Sudden undrivably rough idle, stalling and a long story

I didn’t see anything about the MAF sensor, does this engine have one?

Sadly, or happily no. It uses various sensors to do the job a MAF would do. Its an odd little engine in a lot of ways.

Smoked the engine this morning, and as I feared I couldn’t find one major leak. One tip I can give if you make your own smoker, make sure the charcoal is grey and put all the cardboard UNDER it, not above. Then, in a last ditch effort, I blocked off the booster port, and removed the serpentine belt and ran the engine. The rattle and clank seemed less noisy, but it was still VERY present. Dear god, I hope the chain IS bad. I’ve been chasing this dragon for 3 months now.

I’ve spent the afternoon trying to remove the timing chain cover. I just need pull the crank hub, and then the cover.

Here’s another idea.

Not sure if this would apply in your case, but I recently tuned up my Ford 302 with a rebuilt carb. Part of adjusting the mixture screws involves measuring the intake manifold vacuum and rpm. When the mixture was wrong, the manifold vacuum was low, around 12 inch… After fiddling with the mixture screws while watching the manifold vacuum and rpm, re-adjusting the idle speed, and the ignition timing a couple of times, finally after 3 or 4 iterations of adjusting, getting the mixture and idle rpms spot on brought the manifold vacuum to where it was supposed to be, 18-20 inch Hg.

So you may have the cause and effect reversed. An incorrect mixture may be affecting the manifold vacuum reading, making it read low, rather than the other way around.

Its quite possible George, that’s a good thing to look at if this whole section goes AOE. I haven’t abandoned this thread, or the car, or solved the problem leaving a cliff hanger.

I just now today got the crank hub to budge. The end of the crank is deep, and I had to do several trial and error trips to the bolt place to find the right length grade 8 bolt to go inside the crank end and the right length to put on the puller, as the hub is close to the frame rail and the bolts supplied even with my new puller were too long or too short or didnt have enough thread, to do the job. Images are ran together, click each for the full image!

You’re removing the crank pulley in that photo? When I do that job on my Corolla I loosen the bolt that hold the pulley onto the crank; that bolt goes through the center of the pulley & screws into the hollow end of the crank. I just loosen it a couple or three turns, but don’t remove it. Then the pulley center pushes on the head of that bolt. The only trick to this is noticing when the pulley moves off its pressed on position on the crank, b/c if you don’t notice that you’ll be pulling on the pulley’s outside diameter, but directly against the pulley’s center. And nothing good will come from that. Most likely you’d end up w/ a cracked pulley.

I’d guess even the pros here have probably done that at least once!

The crank hub, not the pulley. I dont know, ive never liked using crank threads to push on, id rather use the center mass of the crank itself.

I’ll reluctantly have to use the crank bolt for installing it later, but only because theres no room for an installer tool to fit in there. Regardless, ill pull it off in the morning and at least pull the cover off
as well. I hope i see obvious damage to the guide or a lot of wear on the chain. Im pretty sure the noise in the video above is the chain hitting the timing cover.

Ok, I think I see what you mean. You remove the existing bolt and install a longer one of the same size and thread pitch, but long enough that it hits up against the end of the crank, but short enough so the puller works, the idea to eliminate stress on the internal threads. Makes a lot of sense. Good idea.

Close… the puller bolt is a slightly smaller diameter, so its threads almost touch the crank threads, but instead slip by them, so the only contact the puller bolt has is on its head, (puller pivot) and its bottom, that pushes against the bottom of the crank hole.

Zero stress on the crank threads. You got the concept spot on though! And thanks!

Got the hub off, then the cover, and saw this…

I think I finally caught my dragon :wink:

(fixed images in previous post)

Well that’s no good … lol … yeah, sounds like you are well on your way to a fix. Good for you for sticking with it!! Best of luck.

How far off are the timing marks? How much did the chain jump?

Pretty bad, between the broken guide and the worn out chain, looked about 5 or 6 teeth off. I didnt count exact tooth number, but i can tell you it was about an inch +/- difference. Makes sense as it was so flappy it was grinding the cover.

Looking at it, im flabbergasted it idled as well as it did. Must be all the new parts, haha.

Its been a while!

To make a long story short I had to pull the oil pan after taking the timing cover off. There was a large amount of debris from the guide in the pan. I have limited time to work on the car with my new work schedule, and removing the pan is a chore in of itself. I just got her put back together this morning. No alternator or water pump or power steering pump. If there was valve damage I didn’t want to waste more time reinstalling their functionality for a test that would last a minute tops.

Car idled… better. Throttle response seems improved ten-fold. However the idle is still loping, and I got a P0122 code again. This time without the accessories turning (and despite the exhaust leak at the flex pipe) I can hear clearly after revving a sound that sounds almost exactly what a blow off valve sounds like on a turbo. Now that the car is making more vacuum, maybe there was a preexisting vacuum leak at the same time the chain guide had failed and I can now hear it? The idle is also still a little high.

Havent done a new vac test yet. I’m going to try and block off the booster again, and remove the cable cover to rev the engine from the bay and see if I can tell where the sound is coming from. It sounds like its near the back of the block or the exhaust flex pipe.

See if you can at least temporarily plug that exhaust leak. You want to eliminate that as the cause of the loping before moving on to other ideas. Modern fuel injected engines are designed to be air tight and just can’t be counted on to run well with any exhaust leaks. I had a loping problem on my truck earlier in the year, caused by a fuel system problem. That’s where to focus for loping imo, fuel and exhaust problems. High idle rpm, focus on air leaks into the engine and engine coolant temp too low.

It’s a vacuum leak. Before the new chain and tensioner I had 6-8 pounds of fluctuating vacuum, now it’s up to 13 steady. :confused: That’s something at least. I think I must have had it before all this, then the guide broke, cam timing changed and the vacuum dropped so much at that point the car could hardly run. The TPS might have been bad or chosen that time to go bad. I cant seem to track it down. I can hear a small hiss but the exhaust is so loud downstream I cant pinpoint it that way either. It’s past the 02 sensor and before the cat (no 02 sensor there) so I wouldn’t think that’s the cause. Plus the exhaust leak is new. (removing it for oil pan removal finished it off)

Ive already bypassed the vacuum tank, and the purge valve and solenoid and no change. I’m currently isolating part by part to find it. I’ve done smoke tests, and sprayed starting fluid tons of places, crimped the booster line and even bypassed it. This is quite maddening, lol.

Well, a lot of progress and more detective work. I’ve now bypassed/verified the booster, PCV system, evap system, map sensor, vacuum tank, vacuum manifold, EGR system and injectors.

This motor has several “experimental” designs that GM managed to push through, so not many of its systems are standard. One of them is the EGR recirculation tube and injector valve.

The only place left a vacuum leak could be occurring is in the manifold. The egr tube, egr injector, injector bores, and throttle body are all integrated into the manifold. That said, the only places left for air to be entering are in the EGR tube, lower or upper manifold gaskets, or injector bores. As the throttle body needs no gasket, because again its cast into the manifold, and the injectors have been ruled out, it has to be in one of those last three areas.

Many of the parts for this car and engine in general have been discontinued. One of them, the EGR tube/injector, has 4 different seals that I cant even track down other than the random rare diagram. So I cant repair them, and I cant replace them. So, the most logical course of action is to at least temporarily do a EGR delete, and a manifold gasket change. This will rule out a bad gasket, and the 4 seals on the egr tube, all of which are possible places for air to enter. This will throw a cell, but better that than a vehicle leaking 6-8 pounds of air, and a good chance to win this fight once and for all!

Diagram of EGR tube:

EGR injector shown: