Engine missing real bad now! Ideas need please.

[aa010175]

Back ground. 2000 V-6 250,000 miles. Owned for 18 years. Did a head cylinder replacement due to a cracked head. Heads rebuilt, replaced water pump, timing belt and rebuilt fuel injectors. Started engine and ran semi smooth. Tripped a PO172 code (system too rich bank 1). I drove it for 100 with a little a little miss once a while. Today I was in a 15 ride when the missing became very bad and the engine would hardly run. It also had some light back fire when running badly. Towed home. I check the timing belt and verified the aligned timing marks were good. I pulled all spark plugs (new wires and plugs) #4 plug was wet and the other 5 were dry. Ideas please. Thanks Dave

 

[19963.4lsr5]

I would think you found your bad injector.

Do you have any spare injectors?


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[aa010175]

I would think you found your bad injector.

Do you have any spare injectors?

Yes I have 3 replacement coming. Would it barely run with one bad injector?

 

[19963.4lsr5]

I would think you found your bad injector.

Do you have any spare injectors?

Yes I have 3 replacement coming. Would it barely run with one bad injector?

I’m going to say no. But you may have more than one problem.


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[aa010175]

I’m going to say no. But you may have more than one problem.

I just Ohms tested the 6 injectors. They were all about the same at 11.0-12.0. One must be bad because I have been tripping code PO172 with system too rich bank 2. I removed the 6 injectors and blew (lungs) the gas out - as I hot wire them. What other test should I perform on them? Dave

 

[Buckaroo]

Back ground. 2000 V-6 250,000 miles. Owned for 18 years. Did a head cylinder replacement due to a cracked head. Heads rebuilt, replaced water pump, timing belt and rebuilt fuel injectors. Started engine and ran semi smooth. Tripped a PO172 code (system too rich bank 1). I drove it for 100 with a little a little miss once a while. Today I was in a 15 ride when the missing became very bad and the engine would hardly run. It also had some light back fire when running badly. Towed home. I check the timing belt and verified the aligned timing marks were good. I pulled all spark plugs (new wires and plugs) #4 plug was wet and the other 5 were dry. Ideas please. Thanks Dave

Is the P0172 the only code you have? Would think maybe you should be seeing a P0304? Wet plug could be too much fuel or no spark. Check your spark plug routing per attached. Look for evidence of arcing on cylinder 4 spark plug boot. You could try disconnecting the wire to the cylinder 4 injector and see if it changes anything. You could swap that cylinder 4 spark plug to a different cylinder and see if the "wet" observation follows it. Make sure the plug to the MAF is secure and do a visual check on the wiring to it. You likely know this but driving with that miss will kill your CAT.

 

[aa010175]

Is the P0172 the only code you have? Would think maybe you should be seeing a P0304? Wet plug could be too much fuel or no spark. Check your spark plug routing per attached. Look for evidence of arcing on cylinder 4 spark plug boot. You could try disconnecting the wire to the cylinder 4 injector and see if it changes anything. You could swap that cylinder 4 spark plug to a different cylinder and see if the "wet" observation follows it. Make sure the plug to the MAF is secure and do a visual check on the wiring to it. You likely know this but driving with that miss will kill your CAT.

I had to have the car towed to my house it was running so bad. I have been driving it for 100 miles with no problem. Down the freeway 70 mph, short trip to the store etc. the only code was the P0172 with rich note. It was running good then all of the sudden it went to very ruff like 3 cylinders and it was back firing every few minutes. I just pulled all injectors and blew gas out of them well hot wiring the ejectors. Plug wires are correct. Thanks for the diagram. The plugs and wire are new 4 months ago.

 

[spartacus]

This might not be your issue but wouldn't hurt to check the maf sensor.

 

[Buckaroo]

I had to have the car towed to my house it was running so bad. I have been driving it for 100 miles with no problem. Down the freeway 70 mph, short trip to the store etc. the only code was the P0172 with rich note. It was running good then all of the sudden it went to very ruff like 3 cylinders and it was back firing every few minutes. I just pulled all injectors and blew gas out of them well hot wiring the ejectors. Plug wires are correct. Thanks for the diagram. The plugs and wire are new 4 months ago.

No misfire codes but obvious misfire.....maybe visually check your wiring to injector #4. possibly pinched and grounding out? Have you ever replaced/cleaned your Idle Air Control valve? have you looked at your fuel trims?

 

[Buckaroo]

This might not be your issue but wouldn't hurt to check the maf sensor.

Good thing to do. Dirty MAF generally associated with P0171 (lean) as is leaking vacuum hose. Maybe clean it. Does seem like we are looking for something not cylinder specific if you had multiple cylinder misfires...but no codes? Do a visual on air filter as well.

 

[aa010175]

Good thing to do. Dirty MAF generally associated with P0171 (lean) as is leaking vacuum hose. Maybe clean it. Does seem like we are looking for something not cylinder specific if you had multiple cylinder misfires...but no codes? Do a visual on air filter as well.

Just cleaned the MAF, throttle valve and cleaned the Idle Air Control valve. Replacement injectors will not be here till 1/3. I don’t see anything wrong with the ones I have. OHms testing in and out of car shows 11.0 in all. The hot wire test worked. Not only herd the cylinder work and was able to blow gas out of all 6 of them. I am finding no smoking gun! Examine the wiring and see nothing wrong with that. All the connections were good. I feel like I should just put it back together and go from there. Ideas on that?

 

[snydmax]

Check coil packs? My experience is that it can take a hot minute or two for misfire code to set


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[aa010175]

I put the car all back together after finding nothing wrong that I can see. The car started up and ran normally. But before I started the engine I looked at the codes again that was tripped. It had a PO300 random multiple cylinder misfire detected and a P0303 cylinder 3 misfire detected and a PO304 cylinder 4 misfired detected. After driving it 2 miles PO172 system to Rich bank one showed up again but nothing else. What would make cylinders 3 and 4 misfire and could a misfire trip a P0172 code? Thanks Dave

 

[Buckaroo]

I put the car all back together after finding nothing wrong that I can see. The car started up and ran normally. But before I started the engine I looked at the codes again that was tripped. It had a PO300 random multiple cylinder misfire detected and a P0303 cylinder 3 misfire detected and a PO304 cylinder 4 misfired detected. After driving it 2 miles PO172 system to Rich bank one showed up again but nothing else. What would make cylinders 3 and 4 misfire and could a misfire trip a P0172 code? Thanks Dave

Cylinders 3 & 4 are not on the same coil pack so that is not the explanation. Maybe it isn't just 3 & 4 - need to think of things that would affect all cylinders. Restriction in air could make it run rich - did you check the air filter and make sure no obstructions in the ductwork to the throttle body ( think mouse nest)? We have not discussed the upstream O2 sensor - are you sure that is working properly? Is it switching?

 

[aa010175]

I had removed the air cleaner. It’s now reinstalled. I drive the car daily so no mouse. Did have one in my 62 Cadillac but that’s a different story. It’s the engine all of the suddenly started missing real bad that bothers me. Finding nothing wrong makes it so that I can’t really trust the car now. I just wanted to find something that was wrong so I know that’s it. I will look at the O2 sensors. Thanks for all the advice I received from everyone.

 

[Bad Luck]

I put the car all back together after finding nothing wrong that I can see. The car started up and ran normally. But before I started the engine I looked at the codes again that was tripped. It had a PO300 random multiple cylinder misfire detected and a P0303 cylinder 3 misfire detected and a PO304 cylinder 4 misfired detected. After driving it 2 miles PO172 system to Rich bank one showed up again but nothing else. What would make cylinders 3 and 4 misfire and could a misfire trip a P0172 code? Thanks Dave

Unburnt fuel from misfire(s) will cause a rich code. Fix your misfire problem and the P0172 will likely go away. If your spark plugs for cylinders 3&4 are wet with fuel then you have a spark problem or too much fuel for the mixture to spark and ignite. A bad injector seal will not show up in resistance testing. Do you still have your old injectors?