2004 Mazda 6 Engine misfire, Black smoke

WILLIEPEAY

MEMBER
2004 MAZDA 6
3.0L
V6
2WD
AUTOMATIC
187,000 MILES

Hello I have a 2004 mazsa 6s 3.0l. Last year the motor blew and I replaced it with a new motor. The new motor has 40,000 miles on it. I have recently started to have an issue with the motor running rough at startup. It has been running rough at idle, hesitates when accelerating with black smoke pouring out of the exhaust. I have checked the cel and it has shown consistently - p0300 engine misfire and has shown p1487 egr valve malfunction code. It was tripped the bank 1 sensor 2 no reding code twice. I have cleaned the egr valve and replaced the 1, 2 and 3 spark plugs and coil packs. It seems to be running rich. The freeze frame data showed the command egr at 51% several times. Could this be a fuel pressure regulator malfuction? What should I check next? Thanks in advance.

Will

6 Replies

JACOBANDNICKOLAS

MECHANIC
108,179 POSTS

Black smoke = too much gas. Have you checked fuel pressure? The regulator could be bad. Also, have you checked the coolant temp sensor? If it tells the computer it's really cold, it will dump fuel. Also, what are your fuel trims?

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Friday, July 24th, 2015 AT 9:30 PM

WILLIEPEAY

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4 POSTS

I forgot to say that I replaced my coolant temp sensor. On the most recent CEL I received today was two p0300 codes and the trim levels were:

Short term fuel trim bank 1 +22.2
Long term fuel trim bank 1 +6.7
Short term fuel trim bank 2 +21.4
Long term fuel trim bank 2 +5.6
Egr command was at 2%
The engine was at idle sitting at a stop light when it threw a CEL.

Thanks again for all your help

William

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Saturday, July 25th, 2015 AT 4:37 PM

JACOBANDNICKOLAS

MECHANIC
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The Short term trims are high as well as the long terms are a bit high, but not too far out. Have you checked pressure?

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Monday, July 27th, 2015 AT 9:58 PM

WILLIEPEAY

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4 POSTS

Hello I haven't tested the fuel pressure yet. I just threw a cel again after cleaning the egr valve. The malfunction code was a p0300 engine misfire no specific cylinder the fuel trims this time were:

Bank 1 STFT -12.5%
Bank 1 LTFT +10.2%

Bank 2 STFT -3.9%
Bank 2 LTFT +3.9%

Spark advance 9.0
Intake air temp 132.8
Command EGR 0
Command evap 0
Engine collant temp 204.8
Engine rpm 950
Maf 1.0lb per min
Tps 17.3%

Based on these readings, what do you think is the issue.
I will get the fuel pressure test done tomorrow. I will let you know what I find thanks again for all your help.

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Thursday, July 30th, 2015 AT 8:15 AM

JACOBANDNICKOLAS

MECHANIC
108,179 POSTS

Both LT and ST should be close to 0. Bank one is all over the place. Are you certain there are no vacuum leaks? Are you certain there are no O2 sensor issues?