Hi everyone, I have a great 2002 S-type 4.0 (pre-2002.5) with all of 39,440 miles on it. For the most part this runs fantastic.
My ongoing problem seems to be that after a few fill-ups, the car seems to start bumping and missing but doesn't throw a code. The mechanic I went to said to try
putting in some Techron fuel injector cleaner. Well that indeed do the trick. Ran great. Then same thing happened after a few fill-ups.
So it seems that the fuel injectors are either bad or going bad, I think. So, my question is, how long can i keep doing this with fuel injector cleaner before something really bad
happens? Also, if it's not throwing a code, how do i know which is bad because it doesn't seem like a good idea to change them all when all I'd be doing is
fixing something that isn't broken.
Thanks for the help.
Boston

 

Based on your description, the cause of the misfire(s) is most likely failed or shorted coil units. Given the age of the vehicle, the cam cover gaskets and spark plug boss seals may be leaking causing oil to enter the spark plug wells and short out the coil units.

Remove the coil units on all eight cylinders and inspect for oil contamination.

Have the primary and secondary timing chains, guides and tensioners been inspected for cracking or wear? If not, remove the cam covers and inspect the secondary timing chain tensioners as catastrophic engine damage can occur if the secondary tensioners fail.

 

Here is an X200 AJ28 with the Bank1 cam cover removed showing the secondary timing chain tensioner. The uprated tensioners have a metal body instead of the original ones with plastic bodies, which are prone to crack and fail.

 

Try running Chevron fuel exclusively. It has Techron already mixed in, at a level that is safe to run continuously.

Chevron is the only brand I will use in all of my vehicles. Yes, it costs more than the bargain brands, but there's a reason for that. And even though it costs more per gallon, you may see an increase in fuel economy. Your miles per dollar may be the same as when running cheap fuel.

Totally unrelated, but I've also found Chevron is the only brand not affected by heat on older carbureted vehicles.

 

Hey NBCat, thanks for the reply (same to you Karl), My question to your reply though is, why does the Techron then help things out for a period of time? It would seem that if oil was contaminating anything it would be happening at a more frequent rate. I guess I'm not understanding how adding the Techron would help things if oil was leaking into the plugs. Is it possible the injectors are just getting gummed up and i need to change those or one of them out? And then still the question comes am I ok with using either Chevron fuel that Karl has suggested or adding Techron on a normal basis when the issues pops up? I think I've read that adding Techron too often can lead to more trouble.
Thanks,
Boston

 

Two separate issues. Your car seems to have a fuel-related issue that clears up temporarily by adding Techron. That's problem #1.

Next is these engines are infamous for oil collecting in the spark plug wells and interfering with normal ignition. We don't even know if you've got this second problem, but it is very common. Pull a couple of coils for a quick look.

If you do find oil in the plug wells, don't panic. You'll just need new valve cover gaskets. The coils may be fine if cleaned up with plastic-safe electronic spray. If replacement coils are needed, go with a quality name brand like Denso or NGK. Stay away from no-name bargain specials.

Possibly, but I'm cheap and lazy. You've already noticed the problem improves by adding Techron. I'd be tempted to continue on that course. Let the Techron finish its job.

​​​​​​​As previously suggested, try running Chevron fuel exclusively for several months. They used to advertise "The Chevron Challenge", to try their fuel for a few tanks and see what happens. Their fuel already has Techron mixed in at a safe level. You can run it continuously with no risk of overdoing it. I'm cheap as can be and proud of it, but I'll gladly pay extra for Chevron. That oughta tell ya something.

 

Karl: For those who have abandoned the densely populated west coast for (literally) greener pastures where SOCal does not maintain operations, I presume that "Top Tier" fuel brands are the best option?

It is my undetstanding the Standard Oil is the sole producer of Techron and sells it to the other refineries.

What is Top Tier Gas and Is It Worth It? (autolist.com)

 

First, I must take exception to your comment about greener pastures. I live in the wet side of Oregon and doubt you will find greener pastures elsewhere, especially at this time of year when the moss goes into full bloom. Why, just yesterday, our dog took her sweet time as usual, picking just the right place to piddle out back and moss started growing on her.

Back to fuel, I was unaware Chevron is not readily available nationwide. This is not to be construed as me being (W word), but merely less correct than usual. So yeah, pick a different brand of fuel, make sure it's advertised as Top Tier, stick with for a while and see if there's any improvement.

In my over-inflated opinion, I don't think Top Tier is the end all designation for fuel. It's a minimum standard, that's all. In my neck of the woods, ARCO is very popular as it's usually about 20 cents cheaper than other brands. I think the big difference is the additive package. They meet the minimum standards, but that's it. I'll put it in a rental car, but not my own vehicles. Is it "bad"? No, not at all. Just not as good as it can be.

There's a run down Stop 'n Rob convenience store near me that sells unbranded fuel. A hand-lettered plywood sign says Top Tier fuel. I don't doubt it, but nothing about the place inspires confidence and I'm not going to try it.

I was taught years ago by my father to pick one brand of fuel and stick with it if it works well. This advice has served me well and I've had only good results with Chevron. I'm sure there are other good brands out there, too, but I have zero incentive to even try anything else.

 

Hi Karl,
Thanks for the great feedback concerning my injectors. And by the way, you and I are cut from the same cloth as I too, am cheap and lazy. Mostly cheap. I will indeed however open my own beer if necessary. So not that lazy.
Anyway, I'll have to look around for something similar as Chevron and Texaco stations are basically non-existent around by me. Closest Chevron is about 50mi away and the Texaco even farther.
I'll probably try a Sonoco if I can or then I'm stuck with the top end of BP as that's the most prevalent station around.
I'll check the plug wells when it warms up and I can spend the time in the garage. Seeing it's not heated it won't be for a while, but I'll post what I find.
Thanks again.
Boston