I've searched but there only seems to be problems with driving and loss of power.

My car (all-stock 2.2 except K+N SRI) will have an intermittent backfire on cooler days. It won't backfire in the summer, but when it either gets below, say 65*F, it will backfire into the intake. The engine will vibrate terribly, as if it were not balanced or something. Though, a quick rev to 2000rpm+ will fix the problem until it decides it feels like backfiring on a cold start again. I wouldn't worry, but the problem seems to be getting worse when it actually happens. I have no loss of power, ever. No problems driving either.

This happened twice last winter before I had the short ram K+N. I'd like to be able to fix it myself, but I need to know if it is possible

 

Check for Vacuum leaks.

 

Is this on startup only? How do the plugs look? Are you using quality gasoline?

 

Which lines should I check? The valve cover-to-intake is good, as is the actual intake connectors themselves.

Only on startup, after the motor has cooled down to outside temperature, in cooler than 65* weather, especially after a rain or snow. Plugs I just checked, they are good. Just a slight bit of brown on the ceramic insulator. I may replace them anyway, it's got 55k. I only use 91+ octane.

 

What's mentioned so far is good to check? BUT the main thing that is overlooked is your battery. Have a shop measure the actual amount of cold cranking amps being put out by the battery.

 

Actually that may be it. It's never been changed and the battery did die a while ago from the key getting stuck in the ignition. I'll check that too. Thanks.

 

it could also just be as simple as idle hunting a issue i have till about 150 engine temp when my o2 sensor is warmed up also and it knows wtf is going on

 

Octane rating doesn't neccessarily indicate quality. If the issue is only on cold starts, perhaps this will help.

#PIP3146D: Rough Idle Crank No Start Extended Crank Or Misfire When Cold Due To Sticking Valves Or Excessive Carbon On Top Of The Valves - (May 11, 2011)
Subject: Rough Idle Crank No Start Extended Crank Or Misfire When Cold Due To Sticking Valves or excessive carbon on top of the valves



Models: 2000-2012 All Passenger Cars with Gasoline Engines

2000-2012 All Light Duty Trucks with Gasoline Engines



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This PI was superseded to update recommended field, model years and engine list. Please discard PIP3146C.
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The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:

Rough idle, misfires, extended crank, or crank no start when cold. The engine may run rough for up to 5 minutes after starting the engine and may exhibit a P0300 DTC too. This may be caused by sticking valves or excess carbon due to fuel contamination


Note: fuel oxidation and volatility concerns can often cause these issues as well, however they cannot generally be checked in service. Trying a different, high quality fuel is sometimes the best diagnostic.

When the engine is cold, the compression on multiple cylinders may be at 0 PSI. The engine also may pop through the intake or exhaust while cranking and the spark plugs may be fuel fouled when inspected. Some engines may also experience valve damage or cam followers that are out of position as a result of this.

This condition can occur in specific areas of the country for a period of time and then it will no longer occur after the suspect fuel source has been consumed in that area of the country.

Recommendation/Instructions:

If the SI Diagnosis leads to a compression loss due to sticking valves, the following information may help:

If there is no sign of valve damage or cam followers that are out of place, perform the following procedure to free up sticking valves and to prevent the valves from sticking again. If valve damage is present or if there are cam followers that are out of place, perform engine mechanical repairs as necessary to correct the concern and then perform the procedure below to prevent the valves from sticking again.

1. Clean the fuel system by following the applicable "Fuel System Cleaning" procedure outlined in SI.

2. Add fuel injector cleaner "GM Fuel System Treatment PLUS, P/N 88861011 (for U.S. ACDelco, use 88861013) (in Canada, 88861012)"... see This PI was superseded to update recommended field, model years and engine list. Please discard PIP3146C. bulletin # 05-00-89-078B, to the fuel tank in the approved quantities.

3. Refill the fuel tank using fuel from a high volume, high quality filling station.

4. Clean the induction system using GM Top Engine Cleaner. Follow the directions on the can but DO NOT force the engine to stall since forcing the engine to stall with liquid Top Engine Cleaner could cause the engine to hydro-lock. * If available use an atomizer with Top Engine Cleaner through the throttle body.

5. Advise the customer to change fuel filling stations. They should use fuel from only high volume, high quality filling stations or they should use a Top Tier Detergent Gasoline if available. See 04-06-04-047I (U.S.) or 05-06-04-022G (Canada) for details regarding Top Tier Detergent Gasolines.

 

i have same car and intake and this has been going on for 2 years for me. only on a cold start for the first 10 to 15 seconds. i dont get it either but it doesnt bother me any more