Timing belt installed, now missing,HELP!

[Steve]

Just got the car back together. Everything went off without a hitch. I rotated the engine at least 10 times while doing the valve adjustment, everytime the lines on the cams matched at TDC. Had to adjust 1 intake and 3 exhaust cams about 1/1000 of an inch. The car started fine, but it tripped a code as I left the O2 sensors unhooked. I pulled the fuse to reset the system and still have this miss. It is consistant from idle to redline. I believe it to be 1 cylinder. Please help!!! Larry you there?
1. If the car were out of time, would it miss or just be sluggish.
2. Could a valve out of adjustment cause a miss?
3. I suspect it is electrical, I noticed that the o2 sensors are interchangable ( they will plug in to each other ) I have reversed the order and it makes no diff.
4. The car is not setting a code.
My car is a 93 with 50k, I/E/H, Bypass pipes,Dinan chip. My main concern is I have dropped the ball on the timing belt job. I will hit it with a timing light to confirm tomorrow. Would it miss with the timing out? I swear I checked the timing 15 times while reassembling!! HELP!!!!!

 

[kpond]

Steve,

Sounds like you believe it is one cylinder as opposed to poor performance from a mis-tuned bank (timing belt incorrect). It seems you were really careful, so let's hope it is a single cylinder and most likely, therefore, unrelated to the actual timing belt.

I suspect it could be a coil pack. My suggestion would be to try to pull one coil pack at a time and try to find the coil that, when disconnected, doesn't effect the miss you have. This will be the bad coil.

Best of luck finding the cause - it sound like it may be something simple.

 

[sjs]

I agree with kpond, and while you have the coils out you should measure their impedance with an Ohm meter. They should read 0.9 - 1.1 ohms. You might also want to pull the plugs. The one that isn't firing should be simple to spot compared to the others. And once fouled, even if you later got spark it may not have wanted to fire properly.

 

[Steve]

If one bank were out of time, how would it behave. My car is running roughly and sounds like a Subaru (boxer motor) when under a load at low RPM's. Could one bank out of time feel or sound like a miss? If I were off 1 tooth on that bank would it cause valve damage, and If so, wouldn't I have felt the valve touching the piston when I hand rotated the crank, or heard it hitting on start up. I marked every tooth on the belt and all 4 cams and the crankshaft. The new belt with the marks matched the cams and the crank, and all appeared to be lined up on TDC. I can't imagine being off. If the belt was correctly marked and matched my marks on the cams I can't see how I could be off 1 tooth. This is driving me crazy!!

 

[Larry Bastanza]

One bank out of time would make the car idle like a big V8, been there, done that. Talk a little more detail about your "Subaru Sound"

I think KP and sjs are making total sense. The first question is, Is it a definate miss. 123m56..123m56...etc. If so,
Slowly go back and retrace your steps on the valve cover reassembly first all coils connected, all spark spugs tight, check for a cracked plug too.

In these situations typically I have found minor things that cause them. If you suspect a valve adjustment issue, you should do a compression test to eliminate that as a possiblility, but only after you have checked all the basic electrical stuff.

Tell us about your timing marks on the COVER side of the cams. Where are they exactly when the crank is at TDC #1

HTH,
LarryB

 

[Steve]

The cam marks where aligned on the #1 ( the line on the intake cam was centered in the square on the exhaust cam. I also looked down a line parallel to the cam bolts on the front side of the cams and this line appeared to be parallel with the cam bolts. Again, I marked the old belt and the new belt and all 5 pulleys. The new belt matched the pulley marks. I then rotated the motor 720 degrees and checked alignment. All appeared well. I have not had the motor over 5500 rpm's but the miss is not extremely noticable at idle unless there is a load on it. It is idleing at about 700-800 rpm's when warm. Also, something peculiar, I noticed the exhaust from the passenger bank is colder than the driver side bank. I assumed I did not have the system totally bled from air in the cooling system. If I run the car at 1000 rpm's and hold the brake and give it gas (in order to load the engine) the miss is very prominant. At higher rpm's it is very obvious to me but not overly obvious to my passenger as he is not familiar with my car. As the Rpm's slow, the miss is more notable by ear. If you start from 1000 rpm's and accelerate, it is down on power and I can hear the miss climb with the revs. By a big V8, I assume you mean v8 with cams lopeing. Mine is idleing quite smoothly. It would take a trained ear to know it wasn't right until you let out on the clutch and load it. Let's assume the worst. If one of the banks is out of time, would it be certain I had valve damage? Larry was you exp. with the NSX and describe in more detail the sound of a big V8. Thanks guys!

 

[DanO]

In my experience, if there were a valve problem, you would hear a miss at idle and it would sound slightly better as the revs went up but it would still sound wrong. My advice is to not run the engine anymore. Do what Larry and others say, which is to recheck the coil packs for electrical connections. If they’re connected and everything looks good, then pull the plugs (inspect the plugs too) and do a compression test. If the compression checks out then try to investigate the coil packs, plugs, EGR, O2… If the compression test does not check out then you might have a timing problem, bent valves or both. I suppose a timing light might help but you can check the timing pretty easily by looking at the marks at #1 TDC on the cam pulleys, an inspection mirror is helpful. Look at SM pg 6-26, using an inspection mirror you should be able to look through the teeth of the cam pulleys to see the marks on pulleys are aligned with the marks on the head. The rear bank takes some time to get the mirror adjusted just right. There are also timing marks on the back of the pulleys.

Good luck!

DanO

 

[sjs]

What DanO said. If you were off only one tooth in either direction I don't think the valves are at risk. The exhaust being cooler on one side doesn't really point to a coolant bleed issue but could be a clue that one cylinder on that bank is not firing, but the engine would be pretty rough if that were true and you should also smell the difference with the same bank being rich with unburnt fuel. If it really is a misfire and gets worse as load increases then I'd focus on the coils and plugs.

 

[Larry Bastanza]

Hi Steve,

Just a quick word of advice. GO SLOW. From what I have read so far you have been very careful and a bent valve would be a low probability at this time. I have been exactly where you are now, with an engine(mine)a few years ago, that was not quite running right and I know all these things just race through your mind. Just go step by step and you will figure it out. Just a short lesson at the school of hard knocks. I find this is where we all learn the most. The beer will taste great later

HTH,
LarryB

 

[DanO]

Just checking: you did step 5-7 on page 6-22? Rotate crankshaft 9 teeth, then loosen the timing belt adjusting bolt and retighten? Just checking to make sure you don't have a loose belt.

.02

DanO