engine swap question

[Trptguy]

So I swapped in a '89 M20 motore into my '87 vert. It was just a replacement. When my mechanic plugged everything into the ecu the car started fine. The tach though does not work. I also feel that the fuel management is a bit off9seems to run quite rich0. I have replace the fuel filter, fpr, plugs and harness and icv. The only thing i have not doen it replace the injectors.

Is it possible that I need a newer ecu to make the swap complete and have the engine run correctly?

Sorry very noob question, and yes i did several searches and nothing really seems to answer my questions.

Positive input would be apreciatted

[FredK]

Did your mechanic switch the engine wiring harness from the 87 over to the 89 engine? If so, you probably need to plug in the C104, a 3 pin plug in the glovebox, to get the tach functional.

If your mechanic swapped the 89 harness and got funky with some water hose routing, then you'll have to tap the C101 20 pin round connector to get the tach functional.

[Trptguy]

my mechanic used the engine harness from the 89 and the stock ecu from the 87. I understand how the tach wouldn't be functional, but would this cause any fuel management issues?

[Trptguy]

also is there anyone in MA that I could take my car too that might know about this?

[jlevie]

Using the 89 engine harness probably explains why the tach isn't working. The econometer should also be dead with C104 not being present on the 89 harness. The simplest fix would be to switch to the harness from the original engine. The next easiest fix would be to transplant C104 from the 87 harness.

Unless the car has a defective DME, it isn't going to be the cause of the rich condition. The 153 DME that the car probably has is okay to use with any M20B25.

[Trptguy]

ok cool, i got rid of the harness and engine from the 87 a while back, so now i will need to find one. Are there any other options? preferably with a diy writeup??

[MR 325]

Using the correct engine harness would be the smartest thing to do. Post a WTB ad for an 87 i/is engine harness. Also, the 87 and 89 M20 use a different o2 sensor (different plug). Do you know if you even have an o2 sensor connected? This could be your rich running issue.

[Trptguy]

Using the correct engine harness would be the smartest thing to do. Post a WTB ad for an 87 i/is engine harness. Also, the 87 and 89 M20 use a different o2 sensor (different plug). Do you know if you even have an o2 sensor connected? This could be your rich running issue.

they use a different O2 sensor shit didn't know that. I will have to check

[jlevie]

ok cool, i got rid of the harness and engine from the 87 a while back, so now i will need to find one. Are there any other options? preferably with a diy writeup??

Since you no longer have the harness, there are two options for fixing the tach.

One is to run the tach & econometer wires to C101. That is rather a pain since you almost certainly won't have the sockets in the body side of C101. The other option is to get a three pin connector pair, replace the body side connector and graft in the harness side connector. Or for an easier fix, replace the body side connector with insulated push connectors and graft in three wires with matching receptacles.

Resist the temptation to simply splice the wires. That would lock the harness to car and require cutting & splicing if the harness or engine has to come out again.

[Trptguy]

yeah, i think i will just get the correct harness and call it a day. I need to check out the 02 sensor. Of course the engine that i swapped in came with everything so i figure the o2 sensor is the right one, but maybe it is bad, although it didn;t through and codes


effing e30's....why do i have to love these cars sooo much