Quick engine Q???

[Primer_72]

This is kinda OT, but my 93 wont idle and will only run long enough to move a few feet (really rough). I pulled all of the pushrods on a hair-brained notion that it was a bent rod, but no dice. So I checked the comp. today which I shoulda done in the first place. Here's what I got

#1- 0lbs
#3- 75lbs
#5- 150lbs
#7- 125lbs

Think its just a slipped timing belt??

[Primer_72]

Ok, timing marks are dead on.... Maybe a wiped out cam??

[bigjimzlll]

sounds like you have trouble..do the rockers go up and down? cam timing has nothing to do with ignition timing...you still can have a timing chain/belt problem

[Primer_72]

Ignition timing? I never said anything about that, the marks on the cam pulley is dead on with the crank....

[Project1970]

It takes a pretty big problem for a timing chain to slip...

I'd pull a valvecover and watch the rockers while cranking it over. Also, did you try shooting oil in and running the test again?

[bigjimzlll]

my bad....I absolutly know nothing about the newer engines..sorry

[Rons71]

What are you working on?

[Blue_71]

my dads 89 wouldn't idle and ran really rough... tried plugs, and a 02 sensor, which is what the computer said, but it turned out to be i broke the clip on the sensor by the thermostat housing, plugged that back up, duct taped it down, no trouble sinse then

[Rons71]

Seeing you have all ot the rockers off, do you have access to a hose(like some of the compression testers with the quick disconnect for the gauge--the hose scan remain in the spark plug hole) and connect to an air tank or compressor to charge the cylinder? Check for the compressed air escaping either out the tail pipe, backing up through the tbi or leaking out of the exhaust at a very rapid rate9as you have 0 compression. You either have blown a piston, bent valves, burnt valves or dropped a valve. Low compression equally would represent a chain that may have jumped.

[Class of 69]

A little more background on when the rough running started would help. Did it come on slowly, or suddenly?? Did you change any parts that caused it ?? A jumped timing chain is very common on high mileage engines. The crank timing will remain the same, but distributor timing will be off about 12 degrees per tooth jumped. Have you tried turning the distributor to obtain a smoother idle??

[bigjimzlll]

or a head gasket

[Primer_72]

I went thru 2 EGR solenoids shortly before allt his happened.
When it actually broke down, it started losing power and the lights dimmed as I was braking down a hill (which is something that happened before because of a vacuum leak at the EGR solenoid, but there is no leak anymore). It restarted, and I got another 1/2 mile to my girlfriends house. After that it wouldnt idle and I could only move it a few feet at a time.... Maybe its the head gasket...I have a split in the rad, but it wasnt running hot at the time. I topped it off as often as possible (winter time). As I said the crank and cam gears were lined up perfectly so I think the timing chain is fine, even though it has 240k on it (yeah Im gonna replace it).

[Class of 69]

At 240k, a major tune-up is probably in order...starting with a complete overhaul!!! Burned valves, and worn out rings were probably contributing to the EGR problems, and are consistent with the compression ( or lack of ) variation. I was going to suggest intake manifold gasket leak.... but the compression figures you listed in your first post , and the very high mileage indicate seriously worn inner components. It could still be the cam finely went flat on a lobe or 2 to cause the sudden loss of power, but I don't think putting just a cam in it is justified. Sorry!!

[lukecp]

I had a similiar experience when i blew the head gasket on my TBI 4.3 equipped S10. It wouldn't idle worth a damn, would die if it got hot, had all sorts of electrical gremlins, and generally ran like crap. It still ran after i did it, but you had to give it more then 1/2 throttle to keep it running, and it popped, sputtered, and backfired.

[Primer_72]

Hmmmm, Im thinkin its something more serious like a head gasket or a flattened lobe. Just because it happened suddenly. Im gonna go ahead and tear the heads off and have them checked, and rebuild the top end...This trucks been too good to my family to leave it sit....I should find the problem (hopefully!) once I get it torn down that far...Thanks for all the tips fellas...

[O'l Buck]

with 0 compression on 1 hole, I'd guess it's a little more serious than a blown head gasket. it should make at least a little compression even with a blown head gasket or a burned valve. I'd say it either had the head fall off a valve or burned a hole in a piston.

[casey]

mine did that once it was a broken valve spring

[Blue68]

based on the 0 pressure at #1 and the next door neigbor, #3 only getting 75 psi I'm thinking head gasket. Especially if the other bank looks fairly consistent. If 2,4,6,8 have 120+ on ALL 4, pull the driver's side head. I'll bet you blew a gasket.

[Blazer1970]

You did put the valve train back together and re-adjusted the valves before you did the compression test, didn't you?

[Primer_72]

Of course...

[lpaine]

TTT