dc893

My 92 with about 300,000 miles is having some A/C trouble. When I turn the A/C on the car feels like it has a miss. It happens when accelerating and just cruising down the highway. It seems to run fine with the air turned off. It will idle just fine with the air on. After checking some compressor prices I am hoping that's not the problem. Not really feeling very good driving around Florida in a black car with no air. Also feels like I loose about 50HP with it on. The gas mileage seems to be poorer than usual when it is on as well.

Any suggestions on where to start looking at this problem? I have had the A/C go bad in other cars I've had, but never fixed it. Never lived somewhere that it got hot enough for me to really worry about it.

Any ideas would be greatly appreciated.

LScowboyLS

the A/C does cost you some hp and some fuel mileage when operating properly, but not 50hp! (maybe 8 max)

a bad compressor with be noisy nearly always

dc893

Well, I checked the car. Just normal noise from the compressor. Took the car out for a drive with the A/C off the entire time. Still has a miss sometimes and not nearly as often or severe as with the air on. I guess the load from the A/C is just amplifying the real problem.

Now thinking maybe a spark or fuel problem. The fuel filter is only a few months old. I know the plug wires are looking old and beat up. I am just not quite sure if it would cause that kind of random hesitation or not.

LScowboyLS

random hesitation could be many things, including bad wires, plugs, caps, rotors or even failing ECU capacitors

have you scanned the car for codes?

johnnyg66

Well at 300k and this is now just happening you have done well. Not knowing all the cars maint history maybe now is the time to give it a good going over. TB cleaning wires,caps,plugs all those things. Do you ever put in any fuel system cleaner? I think it does help once every 5-7k.

Like cowboy says ecu too.

dc893

I have 2 ECUs, tried them both. I will try some fuel system cleaner, did that a few months ago, but I put miles on quick. I have taken the covers off and could see the timing belt looked like it was in good condition. I suppose I should change the plug wires and plugs next. I have been trying to get the maintenance up to date, it's just kind of pricey to do. I'm gonna be shopping around to see where I can find the cheapest NGK wires and plugs. I have no idea what the previous owners put in it.

LScowboyLS

a timing belt can look otherwise good and still have one broken off tooth

make sure you use the factory caps and rotors, and on the plugs make sure you use NipponDenso (the OEM) or NGK ONLY - try amazon and rockauto for good prices on the plugs & wire set

dc893

I know that the t-belt was replaced within the last 50 thousand miles. That was about the only proof of maintenance I could actually be provided with before the purchase. I would probably guess that the last owner just went as cheap as possible on the plugs whenever they were ever replaced.

Looks like I will probably order the OEM Denso kit since it is cheaper than the NKG. I am thinking about using the NGK G-power plugs as well, or should I just go ahead and get the standard cheap NGK plugs? Will also most likely use rockauto for this. Slow shipping in my past experience, but much cheaper than any other place

DENSO Part # 6718143 Ignition wire

NGK Part # 7092 **#BKR6EGP} G-Power

NGK Part # 5553 standard spark plug

LScowboyLS

wires are even more likely than plugs, and caps and rotors are common issues as well, those 4 things should be replaced on any LS purchased, as well as oil change, coolant change and drain & fill tranny at drain bolt with Dexron III or Toyota T-IV fluid (do not do a "flush")

dc893

As long as I am doing plug wires I'm doing the plugs. Already gonna be that far taking it all apart. The tranny fluid is a nice red color. I check about every time I check the oil.

I know I still need to do the correct coolant flush.

Would you recommend a specific NGK plug? There are several different ones.

If you happen to know the plug gap that would be great lol. I can probably find that out on my own.

I had to delay some of these trying to get the ball joints done since that is a safety concern. Thanks for you help LSCowboy.

LScowboyLS

here is your gap and plug choices for NGK as well as the wires

some people like the plain old copper core plug, since they are so easy to change on LS400 and copper is a fine conductor

things like Iridium plugs are better on a vehicle where you need a super long life plug because it is impossibly hard to reach (Mitsubishi 3000GT would be a good candidate!)

I dislike platinum

dc893

Thanks for the tips on with this issue. I have ordered Denso plug wires and NGK plugs. I researched some fuel treatments and injector cleaners. From what I read it seemed like Lucas would be a good choice for that. I am always skeptical of that kind of stuff so I never use additives in my gas or oil. This issue was getting very annoying having to drive 50 miles a day. I ended up putting some Lucas fuel injector cleaner in the gas, and it actually seems like it is running better. I am still skeptical of what it did, if anything. Should have the plugs and wires around the middle of the week. All should be good after that.

Thanks again for the help on what plugs and wires should be used along with the suggestion of running a fuel system cleaner through it. It seems to be running better already.

LScowboyLS

probably the three magic fuel additives that get the best reviews on forums I have respect for seem to be Techron and Marvel Mystery Oil and SeaFoam

dc893

I read some very good things about the Lucas injector cleaner after searching around on here. That would be the only additive that I would actually recommend to anybody. I did use seafoam around January and that didn't seem to do anything for me at all. Wouldn't recommend the oil additives though

I did for a shot time consider running seafoam through the engine but I think that just might create some problems. Even if there is some sludge buildup, I do all my oil changes on time and everything seems to be ok. Seafoam may just free up some sludge and possibly clog up oil passages, then I will definitely have some serious problems to deal with.

LScowboyLS

people use Seafoam both in the brake booster line and the fuel tank and the crankcase all the time and I cannot remember hearing any reports of it screwing anything up. - makes a great smoke cloud to **** off your neighbors when slurped up into the booster vacuum line! - I save some for the 4th of July, cheaper than smoke bombs!

Marvel Mystery Oil is well regarded both in the crankcase as well as in the gas tank, - and it is like crack for your air tools, makes them run better than new (at the shop we call it "gun crack") - when the super oil geek experts at BobIsTheOilGuy.com love something, you can bet it is not fluff, they chew up every miracle elixir and spit it out with sarcasm, so that tells me it is for real.

Techron is also effective in the fuel tank for many people, especially at 2 or 3 times the recommended concentration.

any of these three may or may not have a noticeable effect, but just don't ever seem to see reports of problems arise out of the use of any of them!

Now when it comes to the transmission, I wouldn't dream of adding anything unless it was already toast!