Lq4 Swap has Finally Begun...

[Rich84]

Is the PRNDL indicator plug on the 4l80e only used for the dash or does the ecm need it? It is included in my harness but I had to remove the connector to get it thru the firewall.

[MalibuSSwagon]

Originally Posted by Rich84

Yes..I was talking about the wire from the truck harness.

Thanks, I'll pull it out.

All it does is provide a loadsense to trigger the alternator to start charging, but on the LQ4 that is handled by the PCM. So doesn't effect anything if you just remove it.

[Rich84]

That was easy...

Speedo and tach are another story. I went with the tach gas gauge combo from GM sport a couple of years ago so I really don't want to scrap the stock gauges. I was thinking of using the box to drive the cable speedometer. Is there a better option?
From what I have been reading, I guess that the tach wont work without some changes to the programing.

[Jstock85]

Did you put an inline filter somewhere along the frame is what I was asking.

[Rich84]

Originally Posted by Jstock85

Did you put an inline filter somewhere along the frame is what I was asking.

I have a returnless fuel rail, so I am using the Corvette filter regulator.

[mongocanfly]

I used the dakato digital unit to drive my speedo...works great ..

[Rich84]

Originally Posted by mongocanfly

I used the dakato digital unit to drive my speedo...works great ..

Was it difficult to get it calibrated properly?

[Jstock85]

Rich did end up soaking the injectors in the seafoam? if so how they turn out?

[Rich84]

I did not. I probably should have. I'm hoping to get it fired up this weekend. If there is any issues that is probably the first place I'll look. If there is a problem with the injectors I will either send them out to be tested and cleaned or replace them.

[Jstock85]

i bought a junkyard 4.8 and hopefully will have it ready to go buy this time next month so I'm just doing some pre-troubleshooting! Im sure ill run into similar issues so I was curious Just in case!

[MalibuSSwagon]

You could get a 90-91 electronic speedo cluster and install your GM sport tach into that. Then have the PCM calibrated for your tire size and gear ratio to drive the speedo correctly, and for the tach the PCM can be re-programmed to drive it on the 8 cylinder setting. I had this done, and my tach works great.

[mongocanfly]

Rich..it wasn't that difficult to setup once I understood what they were telling in the instructions..im a technodummy so its hard for me to follow along sometimes...I simply used a gps to calibrate..to adjust the speedo all your doing is grounding a wire that adjusts it..when I first started it was showing me doing 85mph idling in first gear..once set it tracks with the gps very close under acceleration...and at cruise speed its dead on at any mph I checked it at..

[Rich84]

It's alive....Sort of.

I got to start but it won't idle for very long. Fuel pressure is 58 at the rail and the injectors are getting power. So I am pretty confident that I should have at least cleaned the injectors first..No big deal I guess.

I only had one side of the exhaust hooked up and no O2 sensors in. That sucker was LOUD.

[mongocanfly]

Do you have the maf hooked up?

[solidaxel]

Clean the injectors!!!

[Rich84]

That's the plan..It was cool to hear it come alive though..

[LeesTruk]

Rich, you need the o2's for proper fuel scheduling. The PCM is most likely defaulting to a given value, and the engine is going over-rich and causing the stall

[Rich84]

It wouldn't even start without spraying fuel in the intake.

I had the wrong O2 sensors..The correct ones are on there way along with a set of remanufactured injectors.

Then hopefully it's a ride to my Brother in law's exhaust shop.

[ls1nova71]

You most likely have some stuck injectors, thanks to the crap gas we have these days. Sitting 3-4 years is a long time, so I would soak them in some Seafoam overnight, then check them with a battery to make sure they click, then reinstall them. I do this as a preventative measure on every swap I do just so I don't have to take them back out. The engine should start and run fine without O2's hooked up while it's cold, it isn't until it tries to go into closed loop that the PCM starts to get annoyed without them.

[Rich84]

Friday night I put the new injectors in and she fired right up and idled beutifully..it had 3 codes. One for each o2 sensor and one for the transmission. I think it said something about vss. The transmission is not full of fluid yet. I still have to drop the pan.
The other issue that I had was that the relay for the fan on the new wiring harness was clicking repeatedly and loud. The fan never came on.
I was surprised how quiet it ran. I have dual 21/2" to resonators and flowmaster 40's.