'94 GP LIM Repair, ROUGH IDLE

[KCFITZ78]

'94 Pontiac Grand Prix, 3100 with 143k. Here is the story for my car. I had an overheating problem and a loud exhaust at the same time. For the overheating problem I 1st Flushed the coollant….. that was not it….2nd NEW radiator….. helped but not it…..3rd NEW water pump…..that solved it! As for the exhaust problem I needed a new exhaust and also discovered I had a cracked rear exhaust manifold. I bought all new except for the CAT. I put the new pipes on last winter but did not replace the rear exhaust manifold. At the end of this past summer I had still not replaced the rear exhaust manifold. Then I ran into a problem. The engine started to run hot and I was losing coolant. I Looked around and found that I had coolant in the oil. Yes that’s right leaking lower intake manifold (LIM). Looked like butterscotch pudding. By the way I hate butterscotch! So for the fun part, I got real brave! Since I was going to be taking the top engine off, I took it all off. Yes the heads too. With the rear exhaust manifold cracked I figured all gaskets had been cooked pretty good plus this made it easier to pull off the rear manifold and get everything cleaned up. This is labor intensive but it went good, no broken bolts, no scratching my head, came apart nice and went back together nice. Well almost nice. I did not pay attention to the push rods. There are two different lengths for intake and for the exhaust. The correct sizes are in the right location just not back in the prior location before tear down. Once it was all back together it started, but idles really rough and gets hot really quick. It will stall once you put it gear. Also there is a knock ever once I awhile. I did pull the rods to make sure they weren’t bent and put them back and still knocks. I did not check compression seeing that it ran fine before tear down. Did not have the heads checked. Everything is torque to spec, Oil changed, filter changed, spark plugs change, all wiring checked, coolant changed, cleaned TB, no leaks, cleaned, cleaned, cleaned………………………. Any ideas what the problem is? Did I miss a step that would cause it to run like a pig and not be able to drive at all. Any suggestions? I am about ready to junk it but can’t pull myself to do it since it ran fine and drove fine before I beheaded it. I appreciate any help at all so, “Thank you” in advance!

[bszopi]

It'll heat up pretty quick after a rebuild (at least from what I've seen) because you are still trying to get coolant back into the engine. The coolant in the engine is pretty low and the thermostat is still going to open at the desired temp. I was worried about this the first time I took the top of the engine off, but it returned to normal after alittle while.

As far as it not running very well (not sure if it would cause a knock or not), but are the plug wires in the right spots? I've seen this be a problem many times. Might be something to look at.

[onefastV6]

Did you happen to purge the air out of the cooling system? There is a vent screw on the top of the hard coolant pipe that sticks up.

[KCFITZ78]

Ok idle is not as rough any more, but still stalls out once in gear. Coolant is flowing good and engine does not get hot real quick, stays at normal temp. Still is not right.

Rechecked the following:
-Check the wire order again-------------GOOD!
-Check torqe on all bolts I can get to----GOOD!
-Check the solenoids on the EGR--------PUT IN A STOP PLATE!
-Check the value in the EGR------------PUT IN A STOP PLATE!
-Check all vacuum lines----------------READS 17" AT IDLE W/ HARDLY ANY MOVEMENT
-Check all "new gaskets" that I can see-NO LEAKS!

Any ideas?

[tractorman]

Put that EGR back on- it'll set a code without it. Check for vacuum leaks with ether- especially around the egr and that stupid little gromet thingy sorta above the throttle body. Check for a stuck pcv valve.

[KCFITZ78]

The EGR is still hooked up. I made a plate that goes in between the EGR and the manifold so no exhaust can go into the manifold. I did this just in case the EGR valve was stuck open. Also the PCV valve is not stuck, plus I put in a new one. I will try using ether and a working fire extinguisher to find any vaccum leaks. When checking the idle will increase if there is correct?

[KCFITZ78]

SUMMARY OF THREAD:

Tore engine apart, Put engine back together (including new plugs), went to start for the first time a got really rough idle, has a knock but its not consistant and got really hot. It was then hard to start and rough idle. Checked coils, wires, pulled plugs and put new in. Still no change on start up. Tired disconecting CAT, but still the same. Finally got cooling system purged, but still same. Checked torque on all bolts I could get to, checked for visable leaks, checked vaccum pressure, checked coil and wires again, still same. And last I inserted a stop plate between EGR and manifold to keep exhaust out in case EGR valve was stuck open, still same. Also has not thrown a single code during all of this and still idles rough and has a knock.

[bszopi]

Considering at the beginning of the thread, you stated you tore it all down due to coolant in the oil, there might be more damage to the engine that you originally thought. Just because it ran fine before you tore into it doesn't mean that it'll run fine when you put it back together, especially since you only tore down the top end. You also stated that you didn't have the heads checked, so there is a chance that there are issues there.

[KCFITZ78]

So your telling me with every LIM repair you have to rebuild the entire engine? Thats bull.

[bszopi]

No, that's not what I said. There are plenty of LIM leaks that don't leak enough coolant into the engine to turn the oil in, what did you say, butterscotch. With a significant amount of coolant in the oil, there is a potential for damage to bearings and such. There have been several people on this forum that have wiped bearings with minimal amounts of coolant in the oil.

I'm just trying to give you some further areas to look into. If you don't want to listen, its no skin off my back.

[KCFITZ78]

I have no idea and I give up on this engine. I am junking the car. I don't have a place to store and work on the car so there is no reason for me to keep it. I have been all over this and only thing left to do is pull the engine and do a rebuild because something must be broke. Will never know!!!

Checklist
-no visable leaks, good
-sprayed ether and no vaccum leaks, good
-vaccum tested and was fine, 17", good
-pulled valve covers and checked bent rods, good
-blocked off egr in case egr was stuck open, good
-dissconnected cat in case cat was pluged, good
-compression tested 150 to 160 psi throughout all cylinders, good
-checked coils, good
-checked wires for spark, good
-rechecked firing order, good
-black plugs, put in new plugs

Car will idle, but rough. Also there is a knock in the engine but it is not consitant. Was able to drive bout 250 yards, but was down a cylinder or two.

Anyone want to make any offers? Will make a post by end of week w/ pics, car options, replaced parts, and any history as long as I had it.

[KCFITZ78]

Ok, I have some good news for once. The car now idles fine and is back to sounding and feeling like 6 cylinders. The pigtail for the # 3 fuel injector was not connected well and the pigtail for the #5 fuel injector had a wire that was bared. (Used some liquid tape on the wire).

Problem #1
Now…… I don’t think I have oil circulating in the engine. Either the oil pump is blocked with all the old crap oil mix or the oil pump is toast. Yes the oil has been changed 3 times. I want to check the oil pressure, but can’t find my gauge (somewhere in my pile of tools). I think I can just pull the oil pressure sensor and check there. Do I really want to pull the oil pan?………… This is not by far an easy task at all is it?????????

Problem #2
The engine still has an inconsistent knock. Yes the valves are ticking too, because of no oil but there is also a “clunk” sound. The engine idle will change just slightly when I hear the knock (clunk).

Cause?:
No oil circulating?
Borken rod guide/pivot retainer? (Plastic long bar w/ holes for rods that push cam) http://i14.photobucket.com/albums/a3.../100_0379e.jpg <-94CutlassSLCoupe's Pic, I'm borrowing it
Spun bearing?

Problem #3
I have about 3 to 4 hours of run time on the engine now, and that’s a lot of restarts. Think I may be hurting it?