Expert: Van - 5/30/2007

Question
My engine would cycle through sputtering(almost/sometimes dieing)and idling fine, and warm or cold it would die when i can to a stop but would always start right back up.  So i replaced the rotor, cap, plugs, plug wires(some were worn bare in spots), and o2 sensor, and set the timing.  It then ran much better but still had the sputter and OK idle cycles.  Next I replaced the TPS sensor and that has solved the cycling problem, but now it idles really high.  Also the truck feels really under powered, when i step on the accelerator(to pass someone or just to get going quicker) it feels like its straining to accelerate the truck.  How can I fix the high idle?  and why does it feel under powered?

Answer
Hi Mike,

Make sure the EGR valve is clean, and not sitting on some carbon.
Also check for any other vacuum leak, not forgetting to check the brake booster. (Dies when you stop...foot on the brake?)
Check the intake manifold gasket also, by spraying carb cleaner on it while it is running, and check for RPM change.

Next, you need to test the fuel pressure.
It is a pain on an 88, cause there is no test port.
There is an adapter that goes in place of the fuel filter, and there are little fittings that can be inserted in the line at the throttle body.
But you need to verify that it is running on 13 PSI.
A bad pump is possible, as well as a bad fuel pressure regulator, but on trucks around that era, I have found the hose inside the fuel tank, where the pump connects to the supply line, split. It would hold about 7 PSI in the system, and the rest would just spray out inside the tank. Ran just like you describe.

Van