Jinxed myself - misfires 150 miles after HEI mod

[neumann]

I freakin' jinxed myself. I waited 3 or 4 days and 125 miles before declaring victory in my long saga of trying to figure out the wiring on the 94 disty while doing the HEI and external coil mod as described in this thread:

http://www.mx-3.com/phpBB3/viewtopic.php?f=15&t=67376" onclick="window.open(this.href);return false;

No sooner than I think its done, it starts misfiring yesterday. Now I am not exactly surprised, but I do want to track it down. I will be checking all my connections this weekend but wanted to ask for advice. Here is what I thought the likely culprit, in rough order:
Loose connection (likely at the HEI)
some kinda duelling ignitor (eg have I properly discconnected the stock? This was a major element of the "WTF is with the differences on the 94 disty?" issue that caused me all my problems)
physical issue causing electrical intermittency (the aftermarket K&N cone air intake may be pushing on the bracket where I mounted the HEI)
Fouled plug(s). Would not surprise me given how shitty the car was running before the mod.
Leak in air intake
bad ground

I hope it is not some timing related issue, which I guess is not a big deal if you have some time, a timing light and a clue. Unfortunately I have none of these. I don't think it is the Crank position sensor, which I replaced myself two years ago. I am not getting code 02 or 03 or whatever it was when it failed before.

When I removed the disty, I marked the location of alignment of the rotor and eveything and put everything back on in the same orientation. It didn't seem like it was too likely this got messed up.

Anyhow, this weekend I plan on working through it, but looking for advice and wisdom.

Thanks

[wytbishop]

Check the back plug wires. I find that I often don't get them really tight on the plugs.

[SuperK]

I am confused. Please elaborate on how it's misfiring, when it misfires, how bad it misfires, and what rev range. If it is worse at certain speeds, RPM's, temperatures, or any condition. Does it gradually misfire more and more until it's undrivable, and miraculously cure itself over time, or is it steady and always do so under certain circumstances.
I apologize if you have already described it, but I read your other post briefly and didn't find the pertaining information.

I don't know how a mistimed k8 sounds, but the ZE sounds like a huge lawnmower when it's a tooth off or so.

[neumann]

I am confused. Please elaborate on how it's misfiring, when it misfires, how bad it misfires, and what rev range. If it is worse at certain speeds, RPM's, temperatures, or any condition. Does it gradually misfire more and more until it's undrivable, and miraculously cure itself over time, or is it steady and always do so under certain circumstances.
I apologize if you have already described it, but I read your other post briefly and didn't find the pertaining information.

I don't know how a mistimed k8 sounds, but the ZE sounds like a huge lawnmower when it's a tooth off or so.

You are absolutely correct. I was extremely vague. Here is some detail.

After final install of the HEI and coil, the car ran fine for 3 days in which I drove about 125 miles about a 50/50 mix of HWY and City. The range of temperatures was about -8 to +8 Celsius (18 to 43 Farenheit). It pulled hard through the RPM range. The only "abnormal" sound is the oddly loud lifter tick but that has always been there and I assumed it is normal.

On the fourth day it began to have issues while the engine was cold. Initially it was just a slight hesitation accelerating in low gears, eg in first from a stop light. It seemed more like symptoms of an air leak. Car still ran fine in higher gears at speed. Then as I was accelerating onto a hwy it misfired when I hit about 3000 RPM and giving it throttle. Under load was worse, either accelerating or downshifting. It would seem to miss randomly and lurch.

It is more of the inconsistent, gradually misfiring "more and more until it's undrivable, and miraculously cure itself over time" than the consistent problem. Once it starts it seems to remain tthat way for the rest of the drive but might be fine later. I would say it is worst in the peak of the torque curve around 3000-4500 RPM. Certainly seems worse when warmed up. Idle appears fine even in the midst of it. eg if I drop it into neutral it seems okay/

I thought it might have been a physical issue with the aftermarket K&N air intake pressing on the place I had mounted the coil and HEI under load. I moved the position of the HEI which seemed the vulnerable thing and thought I had fixed it.

I thought that it might be a plug issue since the car was running overly rich before the HEI mod. On the weekend I replaced the plugs with NGK 5EK or whatever (the standard thingy) gapped to .42 which is about midline of what i see recommended (41-44) for the K8. The old plugs were not looking so good. They all had a significant level of carbon. Most had additional signs of misfiring or nastiness, with heated hardened deposits. I am of limited skill but having seen anything from normal used plugs to plugs from a car with a malfunctioning Air/Fuel Meter to plugs pulled from a cylinder that was consistently misfiring, I am at least able to distinguish "okay" from "not at all right". The electrodes and insulators on all plugs were fine, but they were filthy with both soft carbon and harder dark deposits. They had a little over a year and 5000 miles on them.

After changing plugs oil and relocating the HEI away from being bumped by the airbox, it drove fine on the weekend in very limited use. Then on Monday it did the bit of hesitation in low gear escalating iinto misfires under engine load to the point of - if not undriveability at least a level of let's get this thing off the road and have another look.

The main air intake hose was replaced at the same time as I did the plugs. I don't think it is a leak there. I also cleaned out the PCV and PCV hose if that is what it is called with some Carb cleaner just in case.

I have been fortunate in that I had other options - took my wifes car Friday as I needed to get winter tires, worked from home Monday - I am running out of flexibility now. My other car has pure summer performance tires and would be dangerous to me and others to drive, so I do need to fix this.

I am concerned that there may be interference from the internal coil. That difference of the 1994 wiring and physical layout of that aspect was the hard part about the HEI mod. I have not cut the ground wire in the 6 pin disty connector, but maybe I should? Just nervous about anything like this due to the pin out and wiring weirdness encountered on this 1994 as distinct from the 92-93 and 95-96.

Any help greatly appreciated. Honestly the reason I bought this car, and the reason I keep it i the huge value of this community.

[SuperK]

The tick might be the little timing belt tensioner, if it sounds like a wierd tick from the passenger side of the engine... I don't think that would cause it to misfire though...

My problem was a gradually degrading issue. If the car set for a week, it'd play nice on the weekend. It'd run good saturday, bad sunday and aweful monday.
The car would idle fine, the air/fuel meter in my car would register OK, but under certain loads and speeds and heavy accelleration, the car would hesitate like a mofo and the air/fuel meter would dance and jiggle.

I have a ZE with the HEI mod. I replaced plugs, wires, disty cap (remodded it twice) and rotor, injectors, FPR, fuel filters, and even redid the HEI setup.

None of this helped. I tried troubleshooting the MAF, and it seemed OK.

Turned out my issue was the MAF. I don't know how to tell if they're bad or not, but I replaced that and it's run like a champ. It could or could not be the problem. But worth looking into.

[neumann]

Thanks for the suggestion. I didn't originally think air metering for the whole issue but maybe it is a component previously masked by some of the other issues.

I took off the VAF (this is labled JE-50, right) and it was certainly dirty. Enought to impede physical operation, i don't know. I have taken carb cleaner to it and will try reassembling.

On troubleshooting the VAF, it does have a bit of a rattle as tought a very small piece is loose inside. It does not appear to be something totall broken of and in free fall, but moving it definitely csuese some noise. More like a broken filament without any loose pieces. Is there an innocent explanation for that or is it sign of trouble.

I tried to check the wiring connections based on the instructions on page F2-150 of the 1995 shop manual.
http://www.mx-3.com/manuals/showimg.php ... F2-150.gif

My digital multiimeter display is half broken so combined with my idiocy makes it difficult. I assume that I am just supposed to be checking circuit resistance, if so then:
E2 to Vs - there is a signal and it varies with the cone movement
E2 to Vc - there is a signal which does not appear to vary with cone movement
E2 to THA there is a signal which does not appear to vary with cone movement

does this (the rattle or the E2 to Vc maesurment) indicate a busted VAF

[neumann]

Per suggestion that it might be fuel delivery related I checked what i could see of fuel lines. Look fine if what I am looking at is right (thought I was following lines from the fuel filter to the fuel rail).

I assume the filter is old. I have not changed it in the 3 years I had the car but it does not look original.

I am close to putting bad money after good in, but mainly it is the time and uncertainty that is killing me. I just hate to spend another weekend swapping fuel filters if that does not actually help.

Any more suggestions?

Also if anyone has the wiring of the 6 pin disty connector for the 1994. As previously discussed in my other post (linked in the first of this thread) My problems with the HEI and external coil were realted to different disty and different wiring of the 3 pin connectpor on the 1994

[neumann]

Anyone think this could be a bad headgasket?

eg is this a likely scenario:

The HEI and coil mod actually worked after you all helped me identify the wiring differences on the 94 GS. It drove perfectly fine for three or four days and 150 miles.

Then started to get misfires under load after the car was warmed up. Still idled fine and short trips of two or three miles didn't warm up the engine enough to see problems.

Oil and plugs were changed on Sunday and have maybe 5 miles on them. No evidence of coolant or water in the old oil.

Then on Monday it starts up and immediately idles like s--- and rpms dancing, with a fair amount of not particularly thick white smoke. There also is a fuel smell in the garage.

No visual evidence of coolant in the new oil, but it has not really been revved

[SuperK]

Try revving it. Note if it refuses to rev highly when heavy throttle is applied, or if it tries to die.
Note if it revs easier with light throttle or if the pedal is "fluttered"

also note to see if there is any liquid from the tailpipe. Or place something to let the white smoke condense on and smell it to see if it identifies as smoke.

If an o-ring on the injector has been damaged or is letting fuel by, it will cause white smoke and will smell like fuel, will have bad hesitation, and poor milage. You can get a oring rebuild kit online for like 7 bucks for all the injectors.


They also have a little spark plug test tool at auto stores that lets you measure the intensity of the spark. i.e. how many volts are going to each plug. This also might be useful, if you're getting spark, to test how MUCH spark and if it's enough to each plug.

[shameem]

How hot does your HEI module get - or did it heat up significantly before - just for testing - get another HEI module and connect it to see if your issues go away (if it doesnt you can always return the module). Make sure the connections are secure and there is lot of metal in contact with the HEI heatsink.

[neumann]

Shameem and SuperK Thanks for the tips. Either of those could make sense.

I will try the revving thing. I did this yesterday but wasn't sure what to look for. This was after it started the white smoke issue on Monday. Anecdotally I recall it was not refusing to rev when in neutral in my garage. It did seem to respond better to gentle throttle. Stomping on the throttle it would rev freely, I think I pushed it to about 5500, but hard applied throttle had two effects:
increased misfire
when I released the throttle it backed of to extremely low idle and wanted to stall.

When I was driving it last week and the problems first started, it seemed to respond much better to gentle throttle, at least in terms of misfire. Gentle throttle would coax inconsistent power. Heavy throttle would actually accelerate in a more linear fashion but with massively increased misfire.

Shameem, I have put my hand on the HEI on multiple occasions and it never felt warm, even after a 20 mile drive. It is perhaps not ideally mounted - heat dissipation wise - but it is mounted to a piece of steel bracket about 3/4 of an inch wide and 4 inches long. This in turn is mounted to a piece of galvanized steel that is mounted to the same point as the Coil.

I have not seen any evidence of thermal damage but I think there is a real chance of physical damage to the pins. The initial mount point I had was being push by the aftermarket air intake.

I guess I can try another HEI module. It is only $20 or so.

If it was an injector seal then the cost seems trivial. What about time? How extensive is the labour on that replacement? It is a question of having to do this work on the weekend in an unheated garage that drives that question. Is this the part we are talking about the Valve Stem Seal



or this

[shameem]

If you want to diagnose valve seal/head gasket/rings/timing belt issues - do a compression test and leakdown test....

[wytbishop]

These are injector seals...

[neumann]

I am beginning to think i have offended the gods in some way.

I manage to get home, run out in the near pitch black, warm up the engine, take out the plugs and prepare to do compression test and....

I cant get the plug thingy in. Looks like I need a deep socket of perhaps 3/4 or maybe 11/16. My 5/8 spark plug socket is too small. My 13/16 spark plug socket could probably make do, but it is too big to fiut in the hole. It is about 20 degrees farenheit and dropping making this a lot of fun scrambling through frozen tools to try and find a deep socket. Maybe it is just an issue with the compression tester I have, but the only adapter it has that will work will require a deep socket around 3/4 but small enough to fit.

Anyhow, I did get a chance to test some things suggested by SuperK while warming up the engine. It was rougher than before when cold it did not want to rev past about 2800 RPM no matter how much throttle given. After I let it sit for a few minutes and started it up again it would rev more freely but misfired more on hard accelleration and felt like stalling when lifted off the throttle. Idle was bouncing between abou 700 and 1300 or so on a period a little faster than once a second.

Exhaust does not smell like smoke. It doesn't smell quite like unburned fuel either but what do I know. The oil looks fine. No evidence of water/coolant mixing.

One of the plugs looked a little oil splashed. Cylinder 6. The others seemed fine. Just a whole lot more carbon than I would expect from about 10 miles driving.

Does this suggest anything? I guess when I have light in the morning I will try to find a socket that can suffice and try again. How crucial is the engine being warmed up? Is it just to distrubute an oil film? Basically wondering if I have to replace all the plugs, fire the engine up, run for a few minutes before attempting the compression test.

[Mazda_Powered]

This is the EXACT SAME THING that is happening to my 93 626 V6.

Does your car run then die the first couple of times you start it up too? (cold start?) because mine does, always dies unil the 3rd try where it always stays running.

My car misfires real bad if heavy load is added once the car is at idle too, sounds nasty. I've replaced basically the same as you, asides the HEI modification. Plugs/cap/rotor/wires.

I thought it might be the coolant temp sensor, because i've had them go back before and the car runs like crap. No change there either. I'm contemplating on cleaning out the EGR valve to see if there's any differences...but decided not to once i pulled the vac line off it and no change was had to idle/throttle.

Are you getting any check engine lights either???? I'm getting stupid angry with this car.

p.s. my car runs fine when driving around with low throttle, i'd say around 15-20% throttle. She runs off all 6 cylinders. Also when I park/neutral rev the car, it doesn't misfire past 1,500rpm lol.

JACK.