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Chevy Suburban Rough Idle and Stalling

95 messages,  Last post on Nov 03, 2009 at 6:57 AM

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#56 of 95 Re: rough idle after new plugs and wires [mkotzur] by woodyj May 19, 2008 (7:11 pm)
Replying to: mkotzur (May 19, 2008 6:17 pm) Double check your spark plug gaps and check your spark plug module harness connection on both sides of the engine. The check engine blinking indicates short/misfiring. If there is short in the harness, you can check it by moving around the wires close to connector one by one while the engine is running. Have your check engine light checked and post the codes. I would have better understanding of what the problem is. Replies to this message: pear69 (May 20, 2008 2:32 am) elorenzo39 (May 20, 2008 6:49 am)
#57 of 95 Re: rough idle after new plugs and wires [woodyj] by pear69 May 20, 2008 (2:32 am)
Replying to: woodyj (May 19, 2008 7:11 pm) Did you install AC Delco plugs and wires? If not you are wasting your time. AC Delco ignition parts are the only parts that work on Chevy engines. I know they are more expensive but that's just the way it is with the high voltage Chevy ignition systems.
#58 of 95 Re: rough idle after new plugs and wires [woodyj] by elorenzo39 May 20, 2008 (6:49 am)
Replying to: woodyj (May 19, 2008 7:11 pm) I have this problem not too long ago on my 99 Suburban after the intake manifold gasket was replaced. I have a good all buddy helped me out on this forum. I bought a non ac delco parts and nothing has change, but when he suggested to replace it with ac delco, the truck ran better. I had a rough engine and showing a code of P0304 misfire on cylinder #4 and a blinking ses light when at a speed of 35 - 45 mph. California vehicle had a special warranty up to 200k mile on their fuel injection system and dealer checked and replaced. Car runs great now.   I did not catch the whole story. Please provide me some symptoms that you are experiencing and what year and type. I will share with you some of my experiences.
#59 of 95 Re: rough idle after new plugs and wires by elorenzo39 May 20, 2008 (7:08 am)
Did it give you any codes?
#60 of 95 Suburban K1500 5.3L misfire by alanrs Jun 17, 2008 (5:13 pm)
Having a problem with my Suburban, began at a little over 80k miles. SES light activated on interstate at 70mph while towing an empty trailer. Filled up with "better" gas, light out within 50 miles. Light back on within 100 miles, showing a 300 DTC. Cleared code a couple of times, returned as 305 or 300. I figured it was time for a tune-up, replaced plugs and wires. [Note: OEM plugs were DENSO platinum type]. New plugs Iridium, 0.60 gap as specified in manual and engine compartment sticker, new Delco wires. Rough idle still present, 305 code returns after clear.    Have since changed/tried: New fuel filter, swapped coil units beween cylinders, sprayed brake cleaner around intake (as leak detector). No change. Removed and sent injectors for professional cleaning. Still no change. I broke down and took the Burban to the dealership. $184 later, and no diagnosis of the actual problem. They say electronics and fuel system are ok, performed leakdown test, with no issues. Wantd to "disassemble" top of engine suspected "grooved camsaft" or other valve train issue. I declined permission to take the engine apart.   Would be happy for any advice I can get at this point.   Thanks Replies to this message: elorenzo39 (Jun 18, 2008 12:35 pm) alanrs (Jun 18, 2008 6:15 pm) arrie (Jun 22, 2008 7:03 am)
#61 of 95 Re: Suburban K1500 5.3L misfire [alanrs] by elorenzo39 Jun 18, 2008 (12:35 pm)
Replying to: alanrs (Jun 17, 2008 5:13 pm) Please tell me what year, what code does it have. What state are you in. I had the same problem before and I was showing P0304 cylinder 4 misfire. Let me know. Check compression on each cylinder while the SES light is still on. My Burb did that for 1 year and the problem on mine was the Spyder injectors that was replace for free in the State of California and is waranteed up to 200k mile. A month later it showed up again P0304 and my compression was dead on that cylinder. I ended up getting the engine replaced then sold it due to high gas price in California. Replies to this message: alanrs (Jun 18, 2008 6:15 pm)
#62 of 95 Re: Suburban K1500 5.3L misfire [elorenzo39] by alanrs Jun 18, 2008 (6:15 pm)
Replying to: elorenzo39 (Jun 18, 2008 12:35 pm) I am in Michigan. The code is 305. The engine passed compression and leakdown tests. This is a 2001, injection has fuel rails with individual port injector units, and a plastic composite intake manifold.
#63 of 95 k1500 5.3 mis fire by pear69 Jun 19, 2008 (7:55 pm)
Try changing or swapping out number 5 cylinder injector with another known good injector. P0305 code is cylinder 5 mis- firing. Denso plugs are ok for these type of coil/over ignition systems but A/C Delco are the best. What is the fuel pressure? Did you check the TPS sensor? Replies to this message: alanrs (Jun 20, 2008 1:39 pm)
#64 of 95 Re: k1500 5.3 mis fire [pear69] by alanrs Jun 20, 2008 (1:39 pm)
Replying to: pear69 (Jun 19, 2008 7:55 pm) The injectors were removed, tested, cleaned, retested, and yes I re-installed with 2/4 and 3/5 in different locations. Injectors are not the issue. The Denso plugs CAME in the engine FROM GM. I was surprised too...... I replaced with Autolite, only because they were only ones I could find with the specified 0.60 gap in an Iridium type. #3 and #5 coils were also swapped. Tech2 showed no issue with TPS, and I get consistent readings from it on my scan tool as well. Dealer says there is no electrical or fuel issue, and BTW, I measured fuel pressure between 46 and 50 PSI.   The Tech2 showed a misire history stored in the computer that was heavily at cylinder 5 (over 50,000 the day we read it), with way too many (but about 1/10 of cyl 5) on cyl #4. Others showed single digits or zero. I wish I knew of someone with an engine smoker in my area, so I could check the intake gaskets.......   This is perplexing. I love this truck, and am bummed that it is running poorly. Been driving for 40 years, his is the first time I have had any issue like this. I run most of my cars/trucks 150K miles or more with no engine problems.
#65 of 95 k1500 5.3 mis fire by pear69 Jun 21, 2008 (9:21 am)
Your fuel pressure should be 55 to 66 psi. Make sure the fuel filter that's attached to the fuel lines is new and installed properly (this filter is directional). If this filter is good then the filter that attaches to the fuel pump (inside of the tank) is probably dirty. This filter ( I believe) is not serviceable. I suggest replacing the fuel pump. When replacing the fuel pump on these chevys it is VERY important to replace the fuel pump chassy harness connector ( this is the electrical connector that plugs into the fuel pump). This connector is a one shot deal -- meaning that it can only be plugged in and out once -- because of a design flaw. Failing to replace this connector will cause the pump to shut off and/or arc creating the potential for a fire. Also, the ground for your fuel pump is connected to the frame close to the fuel tank -- find this (black wire) ground and disconnect it and clean the area around it real good and then reconnect it. This ground corrodes and it is usually better to cut it off and re due the entire connection.    This may not be the mis-fire problem but it is important to have the proper fuel pressure before you change everything else (like is seems you have done already). A code 305 is specific to a mis-fire to cylinder 5. Make sure all the wire connections are connected properly.  Pull cylinder 5 spark plug and pull another plug that is firing. Is there any difference in the appearance? What do they look like?    I believe you mentioned that you sprayed brake cleaner to look for an intake leak. Try spraying some CRC electrical contact cleaner all around the intake--it is safer. Do this with the engine running at idle -- if the idle changes then (of course) you have an intake leak.     Also, is your coolant low? These engines are famous for the lower intake gaskets to fail. If the coolant is low and there is no outward signes of a coolant leak, then the intake gasket may have failed inside of the engine and coolant can leak into cylinder 5 causing a mis fire. Check your oil to be sure that there is no coolant in the oil. Looking at the plugs will confirm whether or not there is coolant leaking in no. 5 cylinder.

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