merlyn

can anyone help me with what mod's need to be done to a MAF plenum to convert it to SD ?????....or is the only differance the onboard mounting of the MAP sensor ???

merlyn

let me give a little more info and ask another qustion as well,i have a 87 Z28 that was just converted from MAF to SD,I.E. new 730 ecm from a 1990 with vats and emmissions removed,9th injector removed and prom programed with the specs of my motor tranny and rearend,MAP sensor was added as well as all other new 1990 model sensors except the TPS,that was only a month old and for the 1987 which is a adjustabel and after just doing some reading i read the 90-92 TPS was non-ajustabel,should that be changed as well ??,i bought the swapping book as well as the 82-92 haynes manual and have searched the net for hours but still cant find a complete guide,i want to make sure that i did'nt miss anything,any help or a point in the right direction would be great.

Zepher

The Plenums are the same (to my knowledge), only difference being the onboard mounting that you mentioned.

Some people will elongate the upper hole in the 90-92 TPS to make it adjustable. Using an 86-89 one works too since it worked on my 87 TPI that I converted to SD.

merlyn

thank you for the reply Zepher,the TPS is whats giving me a problem,i think i'm going to have to take it in and have someone set it for me,everytime i think i have it dead on i take it out for a test spin and then it either starts to idel way to high(1000-1500 rpm) or way to low(200-400 rpm) and dies when you start to brake and slow down,its like the arm on the TPS is sticking cause i'm screwing it on to tight and it idels way to high,if i back off on the screws to let the arm move freely so it returns with the arm on the TB is when it idels to low and dies,i'm allmost tempted to put a couple small washers between the TB and TPS to see if it helps but dont know if that will through it off as well,its allmost like the TPS does not like or fit the new bbk TB.

Willie

There is one difference in the plenums. The SD plenum has an external boss (extra thickness) with a tapped 10mm bolt hole. The MAF plenum does not have this boss and the wall is not sufficiently thick to drill and tap a hole for the MAP mounting bracket. Doing so will result in punching a hole completely through. This is okay but I didn't want to thread a bolt from inside the plenum.... just think if it were to come loose, where would it go? Right down a runner..... yikes!! If you'd like a pic of my solution, please e-mail me. It's too difficult to explain when one pic will do the job.

Now I have a question for you. Did you assemble your conversion wiring harness based on instructions on TGO? I did and discovered what could be a mistake in one of the wire's pin assignment. It might not make a difference, but it could introduce noise that could effect the MAP and/or CTS voltage readings to the 730 ECM.

aklim

OK. Do you have a scantool? You cannot set the idle with TPS alone. You need to set the minimum airflow then set the TPS. I would run the car and adjust the torx bolt on the left side of the TB till I get about 20 IAC counts and then set the TPS. Either that or follow this procedure.

merlyn

thank you for the replys guys,put washers between TB and TPS,just enough to create a gap between the 2 and now i was abel to set it dead on and no sticking of the arm on the TPS after WOT and tightend down,the littel white nub on the back of the TPS that the retainer clip that holds the arm on the TPS was mashing up against the screw that holds the arm on the TB and causing it to stick,grinding down the nub didnt seem like a good idea cause the retainer clip could of worked itself off so i went with the inner washers.

tealman92

Hey the plenums are different 85-88 are the same and 89-92 are the same
the differences are the 85-88 have holes on both sides for the egr tubes that run through the runners and a huge triangular hole under the 2 tb holes in the front of the plunum the 89-92 only has one egr hole for the runners and no triangular hole under the tb holes