Okay, I need some help on this next step. Completely Stock LB9 305 TPI.

Engine started running rough about two weeks ago shortly after a "seafoam" type cleaning (gas tank and brake booster hose injection and soak).

Shortly thereafter, some mild backfire popping at idle and missing while driving and just not smooth. Surging power. If I had to describe the symptoms simply I would say it seems to be missing/misfiring.

Here's what I have changed in the past five months (OEM/Stock parts):

Coil
Cap
Rotor
Module
Pickup
Wires
Plugs (twice- once after seafoam cleaning)
Fuel Injectors (Bosch D3 - after seafoam cleaning)
Fuel Filter (after seafoam cleaning)
MAF
IAC
O2...
All other Sensors EXCEPT TPS (which reads ok last time I checked)
Plenum, runner, and TB gaskets
Air Filters
PCV

Cleaned TB throughly
Verified Fuel Tank Vent System working

Checked Settings:
Timing 10 deg BTDC
Fuel Pressure 35 psi, no leaks at regulator
Vacuum 25 inches at idle
Compression in No.2 180 psi

Cleaned all encountered electrical connections and checked grounds

What I am planning to do:

Valve Stem Seals and Valve Springs (No.2 plug was oil fouled twice)


I am going to hookup my diagnostic tool and look at all the values but I am getting no CELs.

I read somewhere to make sure that the ECM's input RPMs matches the actual on the tach.

I am running out of things to change! The car was running pretty well (healthy) since I got it in February but the idle thing never settled down. I have not been able to achieve a consistent 650 RPM idle. It floats and changes every few minutes seemingly. And now it's "surging" is the best I can describe it.

I suppose my ECM could be suspect now. I may have a broken valve spring (I will find out soon).

 

Base timing for TPI is 6 degrees. Do you have a tune setup for 10?

Have you done a full compression test on all cylinders?

Check to see if there are any voltage fluctuations in what's being reported by the ECM.

GD

 

agree with the above 6 degrees and also 700rpm in gear

Also that fuel pressure looks between 6-12psi lower than stock standard.

 

Thanks.

I do not have a tune for 10 degrees but was reading that it's OK to advance timing from the base 6 BTDC, to 10 BTDC without any bad effects. I should probably put it back though until I get this sorted out.

I have not done a full compression test on all cylinders. The car was running healthy just a few weeks ago so I am thinking there isn't anything hugely wrong.

I will check the voltage at the ECU.

I will recheck the fuel pressure.

 

Well if the rough running started after the "seafoam" treatment then the fuel system is suspect - not ignition. Pull codes? Run a real time data capture/scan? Learn to use the ECM diagnostics or take it to the dealership for a diagnosis before you spend anymore money on parts or change the ignition settings.

 

When you check fuel pressure you need to disconnect the vacuum line. An idling engine will produce about 23 inHg which is ~11psi. If you add the 11 psi to the 35 psi reading you took... You get 46 psi which is close enough to the correct regulated pressure (43.5 psi) that we can surmise innacurate gauges and accumulated mathematical errors would yield that difference.

Given that, I doubt you have a fuel pressure issue.

Being you changed the injectors and fuel filter after the seafoam treatment it's at least reasonable to start out assuming these are ok.

It's easy enough to pull the valve covers and check the springs and rockers. And do a compression test. Verify mechanical integrity before doing anything else.

GD

 

Just out of curiosity, did you check the egr valve?

 

I think the seafoam treatment you did is unrelated to this problem. Yes recheck that fuel pressure. I saw the the list of sensors and saw you checked the TPS. I would go ahead and change that. I too chased a "surging" problem also. All the way until I changed that sensor. It was bad but at times it worked so a volt check of the sensor did not show it was bad. I also Seafoamed the crap out of the engine trying to solve the problem. My buddy has a 92, running rich and rough. He had a mechanic chase that one all the way through replacing the ECM. TPS once again the culprit. I think it is worth a shot, you replaced all the other sensors. Make sure you use AC DElco.

 

Agreed. I should just change that thing.

Also, maybe a clue.

When I was rechecking my base timing (engine cold), I noticed that the timing would jump 4 degrees or so and the idle would would hunt up at the same time. This is WITH the EST bypass connector unplugged so that base timing can be set. I have never seen base timing move like that. It would jump and idle would rise. It would drop and idle would lower.

So I dug into my ECM. Connections and connectors all looked good. I opened it up and cleaned and re-seated the chip. Looks like the ECM was replaced at some point. Everything looked solid. I also played with the TPS seemed to react smoothly when pushed slightly at idle. I did try the EST connector when the engine was warm and likely in Closed Loop. It did reduce RPM, and then back up when I replugged it in.

Car runs ok but I can tell something is not right.

 

What's the mileage? Timing chain ever been done? Mine was sloppy with worn plastic cam sprocket teeth at 150k.

GD

 

117,000. This could also explain that metallic rattling near the front of the engine I can't seem to find at idle. Hmmm. Parts are cheap. I suppose I just gotta keep throwing time at this. Which is the correct chain for 1989 LB9?

https://smile.amazon.com/Sealed-Powe...s=timing+chain

 

Timing jumping around and noises up front would definitely warrant timing set investigation. When I did mine I found the best price on a Cloyes double roller timing set from NAPA. Rebranded buy still had Cloyes made in USA on the package also. I have a LOT of wholesale channels at my disposal being a shop owner and they had the best price by quite a margin. I think it was a whole $35... or $27.... or something. Been a while. I got a new chain cover and "trimmed" it so I didn't have to drop the pan.

GD

 

You can pull the distributor cap, turn the crank back and forth and watch the rotor to see if you have a lot of slack in the timing chain.

 

I'll keep an eye out for that Napa double roller. I take it these cars have single roller stock?

As far as the rotor and crank play, how much would be excessive?

I am REALLY hoping not to go down more rabbit holes BUT this seems promising considering the symptoms all point to the same thing.

Will I likely need to replace the gears also or just the chain?

 

The stock chain is not a roller chain at all. It's a toothed (Morse) chain and the camshaft sprocket has nylon teeth. These are very quiet but can't handle high valve spring pressures. The teeth will strip off them.

GD

 

I am now really thinking this could be it. Worn or broken nylon teeth could really cause a rattle.

Though I did not want to dig in into this motor, I am not ready to begin my big motor build so I need to make this one work for the near future. I suppose I could pick up a healthy long block, but man my budget is waaaay over to date.

So, what parts would you recommend? I probably won't put 10,000 MORE miles on this motor (It's a second car for me).

I am planning on doing valve seals and springs but will keep it stock.

My harmonic damper is missing sections of rubber bead, the front seal leaks, and I have a stubborn lower radiator hose leak at the water pump, so it's not a bad place to go digging to cleanup the existing motor.

What parts would you recommend?

 

Double roller timing set.
Water pump.
Radiator hoses.
Balancer.

And of course, the appropriate gaskets and seals. Solve a host of problems all at once, and since you are already touching every part on the list, no additional work involved.

 

 

If you want to swap out the engine eventually, you could just buy a cheaper replacement chain for it. No need to spend $65 on something you can't feel the difference in.

 

What would be a good quality OEM replacement?

 

Cloyes single chain.

 

I used the Cloyes 9-1100:

https://www.ebay.com/p/SBC-CHEVY-CLO...d=350578897544

GD

 

Sounds like Cloyes for sure. Any particular trouble using a double? Seems more stout for only a little more $.

 

You should check your distributor. The pick up coil, or the ignition control module might be faulty. Also have you checked the ignition coil?

 

I took a look in there it all looked fine. I did not check anything beyond that. They are all AC Delco units and no more than a few months old.

The symptoms of the idle metallic rattle noise, the base timing jumping four degrees inexplicably and randomly, and the weirdness of the engine popping is really pointing at a sloppy chain.

 

Looks like Autozone has the loaner tools - harmonic balancer puller and installer but I didn't find the crank sprocket tool. What can I use for this if I can't locate an OEM style puller? Maybe just a jaw puller?

Cloyes 9-1145 is specd as the dual chain rollercam equivalent for the 305 TPI (F)

 

Most two or three jaw pullers should reach it. I saw the pan gasket in your list. Are you pulling off the pan, that's a pita in the car.

 

I'm just going to drop it enough to get the timing cover off. I'll try to slip a new gasket in there.

Is this a "do it from the top job?" I don't have a lift. I could go and rent one for a day and work there but I got a labor quote for $680 (8.5 hours) to do the job. That's more than I want to pay.

But it looks like there is plenty of room to do it from above.

 

It is done from above, not below.

You're not going to slip a gasket in there without cutting it. I have heard people have success doing it that way and glueing the ends together. But to get the gasket in there in one piece you'll have to do more than drop the front down.

That's why you got a high labor quote. Because to do it right the pan has to come down.

GD

 

You can pry off the timing cover and snip off two inside corners of the timing cover by the pan gasket and it will go on easy without taking the oil pan loose.

 

That's what I did. The seal got torn a little and I have a slight pan leak on the front. Doesn't bother me. The 305 is coming out eventually and it doesn't leak enough to affect my oil level.

GD

 

MMM. Awesome tip. I will do that. Thank you. I need motivation at this point.

Order placed:

 

Ah - yes I don't have the roller cam in my 86 - that's the difference in part numbers. The roller cam has a different cam sprocket.

I didn't use the timing cover gasket. Especially if you are doing the snip the cover method. Just use RTV. You can't easily use the timing cover gasket due to how the cover has to be slipped in with the pan already in place..... You don't need that set - the water pump will come with gaskets for that and you engine will have a one piece pan gasket already.

I tore the pan gasket getting the old cover off. Thus the leak. It works much better if you have a snipped timing cover *before* you put the pan on, then it can be slipped in and out without damaging the pan gasket....

GD

 

Thanks. I hope its the correct timing gear set. I assumed my 89 TPI has the roller cam.

Pulling the crank sprocket, can I use a standard two or three arm puller?

And installing? Do I use a damper puller/installer?

 

You use a damper/balancer/steering wheel puller set. The one with the three bolt pattern. A jaw puller could potentially damage the rubber or tear it apart.

For install they make balancer install kits also.

You can rent both of them from Autozone. They charge you for the kit and you keep if it you like or return for full refund.

The *sprocket* usually doesn't put up a fight. I don't recall using a puller at all.

GD

 

Thanks. I'll tear into it later tonight!

 

Got it all apart started another thread: https://www.thirdgen.org/forums/tech...ml#post6158316