MC Dig

Hi,

I have a 95 with the 4.9l six cylinder and a 5sp. It has 120k miles on it. Beginning this spring I noticed, every once in awhile a slight hesitation at low throttle. It started and ran fine save for that. I just drove cross country and everything was fine until AZ. I started to get an intermittent check engine light, that would go off after less than a minute or so. Then when we stopped for a short break. The truck did not want to start, it finally did then idled very rough. I just kept driving and it started fine each time after that. It continues to idle fine. The hesitation at low throttle positions though persists and seems to have gotten worse. It was intermittant, but has become consistent.

I pulled the codes and got the 565, purge valve canister solenoid. I understand there is a test procedure for this component, though I don't the tools to do that. I think that the 565 code may not have anything to do with the hesitation. I am not sure. It also had a half dozed stored codes.

Just as routine maintenance, because it had been awhile. I replaced the fuel filter, air filter, and pcv valve. I listened for vacuum leaks and sprayed some soapy water on some of the vacuum tubes (not sure if I got all of them) and found none.

I am about to go check the spark plugs to see what kind of shape they are in.

Does anyone have any ideas?

Any help would be greatly appreciated

Aktech

With out knowing what the other 6 codes are we can`t point u in any other detection other then re pull them. Purge has two wires, 1 has 12 volts other is ground. Unplug apply 12 volts and see if it opens and closes. Canister my be full of gas. Unplug engine side and plug it 2 see if it runs better.

MC Dig

Ok,

The other codes are 171 181 542 172 and 173, this set of codes comes after the separator code of 10. The first set of codes again is 565, this is koeo.

So I plugged the engine side. I am guessing I have the right contraption, it is a little cylindrical doohicky, with an electrical connector on the bottom with one red wire and one yellow. There are two tubes coming out of the top of the thing one goes to a canister thing by in the front below where the battery is. The other tube goes to a y connector that then goes to what I am guessing is the throttle body.

I ran it up and down the street and it is not perfectly better but I would say there is some improvement.

Now to test the canister I unhook the connector and apply voltage to where the red wire goes and ground the other one? And I should feel or hear it open?

I do have a voltmeter, is that any help.

Thanks again for your help and input.

Aktech

cylinder 1 has a problem, check for spark and tell us what color is the spark plug. U can use a timing light or ohms test the plug wire to c if it is working. Ur o2`s have a fault or not switching. Fix cylinder 1 to see if o2`s clear first. How many o2`s are on the truck? Make sure ur plugging the tb. Yes u should feel or hear it. It is normally closed so blow in it to c. Apply the volts and blow again.

MC Dig

There are 2 o2 sensors. I believe they are original to the truck, is it a good idea to just replace them as a maintenance thing, or is it possible for them to operate normally indefinitely?

I will go check cylinder no, 1. Would this be near the front of the truck or do you count from the firewall forward?

Aktech

O2`s should be changed every so many miles. I don`t remember how many. U can test them with a ohms tester and a torch but if only have 2 just change them after u fix cylinder 1 if no improvement. If one is before and 1 is after the cat u can switch them to c. The 1 before the cat is the most important. Just for kicks pull engine vac and clean cap and rotor. While ur testing 1 plug wire test them all, there right there and only 6 of them. If you got to get a new set don`t throw the old ones way,test them and keep the good ones. #1 is up front. Check timing also . Don`t 4 get to clear codes also when any work is done.

MC Dig

Ok, thanks again for the wonderful help. I pulled the plug from cylinder one and it looked ok, it had some black carbon on it but it did not look any different than any of the others. I went ahead and replaced all of them, they are 3 years and 9k miles old. I believe the plug wires are a bit newer, I tested number one and got 0 ohms, which I would imagine is the correct reading. The rotor and cap are just less than 2 years and 5k miles old. I may just replace those tomorrow, they looked decent but there was some carbon build up and heat scoring more so on cylinder 1. It is something I could probably just clean off but I will probably just buy a new one.

So, I got out my timing light to check the timing. I set that myself just under 2 years ago and did not really know what I was doing. But I did get it to run decently at the time. So in my service manual there were all these different instructions based on ignition system type. I did not really have time to sort through all of that. So, I just started it up and advanced it a little bit. All that seems to have improved the situation about 90 percent.

Tomorrow I will replace cap and rotor, o2 sensor and see if I can't follow the proper method for setting the timing. Also I still have to check the canister purge valve solenoid thing.

Thanks again for all the help!

MC Dig

I just double checked the timing, at 10 degrees (the big notch) it will barely idle. I advanced it and it runs better but it still idles a bit rough and there is still some hesitation at low throttle.

I also replaced the o2 sensor and cap and rotor.

MC Dig

I just tested the canister purge valve. Just to make sure I'm testing the right thing, it is a shot glass sized cylinder that sits on the passenger side exhaust manifold. I put 12v to one connector and grounded the other. I didn't hear anything, could this thing cause all the rough running?

Aktech

Did you remove the spout when setting the timing and is the purge value open or closed?