93 Intrepid Engine Changed not running right.

[duster]

Maybe someone can help with this problem. I got the engine swapped out in my 1993 Dodge Intrepid, 3.5 liter, Auto tranny. I am going to call the place where I got the 3.5 motor to find out if it came out of a 93, 94 , or 95 Intrepid. The old engine ran fine until the crank messed up. Now when driving it down the road it feels like it trys to shutoff. But if you hit the gas pedal to metal it will run like a scalded dog. Idle fines also. Feels like it is not getting enough fuel or to much fuel and trying to shutoff, but never does shutoff. Sort of like to catalytic converter clog.

This even has the mechanic stumped. I finally got it to kick on the check engine light by letting it idle for a long time and all it showed was a bad oxy sensor. I drove it with the check engine light and it ran like nothing wrong. Didnt feel like it was trying to shutoff. So he took mine off my oxy sensors from old engine and still does it the same thing. Maybe bad fuel pump, but has 40 psi. We are wondering if the computer is not sensing the different motor, the injectors. The wire harness was a little different than mine old motor. Maybe injectors not doing correct thing. This even has me and my mechanic stumped.

He's not much on Dodges but does a lot on Imports. Done this engine change as a favor for me. He said he has known of Toyota and Nissan to do this and had to put the injectors from the old engine in, because the computer would read them correctly. Beginning to wonder if this 3.5 is not compatiable with my 93 Intrepid.

Any suggestions here. I am real good on working on cars , and have a great mechanic, just dont have the time with my occupation, Law Enforcement.
Thanks ahead of time. Car is back at the shop now until he gets some time to tinker around some more on it. No big hurry on the Intrepid, but sure do miss driving her.

[DanD]

The first thing you should have him do is change over every sensor from the old motor.
Even though they may look the same they could be miles different internally.
Even if it means changing hard parts over such as intake manifold to accommodate the original sensors or what ever it takes to use the equipment that came on the original engine. It’s not the 70’s that if it bolts up it’ll work.
Dan.

[Venturi]

I agree with Dan. I don’t know what differences there are between the wiring harness and the component connectors of the two engines or what was done to connect everything but the original in car wiring should not be modified.
One common problem that arises with engine replacements is poor grounding. You have to be really sure that not only the engine is properly grounded but that all ground circuits for the sensors, computer, etc are clean and attached correctly.

I noticed that you said the car seemed to run OK when the check engine light was on. This is interesting because the computer probably went into failure strategy and used a default value for the O2 sensors once it recognized a problem with the O2 sensor circuits. Do you know what trouble code number the computer set for the O2 circuits?

[oldtimer5520]

Hi Duster,
The salvage yard should be able to tell you if the engine they sold you is compatible with your year vehicle and what changes you may have to make to the engine they sold you. In the past on some of the engines I had swapped, I would get the computer from the vehicle that the replacement engine came from and install it in the vehicle I was installing the engine in. In most cases this worked fine. Hope this is of some help.