Hello everyone,

I am a new member to the site, but have been viewing these threads as a visitor for quite some time. I have found A LOT of your advice extremely useful, but I've run into a problem I can't quite put my finger on.

I have a 2000 GMC Jimmy (2dr, 2wd) that is giving me some trouble.

The Start: I had a leaking intake manifold gasket (go figure, right?) so I replaced it. In my haste, I forgot to mark my distributor when I pulled it out. The gasket went in smooth, but when I replaced my distributor I got the dreaded P1345 code. Figuring I was a tooth or so off (since it DID run, just really rough) I pulled it back out, put cylinder one at TDC in the compression stroke, lined up the rotor with the "6" on the disributor, fired it back up and my code disappeared. Thinking I had it fixed, I did a tune up (cap/rotor, wires, plugs) and hit the road. After a hundred miles or so, I noticed my MPG had gone down quite a bit. While I normally got about 230 miles per tank, i was down to roughly 175. I filled it back up thinking I had probably just wasted a lot of gas messing with it in the garage. This tank did the same thing, about 180 miles before fill up needed. I hooked my engine scanner up to it (PLX Kiwi) and watched it as I was at idle, and driving down the road. At Idle, it says my timing is advanced 21-23 degrees (verified this with a timing gun) What could be causing this drastic drop in MPG? A friend told me it might just need a couple of tanks of gas for the computer to relearn where it's supposed to be, but here I am 2 tanks later with no improvement. since I didnt replace any sensors, would a CASE relearn need to be done? I dont have the scanner to do this, and would hate to go pay a mechanic my money for that to not fix anything.

 

When you put #1 @ TDC, did you make sure that the two marks on the balancer were aligned like the tech article shows? EDI Engine Timing

 

Thanks for the reply, Swartlkk.


Yes, I did make sure that both alignment marks were in line. I even second guessed myself and put it at TDC again to check and make sure the rotor lined up.


In a new development, I think I MIGHT have found the culprit. It would appear that my PVC valve has failed AND has a decent sized hole in the line. I plugged my engine scanner in and was running +25 on my fuel trim. With the new PVC valve and hose, im down to +6. Hopefully it will work itself down to 0 in the next couple of days.

To piggy back on this, I have a question. I am still running +22 degrees advanced on my timing. Will the PVC being garbage affect the timing? And, if it does will the computer adjust it back down or do I need a CASE relearn done?

 

Depending on the operating conditions, 22* advanced isn't out of the question. The PCV valve shouldn't affect the timing.

If you haven't changed the CMP, CKP, PCM, or any of the hard parts in the timing system (distributor, cam, timing set, etc), then you shouldn't need to do a case relearn. But if the P1345 code comes back again, you may want to.

A bad PCV valve shouldn't mess with the timing, but it definitely will cause a lean condition on the passenger side (bank 2) especially. Everything should adjust back to normal.

 

awesome.

So 22* advanced isnt 'abnormal'? At least, nothing I should worry about?Im fairly new to the world of internal combustion engines. Im an aircraft mechanic in the Navy, but this is a whole new ballgame.

 

20-30* advanced at idle isn't unheard of. I just looked at an old scan of my '00 Bravada and the timing bounced around 20-25* advanced while idling.