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running rough, engine light flashing.

12-07-2006, 09:56 PM
My wife's 2002 Suburban was running pretty rough (vibration and knocking) today after cold start. She said that it seemed to be worse at idle than when accelerating. She also said the service engine light was flashing. She made about a five minute stop and when she restarted the vehicle, no problems at all. The service engine light had been coming on intermittently for the last month or so but have been unable to get the codes read(tried AZ but said they could only read codes with light on). I will try and find a place that can read the codes for me but until then, any ideas what my problem might be?


Blue Bowtie
12-08-2006, 08:33 AM
There are a lot of possibilities, and lacking further information or analysis it might be foolish to even guess. A flashing light should have stored a pending code. That will be a hint to finding the problem.

12-08-2006, 09:16 AM
Looks like i am going to have to pay $80 to get the codes, none of the auto parts stores can pull the stored codes.

12-08-2006, 01:16 PM
Looks like i am going to have to pay $80 to get the codes, none of the auto parts stores can pull the stored codes.

The person at AZ is mistaken. If the light came on, there will be a code stored and it can be read with a code reader (which is what they use to pull the codes).

You can buy a code reader for less than 80 so that is option. I have this one but only paid 50 for it onsale.


12-08-2006, 07:07 PM
From your owners manual
Your vehicle is equipped with a computer which monitors operation of the fuel, ignition, and emission control systems.

This system is called OBD II (On-Board Diagnostics-Second Generation) and is intended to assure that emissions are at acceptable levels for the life of the vehicle, helping to produce a cleaner environment. The check engine light comes on to indicate that there is a problem and service is required. Malfunctions often will be indicated by the system before any problem is apparent. This may prevent more serious damage to your vehicle. This system is also designed to assist your service technician in correctly diagnosing any malfunction.

Notice: If you keep driving your vehicle with this light on, after a while, the emission controls might not work as well, your vehicle's fuel economy might not be as good, and the engine might not run as smoothly. This could lead to costly repairs that might not be covered by your warranty.

Notice: Modifications made to the engine, transmission, exhaust, intake, or fuel system of your vehicle or the replacement of the original tires with other than those of the same Tire Performance Criteria (TPC) can affect your vehicle's emission controls and may cause this light to come on. Modifications to these systems could lead to costly repairs not covered by your warranty. This may also result in a failure to pass a required Emission Inspection/Maintenance test.

This light should come on, as a check to show you it is working, when the ignition is on and the engine is not running. If the light does not come on, have it repaired. This light will also come on during a malfunction in one of two ways:

Light Flashing -- A misfire condition has been detected. A misfire increases vehicle emissions and may damage the emission control system on your vehicle. Diagnosis and service may be required.

Light On Steady -- An emission control system malfunction has been detected on your vehicle. Diagnosis and service may be required.

12-08-2006, 07:35 PM
hello i have same problem with chevy blazer with runing rich, runing rough and black smoke and idel
plz i need help here
chevy blazer 1997

12-09-2006, 01:09 PM
Paid the $80 and only 2 codes that came up were cylinder # 3 misfire and Bank # 2 Lean Code. The shop that read the codes said they cleared and recalibrated the ECM. Initially my wife said the truck seemed to run better but just got a call from her and now she says it is back to running rough again but not as bad as before. This seems to only happen when vehicle is cold(first start of the day and temp was in 20's overnight) any ideas on what might be causing the cold associated problem?

12-10-2006, 10:07 PM
Having the same trouble with the wife's '03 Suburban - engine light on and rough running on cold mornings (in the teens). Took it to AZ and they pulled 2 codes for banks lean. Guy seemed smarter than your average AZ wage earner and suggested a vacuum leak. Possible bolts loose on plastic intake manifold (hence more noticable on very cold mornings when manifold may contract) or debris on mass air flow sensor - just downstream of air filter. He suggested using a "non-chlorinated" brake cleaner to spray around the manifold and any change in idle would indicate the location of the leak. I tried it and tightened the bolts on the driver's side. Will have to wait until it cools off again to see if that cures it as the temps are back in the 40's/60's.

Good luck and repost if you are successful.

Just my :2cents:


Captain Ron
01-29-2007, 04:58 PM
I have an 02 Sub and the same problems, actually many problems but that is one on the list. It almost stalls when below 55 degrees. Lucky I am in Fla and that is not often but we get it. I seem to lose coolant during these times too and get a slight coolant odor from under the hood. No leaks on ground, only a pint or so every few weeks when cold here, no loss during summer. Code light shows vacuum issues. I sprayed carb cleaner around the intake and it smooths out when shot at the rear of the motor, near the firewall. I am thinking it is a cracked manifold, broken hose or failed sensor in that area. Probably sucking air and coolant into one of the cylinders and steaming out the pipes. Unfortunately I have had this problem for a long time and it was never acknowledged while under warranty. Now with 70K miles its my problem. Along with the weak brakes, smelly A/C, 3 batteries installed, broken A/C vents, split leather seats, clacking steering column, eratic transmission shifts, and leaking sunroof. ALL reported to the dealer when new and under warranty, and ALL issues still exist! I still own it, drive it daily, get pissed when I drive it and am stuck with it and it's problems until it gets stolen, burns or rusts away. I can't sell it with this history and no one really wants it. $44K and nothing but junky product and service.

My last was car and all future purchases are Honda, Nissan and Toyota. Not perfect but better engineering and much better service support.

01-29-2007, 07:17 PM
Sounds like a bunch of fuel pressure regulator problems, on the newer vehicles you can pull the vacuum hose off the fuel pressure regulator and see if any fuel runs out. If fuel runs out replace the regulator. On the 97 blazer, do a fuel pressure test, key on engine off, the pressure should be 59-66psi and hold when the fuel pump quits. If the pressure drops off after the pump quits, you may need a new regulator

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