Manager Forum

Truck is listing P0303 DTC; truck has new plugs; no misfires on other cylanders; misfires on Cyl 3 are intermitant, and when it starts it jumps to over 200 misfires, runs rough, and has significant loss in power; did compression test on each cylander, and all were within specs; all vaccuum hoses are in good condition. Anybody have any suggestions? Possible EGR valve?

premierautohandling wrote:, and when it starts it jumps to over 200 misfires, runs rough, and has significant loss in power;

Do you mean when the truck starts, or the misfire starts. If it is just whe the truck starts, I would be looking for a leaky injector. If it skips at random seeming imes I would be looking at the coils and boots.

not necessarily on 4 runners but i've run across a lot on camry's. mass air flow sensor may be the culprit.

Which engine is it? 2.4L, 2.7L, or 3.4L?

3.4L V6. Compression at all cylanders is low but equal to or has a variance of + or - 5 psi.

Check the injectors Ive had issues with them and it was hard to find

premierautohandling wrote:3.4L V6. Compression at all cylanders is low but equal to or has a variance of + or - 5 psi.

how low? low can equal valve timing. the code alone with no cylinder misfire would lead me to look for a loose belt or a bad cam or crank sensor.

Have ya checked fuel pressure. I have seen at times when a vehicle is sent here and because there is no service port to check fuel pressure it is assumed to be ok because no one wants to remove the fuel filter to check the pressure. On this vehicle there is no test port. I simply use a banjo bolt provided in my testing set and connect it after the filter. Fuel pressure needs to be 33-38 koer, 38-44psi koeo.

These were known for head gasket problems (Toyota was replacing them for free). I've seen them where they didn't overheat, wasn't loosing a significant amount of coolant, and only affecting one or two cylinders. I've also seen fuel injector problems - usually a good fuel injection cleaning (we use a motorvac machine) will cure this if its fuel injection related. Keep us posted.

The problem was a bad injector. Once injector was replaced, all rough idle and running disappeared as it should. Thank you all for your comments and suggestions.