Truck belongs to my cousin...has 124k miles on it...Ran fine till the other day. Was going down the road then all of a sudden it lost power and starting knocking pretty bad is what he described. Was able to very slowly limp it home. I went over there today and looked at it...Oil looks good, no coolant in it. Started it and it didn't knock at all but idled VERY rough. After running for about 5 minutes I felt the exhaust manifold...Rear two cylinders felt very hot, the front two were not nearly as hot, I could actually hold my hand without getting burning on the front two, like they were not firing.

Pulled the spark plugs at those two cylinders and they were somewhat black and a little oily. Replaced with new plugs and started it back up...NO change. Distributer was tight and all wires appeard to be fine. Wires and plugs all changed about 2 years ago.

Also, exhaust sounded weird...Like a "bom bom bom bom bom" coming out of the exhaust, definitely sounded like a miss to me.

One thing I did notice was as I raised the RPM it seemed to smooth out.

Does not seem to be using much oil or anything. No real excessive smoke coming out of the tailpipe.

Any ideas???

How about a clogged cat? That'll make it run like CRAP! Bring the truck up to operating temp (enough so that the cat gets up to regular temp) then use your temp gun to shoot the front and rear of the cat. From what I've heard there should be no more than 10-15% difference in temp, front to back. And I believe the rear is supposed to be hotter. If the temp drop is more than that, try whacking the cat with a hammer and dont be surprised if she spits out a cloud from the tailpipe.

Did you check for spark at all cylinders? Remove the wire and hold the contact real close to the plug and watch for an arch.

How about the o2 sensors? Do they look okay? You might also wanna get the codes pulled -- sometimes the computer will store a code without throwing a CEL -- or his CEL bulb could even be burned out.

Perhaps there's some more specific issues with that engine that I don't know about. Maybe something with the EGR.

def check for spark and also how old is the time'n chain

Check compression, have seen some burnt valves in these 4cyl engines.

PSDfreak said:

One thing I did notice was as I raised the RPM it seemed to smooth out.

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Missed this part. That indicates to me that it's NOT a bad cat after all.

I agree with dave on the valves. You can use a vacuum gauge to detect valve issues. If the needle is fluctuating rapidly, you've got problems.

Ok, I was on the same track... He is going to get a compression tester today and we'll check for spark...

Timing chain was replaced 2 years ago

A guy over on FTE seem pretty confident that the timing belt "slipped a tooth" and should be replaced immediately...

You can check that without too much trouble, there should be an inspection hole on the front of the timing belt cover, just line the crank up at ), and see if the cam is still timed. Otherwise, it is possible the head gasket failed without putting and coolant in the oil, seen them do that before plenty of times. A compression test will be a good thing to do..

PSDfreak said:

A guy over on FTE seem pretty confident that the timing belt "slipped a tooth" and should be replaced immediately...

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Possible, but usually if the belt slips it's not just a tooth, it'll wipe out a bunch and probably won't run at all.

Update!

I posted about this truck before...Its my cousins '88 Ranger - 4 cyl...They were driving a couple weeks ago while everything was fine then all of a sudden the engine started knocking bad and lost most power...

Checked timing and compression...The cylinders from front to back tested 75, 75, 150, 185 on the compression gauge...The timing light also showed the timing set @ 20* rather than the 10* it should supposedly be at...Im thinking bad rings or bad valves possibly...seems odd though that all of this came to a head all at once...The truck was supposedly running just fine before then. Any advice??

Thanks,
Casey

The timing could have been wrong for a long time from slack in chain -- wrong timing isn't always noticeable unless it's WAY off. Though, 20* BTDC if it's supposed to be at 10* should create some nasty pinging with only 87 octane (assuming that's what he's using). My engine pings under load and its only at 14* BTDC.

As for the compression -- NOT A CLUE! I don't know jack about compression tests.

The timing could be the timing belt, while the two matching compression numbers at the front indicate head gasket, even though the pressures are not real low......

The timing on this still may be correct, to check the timing you need to pull the Pill out of the harness to check it. If not alot of times they will read around 20 Degrees.
The Compression #'s are off by enough to indicate a bad head gasket or head. I'm leaning towards the head as he said in the first post that there was no coolant in it. over heated it and cracked a head and it pumped the coolant out the exhaust and not in to the oil.

I have seen more than a few head gaskets fail without any loss of coolant or oil. I would have the head checked all the same, just to be sure there are no surprises. I haven't seen too many heads warp on only one part, but not the rest of the head. Cracks will generally only cause low readings on one cylinder.