5.2L knocking during hard acceleration

[chips2002]

Hi everyone, This is my first post. I have a problem with a 1991 B250 5.2L engine knocking during hard acceleration. I hope somebody could give me a hand with this problem.

This sympton does not really start up until the engine has been warmed up for about 20 minutes. I started to get this problem after I changed the head gaskets that were leaking and the pcv and breather filter grommets that were worn out. What I mean by knocking is that the carburator like chamber over the TBI (throttle body injection) starts to pop up and down and make this "pump pump" sound.

When I drive the car with the throttle pushed down about 1/4 of the way, the problem does not occur. But when pushed 1/2 way or more, the problem starts to occur. The other thing that I started to notice was that the van does not have a lot of power when going uphill. I floor the van on a 30 degree incline, and it is still losing power and slowing down. The van is pretty much empty inside except some minor tools I carry with me for work.

I tried to fix this problem by changing the fuel filter and put in 2 12 oz cans of Chevron Concentrate fuel infection cleaner with 20 gal of 91 octane gas. There still has not been any improvement. I am the first owner of this van and had it since 1991. Ever since i bought it, I only put in 87 octane gas. I have done all the tune ups I can think of (spark plugs -- standard heat range champion 404, cap, rotor, ignition wires, ignition coil, pcv, cleaned out breather filter, TBI cleaning, air filter, coolant, fuel filter). I also tried using Bosch platinum plugs instead of the Champion 404's but still have the same problem.

I have heard of other members having pinging and knocking problems due to there spark plugs. Could it be that I need colder type plugs or different brand plugs? Or could I have problems with my injectors?

I would appreciate it if anybody could give me advice with my problem. Thanks and sorry about the long write-up.

[DEEROK98]

try autolite 3923
these plugs are colder range.

[chips2002]

Where could I find these plugs. I heard everybody goes to NAPA to pick up their parts, but I live in LA and I dont think there is any around my neighborhood. The only auto parts store I know of are Autozone, Kragen, and Pep boys. Do these stores carry this plug.

[DEEROK98]

yes at pepboys.I bought mine for $12.00 for all 8
autozone don't sell them.PEACE