99 Tahoe LT 350 V8, stock P300 Code

[tahoesteve666]

This mornings adventure

Ok, so today I revisited wiring. I had two inline spark detectors which were both utter pieces of total &*%*&%* chinese crap. I started using the first one not knowing I had another. The first one was a hunk of ****, I had to keep crimping it close or it would not hold on the plug. I tossed it and found another I had purchased awhile back and never used. Same deal.

Eventually I made it through and it seemed to me that bank two spark was not correct. I decided to swap my cheap ass chinese wires back to the originals on bank 2 only, because I wasnt sure if they were any good. In a few cases, the conectors were just popping right out of the bushings and they just seemed like complete junk. But it did not seem to help. I retested with the inline spark, it was futile and so I switched over to the cheap ass chinese induction probe.
Again, bank 1 seems reasonably periodic, not perfect but certainly better than bank 2. What I noticed with Bank 2 was that cyl 2 was not too bad, but not as good as any on bank 1. But that as I moved to 4, 6, and then to 8, it got steadily worse.

So lets see so far, two compression tester hoses, two spark detectors, a set of spark plug wires...all complete junk.

That's all I made it to this morning.
Does that seem to have any significance?

 

[tahoesteve666]

revisited fuel pressure

Hooked up gauge to shraeder valve
Key on, 56 psi, waited a few min
Key off, climbed to 60 psi
Waited 5 minutes, steady at 60 psi,
Key back on, 60.5 psi
Turned ignition on, dropped to about 54/55 psi at idle
Slowly added accelerator all the way to about 5000 rpm, slowly drop to about 52 psi @ 5000 rpm
Fast accelerator from idle, peaked to 60 psi, dropped to 52 psi and then stabilized at 54 psi
Turned Key off: stable at 55 psi, left gauge on, which I will check it in awhile

Thoughts here?

 

[tahoesteve666]

Update on leak down

So in the time since the last post, its has dropped to 30 psi. So thats about 1.25 hours

 

[lesterl]

I think the fuel pressure is ok looking at the data you collected. I would pull the cap off the distributor and see if it has any play in it (clockwise/ counter clockwise - it will try to lift slightly as an FYI, check for side to side play of the distributor shaft (worn bearings))....

What all have you done since before you started having issues?

 

[tahoesteve666]

uggh, i typed out a huge reply and the site timed out on me...annoying.. so here is the abridged version:

Before issue: probably 6 months ago, I think the fuel pump crapped out..so thats when all the work happened: New fuel pump (not filter, was rusted and we couldnt get it off, but its been changed recently), new oxy sensors...I think, Im not positive on that, all fluids (oil with additive, coolant, tranny and power steering) oil filter, tranny filter, tranny solenoid, plugs, wires, cap, rotor, pcv.

And even before that, I had replaced a/c compressor and dryer. The bearing was going in the compressor and even seemed to seize up once while I was messing with it, might have been related to charging issue, but seems to cause alot of back pressure on engine so much so that oil vapor sort of burst out of the pcv. So I always wonder about the seals, but after the a/c fix it ran fine and after all the above misc work, it seemed fine also.

Im still suspicious about there seem to be a bank related response in general. I also wonder about:
a) seals in light of the a/c response but I dont see any oil leaks and possibly compression results, though i never really made it through bank 2. Could a seal issue cause bank 2 electrical reponse like that? I would note that it got worse in the order of 2, 4, 6 , 8 with 8 being worst. 2 was pretty close to bank 1, but slightly worse Id say in terms of the periodicity of the signal.
b) cap/rotor/billet assembly in general due to the bank 2 firing response
c) maybe oxy sensors in light of it being a bank related issue
d) low vacuum, as I had measured 10 in Hg, which my understanding is should be around 20. So I will test that again tomorrow, but seems that may be another indication of a compression issue?

I have the compressed cannister coming in next so I will blow out the injectors anyway. And I received a compression leakdown tester today, so maybe tomorrow will play with that for first time.

I will also check the cap/rotor response as you mentioned.

I will also remeasure the IR response of the exhaust tomorrow, making sure the vehicle is up to temp

I will also (once the splice comes in) resume compression testing and try to do both dry and wet to have that data.

And I think the ELM327 scan tool has a higher resolution mode so I will play with that again and see if I can collect a better data set.

thats all I have for now.. thanks for the help. I greatly appreciate it..

I also broke down and ordered a fuel pressure regulator $8 PR203 off ebay, and another fuel pump $25 ebay..but will probably just blow out injectors first and leave it at that.

And for most recent work, it was only diagnostics, revert bank 2 wiring, replace plugs, clean mass air flow sensor.

 

[lesterl]

1st, what brand of fuel pump did you install (ONLY USE OEM on these vortecs - ACDeclo/ Delphi units)
2nd, What brand of cap/ rotor did you use (SAME HERE OEM ONLY.....)

 

[tahoesteve666]

Oh, you can be sure it was the cheapest of the cheap...most likely NOT OEM.

 

[lesterl]

Therein may lie your problem.... Cheap pumps in these suck, sometimes they can deliver the pressure but not the volume needed.

 

[tahoesteve666]

Duubt its pump

I tend to doubt its pump, as this issue is occurring at idle. Would seem the fuel volume supply requirement is minimal.

I still have not checked cap/rotor play yet, tried this morning, but too hot out..maybe this evening

 

[tahoesteve666]

This morning I took off dist cap and checked play in the rotor/billet. There was about a about 5 degree play, all CCW from normal with minimal vertical movement. Based up the threads of the drive gear, i did not think the amount of vertical movement was abnormal.

I did buy a new distributor for the hell of it, but in terms of the amount of play, I didnt think anything was wrong.

 

[lesterl]

Well if you were gonna put a new distributor in it anyway.... I would have pulled it and checked the gear....

 

[tahoesteve666]

The reason I didnt pull it was basically inexperience. Ive been watching video talking about top dead center on cyl 1 and aligning the marks on the balancer and also aligning the marks on the distributor, but my concern was screwing it up as Ive never done it before.

Today I revisited compression testing. I respliced the tester hose and made it through bank 2. The crap hose blew again, but I respliced it. Im running out of hose, but I have some 1/4" copper line that I will use next time as Im running out of hose now. I guess the good news is that the pressure had to peak high enough to blow the hose.

What I found was basically on all 4 cylinders on bank 2, the pressure was peaking up in the 175 psi range uniformly. But it generally was not holding pressure. I dont know if this was due to the crappy splice job or not. If it was real, and not an artifact of the pressure gauge splicing, does this have significance?

 

[tahoesteve666]

Ok...clearly this must be a tester issue .. I broke down and bought another compression tester this evening and will test tomorrow..I am anticipating high compression all the way around and should be able to rule this aspect out...in such case, pointing towards spark.. but will update tomorrow..going to blow out injectors and retest compression tomorrow..

 

[tahoesteve666]

Redid compression test with a new gauge and hose, from harbor freight (500 psi hose) no issues with tool. Got 150 psi across all 8 cylinders, nice and uniform. So Im ruling out any sort of compression issue now.

 

[tahoesteve666]

Ok, this morning I hooked up an ELM327 Device using wifi and used Torque Lite to check a few things. It was telling me my vacuum was about 21 in Hg, (which was difference from the manual gauge reading, so I will recheck the manual gauge later). But basically, in summary, I have fuel pressure of 54 (52 to 60 depending on throttle), so that looks good. I have vacuum of 21 in Hg. So that looks good. I also did compression test and was getting 150 psi across all cylinders, so that looks good. I also noticed that what Torque lite calls the Timing Advance was 25 at idle. I was under the impression that this was supposed to be at 0. Am I wrong here? So my plan was to try to put the timing light on using cyl 1 and verify it at the balancer and also loosen the distributor hold down bolt and rotate the distributor to try to zero out the advance. Thoughts?

Update:
Seems new distributor I have can not be rotated other than at the drive gear. Would this still be the same with the OEM distributor? In such case, seems I would need to rotate the cam itself using a wrench on the front of the engine targeting TDC.

Also pulled EGR valve off and cleaned it, but it was already clean and did not see any issues with it..

 

[lesterl]

PCM controls advance, 25 is not bad with computer control.

New distributor can be rotated (mine was initially locked), all you have to do is buy an aftermarket hold down bracket, or cut the two tabs off the bracket that is on the new distributor. I HAD to do this as my timing was out enough a tooth forward or back that the CEL stayed on. Now I can advance it to get the light off.

 

[tahoesteve666]

ok, so I am getting the impression that timing advance (as shown by torque software) is different than cam retard. And in such case, even if I am able to rotate the distributor, timing advance is not the right parameter to zero out, let alone even check. Is this thinking correct?

In such case, even if I rotate the distributor, I then dont know what I am trying to adjust other than by feel of the engine as I dont have a 'cam retard' indicator. As it seems that is the correct parameter to zero out.

If I were to adjust the distributor rotation, I would probably just adjust the one that is on there already to start.
Assuming it can be rotated. And if it could, it seems if I were to replace it, I could just swap the hold downs then to allow the new one to rotate also.

 

[tahoesteve666]

I ordered a cheap chinese 0-6" vernier which I will use as a TDC dial. Seemed like a really fast, easy way to do it.

I did visual inspection of the balancer. I could only sometimes see the scribe in the balancer when engine OFF. Once, I saw the scribe around the 2 o'clock position, but generally, I could not see it at all.

I also put the timing light on , connected to cylinder 1, to look at the harmonic balancer. I also could not make it out with engine ON using timing light. My intent was to see how stable the position was when varying throttle, as an indication of whether the balancer was good, but I could not see the mark.

I also ordered a distributor wrench. I could not get at it with the tools I had. Also ordered the correct adapter for the pressurized cannister setup for connecting to the fuel rail so I could blow those out. The tool did not come with a large shrader attachment, only the small, so basically that is why that wasnt working...no flow.. So waiting for both of those to show up.

 

[tahoesteve666]

Well, the distributor wrench showed up today. Didnt help. I did locate an angled closed crescent wrench and was finally able to loosen the hold down bolt to the distributor. I tried to slowly rotate the distributor in both directions, but it did not seem to help.

I also looked at the timing advance via the scanner while doing this and could not see any pattern. Just to confirm, timing advance and cam retard seem to be two separate parameters. Unfortunately, I am not able to see cam retard using my scanner setup.

I also hooked up the timing light to see the response there but still cant see the timing mark on the balancer.

I also noticed when I was done, the PCV valve is rattling like crazy now at idle. I did not tighten up the distributor hold down bolt yet

So basically, Im at a loss now, dont know what to do. Any thoughts? My next step is going to have to bring it in...

 

[lesterl]

Sorry was gone for a bit...
You probably cant see timing mark because it is advanced by the PCM.

If your drive gear is worn down you can get your code. Ive had it.

I wouldn't run with the distributor bolted down, your oilpump is run off it... don't ask. ;-)

Has your idle speed changed?

Vacume?

So all you have physically done is move the distributor some?