93 BRMW rough running,ignition? cam? valve?

Having had trouble for a while now....can not pinpoint the problem....need advice.
Started about a year ago with slight surge at idle, only when warming up. After warm up it ran perfect. Now it is idling rough regardless of temp, and it also runs rough at all RPM's, wether driving or reving in neutral. Also it seems to have a bit of ignition "ping" under load when driving.
Today I hooked up my timing light to see if the timing was jumping around. It is not....the timing holds steady, and right on TDC (with advance timing wire disconnected). With the advance wires connected, it also holds perfect at idle. What I did notice though, is when I rev it , the advance does not move steady with RPM's but rather jumps to about 12 degrees suddenly when RPM's hits about 1500-2000. Another indication of trouble is that the Tach is flickering slightly at idle(barely 100 RPM's), and as I rev it up, the flickering becomes more steady and frequent.
Of course it could be something else than ignition problems, and I have considered a worn camlobe,lifter or valve. Would this affect the timing in the way it does?
I also should mention that when I bought the car a few years ago, it had a funny noice from the engine. I investigated, feeling it could be a bad valve or associated component. I removed a valvecover and found it was completely missing one lifter rod. Just gone!
Recently I rebuilt the throttlebody, and replaced the intake manifold gasket. I found the rod....and it had a slight bend. Could this indicate an ongoing problem, like a bad lifter?
Advise is greatly appreciated....I love driving this wagon.

From what you are saying, you may have a bent valve (bent rod is the indicator). This would cause the rough running. The easiest way to tell is to buy a compression tester & use it. Then you'll know.

First off,did you replace the bent pushrod?If so did you measure a straight rod to get the correct
length?When you installed the straight pushrod,how did you adjust the valves?The vaccuum
gauge will tell you what you need to know,just read up on how to interpret the gauges readings!

Jimbeau....I will dig into the valve train today. Mainly remove valvecovers, and do a good visual inspection. Read somewhere about cranking/running the engine with valvecovers off (with protection for oilsplatter) and notice how the different valves act in relation to each other.
Flasheroo..... I did replace the missing pushrod (a couple years ago now) with one from NAPA, supposedly for this particular car. Never measured anything, just assumed I would get the correct one. The lifter arm for this missing arm still had the adjustment locknut on thight, and I figured it never lost its original adjustement, so I did not do any adjustment. It did seem to run great afterwards though.....until the idle surge started (maybe about a year later) .
I will take a look at it today, and read up on compression testing/vacuum gauge testing. Only comp tester I have is the simple "push-on"....think I need a screw-in with long hose.
It really does make common sense that a bent/missing pushrod indicates another problem causing it to bend.
Seems you both are telling me to forget ignition timing, distributor, etc. for now, and concentrate on valves?

zamboni920 wrote:

.... I did replace the missing pushrod (a couple years ago now) with one from NAPA, supposedly for this particular car. ... It did seem to run great afterwards though.....until the idle surge started (maybe about a year later) .

Well, this changes things. You didn't tell us that the pushrod was replaced, and that the engine ran fine afterward. So, for the time being, forget the compression issue completely. I don't know anything about the particulars of the TBI system. Hopefully Nick or one of the other wizards will give you some info. The surging you describe sounds like a vacuum leak. Just for sh!ts and giggles, take a box wrench and check the tightness of your intake manifold bolts. They have been known to loosen up, which would make a vacuum leak likely. Take ten minutes, tops, to do. Get your ear down close & friendly with the engine & listen for hissing. If you hear it, locate it. Report back.

Well Jimbeau....too late ....in the middle of checking valvetrain now. Took a bit to get the right side valvecover off, so I am going to finish this before I move on. Figure I will take out one pushrod at a time (swiveling lifter arm aside) and roll it across a piece of ceramic countertop. As I go along and reinstall, I will adjust valves according to Haynes manual. I am such old school, I am only used to the adjustements with a stud/locknut. Did not know these were adjustable, so the one I replaced did never get adjusted by the book....only matched the exposed thread on mounting stud with the other valves. Learning, learning .
Will post the outcome when this is done. If still issues, I will move on to your suggestion.

And.....of course the pushrod was replaced....it was missing altogether when I first checked for the odd noise(shortly after i bought the wagon). No one I talked to, could believe it was just missing. It was not until later, when I removed the throttlebody and intake manifold, I found it.....just laying there under the intake.

Somebody over-revved that engine at some point in the past. [ahem] In "={olden times}=", the trick with hydraulic lifters was to run the rocker nut out (after the engine was fully warmed up) until the valve gear started clicking, then run the nut back down just enough to stop the clicking, and maybe a quarter turn. This kept the lifters almost all-the-way pumped up so they couldn't float the valves if you got stupid.

Done doing the valve stuff. I replaced two rods that had a slight wobble. All the rocker arms was loose (meaning I was able to wiggle them) with valves fully closed. Following the Haynes manual, I adjusted them to Zero lash , then another 3/4 turn. It did seem a little better running, but not at all as it should be. I sprayed bunches of soapy water, and afterwards also carb cleaner around entire intake manifold and all vacuum hoses/connectors. Not any sign of vacuum leak. I am now thinking ignition related. The timing advance does still not adjust until it suddenly jumps ahead 12 degrees at about 1500-2000 RPM's . Maybe another day .

It could be the ignnition module on the distributor.

With what your engine has been through, it could be almost anything.

FSM says to adjust the valves when closed, until the pushrod is just loose. I followed the FSM, and did the adjustments when I replaced my 305 with a used 350. It runs fine, and has more power than the 305.

Fred....you might be correct about the adjustment procedure. That would explain why I could wiggle(slightly) all the rocker arms before my work. I do not have a factory service manual, only Haynes. Also I did some googling....mostly to find an easy way to id intake valves vs. exhaust valves, wich I did.....and I found almost everyone adviced to do Zero lash + 1/2 turn. Either way....I am not about to redo it at this time, think I'll concentrate on ignition stuff first. I will check/test module, but not likely until next weekend.
Incidently, as I was Googling, I found someone who claimed intake and exhaust pushrods were different on GM 350 engines, one beeing shorter than the other....or was it one beeing longer than the other? . Guess one should never believe everything that is written.

I was checking the manuals I have, and the 305 and 350 in the Caprice manual is 0 lash plus 1 plus or minus 1/4. the 93 (LO5) Cadillac 350 is 0 lash plus or minus 1/4. It appears that anything from 0 - 1/4 to 0 + 1 1/4 is probably acceptable. I would not worry about the adjustment. There was no mention of different size pushrods, so I would assume that they are all the same length. Depending on how much oil is in the lifter, the lash could vary as well. Mine were pretty dry, so I adjusted as though I had no oil in the lifter.

GUYS, do TBI's have an equivalent to an IAC stepper motor?
Running TPI, I know old IAC units can hang up and it can be a source of many idle and surging issues. If so, his IAC is nineteen years old and could likely use a good cleaning.
.

Yes it is on the passenger's side of the TBI. It has a large hex on the end of it, and removal is easy. Just put a wrench on the hex, and unscrew it. It probably needs a good cleaning, and you should clean the passages too.

I think I spotted a comment that Zamboni 920 rebuilt the TBI. If so did you clean it Did you follow procedure to reset it after reassembly and "key on"?

Throttle body completely rebuilt.....including those tiny,tiny little screens. Spray pattern is a beautiful cone pattern.....really do not think the throttle body is an issue.
As far as the IAC.....replaced twice, no difference....then replaced a third time back to original OEM. Pintle was wiggled in a bit as per instructions, then installed and engine started and stopped several times. Has been run extensively since, so I think the "re-learn" mode is well past.
Also.....every single sensor and engine control module has been replaced, most twice.
Have not yet touched anything in, or around distributor, except cap, rotor and wires....wich as of right now, looks still as new.

Could be the Ignition Control Module. Sits right under the cap. I had one go bad and it caused a crap running condition/ fuel starvation issue. Might be worth a look.

I had heat soak issues with ignition modules, which was why I moved it out of the distributor, but that usually is hot and won't restart problems.

I assume you've done simple things like replace the fuel filter?

Did you check your ground at the thermostat? I cleaned the stud, threaded hole, and reseated it, as well as cleaning all of the lugs. Remove the stud only when the engine is cold, so that you do not have water seeping everywhere.

You should check all wires for lost insulation. My connector for the igniition module lost about 1 inch of insulation on 2 wires. I used paint on liquid insulation to repair the lost portion.

Lakeeffect....The new module supposedly comes with silicone compound for heat dissipation. Although I might rather use the compund used for heatsinks on Computer PCU's.
Fuel filters was changed, including screen in fuel pump.
Fred.....I did remove the ground nut at thermostat while having valve cover off. It looked clean and good, but did not clean it....maybe I should.
Wires at ignition module and elsewere looks good. I like your idea of using liquid insulation if needed.
I have used Quick Drying Electrical cleaner on all contacts as I have re-connected. have also been applying Di-electric grease on plug wire boots.
Ignition module should be here in a few days, will replace over weekend, and post results.
Meanwhile I thank everyone for good advice .

Using the compund for heat sinks from radio shck usually works well.

Lakeeffect....Reading the specs of your wagon, I had to check out some of your pictures.....Impressive I must say. A bit too much for my abilities, but I like it.....I would be happy just with my '93 running good .

Regarding grounds and ground problems, I have got into the habit of squirting WD-40 on the electrical connections underhood, at least the battery terminals and grounding points on the engine. The 94-6 models are known to have issues with the main ground on the LF cylinder head here in the rust belt. It's easy to do and I never have corrosion on my terminals.

By all means, use the heat sink compound for computers on the Ignition module. You can get it at Radio Shack for about $3-4.

As I dug into the distributor to remove old module, I didn't quite like the look and feel of the distributor itself. Mine has a "dustcap" over the pick-up coil, and I could not tell if all was good underneat. Also I tested the pick-up coil per my Haynes manual, and seemed to get readings indicating it was bad.
Long story short, I ended up getting a complete, new ditributor with coils and module installed. Don't really think it solved the problem, although it seemed to run a tiny bit better. The timing is right on the mark( with spark advance disconnected), and the spark advance (connected) seem to creep up in unison with RPM's. Not the sudden jump like before.
Will keep searching for the root of it.