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97 f150

I have 1997 Ford F-150 V6 with a rebuilt engine. Mileage is unknown. I changed the spark plugs & wires, & air filter cause I haven’t done in about a year. I took it to get a smog check and it failed. The HC failed @ 25mph and just passed @ 15 mph. The NO failed @ 15 mph & just barely passed @ 25 mph. The CO passed @ both speeds.

Any advice on what I could do to figure out what the problem is and/or to fix my truck so it will pass smog would be much appreciated. Thanks in advance for any help.

Is the “Check Engine” light on?

No but there was a trouble code before. P1537 was the code. Sometimes the Engine light would come on & then without me doing anything it would turn off. So about a week or 2 ago I erased the codes and it hasn’t turned on. Since I have erased the code, I have driven the truck well over 200 miles so I believe all the on-board test have reset already.

P1537: Intake Manifold Runner Control (Bank 1) Stuck Open

The problem may still exist but not bad enough to trip the CEL, but bad enough to throw off your emissions.

HC is unburned fuel…Gasoline subjected to no combustion coming out your tailpipe. The usual culprits are:
Misfire
Burned exhaust valve(s)
Incorrect ignition timing

The first step might be a compression test…

In looking @ the test results 1 mechanic told me that all i needed to do was change the catalytic converter.

The smog guy hooked up a vacuum pump to the EGR valve and pumped it up to 100 & he said the engine should have turned off. It did not turn off. and when he revved the engine the gauge barely moved.

That MIGHT get you past the test, yes, it probably will…But if the converter was shot, the CO would certainly fail too…You would have trouble passing CO with a dead converter…A FRESH converter will indeed burn off the HC but it will soon overheat in the effort…Do the compression test, even a simple electronic test, that will spot a bad valve…If the electronic test spots a suspect cylinder, then put a pressure gauge on that cylinder to see how bad it is…Anything below 110 psi and you have found your problem…

Do you feel any kind of ignition misfire? A thump or pulse in the exhaust? A vacuum leak can cause this too…or a bad injector…

Ouch! The EGR not working (or passages plugged) will cause the NOx failure but not the HC…

A 15 year old truck with a “rebuilt” engine. Mileage unknown. EGR system inactive. Lots of issues here…

pass few months i have notice the gas mileage decrease to 9-10 mpg before it was always @ 12-13 mpg. yes caddyman there r issues, do u think its worth fixing?

what do you think if i try a Sea Foam cleaning? If i pour Sea Foam into the PCV, will it be DISTRIBUTEd EVENLY TO ALL CYLINDERS?

Another bit of info that is probably important. back in 2009 i took the truck to get an oil change @ the local ez-lube. well they end-up stripping the threads on the oil drain plug & installed a temp plug. I have never removed that plug because i didn’t want to risk not being able to reseal it with an oversized plug or another temp plug. so since that has happened, I have only given it 1 oil & filter change by vacuuming the oil out from the dipstick tube. My thought is that there is a lot of oil build up because of the lack of oil changes. So maybe a seafoam treatment might help clean the system out.

I don’t know what to say or where to start…it’s like falling into a back hole…

Ya I think i’m in a tough spot.
thanks all for your input.

You need to get over the oil pan plug and fix it. Its not hard. Any auto parts store can sell you what you need.

But that doesn’t have you failing emissions.

As Caddyman already suggested - before you do anything else, check the compression. Report back with all 6 numbers in psi. If you have compression issues there is no point in chasing your tail about any of it.

If it has a distributor cap, change it.

You have to pull the EGR and clean out the whole system.

Is this rebuilt engine burning any oil? If so, that could account for high HCs and even cause EGR port clogging.

will do a compression test & let you know. thanks

ok here are the compression test results:

Cylinder 1-140psi, 2-140psi, 3-150psi, 4-155psi, 5-155psi, 6-140psi

That’s not great, but its not going to be the cause of the high HC - unless you’re burning a lot of oil. How frequently do you have to add oil? Pull your PCV valve and tube and make sure it is all cleaned out and flowing well.

Assume that the NO comes from the EGR issue. That has to be pulled and cleaned.

Then check out the rest of the ignition system - e.g. distributor cap, unless this has coil pack/s.

Pull the vacuum line from your fuel pressure regulator and make sure that the regulator isn’t leaking.

What should the ideal compression be?

Yesterday I had to put 1 1/2 qt. in . I don’t check very often but the last time I added oil was about 3-4 months ago. It has a small oil leak.

There is no distributor cap. It has a coil pack.

How should I clean the EGR system?

Can I use the Sea Foam Spray to clean out the air intake? & will this help with the EGR system?

What type of cleaner should I use to clean out the PCV and EGR?