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03-25-2008, 09:34 PM #1
- Join Date
- Mar 2008
Misfire Troubleshooting, Clogged Injector, No Overdrive
I have a 2002 Z71 Suburban, 5.3 vortec, 143,000 miles. I have done many things to try to isolate a P0307 (Misfire Cylinder #7) and a P0171. I have installed new (AC Delco) wires, and a new set of AC Delco Iridium Plugs. I'm at the point where I'm ready to move around a couple of injectors to see if the problem moves with the injector. My parts guy at the Chevy dealer says the injector (one) is right around $100. Oh well, I can live with that, if I can be sure it is causing the problem. Apparently it is pretty easy to remove the injectors, by removing two screws, one on each end of the rail, and lifting the rail and pulling out the injector which is held in by o-rings. Is it really that easy? It LOOKS that easy, but how many times have I worked on something on this truck and it almost never is as it appears. Is there a correct method to clean these soleniod/injectors?
Thanks in advance for your help.
Add on: I've put two bottles of Chevron Proguard Injector Cleaner with Techron, and filled up the tank... , let's see what happens now. I can't seem to find the newer verision of the cleaner: Chevron TECHRON Concentrate Plus Fuel System Cleaner except at the chevy dealer. 20 oz. is around $19.00. Can't seem to find it on-line either. I guess it is a HAZMAT material for shipping?
After swapping wires one at a time across the engine, then the coils, then the plugs, I finally got to the injectors. It was pretty easy to remove the injectors, of course there is some gas that comes out each time, no big deal, easily cleaned up. I finally swapped them over to the other bank, one at a time and found the bad one. $120 for a new one and the truck runs great again. I soaked the remaining 7 injectors in top engine cleaner available at Chevy, mixed with gas as it recommends. I then ran about a gallon (maybe less) through the rails while the engine was running, using a pressurized tank setup I made. Similiar setup to the rail cleaner at the shop I normally go to. WOW, that made everything else clean. Poured some of the mixture in the brake vacuum line as it was recommended to me by the helpful parts guy at SUN Chevy on Sunrise Hwy in Suffolk County NY, and then ran the Techron cleaner. Spotless! The techron cleaned everything else up. If you mess with the injectors, buy the seal kit first, just in case you nick an o-ring. Definitely good to have around, especially if your truck has the same amount of mileage as mine. Now I'm at 184,000.
Another side note: I had another problem and did not know it was related. My tranny would not go into overdrive all the time at highway speeds. I took it to several transmission shops, and everyone said it needed to be replaced. Since it was some serious money to do this, I wanted to make sure I fixed all the codes that showed up on the diagnostic reader, before shelling out this money. These codses were the bank lean code and the misfire code. NO CODES for the tranny...
Once I fixed the injector, and both of the codes stopped coming up, THE TRANNY SHIFTED GREAT. I found out that the computer stops the tranny from shifting into overdrive (High stress situation on the drive train) when it detects misfires etc. I must have had misfires for awhile, since this problem was happening and slowly getting worse. The codes were not showing up as check engine, since it was not often enough. I also found out if the code was pending ( it didn't happen three times) and you went through 3 or so engine warmup and drive cycles, it would automatically reset the code. Not all codes reset after this few cycles, only a couple of them, and misfire is one of them.
All I know is that using good gas, that may mean more money per gallon , is better than trying to find where the next misfire is coming from. I now run injector cleaner periodically, to maintain clean injector.
I love my Chevy Z71 Subruban. Here's to another 180,000!
Last edited by Turbocouch; 02-19-2010 at 10:10 PM. Reason: Updating
03-28-2008, 12:30 PM #2
- Join Date
- Mar 2007
Was leaving on a trip in my wifes Yukon and got a hesitation and then the light came on so went back to town and got the code read was basically the same thing.
Cleared it and when trying to get on the on ramp it did the same thing, so to the mechanic for a check.
Suggestion was made for a tune up etc etc but I had a feeling it was fuel related so got some good ole Sea Foam and one bottle of that in the tank and no more issues!
Sea Foam is some good stuff I have come to swear by it.
When Used Thru Injection or Carburetor
* Cleans carbon build up
* Cleans intake valves and pistons
* Gives smoother idle
* Cleans catalytic converter odors
* Cures hesitations and pings
* Restores power and pickup
* With warm engine running, SLOWLY poor 1/2 pint through carburator, throttle body or direct manifold vacuum line that will feed ALL CYLINDERS. Possible sources are P.C.V. valve or brake booster line. Turn ignition off. Restart engine after 5 minutes. Be sure exhaust is well ventilated. Fumes will be extreme for a short period of time.
* For use in injector cleaning machines, use 50% SEA FOAM and 50% fuel.
* Fill diesel filters with SEA FOAM to clean injectors fast.
03-28-2008, 08:12 PM #3
- Join Date
- Mar 2007
- Grand Prairie, Texas
- Blog Entries
You could probably find a better price on those injectors at anywhere but the dealer. Dealer mark-up is terrible on parts.
I dont remember if your injectors are rebuildable, some injectors are. Theyre easy to remove.
03-28-2008, 08:55 PM #4
03-28-2008, 09:02 PM #5
- Join Date
- Jan 2008
- Sarasota, FL
I swear by Seafoam for these types of issues, and use it as a part of normal scheduled maintenance, through the air intake and through the fuel tank. Its also used on my truck every oil change to keep a perfectly clean and efficient crank case. Doing this keeps especially tight areas like your lifters and other upper oil passages clean. I now have 4,000 miles on this last oil change..and upon checking the oil today, found that the oil is still basically the same color as it was when i poured it in.
Run a concentration of 1 pint (can) of seafoam through 10 gallons of fuel and that should clean everything right up.
Also...at places like Advance, its only about $0.43/oz....much cheaper than many other fuel system cleaners, and much more efficient IMO.
Last edited by PontiAddict; 03-28-2008 at 09:06 PM.
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03-29-2008, 10:40 AM #6
i too swear by seafoam. i use it in all motors. i do one can every other fuel up in the gas and one in the vaccum line every 6 months. it gone up in price but it is still worth the $7 a can price.
have you gone to pick-n-pull univerisity? the $2 to get in has taught me alot on how sutuff comes out correctly. i maybe get an injector or two and swap them out for your suspected bad one if the issue disapears then keep going or go get 1 new injector for your beast.
1993 4X4 Suburban
many other toys as well
09-04-2008, 03:37 AM #7
which vacuum line do you pour it into and what is the easiest way to do it? Thanks!
09-04-2008, 09:52 AM #8
pour 1/3 of it into the vacuum line that goes into the brake booster, 1/3 into the gas tank, and 1/3 into the gas tank. seafoam is awesome stuffPETE
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09-04-2008, 10:20 AM #9
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- Aug 2008
- East of Branson, Missouri
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09-04-2008, 11:32 AM #10
yea sorry my bad, the other 1/3 goes in the crank case
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