Maverick H1L

iTrader: (8)

Bone stock 3.1 LHO now... Running on 2.8 system.

I've got the mystery misfire from h-e-double hockey sticks going on here. From idle all the way through the power band. I've been fighting this thing since I replaced the head gaskets a few months ago (was leaking into cylinder 3 which was down to about 85 PSI compression pressure). I can't tell which cylinder is misfiring. I have hooked a Tech I up to it and gotten no useful information out of it. Using the T1 and doing a cylinder deactivation test has yielded no useful data... All cylinders drop the same amount of RPM when disabled. This thing is driving me bananas. The engine shakes like crazy and I haven't been able to drive it in a month now.

So far I have replaced or swapped:
2 ECMs, one with HNL PROM and the other one has ARPL
2 sets of fuel injectors, p/n 523-5136 (would actually prefer 14084888s) but these were new and free so that's what I've got...
MAF sensor with genuine GM 25007557 sensor and have swapped relays to be sure. Throws random code 34 and will be replacing connector soon. Already tested voltage at MAF. T1 on old MAF showed signal slightly high which is why it was replaced. Haven't tested new sensor yet (just installed an hour ago) with the T1 to check signal.
Ignition coil
Both battery cables (starter issue ongoing... getting pretty tired of that blasted starter bark)

Tested:
Secondary ignition wires all test well within specs... 8mm wires and haven't had a problem with them until after head gasket issue
All fuel injectors electrically test well within specs. The set I have in it now has less than 4 hours run time.
Voltage at ignition coil
Voltage on both banks of fuel injectors
Compression in all cylinders ~180 PSI, within about 10 PSI on all 6
CTS output when cold is within 2 degrees of IAT reading (T1)
Fuel pressure within specs and cleaned fuel filter just to be sure and the FPR IS NOT LEAKING
No vacuum leaks and yes I have checked. Retorqued all bolts on intake, heads, and the nuts on the valve covers.

Ran cleaner twice through fuel injectors (hoping to possibly clean the CSI but to no avail)
Cleaned all engine harness grounds and power sources

ENTIRE IGNITION SYSTEM FROM THE MODULE TO THE COIL TO THE PLUGS IS LESS THAN A YEAR OLD

CANNOT SET HOT IDLE BELOW ABOUT 1000 RPM or will not restart or keep running without stalling

Tech 1 was telling me AFR was mostly lean but I haven't tested it since putting in the second set of injectors or the MAF or the ARPL PROM in the second ECM.

Does anyone have any ideas? I'm seriously about to admit defeat and sell this thing if I can't get it going without spending a bunch more money and by the end of the month! There is a decent 93 V6 Bird going on CL not too far from here that is dirt cheap and looking pretty appealing right now even though it hasn't been started in a long time...

Jeremy85

Easiest ways to find which cylinder isn't firing is either to cold start and keep feeling each header tube or manifold equivalent as it warms up. The cold one is guilty. Second choice is clean all plugs, fire it up, rev it up, shut it off, then read the plugs. The wet one is guilty, unless no fuel rather than no spark, which is why this method is not the best choice.

Maverick H1L

iTrader: (8)

I don't have headers on this engine and the manifold primaries are too ridiculously short to feel any possible temp difference. I don't know if any of the guys at the shop has an IR thermometer or not so I could directly test the temp on the short primaries.

This engine had been misfiring after I put it in the car. I finally got it to stop for the most part (somehow I forgot to plug in the #5 injector and some idiot on the packaging line put an R43T spark plug in a package for an R43TSK), but then the head gasket blew. I don't know what's going on... I only had it down for maybe a day and a half while doing the head gaskets and when I started it up again it started doing this... And I already replaced the #3 spark plug, not that it was fouled in the first place. I replaced the PROM in the ECM due to the TSB for cold hesitation, which I had been experiencing from the time I first put the car back on the road in September.

I have been thinking of trying to use the SOLUS in lab scope mode to test the fuel injector and spark waveforms but I have never done so before and have no idea how... And I'd have to get the car to the shop and spend I don't know how long on it to figure it out.

Something is definitely rotten in Denmark with this thing and it's driving me nuts. I don't think it's localized to one cylinder. It seems more random. It also seems like it's on the 2-4-6 side as I have an exhaust leak at the donut on the other and it would be quite obvious if it was on that side as I could hear it coming out of the donut.

11 out of the 12 fuel injectors were new on the shelf on 2 fuel rails. One set had less than an hour on it when swapped in, the ones on it now. The other injector was the only good one on the 3.1's rail when I got it.

tealman92

Did you replace the distributor? It houses the pick up coil and will cause your exact problem

zs&tas

Yeah check pickup coil for sure, also pull the spark plugs should tell you what is happening, and you can check they are gaped right whilst your there.
also check the pcv system is correct and working. That is an obvious vac leak right there.

Maverick H1L

iTrader: (8)

Spark plugs all gapped to .045 as per specification as I already tried that too. All 6 are identical in color, about half black and half normal, iirc. I'll have to pull them again to be sure. Not soaked in gas or oil. Not burning oil either. Oh, and already did a injector leak test and nobody is dripping. As i said, I've checked everything. At least twice. Going to put a replacement module and pickup on the spare dizzy and hope for the best...

If that don't solve this issue, I'm done. I've spent i don't know how much time and money chasing my tail on this and I can't have it running but not driveable. It's pointless.

tealman92

Your problem is the distributor

Maverick H1L

iTrader: (8)

I'm going to go out shortly and have my 9 month old ICM tested as the shop didn't have the proper adapters for the tester. I've already tested the pickup coil as per the FSM and it's right in the middle of the GM specifications at 843 ohms resistance.

I also ordered a GM ICM and P/U (FROM THE DEALER, not a parts house) which should be here tomorrow. To rebuild the old distributor I have laying around (which really all it needed was the ICM but I have had problems in the past with the connector for the P/U coil to the module so I'm doing both).

But I can just about guarantee the problem isn't going to mysteriously go away with a distributor swap/rebuild. As I said, the misfire seems too random and mostly seems to be on the 2-4-6 side.

Does anybody know if the 1227302 uses a single injector driver for both banks or 2, one for each?

RBob

iTrader: (1)

Two drivers, one for each bank (it is still batch fire!). They use a standard bipolar transistor which isn't as rugged as other ECMs that use a MOSFET for the driver.

Also, I believe that there are two injector fuses, one for each bank. So wiring can also be an issue.

RBob.

Maverick H1L

iTrader: (8)

Yep, rebuilding and installing the spare distributor with new GM parts was... As I said before, a complete and utter waste of 2 hours and $90. Same issue.

Yes, I have power to both injector banks. Not sure how I ended up doing so, but I ended up putting one bank of injectors on the ECM ignition supply (remember, I am running a dash with harness from a 93 and had to basically make my own dash harness).

And it would be soo nice if I could find my LC-2's O2S so I can figure out what the AFR actually is... I have no idea where I put the thing and I'm not going to dump any more money into this thing unless I can get it to stop misfiring and then it needs a pair of tires...

zs&tas

Still could be basic vac leak somewhere.

Maverick H1L

iTrader: (8)

And I'm back...

Still having misfire issue.

I have now replaced all of the replaceable components in the distributor. The mainshaft went in a little over a week ago (magnet was cracked in half). That will be $200 I spent on it now. Cap and rotor have the good brass terminals.

Heck I replaced the entire distributor with a NEW aftermarket. Ran WORSE.

Fuel injectors are a NEW Ford/Bosch set. Pintle cap. Cylinder exhaust temps balanced within 10 degrees and the plugs all look normal so I know I have good AFR. As opposed to before when some plugs were normal and others black. This was after getting a "reman" set from eBay that wasn't even a good full set...

I put spacers in between my plug wires and now I no longer have crosstalk between them.

I went so far as to replace the valve springs on the #2 cylinder (which was showing the worst problems) and reworked the valve settings on all 12 valves.

Can't run it much right now... My voltage regulator in the alternator crapped out again...

Question: It seems like the only thing I haven't checked or replaced is the ignition coil, which would be the second one in a year. It seems to me that the ECM is seeing a steady reference pulse sample from the ignition module. but the tach is way off and it bounces like crazy. If the module is producing a steady RPM signal and the tach is going bonkers, then that would mean the coil, right?

Now, I've had enough of these epoxy-filled pieces of trash. I have 2 of them right now that aren't working right if they're not (and the one that died on me a year ago in traffic is still mounted to the bracket on the engine!). I would like to try an old style oil filled coil. Not MSD, Taylor, Accel (ESPECIALLY Accel), Pertronix, or any of that other Chinese made trash. I read a post on a Chevelle forum where a guy who lives and breathes ignitions mentioned the O'Reilly house brand? And I assume I'm going to have to make a custom wire for the coil-to-cap connection?

Maverick H1L

iTrader: (8)

Well, I went out and bought a BWD stock replacement coil today. Started good, started misfiring real quick.

I ended up doing a frequency output measurement on my module output wire (C terminal) and on the coil tach wire. Looks like 2 more modules cooked. Including the GM I bought from the dealer a couple months ago. That was the first one I tested and then it was the one that came with the replacement distributor. Both signals bouncing. And not just a little bit.

Question: I was just perusing the Delco website. Now, the Delco number of the module I have is a D1943A. But they're also listing a D1984 and D1906? Aren't those for V8s? And are there any modules out there NOT made in China?

Another question: New coil is causing my tachometer to not only bounce, but work BACKWARDS. Idle is being indicated around 1800 RPM bouncing (duh). But when I rev the engine up, the tach goes to ZERO and then comes back up? Why? Only thing I replaced before noticing this was the BWD coil... Other 2 coils don't do this.

RBob

iTrader: (1)

On a hunch, check the alternator. A bad diode or open winding can cause all sorts of strange behavior.

Being careful not to run too long, remove the alternator belt and see if the misfire reoccurs.

RBob.

Maverick H1L

iTrader: (8)

Can't run very long right now anyways. The alternator isn't charging again. I'm looking into buying a upgrade/rebuild kit for it as the regulator seems to be dead and I've wanted a 180 amp anyways. But, from past experience, even after replacing the rectifier bridge I was still getting VAC on the output line. Replaced the bridge twice and still was getting AC so I just decided to live with it. Never had a problem of this magnitude (or kind after I replaced the fuel injectors) on the 87 but did end up replacing the ECM a handful of times.

enswrob

I would get rid of that alternator problem first. Replace it not rebuild it. Low voltage wreaks havoc on electrical. make sure after all this time the battery tests good also.

maroe624

Change your fuel filter.