171/174 codes

My CEL came on the other day. I have a P0171 and a pending P0174 code. I have a 99, 3.8L

I suppose I have the infamous TSB for the Isolator bolts. I learned a lot about this TSB about 8 months ago when I had the CEL and thought I had the problem (but didn't at the time).

My question for anyone who has done the fix:

Did you find the rubber gaskets (seals) under the lower intake really needed to be replaced? I was looking at my engine (scratching my head of course) the other day and I thought that if all I had to do was remove the upper intake, clean the ports and replace the bolts I could probably do it in an hour or 2. I just wonder if the seals actually deteriorate or is it just a precautionary (and money maker) for the TSB to list it. It is a lot more work to remove the lower part of the upper intake.

Thanks

When I did my '99's gaskets, I just did the whole shebang. 50 k miles later, my codes have never come back and the van runs well. But. I never really saw anything that I could point to and say "that's IT ..that's the leaker"!

The new lower seals that were installed looked that they were a slightly different design ... perhaps improved over the old ones that were removed. But there was nothing "obviously" wrong or failed with the old ones.

Since you're doing your own work and don't have to worry about a customer that can't understand why the "best" job wasn't done the first time ... I'd do just the top manifold gaskets and isolator bolts. As you say, that isn't much work ... "so what" if you later have to do it again.

Thanks 12Ounce.

Yeah, I thought the problem was really the rubber Insulators around the bolts that deteriorated. I have only seen photos of the bolts but they look like they are basically a rubber washer/lock washer (for lack of a better description) and when they break down the holding power is reduced and thus vacuum leaking occurs.

What is the top manifold gasket? I thought the upper-upper and the lower-upper gasket was a re-usable gasket or perhaps it is something else that you are referring.

One additional thought. I checked the fuel regulator hose that is referrenced in the TSB and mine still feels very tight. I then checked the PCV to intake hose and it was a bit loose at the intake. There was a bit of oil and I tried to dry it and then put the hose back on. I would not think that the valve cover is vacuum sealed and thus the PCV valve when open is basically a vacuum leak and so if this hose is slightly (very slightly) loose it should not matter. Am I missing something? I was going to wrap a hose clamp around it for good measure but I am wondering if this could be my vacuum leak.

Yes, the upper gaskets are moulded rubber and, if not damaged, are reusable. I would suggest removing them all, cleaning/inspecting etc. Also clean out the grooves that they nest into. I like to use petroleum jelly as a lubricant in places like this.

Actually the seals around the PCV valve may all be important. Ford even lists an improper seal on the dipstick as being a leak contributor. You might try some heavy grease as an experiment.

Thanks 12 ounce. Perhaps I will look at this hose first. I have my own code reader so I can easily see the effects of any modification or attempted fix. I erased my codes the other day and theyt quickly returned so this is becoming a hard failure.

DRW1000, is the engine running noticeably rough, maybe just slightly? If so then maybe you can test for the leak by first firming up the PCV line to see if that evens out the roughness. If not then you can do what 12ounce (aka Fordfan) has adviced in the past, push down on the plastic plenum with the engine running and see if that smooths it out. Might narrow it down a bit.

Good advice Lewisnc100