Car knocking like crazy

[devis]

Yesterday my 93 J30T started knocking badly. Well, maybe not too bad... but having never experienced knocking on any of my past cars I have no basis of comparison. I rushed to do an engine flush and oil change. The knocking subsided a bit, but it's still there. I also noticed that at a cold start I need to give it a little gas otherwise the engine RPMs drop drastically.

Tried to pull the codes last night, but for the life of me I cannot make out where the ECU is. I removed the panel righ below the glovebox but I can't seem to locate the ECU. I read the ECU sticky, I also have the technical manual but neither are helping me locate the ECU

I would like to check/change the spark plugs which may just be the culprit. I am also thinking O2 sensors and possibly a fuel system cleaning. I did change the fuel filter about 2 months ago.

Oh, and I also noticed that the AT was overfilled by at least 2 quarts... I brought that down to the required level.

Ideas?

[gr8scott72]

Yesterday my 93 J30T started knocking badly. Well, maybe not too bad... but having never experienced knocking on any of my past cars I have no basis of comparison. I rushed to do an engine flush and oil change. The knocking subsided a bit, but it's still there.

What grade gas you using?

I also noticed that at a cold start I need to give it a little gas otherwise the engine RPMs drop drastically.

Seems to be common on older J's. I've read that the Idle control valve will actually get dirty over time. It can be cleaned or replaced. I've seen them for sale on ebay. It is located on the driver's side of the intake manifold towards the firewall.

Tried to pull the codes last night, but for the life of me I cannot make out where the ECU is. I removed the panel righ below the glovebox but I can't seem to locate the ECU. I read the ECU sticky, I also have the technical manual but neither are helping me locate the ECU

It is right where you are looking. It's behind the pannel just inside the passenger door under the glove box.

I would like to check/change the spark plugs which may just be the culprit. I am also thinking O2 sensors and possibly a fuel system cleaning. I did change the fuel filter about 2 months ago.

I don't know that I would change the O2 sensors unless you where having problems with either the way the car was running or getting terrible gas mileage. (Not that these cars ever get great gas mileage.)

Oh, and I also noticed that the AT was overfilled by at least 2 quarts... I brought that down to the required level.

Ideas?

It sounds like you just got this car? EVERYTHING that I can change on my cars gets changed when I get a new (to me) car, so get busy, plugs, oil, oil filter, air filter, fuel filter (You said you already did), check brake pads, brake fluid flush/bleed, power steering fluid flush, transmission flush w/ new filter, tire pressure, AND only run PREMIUM gas in it. I also add 3 ozs of Lucas upper cylinder treatment to every tank of gas.

[devis]

Prior to this I had a 94 J30 which died a very ungraceful death... wet pavement, I spun, hit the guard rail, insurance totaled it. Odd actually because I was able to make it from Reno to Sacramento in the middle of a huge snow storm and didn't even get stuck once! Fishtailing yes, but chains, 20 mph max speed and having lived in snow prone NorthEast for a number of years did help. damn these rear wheel drive cars I had that for some 1.5 years so I know a few things about it. I ended up buying another J because I was very pleased with the previous one.

But, yea, I have been meaning to get a few of those things done... just didn't have the time.

It sounds like you just got this car? EVERYTHING that I can change on my cars gets changed when I get a new (to me) car, so get busy, plugs, oil, oil filter, air filter, fuel filter (You said you already did), check brake pads, brake fluid flush/bleed, power steering fluid flush, transmission flush w/ new filter, tire pressure, AND only run PREMIUM gas in it. I also add 3 ozs of Lucas upper cylinder treatment to every tank of gas.

Oil and filter got changed yesterday. I had a K&N air filter from the crashed J that I moved over to this one. Fuel filter was changed, yes, brake pads need to be changed and the system does need a bleed/flush. Transmission fluid is actually quite clean, but I've been meaning to take it for a flush w/pan drop and filter cleaning.

It is right where you are looking. It's behind the pannel just inside the passenger door under the glove box.

Guess I will look a little deeper in there.

Oh and I only use 91 or better. Every 2-3 tanks I pour a bottle of Lucas or something else if no Lucas is available.

[devis]

Finally found the ECU and checked the code. Got a code 55 which doesn't appear on the tech manual or in the sticky in this board... I don't know what to make of it. I checked the code like 4-5 times just to be sure I wasn't off by any digits. Same response... 55 all the time.

I am baffled... and the knocking continues. Next I'm going to get the idle control valve out and clean it. That should improve the RPMs a bit but I doubt it'll eliminate the knocking.

[nkawall]

a buddy of mine with a 95 j had the same problem and it turned out being a bad lifter...get your mechanic to check it out and tell him to use a stethescope to listen where the lifters are so he can know for sure where that knocking is coming from

[AlphaKilo470]

My J30 has issues with it bumping and knocking on occasion throughout long drives. It's been happening less frequently since I started driving the car (previous owner tells me the car spent most of it's time in the last year and a half sitting still) and I found a receipt in the glove compartment before I bought the car showing that the engine was flushed at some point this year. I'm thinking that in my car's case, because the seller said the problem didn't develop until earlier this year (a little while after the date on the receipt for the flush), all the crap in the engine that got knocked loose when it got flushed is causing the problems I'm having now.

[NismoChi]

Got a code 55 which doesn't appear on the tech manual or in the sticky in this board

Code 55 means that the system is normal and do not have any code store in the ECU. I hope you don't have bad lifters, cause it would mean major money to replace them, the camshaft has to come out before you can get to the lifter. Have you heard of "Auto Rx", do a search on it, a lot of people said that is one of a few engine cleaner that work, good oil and filter alone with something like that may help you free the lifter. Since, you do live pretty close to me, let me know if there is anything i can help.

all the crap in the engine that got knocked loose when it got flushed is causing the problems I'm having now.

And that is why a slow cleaning process with some good cleaner is the only way to do. IMO. You do not want to knock all the junk in the engine to come lose at the same time, it is just bad idea and going to cause more trouble.

[gr8scott72]

Auto RX is great stuff. I actually just put some in my Explorer about 500 miles ago and have used it in other cars I have owned in the past.

I'm going to do it on the J but I want to do a compression test first so I can see before and after. Kind of my own personal test of the Auto RX.

[devis]

Well, looks like I'm sold. After your recomandations as well as my own research I'm buying AutoRX. Small price to pay for a clean engine.

Thanks guys, you're fantastic!

NismoChi, I may just take you up on that offer... you seem to be quite knowledgeable. Of course help does entail a nice bar outing afterwards, on me of course.

[NismoChi]

NismoChi, I may just take you up on that offer... you seem to be quite knowledgeable. Of course help does entail a nice bar outing afterwards, on me of course.

Sounds good.

[devis]

Here's an update. After using the first stage of AutoRX the knocking has dissapeared. Car idles nice and smooth. Also, it was having some weird electrical problems (constantly blowing fuses and such) that went away after doing a spark plug change. the old ones were completely crap... Now I'm on to the radio, got an aftermarket one installed but I must change the speakers on it since front driver side one is completely dead and rear driver side is in the verge of death as well.

[TJ_94_J30]

i had a "tech" tell me it was the lifters and instead of all the expensive work use something called Royal Purple instead of the oil you currently use. Its a lot heavier and cleans your lifters.you can find it at any oriellys or auto zone i think auto zone might have quit carrying it. if that doesnt help, and i mean help not fix.you need to do something else