Engine shaking badly at low rpms

jmpetre · Jul 17, 2008

I was on my way from work yesterday, and I took a dirt road for about 5 miles. It had bad washboard.

That night, I went out to the party store to grab some milk, and notice my ranger was shaking badly when I started it up. I drove it anyway (short drive). The cab will shake, and it feels just like misfires, from around 1300-1600 rpms. After it gets above that, there are no problems; everything runs smooth. There is no loss of power.

When I got home, I opened the hood and had a friend rev the engine to around 1500 and hold it. The engine was shaking on it's mounts violently.

I plan on checking the plug wires when I get home. My best guess is that something got knocked loose while on the bad dirt road, but I am open to any other suggestions of what I should check. I really don't want to change the plugs and wires...they are poorly positioned in this engine and will be a major PITA.

Thanks!

Edit: The truck only has 40,000 miles on it. I can't imagine too many parts going bad already!!

Big Jim M · Jul 17, 2008

The fact that it seems to smooth out above 1600 rpm is telling me the problem is fuel related. Could be a number of things. I might start by cleaning the IAC and MAF and throttle body to see if that helps.
Big JIm

jmpetre · Jul 17, 2008

Where is the IAC located, and how do I clean it?

Thanks for the reply. I'll hopefully get to this tonight.

jmpetre · Jul 17, 2008

I cleaned the IAC, MAF and throttle body tonight, and it didn't have any effect on the shaking. While I was cleaning the TB, the MAF was off and disconnected, and the engine still shook at low rpms.

A friend suggested that it might be a clogged/blocked fuel injector. Any thoughts on this?

The night that it happened, I had to put in $20 in regular gas. This is the first time the truck didn't have E85 in it for months. Could this have caused any problems?

I plan on taking it to work tomorrow with it shaking, and fill the tank with E85.

jmpetre · Jul 18, 2008

I drove the truck in to work today, and I discovered a new symptom. Once the truck gets rolling and gets beyond the point where the whole cab shakes, the engine evens out but I can now hear ticking coming from the engine. The higher the rpms, the faster the ticking. I've also noticed a significant loss of power near the top-end. Once I get up to about 50 mph, I need to floor it just to keep accelerating.

These are leading me to believe that I have an ignition problem, and I'll probably end up having to change the plugs and wires. I can see that it still has factory wires on it, so I'm guessing it still has factory plugs under them. It just seems weird to me that this problem developed in a matter of 2 hours of sitting.

Anyway, I drove the truck to work today, about 10 miles, and filled it up with E85 from 1/8th tank, and put in a bottle of injector cleaner. While although I'm doubtful this will make any difference, I did it anyway.

Any other opinions are greatly appreciated.

thegoat4 · Jul 18, 2008

Systematically eliminate chunks.

Run it without the belt, see if there is any change.

Disconnect your cam synchro sensor (towards the back of the block, passenger side, where a distributor would be), see if there is any change. You will get a CEL from this.

Stick shift or auto? Check your fluid, check the bell housing bolts to make sure the transmission's not falling off.

Check your exhaust, see if you hit it and caved it in somewhere.

If you don't mind getting zapped, you can disconnect your spark plug wires one at a time. Either pull the three on the right, or pull the three on the left. It's a waste spark system, so pulling a wire on either the left or right will kill both sides of that one coil, so you effectively cut out two cylinders at once.

Unplug your coil and crank the engine over. Listen to it. If you hear some noise that sounds strange, go check it out.

Dump your oil over a magnet and check for metal. A little iron fuzz is ok. Hunks of iron or any pieces of brass is bad.

Do a compression check once you have your old plugs out.

Blacksheep · Jul 18, 2008

jmpetre said:
I cleaned the IAC, MAF and throttle body tonight, and it didn't have any effect on the shaking. While I was cleaning the TB, the MAF was off and disconnected, and the engine still shook at low rpms.

A friend suggested that it might be a clogged/blocked fuel injector. Any thoughts on this?

The night that it happened, I had to put in $20 in regular gas. This is the first time the truck didn't have E85 in it for months. Could this have caused any problems?

I plan on taking it to work tomorrow with it shaking, and fill the tank with E85.

did it do it when u had e85 in it, or did it start shaking after u put normal gas?

jmpetre · Jul 18, 2008

Blacksheep said:
did it do it when u had e85 in it, or did it start shaking after u put normal gas?

I put the normal gas in and drove home, everything was fine. I had to run out a few hours later, and it had started shaking.

jmpetre · Jul 18, 2008

thegoat4 said:
Systematically eliminate chunks.

Run it without the belt, see if there is any change.

Disconnect your cam synchro sensor (towards the back of the block, passenger side, where a distributor would be), see if there is any change. You will get a CEL from this.

Stick shift or auto? Check your fluid, check the bell housing bolts to make sure the transmission's not falling off.

Check your exhaust, see if you hit it and caved it in somewhere.

If you don't mind getting zapped, you can disconnect your spark plug wires one at a time. Either pull the three on the right, or pull the three on the left. It's a waste spark system, so pulling a wire on either the left or right will kill both sides of that one coil, so you effectively cut out two cylinders at once.

Unplug your coil and crank the engine over. Listen to it. If you hear some noise that sounds strange, go check it out.

Dump your oil over a magnet and check for metal. A little iron fuzz is ok. Hunks of iron or any pieces of brass is bad.

Do a compression check once you have your old plugs out.

The engine shakes in the bay while in Park, Neutral, Drive, or any other gear. I shook the engine by hand to check the motor mounts, and I didn't notice any slop. It is an automatic, and the fluid is fine. Engine oil has less than 1000 miles on it, and I can't feel any grit when I rub it between my fingers. I'll check the cam sensor when I get home tonight, and I'll get under the truck and make sure exhaust is ok, and I'll check for any loose parts.

Engine seems to crank fine. I'm going to change the plugs and wires this weekend. I'll do a compression check then. If that doesn't solve the issue, I'll remove the serpentine and report the results.

Thanks for the replies.

jmpetre · Jul 18, 2008

What should happen when I unplug the cam sensor?

jmpetre · Jul 18, 2008

I changed out the spark plugs and wires. No change. The guys at my CarQuest suggested that it might be a clogged catalytic converter. I would tend to believe them - I am having serious doubts that I have bad compression or loss of fuel with the symptoms present. I might just punch the cats out, but that's going to be a huge pain.

thegoat4 · Jul 19, 2008

Unplugging the cam sensor switches the fueling to a less efficient, more robust schedule. Think of it as "plan B."

YOU shouldn't notice anything except the CEL comes on. But if it has a noticeable impact on the skake, your problem is fuel timing or computer related.

Feeling the engine oil is meaningless.

Did you do a compression check?

How did the old plugs look?

Parts guys aren't mechanics--ignore them.

In any event, quit driving it around. Depending on what it is you could do severe damage to your engine. If you get the notion to throw more parts at it to see if that will help, consider spending that money to have a shop look at it.

jmpetre · Jul 19, 2008

I did not do the compression check, I didn't have the gauge with me. The old plugs looked scorched, but the electrodes showed normal wear. The tops of the plugs were burnt brown and showed rust.

I really need the truck back on the road - it is my daily driver. I'm having my mechanic look at it today.

Thanks for all the help though, I do appreciate it.

Big Jim M · Jul 19, 2008

" I can't feel any grit when I rub it between my fingers."

That is a new one on me! I never would have thought of testing oil off of a dipstick for grit.. Nor shaking an engine to "test" the engine mounts..
I think the mechanic should absolutely look at that engine to resolve your problem.
Big JIm

jmpetre · Jul 19, 2008

My mechanic determined that it was a faulty injector, and has a new on on order from Ford. I'm sure I would have figured it out eventually, but I didn't have the time to wait.

I just can't wait to have it back!

Engine shaking badly at low rpms

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