Hello,

After a cam swap I've been having a hard time getting the engine running right again.

Right side is pulling fuel even under load (DataMaster sais BLMs adjusting -5 to -9% less fuel) while left side sits 0% to +3%. Misfires when decelerating and hesitates under sudden load at lower RPM.

-cleaned and tested injectors
-cleaned MAF
-replaced plugs
-have 55-60kpa (8.5 psi) MAP reading at idle, sprayed around intake nothing showed - probably no leaks
-no error codes
-O2s are working great, move fast between 50 and 950 mV
-pressure checked fine on all cylinders
-distribution wheels and chain checked, they are correctly installed
-valves adjusted to 0lash+1/4 (no noise)
-spark plugs I removed showed cylinders 6 and 8 (right side) were a bit blacker, new ones haven’t been checked yet.

Car seems to be pulling OK but not really there. When accelerating sounds pretty fluent.

Any idea what to do next? Could this be exhaust leak? Maybe one of my catalytic converters fell apart and is causing a pressure/temperature imbalance? Could it be the opti? Plug wires?

Thanks,
Felix.

 

A negative BLM means it's subtracting fuel to prevent that bank from running rich. What cells show the -5% to -9% corrections? An exhaust leak before tbe O2 sensor will cause a (false) lean and the PCM will raise the BLM's.

 

Yes, I meant rich not lean

The rich right side condition happens now only while driving, at idle it goes to +2% while the left side goes to +6%, the exhaust smells real good, can breathe in it. Not sure what the cell numbers are but the condition exists both when cruising and when accelerating, BLM goes low on right, backfires some when doing engine break, and it doesn't pull quite as with my smaller cam... Seems slow to accelerate, something holds it back.

Thanks.

 

Can't follow your BLM numbers... they are "-" in the first post, and now they are "+". You are indicating "+" shows "rich", and that's just the opposite of what I tried to explain. BLM's within +/- 5% should not be a concern.

If you have a data log, post it.

 

Ok I'll be more clear.

IDLE: runs great, burns all, no smell, left and right BLMs look normal +2-6% fuel
LOAD-High RPM: backfires when doing engine brake, right side BLMs real low, -7 to -8% fuel, while left side stays around +0-2%.

I will datalog with DataMaster today and post it.
Thank you for your help!

Felix.

 

A short log when at full temperature.

http://www.filedropper.com/test1_15

Thanks.

 

At idle (Cell 16) the BLM's are 128 L (0% correction) / 124 R (-3.1% correction).

Idle appears slightly unstable, and MAP is jumping a bit as well. Is there evidence of misfiring, popping, maybe a sticky valve? Or - more likely - it's just a result of the cam specs. The MAP is good for that cam. Appears to be a good tune in that respect.

System voltage is good, IAC counts are good, Closed throttle TPS is high at 0.90V, but does not appear to be affecting anything. When you go WOT it increases to about 4.20V (but see comment below).

Coolant temp is staying high (210-215*F) and both fans are on. What t'stat are you running? What are the fan on/off temps?

Inlet air temp is excessive (120-123*F). What air intake system are you using? Is the IAT sensor in the stock location (heat soak)?

Mass air flow (AFGS) looks a bit high (12.5 - 13.5).

When driving:

You only operated in a limited number of cells. Cell 15 is used at WOT, and its 129 L / 129 R. About as good as it gets. However, the O2's are on the high side (930-940) during the limited WOT (PE mode). The PCM is trying to drop them by lowering the ST's and seems to succeed on the right side (drops below 900mV), not on the left.

On decel, I do not see any evidence of decel fuel cutoff - injector pulse widths do not go to "0". The exhaust stays slightly rich for the first part of the decel, which may explain the "misfires" on decel - do you actually mean a popping in the exhaust? I wonder if the 0.90V closed throttle reading is affecting all this? Your tuner may be able to clarify.

You max out at 38* of advance at WOT. Wonder if the high IAT is causing it not to add the mysterious 3* that seems to be related to IAT.

Your BLM's in other cells are all over the place:

#6: 124 L/ 115 (-10.2%) R
#9: 130 L / 127 R
#10: 129 L / 120 (-6.3%) R

 

That's a very impressive description

Here's what I can confirm:
Intake is the SS hood scoop one, with the filter on top of the fuel rail.
The engine is too hot, if I turn on the A/C it goes up past normal temps.
I have the stock thermostat and the tune kicks the vents earlier to keep it cooler normally.
At the time of the log I hadn't driven the car for long enough for all the cells to adapt, but there is a CLEAR and obvious trend of rich on the right side, except at idle.

I'm thinking a cylinder or 2 on that side have either weak spark or drooling injector, fuel goes in exhaust and engine cuts fuel to whole right side, the other 2-3 cylinders run lean and overheat engine and degrade overall performance!

Does that sound logical to you?

I plan on swapping injectors and O2 sensors to see if the problem moves, otherwise I'm getting a new wire kit (plugs are new).

I will also drive around a bit more, have it learn all cells, and take a new log.

Thanks again for the elaborate analysis!

 

Sort of.....

"weak spark" means incomplete combustion. You dump fuel and air into the exhaust. The O2 sensors cannot "see" fuel.... but they see the unused oxygen in the air, and read "lean", Then they start to add fuel.

A leaking injector can cause it to read rich, because the excess fuel that enters the exhaust may continue to combine with the small amount of residual O2 in the exhaust and cause a "rich" reading.

 

Update.

- Checked all plugs: one on the problem side was very black, one on the other side was a little black, rest were white and clean.
- Swapped all injectors from one side to the other, moving the injectors of the black plugs to #1 and #2 cylinders, for easy access.

RESULT: Same problem, still on passenger side, still lots of exhaust pop and not so good performance.

- Disconnected O2 sensors.

RESULT: Works overall much better, pulls much better, far less exhaust pop (still has some), revs faster and better.

My deduction: Before I found my injectors were clogged and leaking, after sitting for 2 months, they fowled my O2 sensors and now that I've cleaned the injectors I might still have 1 or 2 leaking that might need replacing, but the fowled O2 sensors are messing everything up anyway.

To do: swap O2 sensors and see if problem moves, check exhaust for leaks. Based on findings buy new O2 sensors and maybe injectors.

Any other thoughts, ideas?

 

Found an older good working O2 and tried to swap it with he passenger side one. Had the same readings.

Doing this I found a crack in the exhaust pipe at the weld of the Y-Pipe.

I'm guessing if I fix that and another big leak down the tube towards the muffler I should get some results

 

Exhaust all fixed up, injectors moved, still same cylinders not burning right. 8 has black smoked spak plug, 7 a little less black.

Out of ideas

Felix.

 

Grab an IR temp gun and see how hot each header tube is getting. You may need to adjust the fuel multipliers for the back two cylinders (possibly the fronts as well).

 

These are my current fuel trims.

ImageShack® - Online Photo and Video Hosting

Can the cam swap from 224/230 to 227/235 modify temperatures and require trim modification?

Thanks,
Felix.