Hi all,

NB: I am *not* an expert on cars, and I have what I would consider slightly above average, yet relatively limited knowledge of the inner workings of automobiles, so please forgive me if I don’t describe or understand the situation any better than I currently am able to. I will do my best to explain and I appreciate your time very much:

TL;DR: The connection on the wiring harness for the map sensor does not fit the Bosch MAP sensor installed into the LS4 intake manifold. Can I purchase an adapter to make it fit, or will I run into issues?


BACKSTORY

In 2016, I purchased a 1986 Firebird that came with its original V6 automatic engine. A few years down the road, after a number of persistent issues with the engine and at the advice of my primary mechanic, I decided to pursue an LS swap, and eventually found what I felt was the best overall automotive shop in town at that time who was willing to take on the project. He quoted me a *very* reasonable price for the entire project, and he estimated it would take three months total.

Covid unfortunately hit shortly after I signed the paperwork, and long story short, I decided to retrieve my car from the shop *three years* later, after a seemingly endless set of excuses (some of which were certainly valid, such as shipping delays, couldn’t find reliable workers, workers stealing from him, heart attack and quadruple bypass, etc).

I would estimate that he got fairly close to finishing the project, although I fully recognize that to guess how much work might or might not be left on the project would yield a range of possibilities. I have since called just about every mechanic in town ever since retrieving my car, in hopes of paying someone to get it fully running, but I have been unable to find anyone who will finish it for me for the understandable reason of them not wanting to come in after someone else’s work. Thus, I am taking it upon myself to finish it, come hell or high water.


ENGINE SWAP SPECIFICATIONS

Here is a brief amount of immediate specifications regarding what is currently in the car:

Engine: Completely rebuilt LM7 (Silverado, 2001)

Transmission: Brand new 4L60E

Wiring Harness: Brand new “Performance Systems Integration” HAR-GEN3-DBC

ECM/ECU: “Delphi Automotive J1 Blue” (I believe this may have been pulled from the same truck as the engine)

Intake Manifold: Gen III LS4 Impala/Monte Carlo – P/N#: “12604786”


THE ISSUE(S)

Currently, the engine and transmission are mounted inside the vehicle, and the wiring harness has been threaded through the firewall and into the ECM -- however, it has not been fully connected in the engine bay to the MAF sensor, the MAP sensor, both oxygen sensors, etc. I am also unclear as to whether or not the ECM has been tuned appropriately. The biggest foreseeable hurdles to complete the project are to finish the wiring job, and to have the exhaust welded on.

The current roadblock I am running into right now – and seeking advice on – is that the plug from the wiring harness does not fit the connection on the MAP sensor (which is currently a “Bosch” sensor, as it is my understanding that that is the correct sensor for these particular manifolds; please correct me if I am wrong). I have been in touch with the wiring harness manufacturer (PSI) to inquire about whether it is feasible for them to send down an adapter to make the connection work; however, the gentleman on the phone advised me that I would most likely run into issues with the throttle body not fitting, compression, the ECM not being tuned correctly, etc.

I came here to the forums to see if anyone else has perhaps run into this dilemma or has an understanding of this particular conundrum, and what, if any, steps should perhaps be considered to circumvent the potential issues or solve the problem as a whole. Perhaps it might be the best course of action to pursue attaching a different intake manifold, which I am willing to do so long as it clears the hood.

Any advice would be very greatly appreciated, and please feel free to ask for any clarifying information if I have left out any pertinent details.

Thank you kindly in advance,

JB

 

Just to clarify, your harness has a different plug than the senser accepts or your harness isn't long enough? The LS4 intake is probably one of the worst intakes due to the necked throttle body required for the FWD applications. A different intake won't solve the connector issue, but will help the performance a bit. Any pictures to show us your dilemma? There are a variety of sensor alternatives. Your PSI harness instructions should have a cross reference chart of various sensor numbers.