Idle issue

ok here is the deal...
88 XJ 4.0 auto trans, swapped in 96 4.0, 95 standard trans. Items used on 96 motor in my reply below.
Map sensor removed from 96 throttle body and vacuum hose routed from there to 88 MAP on firewall. TPS input = 4.66 output adjusted to .77 left auto 4 way plug unplugged. NSS jumpered at connectors under hood near dipstick tube.
Here is the problem.......Rough idle when cold. When warm it will idle fine for 30-60 seconds dip down 200-300 rpms and then climb back up and idle fine again for another 30-60 seconds and so on. Other than this problem it runs fine and have no other problems so far. The swap as fairly simple except for the belt routing. TPS adapting was done with a roll pin and 2 brass flare nuts. Pretty good on gas, but a stong exhaust smell sometimes. Any input would be helpful.

I would suggest using a Renix CTS. I know when I did this swap I used ALL of the Renix sensors including the IAC. Mine didn't run right with the HO sensors even the IAC, which others have used it. I would try that since you say after it warms up it does okay.

My post was all messed up.....here it is again.
off 88....knock sensor, cps, cts, tps, mat, map, o2, distributor, cap, rotor, wires, plugs. everything new except knock, tps, mat, map
off 91-95....fuel rail, pressure regulator, injectors
off 96... throttle body minus map
adapted auto tps to 96 throttle body, left 4 way auto plug unplugged.

I was going to say the injectors might be the problem but since you do have a true HO engine I suppose maybe they want that. I know if you're just using an HO manifold on a Renix you want to use Renix injectors but I dunno about the combo you're using. Ya know I'm thinking maybe it's the distributor you're using, the HO uses a different distributor than the Renix ones do. If the dizzy isn't matching the engine I would say that may be it.

If i am using the 91-95 ho fuel rail with pressure reg. the 91-95 ho injectors should be used also, correct?

I think all the injecters are 19# per hour, HO or RENIX. I may be wrong. The stock injecters in my 90' are 19#ers.

xjtrailrider said:

I think all the injecters are 19# per hour, HO or RENIX. I may be wrong. The stock injecters in my 90' are 19#ers.

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I know for a fact they definitely aren't the same. There have been a few people who have tried running the brown HO ones in their Renix and it runs like crap. When they switch it runs fine.