Need some advice with an engine with 62K miles on it that ran well until I overheated this past June and found coolant in the oil. Towed it home & tore it down to the block even though I am fairly sure it was an intake gasket leak. Aluminum heads resurfaced, new seals, checked etc. by an excellent shop. Rest of the work done myself which was basically tear down, cleaning, new gaskets, rebuilding, and replacing some rotten rubber hoses as required.

When starting it up had various minor issues but after properly timing (tough with it missing), swapping a couple of plug wires at the distributor, and reseating one at a plug, I still have an engine miss. It acts like another plug disconnected but that is not the problem.

I have used a timing light on each plug wire and the indication is that all are firing similarly. I am checking the HEI distributor ignition coil per my Chilton's manual but cannot make out the ohmmeter connections for the 2nd test. There is a #91032G03 on the figure that I believe is the GM OEM page number? If anyone could let me know which connectors of the 3 the meter needs to be on, I would appreciate it. (I bought a CD of my year OEM manual last night so should figure it out in a week or so if I am incorrect.)

If there are any other suggestions as to where I should troubleshoot I would appreciate it. Four + months of not being able to drive it, and being so close is frustrating.

Do most of my own basic work but the last time I fooled this deep in an engine was as a senior in college (83') when I pulled an engine out of a 72 MG had it bored and replaced, then couldn't get it to run. (Distributor was 180 deg out.) Worked all night while the movers loaded our furniture for our move to my new job... but that is another story.

Appreciate any help.

 

Have you tried running the engine in the dark and looking at spark plug wires then?

Good luck. Let us know when you figure it out.

Mike

 

Good point, intend to but I believe my plug wires are okay since they were before I started working on it. Can never tell though.
Thx

 

Vacuum leak?

 

Don't think so as I have checked all vacuum lines.

It may be in the distributor as I had a broken plastic cover on the connector assembly that goes to the ignition module and pickup coil. Superglued it but it cracked again with all the distributor on and off. (I also had it off a tooth or so.) Hope all that it is is a connector but it might have some electronics in it. Will find out after I do these other checks.

Mark

 

check your valves for one that 'tightened' it self up .

 

injectors?

 

Good place to look..

 

First off, you need to find the cylinder that's not firing. You have 2 options.
1. use an insulated pair of ignition wire pliers and pull one wire at a time off the distributor.
2. pull the plugs and "read" them. A plug that's not firing will be abundantly clear.
A.Once you find the plug that's not firing, change the plug to another cylinder. check to see if the situation has changed.
B. swap plug wires on non firing cylinder with one from a known good cylinder. and recheck the original problem cylinder.
C. Recheck firing order.
D. remove cap and check for cracks, carbon tracking, bad or shorted rotor, loose pins where the module and tach and battery hook up.
E. Remove rotor, and inspect the underside and the piece that it screws to.
F. unplug the tach filter. see if it runs better.

 

You can listen to the injectors with a mechanics stethoscope. If one isn't clicking, check the connector.

 

I'm with coupeguy2001 on this one. You may eventually find and fix a problem with a broad brush approach but isolating the miss to a specific cylinder will narrow the problem.

 

Appreciate all the info. Agree that narrowing it down to the specific cylinder is what needs to be done. Gonna hit it this weekend and I'll post what I figure out.

 

With the engine running, I would pull one spark wire at a time off the dist cap. You should hear the engine drop a few hundred rpm's if that cylinder is healthy. If you pull a wire and nothing changes, You have found a dead cylinder. This is a power balance test. Make sure you have WELL insulated pliers when doing it. I actually have plastic pliers I do it with. But you will easily find the cylinder that is weak.

 

You can get the same effect by pulling the injector connector. It's easier then pulling the plug boot while the engine is running.

My gorilla armed brother in law bent the electrode on an E3 plug during a tuneup. Engine ran like crap. Pulled injector plugs until we found which cylinder then made sure the injector was firing my using a stethoscope on the injector then pulled the plug and replaced it. I have pictures of the plug

 

If you want to go farther if the preceding didn't fix your problem, it's a pain, but a compression check will isolate a bad valve or one that is too tight and slightly hanging open.....

You did readjust the valves didn't you?

 

Well its been a couple of months and I can't spend the time I would like to on my car but here is where I am at. Initially when re-building I had the cylinders id'd wrong in my head (1234 vs. 1357, etc.) when I set the valves. Really hate to admit that but anyway I did reset them correctly (I thought) before finishing the rebuild. Then came the start-up and my problems with an engine miss described earlier in this thread.

Neighbor (knows his way around engines) who has been following/assisting me in this endeavor first heard the miss and thought it was an exhaust valve too tight. Said I should reset valves as others in this thread indicate (though he said I should do them hot). I re-adjusted the valves two weeks ago cold and now the miss seems to be an intake as it sounds like it is mis-firing through the intake.

I am looking for some advice on setting the valves as apparently it is not as straightforward as I thought.

Here is how I did it (following both my Chilton's & instructions from 87 shop manual on CD):

First removed dist cap so I could easier see where I was at; Engine cold, set engine @ 0 deg TDC with dist sitting on #1 and set Exh 1,3,4,8 & Intake 1,2,5,7. Bumped engine around one rev to #6 on dist with timing mark @ 0 deg TDC and adjusted Exh 2,5,6,7 & Intake 3,4,6,8.

Adjustment procedure, I backed off on the rocker arm nut until I could rotate the push rod slightly then tightened up to no movement then an additional ~7/8 of a turn then went to the next (Chiltons said 1 full turn when I previously adj). I did not use a torque wrench as I thought this would be adequate. In my shop manual however it indicates tightening from 55-125 in lbs.

Note the 87 C4 has hydraulic roller lifters (first year with them from what I understand).

Questions: Should I adjust the valves hot or while running like I have read elsewhere concernig Chevy engines? (Don't really want the mess as I have cleaned up the top of my engine quite a bit during this re-build.)

Should I re-adjust one more time static and cold, using a torque wrench maybe to the lowest Tq setting of 55? (I did utilize the torque wrench on all other bolt torques when rebuilding.)

Appreciate any/all advice, enjoy the forum, don't post much but get plenty of good info here.

 

Has the problem cylinder been isolated yet? otherwise a lot of instead of narrowing down the problem. If the valvetrain was assembled out of time maybe it's a mechanical problem, bent pushrod etc.

 

Good point, haven't done that. I guess a compression check? If so what should I see on the cylinder that is giving me problems?

 

I kinda had the same issue after my rebuild it end up as a bad Air Control Valve it's under the TSP on the TB it's a 4 prong plug it cost $39.00 at Napa.

My post is called Dog chasing it tail.

 

Thanks I'll check it out also. Want to confirm which cylinder if it is first. Too cold tonight.