Engine running on front cylinder at 4 grand or

Check for vacume leak including intake. Spray some carb cleaner around intake and vacume hoses and listen for engine rpm to change.

Need Make/Model/Year/Engine Model/Deck Size, and hours on meter if you have one. A short description of the events preceding the beginning of the problem is also helpful.

Several possibilities:
1. Needs a valve adjustment or a valve job. Start with adjustment.
2. Needs new plugs. Start with new plugs.
3. Shear pin under flywheel is slightly damaged throwing off the timing. Remove flywheel examine shear pin for any damage. Just go ahead and replace it; if it even looks nicked or sliced.
4. Coil, or spark plug wire, is going bad. Very hard to test a coil for weakness without test equipment that the average person doesn't have. Check the first 3 problems, first. If it still backfires, then replace coil.
5. The other thing that causes backfire is fuel mixture too lean. On a small engine this is not usually an adjustment problem. It may be the fuel system/carburetor is dirty or partially clogged. It may also be an air leak in the gaskets of the intake manifold. If nothing else solves the backfire, remove the carburetor and clean or rebuild it. This is the least likely of the options so save it for last.

If compression is good and cylinder leakage is minimal, but a cylinder is misfiring or shows up weak in a power balance test, it indicates a fuel delivery or ignition problem (fouled spark plug or bad plug wire). A power balance, or cylinder balance, test should be run on a twin cylinder engine.

If an engine is hard starting, runs rough, misses or lacks power, run a cylinder balance test to determine if both cylinders are operating to their full potential. You will need an engine tachometer, a spark tester, and an insulated screwdriver.

1. Using the spark tester, with the plugs in, start engine and verify spark is equally good on both cylinders. Remove spark tester.
2. Connect engine tachometer.
3. Run engine at top no load speed. Note rpm.
4. Ground one cylinder spark plug with screwdriver. Note rpm.
5. Ground other cylinder with screwdriver. Note rpm.

The difference in RPM between the cylinders should be less than 75 rpm. If the difference between the two cylinders is greater than 75 rpm, the cylinder with the least rpm loss is the weakest and is a potential problem.

Note: If the spark plugs are new this could be an indication of a weak coil. Of course it could also be compression (rings), or valves.

Just a hunch. Clearly there is a fuel issue on one of the cylinders. Although you cleaned the carb, please confirm that the intake valve is clean and/or reed valves are working properly. It is possible that the 2nd cylinder is only firing occasionally even at the higher RPM but it's less noticeable because of the engine's inertia at that speed makes it "seem" to be running smoother. The clue lies in the fact that the engine runs smoothly at idle when the choke is applied and starts to miss when choke is open ... this is indicative of fuel starvation. And yes, on a 2 cycle, a lack of fuel means a lack of lubrication.

Out of curiosity, take both spark plugs out and crank the engine. Do this outside away from an open flame. Compare the amount of misted fuel that comes out of each cylinder head with the choke closed and then again with the choke open. If it isn't even then the cylinder that is blowing less fuel is being starved. This should identify the problem cylinder and help to narrow down the elements left to troubleshoot and replace/repair/clean. Good luck and hope this helps

The spark plug firing order is ( 1 - 4 - 2 - 5 - 3 - 6 )

The engine cylinders are 1 , 2 , 3 from front to rear on the passenger side of the engine and 4 , 5 , 6 from front to rear on the drivers side of the engine

The coil pack towers are numbered 1 , 2 , 3 from front to rear in the row nearest the passenger side and 5 , 6 , 4 from front to rear in the row nearest the drivers side

hope this clarifies the situation for you

Check the transmission. The O2 was a problem but wasn't the root cause of teh problem. Also check the compression on all cylinders to make sure it is within 10 to 15 lbs of compression on each cylinder. ie If you have 135 psi on cylinder 1 all the cylinders should be between 125 and 150 psi. Extremely high or low psi on anyone cylinder when compared to the rest will cause this problem. You have described a situation where the motor is only running on 3 cylinders in a 4 cylinder motor or 4 to 5 cylinders in a 6 cylinder motor. The higher RPM is needed to get the same speed and result as a lower rpm in a motor using all cylinders on the motor.

I am not sure if the bike is a 650 or 1100 but in either case it sounds like a fuel issue or and air leak. When the carbs were off for re-jetting did they get cleaned? The slow circuit controls to about 2000 rpm and it sounds similar to your problem.

The first thing to look at is the carb synchronization. If the front cylinder is lagging, it can give the same symptoms. I do not think that the exhaust is a factor because the front is cold when running.

Spray some WD 40 at all the intake manifold area when the bike is running and see if the idle changes. the idle will change and push some smoke out of the exhast if the intake is leaking.

If both of these check good I would pull the carbs back off and clean the slow circuits out completely. This is delicate work and shoud be done by and experienced tech.

If I can help some more just send message.

I hope that his helps. Steve

#5 cylinder is the last cylinder at the back of the engine ( the one closet to the trans. )

cylinders at the front of the engine are from front to rear are #2 #4 #6 cylinders at the back of the engine closest to firewall are from front to rear #1 #3 #5 ..........Hope this helps

2004 Pontiac Grand AM 2.2 liter DOHC L4 VIN "F"...




2004 Pontiac Grand AM 3.4 liter V-6 VIN "E"...




Hope help with this (remember rated this).

Here is the first half of the codes look till you find the one you have
111 System PASS.
112 ACT sensor circuit grounded.
113 ACT sensor circuit open.
114 ACT sensor is out of Self-Test.
116 ECT sensor is out of Self-Test.
117 ECT sensor circuit grounded.
118 ECT sensor circuit open.
121 TP sensor is out of Self-Test.
122 TP sensor input is less than Self-Test minimum.
123 TP sensor input is greater than Self-Test maximum.
124 TP sensor input voltage is greater than expected.
125 TP sensor input voltage is less than expected.
128 MAP vacuum hose damaged or disconnected.
129 Insufficient MAF input.
136 HEGO sensor circuit indicates system lean (Right HEGO).
137 HEGO sensor circuit indicates system rich (Right HEGO).
139 No HEGO switching (Front Side).
141 Fuel system indicates lean.
144 No HEGO switching (Left Side).
157 MAF sensor circuit open.
158 MAF sensor shorted to power.
159 MAF sensor is out of Self-Test.
167 Insufficient TP input change.
171 Lack of HEGO switching (Rear Side).
172 HEGO sensor circuit indicates lean. (Rear Side).
173 HEGO sensor circuit indicates rich. (Rear Side).
174 Check for diluted engine oil.
175 Lack of HEGO switching (Front Side).
176 HEGO sensor circuit indicates lean. (Front Side).
177 HEGO sensor circuit indicates rich. (Front Side).
178 Check for diluted engine oil.
179 Fuel system at part throttle lean adaptive limit, system rich (Rear Side).
181 Fuel system at part throttle rich adaptive limit, system lean (Rear Side).
182 Fuel system at idle lean adaptive limit, system rich (Rear Side).
183 Fuel system at idle rich adaptive limit, system lean (Rear Side).
184 MAF sensor input voltage is greater than expected, in range.
185 MAF sensor input voltage is less than expected, in range.
186 Closed loop injector pulse width longer than expected.
187 Closed loop injector pulse width shorter than expected.
188 Fuel system at part throttle lean adaptive limit, system rich (Front Side).
189 Fuel system at part throttle rich adaptive limit, system lean (Front Side).
193 Flexible Fuel sensor circuit failure.
211 PIP circuit failure.
212 Loss of tachometer/IDM input.
213 EEC SPOUT circuit open.
214 CID circuit failure.
215 PCM detected coil 1 primary circuit failure.
216 PCM detected coil 2 primary circuit failure.
217 PCM detected coil 3 primary circuit failure.
218 Loss of ignition diagnostic monitor signal-left side.
219 Spark timing defaulted to 10 degrees, spark output circuit open.
221 Spark timing error.
222 Loss of ignition diagnostic monitor signal-right side.
223 Loss of dual plug inhibit control.
224 PCM detected coil 1, 2, 3 or 4 primary circuit failure.
225 Knock not sensed during dynamic response test KOER.
226 Ignition diagnostic monitor signal not received.
232 PCM detected coil 1, 2, 3 or 4 primary circuit failure.
238 PCM detected coil 4 primary circuit failure.
241 Ignition control module to PCM ignition diagnostic monitor pulse width transmission error.
244 Cylinder Identification circuit fault present when cylinder balance test requested.
311 Secondary air injection system inoperative during KOER self-test (bank #1).
312 Secondary air injection system misdirected during KOER self-test.
313 Secondary air injection system not bypassed during KOER self-test.
314 Secondary air injection system inoperative during KOER self-test (bank #2)
326 PFE sensor circuit voltage lower than expected.
327 PFE sensor circuit voltage below Self-Test minimum.
328 Exhaust gas recirculation valve position sensor closed voltage lower than expected.
332 Insufficient EGR flow.
334 Exhaust gas recirculation valve position sensor closed voltage higher than expected.
335 PFE sensor circuit voltage out of Self-Test range.
336 PFE sensor circuit voltage higher than expected.
337 PFE sensor circuit voltage above Self-Test maximum.
338 Engine coolant temperature lower than expected (thermostat test).
339 Engine coolant temperature higher than expected (thermostat test).
341 Octane adjust service pin open.
381 Frequent A/C clutch cycling.
411 Cannot control RPM during KOER low RPM check.
412 Cannot control RPM during KOER high RPM check.
415 Idle Air Control system at maximum adaptive lower limit.
416 Idle Air Control system at upper adaptive learning limit.
452 Insufficient input from VSS.
453 Servo leaking down.
454 Servo leaking.
455 Insufficient RPM increase.
456 Insufficient RPM decrease.
457 Speed control command switch(s) circuit not functioning.
458 Speed control command switch(s) stuck/circuit grounded.
459 Speed control ground circuit open.