It died on me today in the middle of nowhere. Rough idle as long as I've owned it. Service engine light as long as I've owned it. No one in these parts pays for Tech 2 software anymore, so there are only OBD II diagnostics. I'm second owner. It was Mom's car. Approx 100k on it. New parts, one or two at a time as follows. New BCM 25k ago. fuel pump, fuel pressure regulator valve, MAF, EGR valve, injectors, Bosch coil packs. iridium plugs, coolant temp sensor, thermostat,
( yes, it really was a pita), rebuilt that pos crankcase breather box off the rear head, (hand fitted viton rubber flap, riveted in place) block to lower intake spacer gasket, lower intake gasket, upper intake o ring, another throttle body, (used,) PO 300 has been a constant with this car. Learned to deal with the rough idle. Neutral at a stop, Ac switch on at all times to get the 100 rpm bump that brings, The irony is that this car runs so well at speed. Firm crisp acceleration,Smooth on the open road with plenty of motor to pass with. Then today it just died. Waited a few, it started, 15 miles closer to home, it died again, waited a few, it restarted. Got it home. Compression check. 190-210 across all 6. No busted timing belt. Read the codes. PO 727. Engine speed sensor. Local GM dealer doesn't' even know what that is. Nearest guess is crankshaft position sensor. U2105. Input from some sensor to ECM communication breakdown. P1780 Transmission selector switch. And the ever-present PO 300. Tomorrow will bring a timing inspection, maybe the belt is soft, frayed, skipped a tooth. IDK. I am fairly certain it's the OE belt. So it's really overdue. Input is appreciated.

 

Be patient and hopefully Andy will be along to help you out. He's the resident L series guru. I don't know diddly squat about anything anymore.

 

I am out of town this week. I will look at this Saturday when I return home.

 

Thanks for the reply. Update... got to the timing belt. Wow. It's been replaced. No name, not an AC Delco, Dayco or any other name brand. No yellow alignment marks on the belt. But the belt "looks" fine. Not cut, torn, frayed, no missing teeth. The previous mechanic marked cam gear notches with white. I have a manual. Crankshaft notch is centered. And the cam marks at TDC don't line up. Rear exhaust cam shows retarded by two teeth. Front exhaust cam shows retarded one tooth. It's got to be one of two things. Either the previous wrench didn't keep the alignment right as he put it back together or somehow it's jumped teeth. Kinda hard to believe someone couldn't see what I see. The notches do not line up. Begs the question.... how can two cams get out of sync on their own. Tensioner wore out? Belt stretch from a no name belt? I've done a couple of DOHC chain timed engines. Never a quad cam. Never a belt. So these marks not lining up is puzzling. It looks like it explains why it idled so poorly. I'm a veteran shade tree. Don't know squat about valve timing and how it relates to vacuum. And vacuum was low. I forget how low, I just remember low. So I went after vacuum leaks. All the way down to the lower manifold block spacer. And why no matter what LetsTryThis stuff I threw at it, nothing cured it. I am encouraged tho. At least I found a real issue that isn't that hard to fix. I'm hoping these two pics load. I'll need to learn how to load thumbnails. Thanks for looking. I really do like the car. It's my commuter. I do have a backup car. A 94 Crown Vic LX. Tried and True. But it's showing its age. Don't want to have to replace the Saturn with something that would probably have more miles and more wear on it than this one.

 

I bought a Chinese knockoff tool kit for this engine. Even with the kit it took some concentration to get it right. My car is a 2002 and I bought the wrong kit. There is a serial number split and I still bought the wrong kit. The belts are the same but the aluminum base and the idler pulleys were different. I used my original base and pressed the offset inserts out of the idler pulleys. My car runs great now. It had the original belt that looked terrible.

I just did all the same stuff to a 4 cam Hyundai v6. No tool kit available but the free manuals worked great.
The tool kit was inexpensive and makes it easy to hold everything in time.
They run lousy with the cams out of time.

 

Would this explain the loss of communication code, the engine speed sensor code, and the gear selector code? More questions. Do you think this jumped due to worn tensioner, or cheap belt? Or is it more likely that the previous wrench just didn't put it back together right?

 

While I've never worked on one of those, I would think it's because the previous "mechanic" didn't get it quite right. I'm one of those fools that always starts a car for a minute after replacing timing components to see if it starts and runs smoothly. If not, I shut it down and go back over everything until I'm 100% satisfied with it. I always rotate the engine two full rotations before I ever fire it up. That's just to make sure the timing marks still line up. I guess I should have said that first. I have a feeling that you're going to do the same thing. As far as that explaining those codes, I have no idea. Maybe Andy will be able to tell you. Going back and looking at those photos, I can't be sure that those teeth marked on the cams are the true timing marks. Can you confirm that? I see what looks like a couple of notches on the gears and wonder if THOSE are the marks?

 

P0727 is a transmission code for invalid rpm signal from the ecm to the tcm. It may be a ghost without a crank position sensor code.
U2105 is a transmission code for lost communication with the ecm.
P1780 is a transmission code for a invalid torque reduction signal from the ecm.


Put the timing belt on correctly and see what comes back. You have the same timing pieces that I do. The middle idler and the front idler are offset so you can get everything perfectly aligned.

Where are you? I can help with the cam timing narrative if you purchase a tool kit.

 

Rubehayseed said "Going back and looking at those photos, I can't be sure that those teeth marked on the cams are the true timing marks. Can you confirm that? I see what looks like a couple of notches on the gears and wonder if THOSE are the marks?" Me too!! Maybe a magnifying glass will help on my end. Also was wondering why it looks like two sets of marks on forward set. I am also getting an "engine speed input signal" code. po 727. Our GM dealer doesn't know what an engine speed sensor is for this motor My guess is a crankshaft position sensor. I just bought the tool kit. I live in Eastern NC, a long way from you. I'm going to get both belts. Wondering about idler pulleys. Also wondering about a new tensioner. If it's not raining again tomorrow I'll have it off and will be able to check out side play and bearing noise on the pulleys. My Hanes manual has a long drawn out procedure for using this set of tools. But I'll use all the advice I can get. Will post up when I find out for sure which marks are which. I had to stop working on it and won't be able to get back to it in earnest till Tuesday. The tool kit will be here Sunday. I'll have parts here by then too. I'm going to replace every pulley in there. Thanks in advance.

 

Since you're going to be replacing the belt, I'd suggest you go ahead and replace the tensioner and the idler pulleys. That way you'll KNOW what is new and what isn't. I wish I could help you determine which marks are the correct marks for the cam gears, but I don't own one of those and don't work on anything but my own cars anymore. I'm sure once Andy gets home, he will be of a great help to you. Dude knows his stuff!