4.0 -- shaking and rough performance

[macoffma]

It's a 93 4.0 with about 80k on it. About October I started noticing that the engine sounded rougher at anything greater than an idle--it was much throatier than it ever had been before. When I would drive at higher rpm's, especially when I would be on the interstate above 60 mph, the truck would almost automatically start to violently shake back and forth, and I had very little power. I was also getting the rattling noise from the engine, especially going up hills or when accelerating at the higher speeds.

I replaced the air filter and thought I had cleaned the MAF sensor, but there was no change in performance. I then replaced the spark plugs, which had never been changed. I replaced them with the Motorcraft plugs. This caused a dramatic improvement. The vehicle would still shudder at idle, but interstate driving was much improved and the power had returned. The engine was still much throatier than I remember.

About a month ago, the symptoms returned. I had read other posts on the board that suggested changing the wireset, so I did this and the situation again improved. The car would shudder at idle, but the violent shudder at high speeds was gone and so was the rattle.

In the last couple of days, though, it seems to have gotten worse. It seems like each thing I've done has made it better for awhile, but it seems to eventually regress each time.

I noticed there was a bit of oil on the plugs when I replaced them. Also, the transmission has become much slippier since all this started (which I think may just be a result of the power issues). Most strangely, the problem seems to be worse the warmer the air is outside. We've been pretty cold here this winter, but as soon as it warms up it seems to make the performance worsen.

Thanks in advance for any help!

 

[poconosms1]

How's your mpg?

Some things to consider

Try a different gas - octane and distributer - maybe there's water in the fuel?

did you reset the computer after cleaning the maf?

fuel filter and o2 sensor

Pull the codes - you can get a reader from radio shack $40

A bad catylitic converter can cause this problems too


Perhaps a bad computer?

 

[macoffma]

Will I be able to pull codes even with a bad computer? One thing that has never happened through all this is a Check Engine light. I also wondered about the catalytic converter--is this easy to test?

The fuel filter was replaced by the previous owner at 60k. Regarding the MAF, I had read on a previous post that using Windex was better than cleaning with Intake cleaner. Does this make a difference?

Thanks!

 

[poconosms1]

If it's not the computers, then the codes should be ok. cpu's are really expensive.

not sure how to test a catalytic converter. Just had one go on an olds - similar to your experinece, the fast i tried to go, the more the motor rattled and bogged down. The way it was described to me by the mechanic was you have all this intake air, and the converter, after the motor tries to prevent it from exiting.

the maf is an electronic filiment. not really sure, but seems to me electronic cleaner would do better than windex.

some auto parts stores have testers you can use on site.

did you reset the computer after you cleaned the maf and what about the o2 sensor?

 

[macoffma]

I did reset it after I cleaned the MAF and again when I changed the plugs, but that's it. It's been so long since I cleaned the MAF that I probably will try that again tomorrow morning with real electronics cleaner.

Your description of the problems with the catalytic converter are very close to mine and make sense. It just seems like it's some kind of issue with air mixture or exhaust... I have not done anything with the O2 sensors, but I imagine those are pretty simple to test (probably a job for an ohmmeter?)... I will post with the results on cleaning the MAF again and then checking the O2 sensors.

Thanks again...

 

[poconosms1]

You can do a search on o2 sensors and testing. A new one costs about $50. compared to the several hundred dollars for a cpu or converter.

 

[MattPersman]

any idea on oil change frequencies before you bought it? if poor maintenance occured on this truck, the engine could be in semi poor condition, blow by and what not. After doing the typical maintenance replacement things, O2, fuel filter, PCV, etc. and it still persists. Change the oil and add some of that Restore for 6-cyl vehicles in it. It really helped a previous car i had with close to 200k miles on it. just a 6 dollar shot in the dark but if it could help why not

 

[macoffma]

Restore for v-6? Is that an oil additive? I don't think I've heard of that, but for $6 I'd definitely be willing to try it.

I thought it was pretty well maintained when I got it--this problem seemed to suddenly occur a few weeks after I started driving it (shudder to think it was something I was doing).

I didn't get a chance to work on it over the weekend, but I'm still aiming to test the O2's (got the instructions on that now), recheck the MAF, and possibly use the additive if I can find it.

 

[ExplorerEB96]

well I know what you mean

My 96 (new engine 1 year) has been rattling for about the last month. ok it seems too simple to be true.... I have a Superchip in it (does yours or do you know if it does?) I know with the gas crunch, I started using 87 gas..... oh boy what a change.....shudder...shake clatter..... then a check engine light.... pulled codes (02 sensors are new, no MAF codes).....senser codes.... what I did...... ran tank almost dry.....put in 94.....pulled superchip...... disconnected the battery.... replaced superchip....reconnected the battery...had oil change....ran with check engine light for about 50 miles then.... waaalaa check engine light went out and the shakes have but slowly subsided..... i have to run 89 and up now it is every third tank is 94..

Karol

 

[MattPersman]

Yes its an oil additive

You can buy it really at any autoparts store or walmart. its in a silver can a little taller than a coke can. When you change the oil you replace 1 quart of oil with it. It helps seal the engine better if its real warn.

I also recommend pouring a good fuel system cleaner in the tank on your next fill up. I like the Valvoline Syntech Fuel System Cleaner, its about 8 dollars. Additives can go along way sometimes. Sure they are bandaids of sorts, but I know in a lot of areas in Winter they have crappy gas at the pumps, ya know "winter-blend" that gives some poorer gas mileage and leaves more residue and whatnot in the tank and lines.

I figure its the easiest thing to try. Oil change with Restore and a bottle of fuel system cleaner. You may be surprised with the results.

Good luck to you. A poorly running vehicle can make days not too great.

 

[RickPA]

Whatever it is is causing all of your downstream parts to fail. Have you noticed increased oil consumption? The oily plug makes me wonder about valve guides/seals possibly fouling the plugs.

 

[macoffma]

RickPA-- yes, I have noticed increased oil consumption. I have to add about a quart every 4-5 weeks. What would you recommend as far as checking or fixing this?

 

[TPLYNCH]

try retourqing the lower intake manifold bolts. Is you #5 plug fouled but the rest look ok?

 

[RickPA]

I think TPLYNCH's post was about carbon fouling due to a lower intake mainfold leak. I had that on my '97 and it will cause a rough idle. So let me ask; was the fouling on the plugs wet or dry?

If dry it could be carbon fouling. If wet, we're talking about an oil problem. Is it on all plugs? Do you see any smoke under acceleration or smell oil in the exhaust?

Lastly, is the check engine light on?

 

[macoffma]

RickPA -- The oil residue was definitely on all of the plugs. I have not noticed any smoke from the engine compartment or from the exhaust. The CEL has never come on, which is definitely strange, leading me to believe the engine diagnostics might not be working correctly.

TPLYNCH -- Would loose intake bolts cause the oil residue on all the plugs and not just #5? That was a suggestion I had read elsewhere, but I really didn't want to take the whole thing apart unless someone felt it was a very good candidate.

Thanks again to all of you for your help!

 

[TPLYNCH]

Sorry, I don't know the specifics. Info came from what I've read on this site, and I can't remember the details. Hopefully someone w/more experience with this will chime in. If you haven't yet, try searching for threads relating to the lower intake manifold and/or the #5 plug fouling.

 

[jeisbell]

I had the same problems...
Fixed though with cleaning the MAS sensor with electronic cleaner, new air filter, and running an can of gumout through the throttle body.
This seemed to do it for me...
I would also suggest checking the EGR, O2, and exhaust.

 

[macoffma]

OK, one more wrinkle... Temperatures have gotten considerably warmer here the last couple days, and the problem has gotten considerably worse. It's been cold here for so long that I think it's been masking the problem. Now pretty much anytime I drive over 55 I get an almost unbearable shudder, the engine sounds very throaty, and I am feeling it almost stumble while accelerating at various speeds.

I've got a can of electrical cleaner for the MAF, and the Gumout sounds like a good idea. Is this similar to the sea foam I see mentioned here (it seems like there have been problems with Seafoam for some people).

Thanks again to everyone for their suggestions....

 

[jeisbell]

Some have used Amsoil foam or other throttle body cleaners...I just went to Pep Boys and got a can of gumout. I have never used seafoam.
When you take the pipe off the throttle body and look in with a flashlight, is it full of carbon and crap? Mine was pretty gross, and the gumout seemed to do the trick.
Lots of gunk comes out the tail pipe so don't be alarmed.