New Engine. New Problems.

mikedenton49

Registered User
So here's the story. I bought a new engine from AER. (see old posts for why if ya care), IF you have quesitons about that, pm me. I had a reputable shop do the install, i don't have the tools or the time, and after two long weeks, I got my baby back.:D, The next day, a serious miss started and so I had to take it back. The mechanic said the plug on cylinder 6 was fouled out. So okay, Why? Don't know. Okay. So I take off, into the sunset, running well, the next day? Yep serious misfire. Now what? Took it back to the shop. New plugs all around and they are all sooty. but number 6 was fouled out again. So we did a smoke test, vac system checks out tight, compression test, perfect, flow tested the injectors, within 2 cc's of each other per hour. and now I'm outta ideas. Please, one of you SC magic men, chime in on this. I'm outta money, and frustration is setting in. I got a handful of sparkplugs for ole' number 6 and change it everyother day or so. It's getting old. HELP!!!!!!
 
Funny u ask. The need for the new engine was precipitated by a headgasket failure followed by rod bearing failure shortly thereafter. So? new engine. But when the gasket went surely it got the O2's. But it seems that it would have ran badly right after the headgasket change. But it didn't, it was top notch for a lil' while. So i'm not to sure. Hate to throw parts with my fingers crossed. Gets kinda expensive with this car. Has been so far neway.
 
Make sure the injector is actually firing. Do an engine balance test. This test will shut off injectors in turn and will pinpoint a non-firing cylinder.

Is the plug oil fouled or carbon fouled? If it is oil fouled you could have a bad valve seal and/or valve guide allowing that cylinder to suck oil

Any clear pictures of the fouled plug?
 
Fouled out how? Oil or gas? If it's oil might be a valve stem seal on #6 giving you grief... losing seal when running. If it's gas, check electrical like coil pack, plug wire, and even DIS. Best of luck.
 
Good question, didn't think of that. It's carbon fouled, very dry by the way. No oil there. Good thought though. What did you mean by Coil pack, etc? Brand new plugs and wires, not sure on the DIS, other than it seems to work fine right after fresh plugs, I'll work on that picture. It'll be a cell phone shot though. Basically, it looks just like carbon on a rather new looking spark plug. Unremarkable really.
 
Balance test? Like a drop test? He said he checked the compression and all was great. No oil at all. Just running rich. Missing worse tonight, just changed the plug a few hours ago.


Make sure the injector is actually firing. Do an engine balance test. This test will shut off injectors in turn and will pinpoint a non-firing cylinder.

Is the plug oil fouled or carbon fouled? If it is oil fouled you could have a bad valve seal and/or valve guide allowing that cylinder to suck oil

Any clear pictures of the fouled plug?
 
Just noticed that the vac guage is reading about 15. That seems a little low. It usualy reads about 17 to 19 in HG.
 
Im having the same problem after I installed the new engine, bad miss and I spent all day trying to figure it out. I changed the DIS, tryed 3 different coil packs, changed the cam sensor. I havent took the plugs out to check them there all new I didnt gap them if that matter to much.. I running out of idea as well.


Jerry
 
I've had similar dry carbon fouling problems myself that turned out to be O2 sensors both times. Once it was from coolant leaking at the intake manifold and the other was leakage at the headgsket. Once the coolant coats and burns onto the O2 sensor it will quit reading and cause a rich condition as the eec tries to compensate for what appears to be a lean condition. I got O2 sensor lean codes both times on mine. Do you get black smoke out the exhaust? The vacuum at 15 shouldn't cause a plug to foul with carbon. Can you tell if the motor is consuming coolant?
 
Balance test? Like a drop test? He said he checked the compression and all was great. No oil at all. Just running rich. Missing worse tonight, just changed the plug a few hours ago.

The EEC has a specific self-test to determine weak cylinders. You have verified that the injectors are fine but a bad injector driver could cause the injector to run open. A cylinder balance test involves the EEC shutting off each injector individually to determine how much "pull" each cylinder has.

#6 tends to run a little richer than the rest from to lack of airflow due to the configuration of the stock manifold so if all cylinders on that side tend rich, #6 will foul first. The fact that #6 is fouling doesn't always mean there is a specific problem with #6.

Also, what year is the car? This is important. Do you have access to a scanner?
 
The EEC has a specific self-test to determine weak cylinders. You have verified that the injectors are fine but a bad injector driver could cause the injector to run open. A cylinder balance test involves the EEC shutting off each injector individually to determine how much "pull" each cylinder has.

#6 tends to run a little richer than the rest from to lack of airflow due to the configuration of the stock manifold so if all cylinders on that side tend rich, #6 will foul first. The fact that #6 is fouling doesn't always mean there is a specific problem with #6.

Also, what year is the car? This is important. Do you have access to a scanner?

How do I perform this test? The car is a 93' and i don't personally have a scanner, but i can take it to my shop with something for them to look for, as they have all different kinds. And your right, it's not just number 6. THe others are starting to foul up as well and the changing of 6 isn't working sa good as it was the other day. So I think your on to something there. Should I put in new O2 sensors? By the way Dave, I've read a million posts, and have seen all the people you've helped. Thanks. That's all.
 
I've had similar dry carbon fouling problems myself that turned out to be O2 sensors both times. Once it was from coolant leaking at the intake manifold and the other was leakage at the headgsket. Once the coolant coats and burns onto the O2 sensor it will quit reading and cause a rich condition as the eec tries to compensate for what appears to be a lean condition. I got O2 sensor lean codes both times on mine. Do you get black smoke out the exhaust? The vacuum at 15 shouldn't cause a plug to foul with carbon. Can you tell if the motor is consuming coolant?

Well it's not consuming it now. But a catastrophic headgasket failure at high speed coated them right up I'm sure. Man I guess i should just change them. But like always it's just throwing parts. Dave knows the answer, he will tell us.
 
You can either just change the 02 sensors or you can watch them switching on a scanner (if it's a good one) to verify proper operation. Watch for uniform wave generation and a full switch from about .02v to .7v or higher. A good scanner will also tell you how much fuel trim the EEC is commanding. This will tell you what is going on, anything else is guessing at this point.
 
So I put in the new O2's both sides just for overkill. Put in new plugs, so far so good, but I still detect a miss much like it does everytime i change the plugs. In other words, it's about to do the same thing again. any more Ideas would be very welcome here. Anybody?
 
I'd check for a cracked plug. The last couple of times I've looked at an SC with a misfire it was a cracked plug. They're easy to accidentally crack when installing.
 
Make SURE the plug wire is seated all the way down!

So you did the smoke test, Im not familiar with that, Does that pressurize the intake system?
Id recommend pressurizing the intake system up to 10+ PSI, or "normal" max boost, although be careful not to go over 15psi on the gauge or it will bust.:eek:

Use soapy water, and make certain there isnt some broken or cracked vac lines., It may be tiny.

I think you still have a vac leak, even though it is running fine at the time of new plugs, the driving is either fouling it out, then its not hot enough at startup to burn off the built up carbon, then can never recover because it is an intermittent miss? or all time miss?

Ok, did you try a new plug wire? It may be a heat related issue?
 
So I put in the new O2's both sides just for overkill. Put in new plugs, so far so good, but I still detect a miss much like it does everytime i change the plugs. In other words, it's about to do the same thing again. any more Ideas would be very welcome here. Anybody?

You are guessing again. I would not have installed new 02 sensors without first verifying that you had a bad one. Do an engine balance test to determine if you have a weak cylinder. Get a scanner on the car and watch 02 sensor operation.
 
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