This is going to be long winded and hopefully as descriptive as I can remember. Mod's are listed in my sig.

Right after I got the car, about 3 years ago, the waterpump went. It was my only car at the time so I had still drove it a few times, refilling the radiator with fluid. This in turn lead to the opti getting soaked, but no problems with it during or after the install. Although my dad did the first install something went wrong with the water pump drive seal (he's no slouch, ASE certified for 15 years, changed jobs about 10 years ago, still works on the side). So we did it again and go it right. But even after that I had a slow oil leak somewhere on the timing cover. Again the opti got covered but no problems.

A year after that the car started running very hot, all the way up to the coolant gage redline. My dad said it was a head gasket going out. So he and a friend pulled the intake/heads/etc. He had the heads checked and decked. Although the gasket wasn't fully worn away it was on the verge of being completely worn/erroded. At the same time I installed Pacesetter headers and y-pipe, NGK Iridium plugs, and Taylor wires (planning ahead for the LTCC as they reccomend Taylor wires).

After that it still would get hot. Then one day I could see it was the overflow tank leaking at the edge of the bowl and battery tray. So I grabbed some RTV/Silcone/whatever I had at the time and fixed it up until the new one I ordered came in. No problems.

A year after that I finally installed my LTCC setup. I decided to go this route since I had the occassional 5K rpms miss at the track, and figured the opti was on the way out so why not get rid of the high voltage through it and prolong its life. I got it all installed right and it started right up on the first try. I didn't have any brackets so I just zip tied the coils to the fuel rail. I got it all patched up and drove it a few times no too far or long. I noticed oil was covering the entire timing cover, but not sure where it was coming from. It wasn't a terrible leak, as the oil level only dropped every other month or so, never needed a full quart. No more miss at 5K rpms, yea!

A couple days later I took it to the track to see what kind of MPH I could get out it, my launching needs much practice. I get in line and the car gets fairly warm (200-210) wherever the second fan kicks on. A few seconds later the car starts missing, bad (SES light started blinking). I was too close to the staging lanes that I just went through and putted down the strip, not getting on it. I didn't know what happened, so I let it cool. Then after almost and hour I started it up let it get a little warm and it started missing again. So I let it cool for about 30 mins, then went home. It missed a bunch for a while but once I got up to around highway speeds it seemed to die off.

From then on out it would do the same thing. Once the engine got up to temp it would have a soft stumble/miss around idle but once there was a load it would really miss all through the rpm's. Once I got moving around highway speeds for a few minutes it would dissapear. It was very intermittent. Sometimes on the highway it would start up again under a little more load, but it didn't last long.

I would do occasional peak ins at the wires looking for burns but didn't find anything. I didn't bother much since I was poor, busy with school/work, and had a daily driver.

Fast forward to a few weeks ago. I decided to move the coils down to just behind the air damn (similar to Injuneers setup, Not LTCC but coil on plug nonetheless). I also pulled all the plug wires to see what they looked like. I found one was burnt through the rubber layer but the rest was still together. Obviously I assume this was the cause for the miss. Since the coils were in front of the engine I used a few of the original wires (pre-headers), a few of the Taylors, and some from a new set. I had to do this since I need the longer wires from all the sets. I inspected them real quick and they all looked good. Another one of the Taylor wires had some burn marks so I didn't even mess with it. Once the car got warm, it started all over again with the missing. Frustrated, I gave up.

A week or two later, I figured the car had/has around 170K+ miles and since I have all the cars records it never had the opti replaced. So I figured with that many miles and being covered in water then oil, it was time for a new one. I got a used one from a running engine that had around 20K miles on it. At the same time that I put the new opti on I decided to go ahead put on an electric waterpump. It took me awhile as it was my second major mechanical car undertaking (LTCC was #1). I double checked my grounds, took out the A.I.R. pump, double checked all my vacuum lines I removed (from opti/intake elbow and A.I.R. pump), did the coolant TB bypass, installed new opti and waterpump seals on the timing cover, and put new plugs in (my dad helped with those). The old plugs looked real good, light brown color on the porcelain. The passenger side plugs looked a little bit more black but nothing extreme. I rechecked the plug wires, they look good and reroute them safely away from the headers.

I get it all done and taken care of and sure enough the miss is still there. My dad and I talk about it and he suggests possibly a coil or injector is bad. We take a quick check at the resistance of injectors for #5 and #7 both were 13.5 ohms. I was too pissed and tired to do the rest. So I get a new coil. I log data with my software and find cylinder #7 has a ton of misses and they tend to run consecutively. I do a quick swap of coils and sure enough the miss is still there. Cylinder #2 had the second most misses (less than 10% of #7) so I swap the new one with #2, still missing. Although the timing cover still looks clean, so the new seals much have done the trick.

I'm not sure where to go or what to look for but here is a list of things I've put together to check/do:

Check resistance of all injectors
Check all the LTCC wires/plugs and make sure they are in good on the coils
Check supply voltages from LTCC on each coil while running
Install all brand new wires with some type wire protector/boot covers

And finally, if nothing works, sell the car and spend the money on guns.

I'm open to any suggestions, I have tried my best to describe the life of my car but I can go back further by looking through the reciepts I have from the previous owner.

Thanks guys.

 

Sounds like you've checked the electrical and fuel pretty well.

Were the other injectors around 13 ohms?

If it is consistant, then it could be a mechanical misfire. Run a leak down gauge or compression test to see of #7 is close to the other cylinders. Those plugs can be a pain to get to.

 

After going to all that trouble (shotgunning), you put on a used opti

So if I understand your setup, you are not using the high voltage side of the opti. That is handled by some other ignition system that uses a coil for each cylinder and has a wire to each spark plug. Correct?

Incidentally for future reference that type of system is NOT refered to as "coil on plug". A coil on plug is just that, the coil actually sits on the plug and there is NO plug wire. Back to the problem.

If you remember your firing order 1-8-4-3-6-5-7-2. You notice your problem cylinders are sequential. 7 & 2. Ignition ?????? You wouldn't have the wires from these 2 cylinders reversed would you??????

Perhaps if after you swap injectors from a good cylinder and you still have the problem. You could try running temporarily on the opti's high voltage side to see what that does as far as the miss.

May also want to check compression but I seriously doubt that is a problem since both misfiring cylinders are at opposite ends of the block.

 

At the time when I got it I couldn't afford a new one, plus there were no problems with it before.

Right, you can do a search on LTCC. It's a fairly simple setup.


Ah I didn't know that, thanks for the heads up.


I don't know the ignition by heart, but I was almost positive they were consecutive. No I didn't cross the plug wires. The wires that plug into the coil (tell when to fire) were labeled 1-8. The spark plug wires wouldn't reach to the other banks set of coils. So unless for some reason they were wired wrong originally (by the company) it should be ok, but this could be a possibility I didn't think of.

I plan on first testing all their resistances then possibly doing this, good idea. I will have a hard time with swapping in the old ignition since the old coil/module is not on the car and had to splice their wires with the kit.

I'll leave this as sort of a very last diagnosis, since it doesn't seem as possible.

 

Update to an old thread:

I put in a set of new injectors with no change.

I also took a look at the rockers while running and the rockers on cylinder #7 looked like they weren't traveling as far as the other cylinders. I also put my hands on each of them while running and could feel a difference in the travel. I pulled the pushrods for #7. I looked at them closely and rolled them on a flat surface and they appear very straight. I measured the diameter at varying points on both and the largest variation is 0.0025".

My dad suggested that the cam lobes are worn, which seems very possible. I have yet to check compression but I will try to do that.

Anyone else have some ideas of what may be going on?

 

Ok Fellas, I now Own this very car as He has opted to Sell it and buy guns.

What I have done is this that he didnt, checked fuel pressure. Fuel pressure is ok but it doesnt hold pressure when you turn the key on, it drops almost instantaniously. So I changed the Fuel Filter, Bingo!! Now hold pressure when you turn Key. ( NOT STARTING IT.)

Still this MISS he and I now have is a Hit and miss thing. Seams to be when it gets warm or when you drive it for longer periods of time. And it starts ( For me ) when you stop at a light or stop sign and then have to start again.

I,m thinking Fuel Pump is on the frits. It also starts hard sometimes.

I just have a hard time thinking its a Cam issue since its not a ALL the time problem. What the miss feels like is like someone just took two of the wires and criss crossed them, it stumbels and back fires and idles real ruff. Park it let it cool down for an hour or so and Walla Good as new.

Tell me this doesnt sound like Fuel PUMP.

 

I still think it is the cam because when cold it runs fine because the heads/intake are cooler which keeps incoming intake air cool, but when the engine heats up or sits and idles, it heats up incoming air or brings in hot air from the engine bay. The exhaust valve on #7 has reduced lift, not allowing enough of the exhaust gas out. When the engine warms up the exhaust valve isn't opening enough to allow enough exhaust gas out/intake air in. Remember the exhaust valve also aids in bringing in fresh air (i.e. the purpose of headers). This explains the rich condition on bank 1, which a faulty fuel pump cannot. If you let it get warm and idle long enough, you can hear gas exploding in the exhaust. This means there is a lot of unburned fuel getting pushed out of the cylinder.

The miss codes have been for cylinders 7 and 2. Since cylinder 2 follows 7 in the firing order, the stumble is bad enough for the computer to think that both cylinders are not firing. When you think about engines running at thousands of RPM's (even 16 revolutions a second at idle) one knock sensor can only be so accurate.

To test it out, you need to check the lifts on the exhaust valves. I and others could visually see and physically feel the rocker not achieving the same amount of lift.

Even if the fuel pump is bad, it would effect all cylinders equally especially with injectors that have less 2k miles on them. Also, if the fuel pump has reduced pressure the long/short term fuel trims will adjust accordingly. That's why you have to change the performance table for boosted/higher efficiency heads. Just increasing fuel pressure isn't going to adjust to the increase in airflow.

Also, you may notice that when you start open the throttle the miss starts to clear up. Fuel pressure hasn't changed, but the increased air velocity helps clear out unburned fuel.

 

Sorry, but I have to disagree. I do not think the cam is at fault. Remember, this is a roller cam and not a flat tappet.

Put a fuel gauge on it and take it for a drive and see if the needle bounces around. THAT will tell you if the pump is going.

I still think your problem is ignition. It sounds like a classic LT1 ignition problem. Ohm the rest of the injectors just to be sure. It could be the ICM, since it is heat related.

 

Well you may be right, but when we hooked up a computer to it, one of the high doller ones that lets you change things and turn things off and the sort, it was actually LEAN on bank 7 and a few others. It was also throwing O2 Sensor codes on both sides, I dont remember are there O2 Sensors after cats on Lt1's?? Also when the miss gets real bad the Engine light blinks at you. Also If I give it throttle ( ALOT OF IT ) while its missing it does not clear up.

The one thing I am going to do is get a feul pressure gauge for the inside so I can see pressure when driving. Just to rule out Feul pump. Its just that in all the reciepts for stuff none were for Feul pump that I could find. Hence its got 180 K miles on it.

I dont know. Someone on another forum suggested that the optical sensor on the Opti was bad since you did put a USED one on it.

 

The ICM is gone, it has a LTCC. The opti has been bypassed.

The injectors are practically new.

I also have a scanner that has bi-directional control. There is no bank 7. There is only bank 1 and bank 2. The oxygen sensor codes are probably for the rear O2's, whose only purpose is to look for a difference from the front O2's through the CATS, but since the CATS are gone it sees no change and sets the code. The rear O2's are not connected. There were O2 simulators on them to keep from throwing codes.

You cannot see which cylinders are lean/rich, only banks. You would have to have an 02 sensor for each cylinder to have that info. When checking the spark plugs in the past they have all had the same shade of brown, except for cylinder 7 which was slightly darker.

A fuel pump is not going to create sporadic missing on one cylinder. Especially when it will occasionally clear up

The opti is either working or not working, there is no in between. All it is now is a sensor. There is no voltage being passed through it. It had less then 20k miles on it and ran fine off the car it came off of. The LTCC controls and fires all of the ignition. Something like the optical sensor is either working or not working. If the opti is bad, the car wouldn't run, period.

Get a dial indicator and check the valvetrain movement even before you would think about pulling the cam. Just the driver side, do all 8 rockers and compare lifts.

I have helped as much as I can so I am going to gracefully bow out.

Good luck.

 

The Opti hasn't been bypassed completely... its still using the optical sensor. How about heat soak of the optical module?

How about heat soak of the LTCC box? Have you asked Bob Bailey for input?

 

Did I read you have split Banks with one side lean? I had that once.

It turned out to be a leak in the Intake Manifold on the back side next to the EGR Pipe. The pipe was a bit close to the intake and would heat up the gasket sealant, which created a leak. The reading resulted in split bank values and a misfire.

The EGR Pipe gets very hot so you want to be very careful if you spray around there while checking for an RPM rise.

It was the very back lip of the intake at the lifter valley next to the EGR pipe. It is very tight back there and will be very hot with the engine running.

I pulled the intake and put some copper RTV on the back seal to help resist against the heat. Then, put some exhaust header material around the EGR flexible pipe and clamped them with small ring clamps. So far, it seems to be working after a year.

Plus, you said it got hot once which may have affected the intake manifold seal in the back.

I haven't tried this but it may work... on a cold engine remove the dipstick and put an air compressor nozzle up to the tube. Gently, starting with low pressure, start to put air into the dipstick. You may be able to feel a slight breeze of air behind the manifold which would indicate a leak. Do not hook up 100 psi shop air but press very slowly. This way the engine is cold and your not spraying a liquid near a hot EGR pipe.

 

I dont know, I got all the way home an even let it sit running for a few minutes when I picked my daughter up after work. It got warm like 200, and went right back to 170 or so when we got going. Didnt have any problems all the way home.

I do have a header leak plus there IS and I repeat IS a bit of Rocker Noise on the last rocker on the right side head, and this is when it gets warm. Sometimes you hear it on a cold start but most the time you dont.

I do not belive the LTCC is to blame as he had this problem before the conversion thinking that the LTCC would fix the problem and it didnt.

The Opti could be to blame but got one guy telling me NO WAY and one saying it could be.

I,m lost and really dont want to pull this thing apart put a new stocker cam back and find out it didnt help.