Good day all.

I finished up the swap of the donor transmission from an 06 Accord into my 2003 TL last week. I'm having some engine issues. No codes, but when starting cold you must crank for some time before it finally fires and starts, and even then, it's like it just barely starts. Until it gets warm it idles and runs really rough. After warmed, it purrs like a kitten at 750 RPM idling.

While parked, if you stomp on the gas real quick, it hesitates for a fraction of a second before picking up RPM. If you are driving, all is well if you take it real easy, but if you try to accelerate more than slowly and gradually, the engine bogs down and loses RPM. It won't speed up or recover RPM until I let up on the throttle and go back to driving like the stereotypical grandpa, of which I am certainly not!

The donor transmission seems to function fine, runs through all 5 gears smoothly, I just can't stop on the throttle! It's almost like it's running lean. I have access to a real-time data logger (BlueDriver) but I'm not sure which function to monitor or what the normal ranges are of what I'm monitoring.

Is there anything involving the swap that would cause the engine to run bad? I've checked for vacuum leaks or electrical plugs disconnected or anything that I may have overlooked, but I'm not finding anything. Looking for wisdom from those more experienced at this than I am... Any guesses?

Thanks,
Glen

 

It doesn't sound like a transmission problem to me. sounds like something in need of a tune-up but..just in case:

Did you clean the mating surfaces and refasten both the grounds straps? one near the the thermostat and the other near the external transmission filter?

 

So, on an ECM controlled car, what constitutes a tune-up? Spark plugs? Done.... TPS voltage adjustment? Done. MAP sensor replacement? Done. Am I missing anything? I'm sure I am...

Yes, both ground straps cleaned and connected. I'm not sure it IS a transmission problem, but the engine ran perfectly before the swap, in fact just 5 hours previous to the swap I changed the timing belt and water pump, cam and crank sensors, blah, blah, blah. Oh yeah, cleaned the EGR passages in the intake and adjusted valve lash. As I said, all was perfect before the swap.

I haven't found any electrical connector not plugged in, but most of those are transmission related. It may be that one of the transmission connections is dirty or not making contact but all of the throttle body connections have been under cover by a roof during the swap. As a "hail Mary" I may disconnect and clean every connector with electrical contact cleaner and reconnect and see if that matters.

Like a said, it acts as if it's running lean, like it has a huge vacuum leak, but I would suspect something like that would trigger a MIL...

Just as a thought... Where is the ECM on the 03 TL? I have the console removed and many things are disconnected. I hardly see how this could affect the engine, but maybe I disturbed an ECM connection while I was removing the console, assuming that's where it is...

 

After your new information: I am leaning towards that TPS adjustment you mentioned.

Were you able to stomp on the gas pedal between the time you changed all that other stuff and the transmission swap? that would rule out any of that other stuff you said you did before the swap, right?

 

That sure is odd, I can't think of anything tranny related that would cause that. I'd guess something else on the engine got disconnected or dislodged or something. Too bad there are no codes to go off of. I would start with double checking everything intake related, all hoses including vacuum, electrical connections, etc.

 

So as I have been thinking about the engine symptoms, I started to think they may be fuel related. Obviously, a vacuum leak would cause a lean condition that the ECU may not be able to compensate for. I checked for vacuum leaks with an unlit propane torch. No RPM increase as I passed the torch over all the probable spots where an intake leak may be.

Since I have the same year CL as this TL that I'm working on, I swapped fuel pulse dampers between vehicles. No change. Then I swapped fuel pressure regulators. No change. I didn't have the proper adapter to hook up my fuel pressure tester, so I decided to swap fuel pumps.

She fired right up and ran like a mechanical masterpiece! So now I can start driving this one while undertake the same items on my CL as I just fixed on this TL!

 

Awesome, nice job!