knightinblackar

Hey guys,

I still have a problem with misfiring. I have replaced the following with new/remanufactured

Injectors
Plugs
Leads
Cap
Rotor arm
Coil pack
Fuel pump
fuel filter
Fuel feed line
Fuel return line
Fuel tank
All vacuum pipes & lines
Pacesetter headers
K&N filter with custom ducting which includes stock MAF

I have removed the following

EGR complete system
Air/smog pump and all associated piping
Carbon canister and all associated pipes wiring
Cat (replaced with straight through)

The following are original NOT REPLACED parts

Fuel pressure regulator
Injectors harness
O2 sensor
MAF
Coolant temp sensor

Currently NOT running a MAT/MAP/IAT or whatever they're called in these cars. I binned it by accident so a new one is on the way.

I retimed it to 10BTDC (OEM) yesterday as it was about 5 degrees out and since then it's been misfiring like crazy. And yes I did it at operating temperature so the lack of IAT sensor readings wouldn't affect it.

Anyone got any idea why I have a random misfire? It's driving me absolutely mental.

cosmick

Dunno what you're running, but my 94 3.4L Camaro has a misfire problem I haven't been able to help in the last 18ish months, and the online advice says it must be either a bad ignition control module, or a fuel pressure problem. Only those can't be it, because a wot pull through first and second one after a cold start results in no misfire. It's not until after it warms up that the random misfire gets going. But just when the demands on both the fuel system and ignition system are greatest, top of second gear, full throttle, cold air and cold engine, neither is lacking. Same thing summer and winter.
No point trying any 3500 heads, nor a turbo, until it is solved. But being a V6, and having an LSx V8 for it, the V6 isn't worth investing a dollar in. It isn't my only car.
So if you're playing with a 3.4 swap, or a DIS swap, don't try to fix it. Just find a different engine you like better, even if it isn't a V8.

Six_Shooter

iTrader: (2)

First thing to do in diagnosis:

Repair or replace KNOWN bad or missing parts, then move on. Without having the proper sensors and actuators in place you may not ever fix your problem.

With no IAT/MAT the default value is really hot, that usually retards timing...

So fix what is known wrong then move on.

Six_Shooter

iTrader: (2)

Terrible advice.

Just because you can't find the problem, nor want to believe that the problem could be the ICM, coils or FPR, you'll never find the problem.

There's some very different things that happen when an engine is cold to when it's warm, both in the tune and mechanically speaking.

Also some of us don't want to swap to a different engine, which is like burning down the house just to get rid of a few mice...

Some of us don't have the time or inclination, knowledge, time, resources to do a swap.

Please give helpful advice in the future.

Gumby

run the sucker in the dark with the hood up, look for spark leak. juice will take the path of least resistance to ground. Have had it jump right out of the side of the coil rather then fire the plug.

knightinblackar

Did what you said and not even a glimmer, I sign of arcing anywhere on the block in the pitch black!!

Right just did a code read.

23 - IAT as expected as it isn't there and
42 - EST circuit grounded or fault at direct injection system or fault at fuel cutoff relay.

So someone please translate that?!!

fasteddi

iTrader: (2)

Imo this is just terrible advice. Really.. just my 2 cents. If you did a 3.4l swap hybrid swap or dis swap and it's messed it, it's because you didnt do it right. Period. So many of us have done hybrid swaps and 3.4l swaps had much sucess. Myself included. My hybrid and dis swap was easier to do then I ever expected.

I'm sure you can find the problem op. Just start ftomorrow square one. First make sure you replace the iat. And another sensor that is currently broken or damaged. Having any unplugged with throw off your timing and other things because it will read way out of value.

Check your grounds on the head. There is about 3 or 4 total wires. They will bolt to the head.

So fix those items you have that are broken. Reset the timing again being sure to disconnect the est. be at a warm idle. Then reset ecm and hook it all back up.

Start there then move forward.

knightinblackar

Thanks, will do!

Gfunkill

I think Gumby may be onto something.
In my situation, my car has ran great since the 3.4 swap until lately, when I get a random miss or something between 3500-5000rpm. Hadn't thought about troubleshooting because honestly, I have a work truck, and don't use the car that much now.
So, fast forward to last weekend (or rewind?..whatever) and I was messing around in the bay with the engine running. I touched the wires on my dizzy and received a nice little shock. At this point, I'm pretty convinced that I need to;
1. Check my wires in the dark.
2. If they're the culprit, fix it. If not, check codes for anything other than EGR, since I always have that one (there is no EGR anymore)


But, what Fasteddi and Sixshooter said are true, if you have faulty sensors, it will do many, strange things to the engine. Just ask me how well these things run with a trashed o2 AND an MAF not functioning. (hint:not great)

Also, also,
With that code 42, unplug your battery to reset the codes, then check codes again. If you were messing with the timing and had the EST unplugged, you'll get that one. If you reset it and still get that code, something is wrong there, and that could cause issue.

siuol

Hi, I had a Buick that had misfired on occasion. An old timer told me to spray the spark plug wires with silicone spray. It worked for a few months and then I had to spray again. Sometimes, if you don't have the best wires, one will arc to ground at times causing a misfire. Spray a light mist of water on your wires at night and start the car. You might see if it arcing somewhere.

Louis

Gumby

^ yea the next step would be to mist the wires or engine with water, to help you see it, as it will "leak" better. Our Subaru was like that, misted it down and it was a light show of leaks from the wires.

drunkinftl

electronic spark timing grounded..you have a short circuit.. a bad wire some where

fasteddi

iTrader: (2)

Did you ever happend to change the Ignition contol module? Just asking to be sure you put the dielectric down under it if you installed a new one.

knightinblackar

Ok so I found out that resetting timing and not resetting the ECM causes code 42 so I'm gonna reset ECM, install IAC and start again!! I'll keep you posted.

drunkinftl

3 things that jump out.. 1) K&N filter too much oil on this thing can screw up the MAF sensor you can get MAF sensor cleaner from ebay/amazon, I must confess I doused my filter in oil! Unhook the MAF sensor see how it runs 2) When you removed the smog pump did you unhook all the electricals? I removed mine and unhooked the electricals and it ran like a pig! I plugged the electrics back just removed the pump in it runs fine.. 3) the distributor I think I had a code 42 and had to replace mine.. £85 from amazon USa to my door within 5 days.. over a weekend too! Rockauto are good suppliers

knightinblackar

I've never put oil on the K&N! Smog pump only has one wire going to it, the rest is EGR related and yes, everything is disconnected. There's nothing left to connect to, it's all gone. Once I get the ECM reset I'll unhook the MAF, I actually have a spare somewhere that I kept as it was good. I'm going to order some cleaner anyway, just in case! Thanks for the advice.

drunkinftl

On my 88 5.7 ltr formula the smog pump was attached to a valve that has two plugs 4 cables going to it.. I had to reconnect the cables to the valve/solenoid before it ran again properly.. but I think I'd be looking at the distributor ...1985??

knightinblackar

Just one item on this smog pump, and its loooooong gone!! Once I've cured the misfire I can get the chip tuned to get rid of all these extra sensors it now doesn't have.

Yeah it's an '85

drunkinftl

I note you have not commented on the distributor?

knightinblackar

Have I missed something? Distributor? Erm it's working? All the sparks are nice and bright and strong and there's no variation. What else can I test?

W.E.G.

Can I chime in here and ask a sort of stupid question?

What is the manifestation of the "misfire?"

My 2.8 will run just dandy like the grandiose go-cart that the 2.8 is, and then for no obvious reason it will do a thing that maybe you are calling a "misfire."

Basically, its like the engine cuts out for a half-second, and then it refires on its own, causing a whiplash sort of behavior. Harsh enough when it happens that it truly hurts. It bogs (no power), then it comes back on and kicks me in the ***. Sometimes it will do this in fairly rapid succession. While I'm trying to ride one bog, it cuts out, and then cuts back on, and then out, and then on. All this chaos until my muscular reaction gets out of sync with the bog/re-start that's happening, and I end up getting beaten up pretty good.

Is this what you are getting when you experience your "misfire?"

I'm just trying to figure out whether what I'm having is the same thing you're having.

project89

iTrader: (1)

just be happy u dont have to deal with this

knightinblackar

I'll take a video this weekend and show everyone what I'm experiencing then maybe you'll get what I'm talking about. It's basically a consistent Miss in the smooth running of the motor, like a cylinder randomly drops. Then it'll back fire, and drop again. Like I said I'll put all the new stuff I've ordered on this weekend, AGAIN, and take a video.

drunkinftl

My chilton manual says code 42 is electroinic spark timing and code 23 on 2.8 is Mass Air Temperature sensor.. Am I right in thinking you have disconnected this If so I must ask why?
I have attached copy of Chilton diags for code 42 (well I think I have attached them)

This is handy http://www.airtexve.com/sft696/sureyoucan.pdf
http://www.airtexve.com/sure_you_can.html

knightinblackar

Yeah I know what they are and yes the IAT was removed because that whole area including carbon canister was a rotten mess. I hadnt realised I needed it so didn't reconnect it just got a new one which I'm gonna fit at the weekend. The 42 I think is due to me not resetting the ECM when I adjusted the timing. I'll report back after the weekend. Thanks for the info.

knightinblackar

Here you go guys, this is todsy.

Six_Shooter

iTrader: (2)

I don't hear a misfire there.

There was one time, where it sounded like it may have loaded up a bit when you were revving it, but that's pretty normal, especially for stock programming.

knightinblackar

Turn your bass up and you'll definitely hear it. Especially when it's warmed up.

knightinblackar

I sprayed easy start all over it, every solitary connector, pipe, union, joint in the vacuum lines. I evens sprayed the heater control vacuum connections and pipe. Not a glimmer of difference.

I disconnected the MAF cold and it made no difference, I disconnected it warm and the revs picked up.

I disconnecte the TPS warm and the revs picked up until I plugged it back in.

I unplugged the IAC valve warm and nothing changed at all.

Strange thing is that the temp gauge never gets anywhere further than you see in this video. Just over cold. But the fan is cutting in and out and at the sensor the temp is about 89C (using infra red thermometer).

This really is causing me some pain now. I can't drive it 1000 miles like this. I won't have a piston left.

Gfunkill

yeah, if there is no change in the MAF, it's probably bad.
As far as the miss, I can hear something, but I've heard way worse.

knightinblackar

Listen to the last bit of the video where it's missing almost every revolution of the motor, surely it shouldn't be like that?

fasteddi

iTrader: (2)

Do you have a aftermarket cam in that engine? If not, its definitly got something wrong at idle...... Your video from 30-40 sec sure sounds like it has a cam. Not a big one but something is making it run rich to cause that lope effect..... heres what a big cam sounds like. Choppy.

knightinblackar

No it's a stock cam I'm almost at the end of my tether. The only point to mention is that is hasn't been driven anywhere since being rebuilt/re-timed. Does it need to be driven for the ECM to learn? Surely it should idle without this misfire whether it knows how you drive or not?

fasteddi

iTrader: (2)

Yes after setting your timing and hooking everything back up you should do a idle relearn process.

Google "idle relearn thirdgen" and you will find alot of help on the matter. The ecm does learn a bit specifically in the iac control for idle and coming to and from a stop.

knightinblackar

Ah I see. Well that may be the reason I'm having so much trouble with it. Like I said when it's cold ie first start, there's no misfire, but as it warms up, well you've heard.

What else should I be looking for Eddie?

RBob

iTrader: (1)

The MAF cars with the 2.8l engine don't require an idle learn. That is reserved for the '90 - '92 MPFI cars with the 3.1l engine.

In the vid the misfire doesn't really sound like an ignition misfire. When the camera is at the exhaust I get the feeling that there is a bad valve or such.

You now mention that the engine has been rebuilt, this puts it in a different light. Because valve adjustment comes into play, along with the cam timing.

I'd do a compression test first and see what that shows. If there is a valve train error it should show up.

Also, in the 1st post, the list of parts that have been replaced. Was this done before or after the misfiring started?

RBob.

fasteddi

iTrader: (2)

Opps sorry I did not know that there was no idle relearn on pre 1990 thirdgen.

knightinblackar

All the parts were replaced after the initial startup. It had NO misfire before the tear down. The engine wasn't dismantled. The valves were checked but not adjusted. Compression was at 150-160 for all 6 cylinders. It had new inlet gaskets and everything up from there new including water pump. I don't know. Honestly.

rhyspat

I will be keeping an eye on this as I have the same lumpy cam sound when warmed up.

knightinblackar

Could this be caused by a worn cam chain?

fasteddi

iTrader: (2)

Its possible.

rhyspat

Have you tried driving it at all?. Does it drive okay?
The reason I ask is because mine will buck a bit at part throttle but pulls strong if I floor it with no more hesitation.

knightinblackar

Not had it out at all since the retiming was dons. Previously had it into second at about 10 mph!!

Six_Shooter

iTrader: (2)

Sooo...

If the engine wasn't dismantled, what EXACTLY was "rebuilt" then?

I still don't hear a misfire at all in your vid. MAYBE a slight loading up of fuel, like I already mentioned but zero misfire is heard.

As mentioned maybe go through and recheck valves, as a maladjusted valve could cause a slight quiver or uneven running.

knightinblackar

I could've sworn I replied to this. Nevermind.

The motor was stripped down to the valley. So basically I replaced all the gaskets from the inlets up. I checked all the compressions before the motor was removed and everything was fine, once out I checked clearances on the valves and signs of wear and there was nothing noticeable so I didn't tear it down as I know they're a nightmare to reset the lifters on.

It's a misfire. Absolutely no question. Like I said if you play the video through your headphones or speakers with the bass up you'll hear it no problem in the last few minutes when the video is shooting the tailpipes. It's almost a constant miss on one cylinder at that point. Have another listen. Also watch the can on the inlet. When it wobbles there's a miss.

As I said the valves haven't been messed with at all since I first started it. And there was no misfire then.

fasteddi

iTrader: (2)

So did anyone ever take out the cam or the lifters? I would bet something is wrong on the valve train somewhere because for being a stock cam, it sure doesnt sound like it. Its like its loading up or something. How does your exahust smell? Rich or very lean? At idle..

knightinblackar

No the cam and lifters have never been out. It's as if was from the factory, it's only a 70k mile engine.

It's smells rich at idle. Lot of unburned fuel. .

fasteddi

iTrader: (2)

and you cleaned up the MAF and such so you know thats good to go? Im a speed density guy. I hate maf and dont want to know much about them either....lol

knightinblackar

I don't either to be honest. The MAF made no difference when unplugged cold, but once it had warmed up it noticeably altered the engine note, so I assume it's working. I'm gonna test the IAC this weekend and double check my lead order.

RBob

iTrader: (1)

What temperature does the engine coolant sensor for the ECM report once the engine is up to temperature? Will need a scan tool of some sort to get this information.

RBob.