No 1 Cyl not firing

[Chuck Leeper]

Cam going flat.....
A cam sensor won't make just 1 cyl fail to fire.
Crank sensor checked out?
115 cranking sounds fishy...
Time for a leak down test.
U have a FAST, how about some data logging??

 

[TurboBuRick]

First

Take a new spark plug and plug #1 wire onto it. Set it on the intake and crank the motor a couple times, does it fire?
(NOTICE!) Make sure you don't have any fuel leaks close by.

Post back your results.

 

[KevinB]

I fought this issue on a car recently. Ecu had a failing injector driver. I switched #1 & #3 injector plugs and the miss moved from #1 to #3. That's how I came up with my diagnosis.

 

[KevinB]

Also, if all cylinders are 115 psi....I wouldn't worry. The cylinder pressure readings can vary depending on how hot the engine was when tested, cam profile, cam timing, etc.. 115 isn't bad...my tsm engine runs mid 9s and has 112 across the board due to the duration and overlap of the cam. It bleeds a lot at low rpms but Rips way north of 6k rpms.

 

[pajo]

test

Oldie but goodie way to check for spark - you need to connect spark plug to plug wire in your case #1 and a ground strap or jumper from ground to the main metal part of the plug. Next start your engine with the spark plug just hanging there of the side and observe - spark or no spark..

 

[wahoo50]

Well back to my favorite problem. I have confirmed with a noid light the signal is arriving at the injector, I have replaced the injector, no help. Replaced the coil pac and ignition module, no help.

As I drove the car today, the missing will stop, engine runs smoothly, then starts missing again. Seems to fire all 6 when I accelerate, when I back out it begins to miss again. I don't build boost because it will backfire loudly through the exhaust.

I have not inspected the cam or crank sensor because I don't understand how it can affect only the one cyl.

Need help with this one.

 

[Black Power]

Well back to my favorite problem. I have confirmed with a noid light the signal is arriving at the injector, I have replaced the injector, no help. Replaced the coil pac and ignition module, no help.

As I drove the car today, the missing will stop, engine runs smoothly, then starts missing again. Seems to fire all 6 when I accelerate, when I back out it begins to miss again. I don't build boost because it will backfire loudly through the exhaust.

I have not inspected the cam or crank sensor because I don't understand how it can affect only the one cyl.

Need help with this one.

#4 should be sparking at the same time as #1, so I agree with you on the crank/cam sensor part. If one of those was screwed, you would probably be having the same issue on #4 also.

This doesn't make much sense...have you rolled it over with the driver's valve cover off to make sure it's getting full stroke?

 

[wahoo50]

Removed the drivers side valve cover, cam action same on all rockers. Didn't find any too tight.

 

[jasjamz]

Faulty ECM/ECU?
Did you inspect the cam sensor?

 

[wahoo50]

Thanks for the input. Running FAST. I have not gone after the cam or crank sensors, don't see how either can affect only one cyl. But if someone has seen this kind of problem solved adjusting them I will do it tomorrow.

 

[UncleDave]

Could the fast ecu be acting up, maybe a driver going bad? Do you have a data log on the Fast from when it's running poorly?

 

[wahoo50]

I don't have any logs. Simply put, it's No.1 cyl missing most of the time and backfires sometime while cranking the engine and when boost starts to build.

 

[Phoneguy]

The crank sensor gives the ecu the reference for the number one cylinder. If the sensor is bad or the crank bolt is loose allowing the balancer to wobble you will have erratic backfires due to number one not being seen. HTH

Bryan

 

[wahoo50]

How do you test the crank sensor? Harmonic balancer bolt is tight.

 

[turbot990]

re a no 1 cylinder

How do you test the crank sensor? Harmonic balancer bolt is tight.

Replace it it,s not hard at all to do just make sure your air gap is correct :smile: Did you pull your cam sensor cap and make sure your the center screw is tight and the reluctor ring has not moved

 

[wahoo50]

Thanks for your reply. No, I have not explored what, if anything, might be a problem with the cam sensor. I do have a new one I can install. Just still don't understand how it can be causing one cyl to missfire. But these cars can be a bit tricky.

 

[turbot990]

Yes they can be a bit tricky have you checked to make sure a lobe on the cam is not worn and check compression if your compression is low on the number 1 cyl. it can cause that bud

 

[6 to go]

Did the problem ever get solved?
I am chasing the same problem on the # 2
cylinder!
Mark

 

[turbot990]

what all have you checked bud

 

[wahoo50]

I have checked all I know to check. I have not explored the cam or crank sensor yet, I don't see how either can cause a one cyl miss. I have not found the problem.

If you go back through these posts you can see results of what has been checked thus far.

Running down the road the No.1 cyl goes and comes. While idling, I can hear a small backfire in through the exhaust pipe.

Compression is balanced throughout, cam action is perfect.

Thanks for the help.