Back firing/popping when accelerating on V8
Discussion
I'm not all that familiar with the V8s, but generally speaking, backfiring usually means unspent (combustible) fuel in the exhaust. The more common, less serious ways for this to happen are bad ignition timing or other types of ignition failure, and too much fuel going into the engine in the first place. One of the more serious causes could also be bad valve timing.
I know that valve timing problems can be fatal on a 4 Banger. I don’t know about the V8s, but I suspect that it may be just as serious. So, you would do well to first make sure that there are no problems there.
I'm inclined to think that your problem may be from one of the less serious causes because it seems to happen only on acceleration. I don’t know how much you can or want to do on your own, but you might try some of the following. They are not too tough, and you might catch something, and save yourself a trip to the shop. And as always, remember that a good rule of thumb is…eliminate the easiest stuff first.
As for potential ignition problems…I’m not even sure what type of ignition a V8 has. If it is direct ignition like on the SEs, you can try a couple of things. Do a visual inspection on the ignition coils. Look for leaks, or corrosion on the high voltage terminals. You might also be able to have the ignition module(s) bench tested at your local parts vender, but check to see if this service is actually available before you go to the trouble of removing it. And don’t forget the really simple stuff. A bad spark plug or two, or bad secondary ignition wires can cause this sort of problem.
If you can’t find any ignition problems, there are three engine sensors that have the greatest impact on the amount of fuel being metered to the engine. These are O2, MAP and TPS. If you can locate these sensors, you might be able to run some simple tests, and detect a problem.
The TPS is not a likely suspect because things would likely be screwed up across the full range of throttle movement. However, it can be tested with a hand held electronic multi-tester, but I don’t know what the readings are supposed to be. Someone else might be able to advise you if it comes down to that.
If the car seems to stumble before the onset of backfire, the O2 sensor is suspect. Try disconnecting the O2 sensor(s) (disconnect them one at a time if there are two) to see if there is any change. If there is no change, then it may be a bad sensor. This test is valid on 4 Bangers, but I don’t know about the V8s. In any case, O2 sensors are always suspect if you are having a serious drivability problem.
You can also test the mechanical side of the MAP sensor with a vacuum tester to make sure that this circuit holds a vacuum. I think that the electronic side of this sensor can also be tested with a hand held multi-tester, but it is kind of tough to get to, and again, I don’t know what the readings are supposed to be.
Good luck! I hope that this stuff helps. Walt…’91 SE.
I know that valve timing problems can be fatal on a 4 Banger. I don’t know about the V8s, but I suspect that it may be just as serious. So, you would do well to first make sure that there are no problems there.
I'm inclined to think that your problem may be from one of the less serious causes because it seems to happen only on acceleration. I don’t know how much you can or want to do on your own, but you might try some of the following. They are not too tough, and you might catch something, and save yourself a trip to the shop. And as always, remember that a good rule of thumb is…eliminate the easiest stuff first.
As for potential ignition problems…I’m not even sure what type of ignition a V8 has. If it is direct ignition like on the SEs, you can try a couple of things. Do a visual inspection on the ignition coils. Look for leaks, or corrosion on the high voltage terminals. You might also be able to have the ignition module(s) bench tested at your local parts vender, but check to see if this service is actually available before you go to the trouble of removing it. And don’t forget the really simple stuff. A bad spark plug or two, or bad secondary ignition wires can cause this sort of problem.
If you can’t find any ignition problems, there are three engine sensors that have the greatest impact on the amount of fuel being metered to the engine. These are O2, MAP and TPS. If you can locate these sensors, you might be able to run some simple tests, and detect a problem.
The TPS is not a likely suspect because things would likely be screwed up across the full range of throttle movement. However, it can be tested with a hand held electronic multi-tester, but I don’t know what the readings are supposed to be. Someone else might be able to advise you if it comes down to that.
If the car seems to stumble before the onset of backfire, the O2 sensor is suspect. Try disconnecting the O2 sensor(s) (disconnect them one at a time if there are two) to see if there is any change. If there is no change, then it may be a bad sensor. This test is valid on 4 Bangers, but I don’t know about the V8s. In any case, O2 sensors are always suspect if you are having a serious drivability problem.
You can also test the mechanical side of the MAP sensor with a vacuum tester to make sure that this circuit holds a vacuum. I think that the electronic side of this sensor can also be tested with a hand held multi-tester, but it is kind of tough to get to, and again, I don’t know what the readings are supposed to be.
Good luck! I hope that this stuff helps. Walt…’91 SE.
It's probably a serious problem with the car. Better sell it real fast. Hey I think I know a guy in Minnesota that might buy it real cheap or trade you a trouble free SE for it
.
Just go through the standard checks we discussed and all will be fine hopefully. The plug conditions would tell you a lot. Compare all the plugs, check gaps, check plug wires, coil packs, and test injectors using the standard spray test. Use the OBDII scan program on your laptop from www.ODB-2.com and give us the reports. Also thanks again for your old ALDL cable that you sent me. I have the car out today. It's 38F, no snow or ice and tomorrow is forecast the same. Then it's back under the cover and storage. Who would have guessed that it is so nice here in the usually frozen north lands of the USA.
Calvin
. Just go through the standard checks we discussed and all will be fine hopefully. The plug conditions would tell you a lot. Compare all the plugs, check gaps, check plug wires, coil packs, and test injectors using the standard spray test. Use the OBDII scan program on your laptop from www.ODB-2.com and give us the reports. Also thanks again for your old ALDL cable that you sent me. I have the car out today. It's 38F, no snow or ice and tomorrow is forecast the same. Then it's back under the cover and storage. Who would have guessed that it is so nice here in the usually frozen north lands of the USA.
Calvin
Well, a few things to think about..... my experience has shown the ECM in the V8 to very picky, ie, you can get a check engine light from switching gasoline brands. Hence, if you have something seriously wrong, you will (should) get a check engine light.
Beyond this, how many miles are on the car?? Have you had the cambelt service done yet? It should be done every 12 months or 12K miles.. LCU covers this cost for 10 years or 100K miles... don't neglect this one! The fact that it's a 2000MY, it should have had at least one cambelt service by now. Valves should be okay as they are hydraulic and require no maintenance and/or adjustment.
If the spark plugs have been checked/changed be certain that the covers were properly sealed. Early V8 cars had some water leaking down in the spark plug towers due to improper sealing. The water was shorting out the ignition. As for the spark coils, there are lots of them, all buried beneath the intake plenum, hence major effort to even look at them.
If you have access to a decent scan tool, you could check to see if any freeze frame data has been captured and you could monitor the O2 sensors realtime to see if they are okay. I check mine every once in a while. With almost 11K miles on the car, it still runs superb. Hope some of this helps.
Regards, KM
2000 V8
Beyond this, how many miles are on the car?? Have you had the cambelt service done yet? It should be done every 12 months or 12K miles.. LCU covers this cost for 10 years or 100K miles... don't neglect this one! The fact that it's a 2000MY, it should have had at least one cambelt service by now. Valves should be okay as they are hydraulic and require no maintenance and/or adjustment.
If the spark plugs have been checked/changed be certain that the covers were properly sealed. Early V8 cars had some water leaking down in the spark plug towers due to improper sealing. The water was shorting out the ignition. As for the spark coils, there are lots of them, all buried beneath the intake plenum, hence major effort to even look at them.
If you have access to a decent scan tool, you could check to see if any freeze frame data has been captured and you could monitor the O2 sensors realtime to see if they are okay. I check mine every once in a while. With almost 11K miles on the car, it still runs superb. Hope some of this helps.
Regards, KM
2000 V8
Thanks guys for all the info. I'm in the process of replacing my NGK spark plugs. They look a bit rusty and have not been changed in 24K miles. We'll see what happens after this. I changed all belts about 800miles ago and there is no Check Engine Light coming on. It doesn't back fire too much. About 4 - 5 pops when accelerating hard. If I accelerate slowly... no back firing or pops and all is good.
Calvin-
Glad to hear you're enjoying the car a bit still. I'll think about your offer as soon as I test the new plugs.
Ed-
Calvin-
Glad to hear you're enjoying the car a bit still. I'll think about your offer as soon as I test the new plugs.
Ed-
egomes said: Thanks guys for all the info. I'm in the process of replacing my NGK spark plugs. They look a bit rusty and have not been changed in 24K miles. We'll see what happens after this. I changed all belts about 800miles ago and there is no Check Engine Light coming on. It doesn't back fire too much. About 4 - 5 pops when accelerating hard. If I accelerate slowly... no back firing or pops and all is good.
Calvin-
Glad to hear you're enjoying the car a bit still. I'll think about your offer as soon as I test the new plugs.
Ed-
Ed - and this will sound silly and trivial, because of the lack of a check engine light, and the fact that you are having an engine related problem, you may want to check the bulb on the check engine light. Just a thought...
ErnestM
Guys - i recently had a problem with a 'stumble' type of thing on full throttle. Not bad enough to be a proper miss-fire, just a sort of hesitation before it really starts to pull. It was also popping and banging much more than normal. A new set of plugs cured the problem. It still pops a bit, but less than before.
I didn't ever see a check engine whilst i had this problem.
You can check if the 'check-engine' light bulb is still working easily as it lights for a short period when you switch the ignition on.
cheers
Rob
I didn't ever see a check engine whilst i had this problem.
You can check if the 'check-engine' light bulb is still working easily as it lights for a short period when you switch the ignition on.
cheers
Rob
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