Got a 92, 3.0 with spark knock. It starts after the engine gets warm and only when accelerating or under load (up a hill etc). It has no EGR valve since the intake was replaced 2 years ago. Thinking of cleaning MAF, already checked plugs. It does have exhaust leak at No 3 cylinder, bolt broken in block, I am not going to try and get this fixed due to age and mileage (JB Weld worked). A mechanic told me to also check the anti-knock sensor, where is this located on this vehicle? Any other info or tips would be appreciated. Engine has 160,000 miles on it and tranny leaks, but cannot tell from where, I know it is not the pan gasket. Thanks for any help.

 

you might be leaking from front transmission seal. very common on aerostar.
good chance your engine is carboned up.
alot of guys use a spray bottle with water on the air intake
running at fast rpm to get rid of carbon or a safer way is
to try stuff from autoparts store. your on your own about which
one is best.

 

I got some additive that supposedly will help rid the carbon. However is there anything else I should be looking at? It only knocks when warm and under load (accelerating, hills). Will cleaning the MAF help? Since it has no EGR I am not sure what to look for.

Will check the tranny, but don't see where that would play into it other than I need to get the leak fixed.

 

pull the line to to the vacuum modulator on the trans see if it's full of tranny fluid if it is, you might have found your leak and spark knock problem, just decarbon the engine after you replace the vacuum modulator if it is bad.

 

Thanks I will check that out. Open to other suggestions as well.

 

forgot one thing with the vacuum modulator, if it is bad replace the rubber parts of the vacuum line that goes to it. I think it was the trans fluid that did it but mine were all kinds of rotted.

 

Yep, modulator was toast, not surprising after 160K on it. The hose seemed fine, still flexible. I took it for a drive and had a little spark knock still, but after about 10 miles it subsided and later in the day when I used the van, no knock at all. Thanks a bunch.

 

Glad to hear it.

 

where is this modulater? what does it look like?

 

Passenger side of the trans, kind of round looking, it's the only thing there that has a vacuum line on it so you could probably just trace that.

 

On my 92 3.0 it is located on the right side (passenger) about the middle of the tranny. The catalytic converter hides it some. It is a round device with a nipple on it, which has a vacuum hose going to the nipple. It is in an awkward place if working from the ground, but only one bolt on a hold down clamp, which keeps the modulator from backing out of the transmission. Modulator cost me $18.