. You can use a laser thermometer or something as simple as a damp rag on each one. The cylinder that is not firing will not heat up the manifold. Obviously, there is a limited time window until the heat from the other cylinders conducts across the entire manifold, but for the first minute or so, the non-firing cylinder(s) will be colder than the others.

From there, you can look at the injector, plug, wires, etc. for that specific cylinder.

 

[wcamaddox]

Yes all those readings are in closed loop. Even the short term fuel trim. I can watch real time on my scan tool and watch the temp creep up and as soon as it hits 180 degrees, starts missing. I am honestly thinking it is my O2 on the bank2 as the voltage on it does not vary like bank1. The .720-.730 is the most it varies period. I remember reading in some manual that some O2 sensors when they fail that they default fail reading rich. Is that my case, I dunno but at 160,000 miles it may have picked this exact moment (after all the other work) to fail just to make me
Anyway, this was getting on my nerves and thought I would see if anyone has had a similar experience........
Bill

 

[buickwagon]

The lack of response could simply mean that the PCM can't compensate sufficiently -- it won't fluctuate unless it can cross between lean and rich. But yes, it could be a failed sensor.

There's an easy way to find out: replace the O2 sensor. If pennies are tight, swap left for right first to confirm the diagnosis. If the problem goes away (or moves to the other side) then the O2 sensor was at fault. (I've also heard of guys testing an O2 sensor with a propane torch and a volt meter, but I've never tried that personally. Google it.)

 

[wcamaddox]

Well upon further testing I lose fuel pressure pretty rapidly. So after watching the pressure drop I pulled a couple plugs and smell raw fuel. Looks like I have a couple bad injectors. Ordering a set of the Bosch from Fuel Injector Connection...... Have heard good things. After I get them in I will let everyone know how/what happens and if indeed thats what it was. At this point I am pretty certain.I don't want to be "that guy" that shows up asks a question than disappears with no clue if it was resolved or not..... I really hate that its pretty dang annoying........

Bill

 

[buickwagon]

you've pretty much covered all the other bases with your rebuild and obviously there's a problem with the injectors, so that's a reasonable next step. Even if the new injectors don't cure the miss while the engine is running, flooding the engine with raw gasoline after shut-down is a Bad Thing (since it washes the oil off the cylinder walls and potentially leads to metal-on-metal contact next time you crank it over).

Are the leaking injectors on the same side as the miss?

I look forward to learning how you make out with this.

 

[SmallWoody]

I have the same kind of problem on my 95 rmw it runs fine for 2-10min and ok when its cold out but when its warm and i drive for 10+min the car starts to bog and have a really hard time accelerating unless i ease into it. and it will hick up when i get on it. i think its bad cats it has 175k and this started happening after i did spark plugs and wires... no one can figure it out

 

[paart]

Does it set any codes?
"Bad" cats usually means "clogged" cats. A way to check for this is to attach a simple vacuum gauge to the intake manifold on a fully "warmed up" engine. At idle, the engine should pull at least 16-17" and usually closer to 20" of vacuum. Anything below 15" is very suspect.
The fact that the problem only occurs once the engine is warm, makes me suspect that the issue is elsewhere. Clogged cats usually show up as lack of power, which gets worse with increasing engine speed, and increased fuel consumption that also gets worse with higher engine speed.

 

[wcamaddox]

Ok. So the injectors came today and I got them installed..... Car runs great and has scads of power..... until it warms up. still p0304 misfire.I am not upset that I bought them actually thankful. The two injectors that were leaky had corrosion that I could visibly see and there was junk in the fuel rail. Cleaned that all up so thats one less worry. So just to be certain I did check compression 150-160 average on all cylinders. Also took the throttle body off cleaned it up well. I had to make a new gasket for the top plate. Also got the multimeter out and checked the TPS. Well it has a bad spot in it. Starts off ok than the reading goes from 570 slowly up jumps bak to 570 than goes back up again(in ohms as it was off the car) . Because it was after 9 the local store was closed so I will take care of that tomorrow. Now I did however run a different plug wire from the opti to the #4 plug and still get the 0304 and it still pulls -50% short term from bank2. plug 2,6,8 are white from being lean. #4 black. I may try unplugging the battery until tomorrow and put a fresh plug in it when I change the TPS. I read somewhere the puter will shut a certain injector down if it gets the 0304 until its reset? who knows wont hurt anything to try it. after this im going to replace the O2 sensor with a new one. Its a bosch but the price was right (free and new).
Would a faulty TPS cause a misfire? Would a Opti thats on its lasts legs cause it? Who knows. Anyone have some spare rope because I am at the end of mine lol
bill

 

[200OZ]

Yes, a bad distributor will cause a missfire, and with 160,000 miles the opti's cap and rotor, that would be what I'd look at first. 160,000 seems to be a magic number for untouched factory optis.

Mike

 

[buickwagon]

TPS would affect all cylinders on both banks. You have one cylinder significantly different from the others, so that's a strong indicator that it's ignition related -- plug, wire, cap or rotor. And you already tried the wire.

There is one other possibility that I can think of. The #4 plug: is it dry satin black, or oily shiny black? A bad oil control ring or excessive big-end clearance could be oil fouling the plug, affecting the O2 readings and will not show up in a compression test. A dry carbon fouling suggests misfiring (not necessarily rich mixture, but a misfire that will act like a rich mixture).

 

[paart]

There really isn’t much to an OPTI. The housing, bearings, the shaft, a timing disk, with an optical pickup and a large, complex cap and rotor. I replaced my cap and rotor at 85K and it looked as if it really needed it. As pointed out above, 160K is a lot and it’s worth consideration if you suspect it.
There are two rows of slots on the rotor. The outer row with 360 slots that tells the ECM the exact position of the engine, and an inner row that provide the “firing” signals for the individual cylinders. One poster here, stated that his disk was bent, which I’d guess is a very unusual situation. I’d assume that it was accidentally damaged, when the distributor was open, keeping in mind that the disk does twist when the rotor is removed. The rotor secures the disk down in place. I guess that it’s possible that a piece of dirt could lodge in one of the inside holes, blocking an individual cylinder from firing.
That leaves the bearings which, I understand are very difficult to replace, because of lack of availability, and the pickup, which seems to be pretty reliable. I’d guess that failure of the pickup would cause a “no start” situation, but with electronic components, anything is possible, if rare.
If you pull the OPTI, replace all the seals. FelPro sells a kit. The OPTI seal installation requires special techniques and probably a special tool , otherwise it will leak oil.
This procedure is well documented on this forum.
BTW you’ll need a set of small Torx tools to do the cap and rotor. Bought mine at Sears.

 

[wcamaddox]

Oh yes I learned all about the ABIT? optispark distributor, and how advanced it was in the late 80's when the concept was derived and brought into a production vehicle from my dad when we had it apart..... He was an engineer at Delco Remy when it was first introduced.... Wealth of information that doesnt help me right now lol. Although He does have a stack of bearings for the opti so I may try rebuilding mine with a nice delco cap and rotor and keep it in a box for in case...... When I had the engine out with the tranny I replaced all the gaskets/seals except head gaskets.... the plug is dry sooty black. And I definitely agree that if one of the holes is dirty, especially one of the leading edges(according to my pop), it would cause a problem. I did try my best when I had it apart to clean it all with rubbing alcohol but who knows I may have not been careful enough or may have gotten a small bit of loctite on the wheel when i put the rotor on, Who knows. All I know is I will as soon as rockauto gets me my new opti here in the next couple days. I am sooooo ready to drive this thing. I miss my Roadie, I am a big guy (6'8" and 350lb) and this car is comfy for the whole fam damily.
the jury is out on whether or not the wife gets to drive it. I keep reminding her that its her fault I am doing all this work on it in the first place.... something about the reverse sunshell in the 4l60 not liking being dropped from reverse to first while its still moving backwards.... I swear I am going to find her a job testing transmissions, 4 trannys in 3 different cars.... oh well.
Thanks everyone for the advice on things so far, its nice talking to people who understand what your talking about. Most times I get a blank stare when I talk about car things to people.....

 

[paart]

I hope your issues are solved with the new OPTI. I looked at RockAuto’s selection and was surprised. There were NOS OPTIs available for awhile, but I was under the impression that the stock was gone. I now see Delphi shows three.
They were/are available from MSD, but the “scuttlebutt” seemed to indicate that they were not the quality of the GMs.
From the listings, it looks like someone is again making them, but I wouldn’t want to guess the country of origin!
The bearings do wear over time. The rebuilt ones listed do not suggest that the bearings are replaced. There was a web video some time ago about replacing the bearings in the distributor, and there also was a post on a forum (Corvette forum-?) about replacing bearings, that I once read. The issue is not so much the technique of bearing replacement, but it's a matter of finding bearings of the correct size. The fellow that posted the video spent a lot of time searching, and couldn’t come up with the correct size. As I recall he adapted another bearing to fit, possibly by machining the housing or sleeving the shaft. I don’t remember, it was so long ago.
I and probably others, would be interested in your thoughts, and certainly your father’s, about your purchase from Rock Auto.

 

[buickwagon]

Before changing the opti, there is one other thing you could try: install a fresh plug with the new wire. It is possible -- if the other wire was truly leaking voltage -- that the bad wire caused the plug to foul and now the fouled plug won't fire the mixture.

But if that doesn't work, then I'd have to agree that the dry soot suggests ignition, and the opti is the only thing left in that chain.

 

[wcamaddox]

Yes sir I tried a brand new plug, Thinking that maybe once it had fouled that even wire wheeling it clean may not even help it. It was worth a shot considering the spark plug was cheap, well cheaper than the opti.

I did get the new opti today. Dad came over and looked it over. We took it apart so I could Loctite the rotor screws and put a little bit of anti-seize on the cap bolts. He looked for a couple of things on it. He said its a definately a Delco-Remy part. Casting numbers for the base and part # on the optical wheel are the same. Mitsubushi optical sensor. He was impressed considering it was made in mexico. Only thing he wasnt impressed with was the casting had a little more flash on it than he cares for but it wasnt in any critical/machined areas.
He believes that my old opti's cap/rotor was just deteriorated past the point of servicabilty. As evident from the rotor crumbling apart when we were looking at it. Oh well. I will order a cap/rotor set and press a new bearing into it and put it in a box for later. Heck been thinking about putting an LT1 in My Regal..... Would love to post that its up and running but that horrible thing called work that prevents me from constantly tinkering in my garage for hours and days on end was calling.......
Will definitely be posting to let yall know how I turn out.
Bill

 

[buickwagon]

As evident from the rotor crumbling apart when we were looking at it.

That's not usually considered a good sign... 😱

 

[paart]

Can you advise which of the RockAuto OPTI's you purchased? They offer six; three are new, three are rebuilt.