LS400 Problem: Can't rev above 2K RPM.

[thenewmexican]

1991 LS400

I just recently had my entire exhaust system replaced because someone told
me that the cats were clogged. Well. Replacing the exhaust made a HUGE difference.
The car really wants to go. Lost more power. However. When I get to 2K on the tach.
the engine stutters badly, as though it wants to die.

When. I'm at a stand still,I depress the gas pedal to the floor, and tons of black smoke
comes from the tail pipe. But. The engine still will not go above 2K RPM.

I checked the computer code. It give me a 31 which is the MAF. I checked the resistance of the MAF using an OHM meter and the specs. It checks out fine.

Also. The engine runs the same whether or not the MAF is connected.

Any help is greatly appreciated.

Thanks.

 

[dar_sbb]

dont know if this will help... i also had a similar issue... but it was my ignitors that were causing the issue.. but i run a afm.

 

[thenewmexican]

Thanks for the info.

Is there a way to test the igniters. And. Also. What does an igniter do ??



Thanks.

 

[Lextreme II]

Perhaps you should check the coils too. There are few articles on testing the coils. There are two of them. One is on top of the engine just near the water bridge and the second one is located near the ac compressor. You can test for spark and trace with coil is malfunction. If you dont see spark, then it is most likely one of the coils is bad.

http://lextreme.com/forums/showthread.php?t=9938&highlight=coil+testing

http://lextreme.com/forums/showthread.php?t=8926&highlight=coil+ohm

 

[Zuffen]

Bear in mind if a coil hasn't got any spark it could be an igniter.

Only yesterday I was chasing a loss of spark and it was an igniter.

Easiest way to check is one distributor runs 2 spark plugs on each side of the engine.

Ascertain which 2 spark plugs don't work on the left side of the engine.

Swap the conections between the 2 igniters and see if those plugs have started firing.

This will confirm you have either a faulty igniter or bad wiring.

If swapping the igniters over doesn't make any difference it is most likely a coil.

You can temporarily swap the coils (they don't bolt on properly but will fit well enough to run it) to see if the lifeless plugs now fires. If i hey do you can check the other two plugs on that side of the engine and they should have stopped firing.

Hope that all makes sense but it is a simple process of elimination.

If you don't check carefully you may buy parts you don't need.