99 Tahoe LT 350 V8, stock P300 Code

[tahoesteve666]

no problem, thanks for the followup.

The only thing I have done is rotate the distributor. But I got fed up and brought it in for diagnostics.

I gave them a rundown of what I did and found and and let them know the distributor bolt was loose and I had tweeked the idle just a bit. They supposedly checked it out and tightened the hold down bolt back. They also indicated they checked and adjusted the timing.
It was still running like crap when I picked it up.

They were indicating that it was most likely the spider injector poppets going to cyl 2 and 4 that they thought were not turning off properly and wanted $1000 to replace the injectors. Basically, the vehicle is only worth $2.5-3k, and is a rust bucket with a ton of new parts on it, but Im not inclined to put that sort of money into it as Im quite poor and dont work, so I stopped it at the diagnosis.

I forget that I wanted to still blow out the injectors still before bringing it in. I was that fed up with it. Im still waiting for the correct quick connect for my pressurized cannister to show up that fits the chevy rail, but expect it monday or tuesday latest. So I will do that and see if it helps.

Do you believe the injectors is consistent with it all? I am starting to review videos on swapping out the injectors now.

Vacuum was fine last I checked. I did not notice any difference in idle speed when rotating the distributor other than it cutting out completely and turning the engine off effectively if i rotated too far.

also, i think you meant you wouldnt run without the distributor bolted down..correct?

 

[lesterl]

Injector assembly is $250 and not hard to replace.

If you had 2 injectors (#2 and #4 overfuleing you should have a P0302 and P0304 not P0300)

YES bolt down the distributor....

 

[tahoesteve666]

ok,

so the injector attachment for the fuel rail arrived and I used it blow out the injectors through the fuel rail using the pressurized cannister with seafoam. Generally, I had to mix the seafoam with about 1/2 gas to get the car to run. It indicates that on the directions as well on the side of the bottle. As 100% seafoam, I could not get it to run.

Other observations: I did not seem to get a tremendous amount of smoke. There was some, but I was expecting alot more. Ive seen the injector blow out using the cannister in the past so had some reference.
Also, i was really expecting the cannister of about 20 oz to take a long time to burn through, but it seemed to take only a few minutes at most. (At the shop, they seemed to indicate injectors 2 and 4 were stuck open, so maybe this is consistent with that?) But I did not see any change in the idle level as I would expect for alot of fuel burning, unless the fuel was not being ignited. I also didnt really smell gas anywhere that I might expect from a external fuel leak.

And then after going through about 3 bottles of seafoam this way, and resetting the engine light, the new code was now P304. I am not longer getting P300.

I also rechecked fuel pressure and fuel pressure leak down, no issues, it was solid at 55-60 psi and no drop over time. Seems if fuel injector was stuck open, I would get a pressure bleed off? Not sure, dont know if injectors are isolated from fuel when car is not started (meaning off, or key on, but not running).

Thoughts? Maybe possible to go through more seafoam or some other chemical to see if it corrects cyl 4?

 

[lesterl]

Pull plug on Cyl 4 and see if it is wet/ black. Could be an ignition issue and not an injector issue.

Might put a bare plug in #4 wire and ground the plug to see the spark.

Perhaps the injector is stuck closed?

I would warm the engine up and seafoam the intake through the brake booster or large vacume line.

P0304 is a Cyl 4 misfire. Check your wires and plugs as well.

 

[tahoesteve666]

Pull plug on Cyl 4 and see if it is wet/ black. Could be an ignition issue and not an injector issue.

Might put a bare plug in #4 wire and ground the plug to see the spark.

Perhaps the injector is stuck closed?

I would warm the engine up and seafoam the intake through the brake booster or large vacume line.

P0304 is a Cyl 4 misfire. Check your wires and plugs as well.

ok, so just so I understand, if the plug is wet/black, that would indicate the injector is not closed but it still could potentially be stuck open.

I can check spark a number of ways on cyl 4. I will keep the plug still in and remove the wire from it and attach it to another plug and ground the plug to visually inspect the spark. I also have an inductive timing light which I will put on cyl 4 and I think I have one of those inlight lights that I can check as well. But basically all should say the same thing.

I dont really understand the intended purpose of the seafoam through the vacuum as this will bypass the injectors. Can you explain purpose? I had already done this before through the vacuum line as well a week or so ago, but its simple enough to do again.

 

[lesterl]

Wet/ Black means either a stuck open injector or dead ignition in that cylinder.

The best bet is to use a plug to check spark as your timing light might pick up too low of a voltage and trigger anyway. Visual is best.

Seafoam in the intake is to clean intake and ends of injector poppets.

If you get a new injector set, look for the MPFI fuel injector upgrade, the old CSFI injectors were more problematic.

Definitely isolate from fuel issue to spark. NON OEM Distributor Caps can cause issues as well, even new aftermarket ones have been known to be crap caps.....

 

[tahoesteve666]

ok, the cap was ordered off ebay, so based upon my experience there..I would not be surprised at all if it was crap... and its simple enough to change. I still have the new distributor as well, but obviously easier to just replace the cap.

I understand what you are saying about debugging between spark and fuel.
I will get back into it tomorrow.

 

[tahoesteve666]

So I warmed up the engine and pulled the plug, the images above are after removing the plug from the warm engine out of cylinder 4. To me, it seems oily and wet, no buildup (these are new plugs).

I also took a video of the cyl 4 spark using one of the inline testers that I picked up fromharbor freight. Seemed to work much better than the ones I had before. Here is the URL for cyl 4 spark https://youtu.be/RvRo4OFzhoA

The video is pretty grainy, but what it seems to show is a periodic signal with a low glow and then random flashes/high glow conditions. Im not sure how to interpret this. Clearly there is spark, but the spark is not correct. Does this mean the ignition side has an issue, or can such a spark be altered by the fuel side?

I also did seafoam through the intake, not through the vacuum. I only had one can of the spray version with the straw that is stuck in just before the throttle body. I did not really see any smoke at all through the exhaust (but I had cleaned this through vacuum before, as well as through the injectors. In all, I have put 5 bottles of seafoam into the vehicle over the last few weeks either through the vacuum, rail and now throttle body) and this is in addition to cleaning the throttle body directly with carb cleaner.

After putting the seafoam in, the vehicle really ran like crap though and when trying to burn off the seafoam afterwards, the engine light started flashing, so I turned around and came home.

 

[tahoesteve666]

Also, I am thinking about replacing the cap and rotor (and maybe the wires also as they are original, but Im sure its not the wires) as well as the spider injector to multiport. Do you have suggestions as to which brand is good and similarly which brands to avoid?

 

[tahoesteve666]

I started pulling it all apart. Last thing holding the intake and cover on is the fuel rail and one 10mm bolt under it. Having some difficulty with it. Seems like the bottom portion is screwed into the top. Any particularly trick here. Is this a normal righty tighty, lefty loosey pair?

Seems like also with all the room once the intake is off, I could tackle the distributor also. Still a bit weary on that though.

 

[lesterl]

Fuel rail has a nut on the drivers side top transmission bellhousing bolt (stud), there is also a bolt that bolts down straight into the intake that just needs to be loosened.

Your spark sucks on #4, can you check another cylinder to see if it is erratic also?

Have you done a compression test?

 

[tahoesteve666]

I did a compression test earlier , was getting 150 across all 8 cylinders.

I got the fuel rail disconnected and the hold down bolt undone. Everything is loose now. I just need to pull the fuel rails out of the top of the manifold. They are in there pretty good. I sprayed it with wd40 and will try pulling them out tomorrow morning. And then I need to take out 2 of the 3 bolts on the intake itself. After that, the entire manifold should come off.

I have everything apart now, so checking spark on others will have to wait. Should I just go ahead and replace the cap, rotor and wires? Im pretty hesitant about replacing the distributor itself. Im afraid of screwing up the timing, but it certainly seem readily accessible now..

 

[lesterl]

Ok, seems kinda low on compression, but I bet it was cold.

Fuel lines in top are a little snug, make shure your hold down bolts/ nuts are taken care of. Should be 2 nuts and a bracket where lines go into fuel meter body, 1 bolt to loosen at bracked on back of intake, 1 nut to remove off bellhousing stud top drivers side.
Pull straight up.

Sure, put a new cap and rotor if you can find an AC Delco or Delphi parts.
Distributor isn't hard, but getting it timed properly is kinda a PITA....

 

[tahoesteve666]

Yea, it was a cold engine and dry test.

Injector out, old style central port, very wet inside manifold, alot of the injector tips were quite dirty, not really the poppets themselves, but around the tips of the poppets alot of buildup. Didnt see anything broken.

Have acdelco cap/rotor on order, new multiport injector on order. Probably at least a week before the parts show up. will spend time cleaning and post after I get it all back together.

 

[lesterl]

Ok, let us know...

 

[tahoesteve666]

Ok, here is the latest on the tahoe. My approach on dissassembly was to
a) leave the a/c compressor in place,
b) remove all the plug wires and cap and rotor) as i was replacing it all anyway, but seems really only need to remove the plugs off the cap for the first bank, in order to get at the fuel connectors and bracket bolt easily
c) remove the assembly at the back of bank 2 (this was a major pain and I actually had to bend the bracket that holds some cabling and sits just over the ignition control module attachment in order to get at the bolt) and unfortunately, I dont remember exactly the bolt scenario to put it back..more below
d) disconnected the upper coolant line, lost minimal coolant
e) remove another support hose bracket (and now cant remember where it goes) see attached image

Install of the injector went smoothly, so now Im back at reassembling it all and have multiple questions..since my memory is so poor.
1a) for the fuel line clamp/bracket on top of the manifold. Is the protruding metal part supposed to face up or down? And is this metal portion supposed to face forward? Right now, I have it protruding up and facing forward.

Update: I found this picture online: https://i.ytimg.com/vi/8VmqgxlMQhE/maxresdefault.jpg so it shows I have the bracket upside down, the raise portion should be pointing down apparently to hold the fuel rails. So I will fix that.

1b) for the single bolt that holds the back of the fuel lines (where the connectors are), I used a style of a bolt that had about a 1/4" cylindrical flat tip without treads at the tip of it. Was this the right screw to use here?

2) how many bolts are in the front and the back of the manifold (not on the sides). Right now, I think I have one stud style bolt in the back. But I am missing one of the stud style bolts, so am questioning this bolt choice in the back. Is there only one bolt needed in the back and it is a stud style, or something different.

3) There is a bracket that I took off and dont recall where it goes. It was to support some hose and is shown in the picture, but I simply dont recall where it goes. This bracket is shown in the first image.

4) for the throttle cable bracket, there are two bolts. One goes into the throttle body and the other goes down below. For the one that goes into the throttle body, I used a very conventional looking hex bolt with a flat end (i think). It was not a stud type like those for the manifold and it did have a pointed tip. Does this sound correct? I think for the lower bolt, that was a stud style as it also feeds into the manifold..(doing this from memory, so not sure)

Update: The same image above shows the upper bolt, so I think I got that one right also.

5) For the pressure sensor, I am pretty sure I used the correct bolts for that..they were shinier than the others but they were also long like the others

6) There are two stud type bolts which were shorter than the others. I used these for the ignition control module bracket assembly in the back left. These do not hold the manifold in place, but thread into the block itself. I had major difficulty getting at the back left bolt for the manifold and had to remove the support bracket but now I dont recall the correct method to reassemble. Do the two short bolts belong here? Does the ignition module go above or below the other bracket? Am I supposed to use the short studs here? Any clarification here would be very helpful. The 2nd and 3rd image are low angle shots looking at this assembly.

7) I seem to be missing one bolt for the manifold, but have one extra bolt that I dont know where it belongs. The extra bolt has a pointed end, and is not a stud type. But I simply have no idea where it belongs. It is also shown in the image.

8) I also ended up with some extra nuts, some with wide washers..some with narrow.as shown in the image...Im not sure which ones belong where..

Any comments on any part are appreciated..

 

[tahoesteve666]

reassembled everything, still have that extra bracket and a few extra nuts, but vehicle running smoothly. Fired it up, got an extra P102 code, and had the P0300 from before, so just cleared it all out and seems to be running quite smoothly.

The only thing I noticed is, while parked, with rapid depress on the acceleration, there is momentary hesitation as the rpms did dip slightly right before it ramps sharply. I have not taken it for a drive yet, but at idle, no codes so far.

I also noticed the idle rpms went up. I had adjusted the idle earlier right at the throttle body, so I will adjust it back down tomorrow. Can you tell me what idle rpm should be?

I have the cracked small plastic line which runs right across the cover at the back of the throttle bottle glued, used RTV, so hopefully by tomorrow that will be sealed there.

Thank you so very much for all your help. You gave me the motivation to tackle this which I would have never done otherwise. It is by far the most in depth work ive attempted on a vehicle.. saved me at least $500 and I learned quite a bit.

Going for a drive to celebrate with some take out....

 

[lesterl]

Should not set idle manually, PCM controls that.

Rapid depressing of the accelerator might be causing that due to the PCM relearning perhaps? It does cause a quick loss of manifold vacume. Might clean the MAF sensor.

I left that bracket off mine, it supports the wire harness that goes over the back passenger side of the intake. PITA to deal with.

The line you glued was the EVAP purge line.

Glad you got 'er going. Keep us up to date.....

 

[tahoesteve666]

Well, i started driving down the road, got about 1/4 mile and all hell started breaking loose. Sounded like broken parts inside the engine...it was a complete disaster.. i basically had to stop immediately...got it towed back and believe it or not..donated it to someone after stuffing about $600 bucks of new parts into it.

I noticed I had forgotten to hook up the connectors to the mass air flow, and two other items right next to it, not sure what they go to...so I did plug them in, but it didnt resolve..just got worse.. never heard any engine sound like it.


Other than having rust underneath from being back east, interior was in great shape, everything working completely..but alas, shes gone..shes gone..nothing gonna bring her back..

 

[tahoesteve666]

Well...last posting here.. couldnt figure out what had happened. But the people I gave the vehicle too said water in the engine. It came to me last night...Now I know what happened..I forgot to purge the coolant line after reconnecting it. I had disconnected it to make removal of the upper intake cover more easier. So I am assuming after i fixed everything..and checked it at idle, the enginesimply was not hot enough..but as I drove it and the engine heated up, the air expanded..couldnt escape, blew one of the gaskets and then all hell broke loose.

One dead engine all because of early senility...ridiculous..... so long...