Bad Motor?

[916MINI]

Hi everyone. I just picked up a 91 for a good deal but i think the motor is dead. It runs and drives but burns oil and smokes REALLY bad. It burned a quart of oil in 200 miles. Any ideas what it could be? The car was sitting for several years before I got it. I was told someone got it running a couple years ago and once they got it started they beat it pretty hard then parked it again. Any advice? Thanks!

 

[LJRuddy]

If it is smoking, you more than likely have some bad piston rings and/or destroyed valve seals. Does it smoke non stop or does it only smoke on a cold start up and high rpm driving?

Either way, you will be looking at some intensive repairs for the engine.

Best of luck! I'm sure some more knowledgeable people will chime in soon. These forums are D.E.A.D. after 11pm Central Time. :wave:

EDIT: I suppose I can add some more useful info while I'm here...

To find out if you have bad rings, you can confirm this by doing a compression test on each cylinder. If I remember correctly (SHOForum, correct me if I am wrong), you should see a minimum of 180psi per cylinder. If you are getting a reading substantially lower than this number, pour some regular engine oil into the plug well and test again. If the psi readout rises quite a bit, you have bad rings.

If you have bad valve seals, you will notice tons of blue smoke spitting out of your during cold starts as well as during high(er) rpm driving. I had some bad valve seals on my previous SHO and when I started her up after having it sit in the college parking lot all day, she would spit blue smoke out the exhaust for a good 3-4 seconds. Even worse, merging onto the highway... During a WOT shift, my car looked like something out of a James Bond movie as I shot a smoke screen of blue smoke towards the cars behind me.

Do you have any external oil leaks that you can tell? Some common areas to look are in the spark plug wells, valve cover gaskets, and the front main seal around the crankshaft. How many miles are on this engine? Do you know if it has had any major maintanence performed on it recently? What type of oil are you using?

EDIT 2:

Found a video of a member here (93rev2sev) doing a compression test on his SHO engine.

[YOUTUBE]NUHHBd67tic[/YOUTUBE]

Notice how the first test he only got around 140psi. After adding some oil, it bumped up to around 170-180ish. That is a sign of a bad ring.

Your engine does not make any out of the ordinary knocking/ticking/slapping/fapping snicker: ) noises, does it?

 

[rubydist]

These engines get sticky rings quite easily, and my experience is that leaving them stand will often result in stuck rings even if they were fine before it was parked. Sometimes, some seafoam and then synthetic oil for several thousand miles has loosened them up, and other times they need to get pulled apart. Several guys have reported that they have removed the pistons and rings, cleaned everything up and put in the same parts back in - often even 200k mile engines will still show the cylinder honing marks from the factory.

If you are going to remove the heads, then I would certainly change the valve seals at the same time.

The approach I've described is not particularly expensive, although there is a fair amount of work involved. A few hundred bucks in seals and gaskets.

And, of course, you should change rod bearings also, unless you know that they have been changed recently.

 

[916MINI]

Thaks for the grat info guys. It does smoke on start up and while heavy acceleration only. Driving normal its fine. So you think valve seals? What can I do to test if they are bad? The car has no external leaks at all, the motor sounds pretty good, no major knocks but it does tick.

 

[93rev2sev]

Do a comp test like you see above and hope they are all fairly consistant. My 90 that you see in the video is still sick but runs fine. It's either a cylinder wall or an exhaust valve not sealing.

If your only symptom is burning oil, I'd say you've got valve stem seal issues. The smoke you see in the rearview mirror on hard accelleration might be unburnt fuel which is usually black, not bluish (like oil). You might still have some nasty gas in there. You might also just have a tired engine that can't burn all the fuel the injector is wanting to give it. New cats might help burn some of that excess fuel up, but don't count on it.

These engines seem to run pig rich at WOT and almost everyone reports smoke during accelleration.

 

[916MINI]

Has anyone used any of those Engine Resotre products? Think it may help at all? I still haven't done a compression test, too busy trying to fix all the little things that keep going wrong, off to do brakes right now.

 

[93rev2sev]

If having a bad engine is potential for you to get rid of the car, it might be wise to do that comp test BEFORE dropping a bunch of cash on other parts.

 

[rubydist]

+1 I'd find time to do the compression test so you know what you are dealing with sooner rather than after you spend a bunch of other money.

 

[916MINI]

I LOVE this car! I don't plan on getting rid of it. If the motor is bad I was probably going to replace it. I have done several motor swaps but never rebuilt a motor before, to be honest I'm kinda affraid to. I have been looking around for a new motor. I was also wondering about a 3.2 swap. Is it a straight swap? There is a wrecked 94 auto SHO and the local junk yard I was thinking of pulling.

 

[rubydist]

The 3.2 will either need to have the accessory drive converted to the 3.0 style (2 belts) or you will need to fab custom motor mounts to make it work with the stick. Otherwise, its pretty straightforward.

 

[LJRuddy]

The 3.2 will either need to have the accessory drive converted to the 3.0 style (2 belts) or you will need to fab custom motor mounts to make it work with the stick. Otherwise, its pretty straightforward.

You will also have to either swap out the 3.2 oil pump and replace it with the 3.0 unless you don't mind an opening in your lower timing belt cover.

You will also have to use the 3.0 oil pan.

If you stick with the 3.2 accessory drive, you will have to do some electrical work as I believe some of the 3.2 accessories use different plugs/connectors than the 3.0 does.

Be sure to use the 3.0 o2 sensors as the connectors for them are different from the ones used on the 3.2.

:wave:

EDIT: I just noticed that you drive a Gen 1 SHO. If you do plan on using a '94 3.2 engine, I suggest keeping the 2 belt accessory set up and use the wiring harness from your current engine. Otherwise, you will have a very difficult time with wiring as the engine harness had minor changes almost every year the SHO was built. With that said, throwing a 91 wiring harness on a 94 engine with 94 accessories would not be fun. And if any accessory needs to be replaced down the road, buy the part for a '91 SHO as that is the harness you will be using.

 

[916MINI]

So If I get the 3.2 just take the long block and put all my 3.0 parts on it and it should work fine? If I don't have to get into wiring I'd rather not. Will the 5 speed bell housing mount to the 3.2 the same as the 3.0? This dosen't sound that bad at all.

 

[916MINI]

By the way I would just like to thank everyone so far. This is one of the best forums I've been on, everyone is very helpful and know what they are talking about!

 

[Ocnaj]

So If I get the 3.2 just take the long block and put all my 3.0 parts on it and it should work fine? If I don't have to get into wiring I'd rather not. Will the 5 speed bell housing mount to the 3.2 the same as the 3.0? This dosen't sound that bad at all.

Yep, just take your 3.2 long block and put all the 3.0 parts on it. That way you don't have to do any wiring.

The MTX-IV(5 Speed Transaxle) bolts right up to the 3.2. Just bolt your 3.0 flywheel to it.

 

[LJRuddy]

The 3.2 will either need to have the accessory drive converted to the 3.0 style (2 belts) or you will need to fab custom motor mounts to make it work with the stick. Otherwise, its pretty straightforward.

Yep, just take your 3.2 long block and put all the 3.0 parts on it. That way you don't have to do any wiring.

The MTX-IV(5 Speed Transaxle) bolts right up to the 3.2. Just bolt your 3.0 flywheel to it.

In addition, using the 3.0 cams on the 3.2 will net you some extra power to boot! The intake (or is it exhaust? I don't remember) cams have a slightly bigger profile.

But yes, all you want/need from the 3.2 engine is the short block. If I were you, I'd leave the 3.2 timing belt set up on there as I think it is much easier to work with. :wave:

By the way, there is a large number of California SHO owners here on the forums... Check out the "SHOCal" section and see if anyone is close by and would be willing to help out with the swap and maybe give some face to face advice.

 

[Devin]

Rebuilding isn't hard. The engine is actually quite simple once you get it all torn down. Transmissions on the other hand...

Get a couple books and Alldatadiy.com.

 

[rubydist]

I think some of you guys aren't seeing the forest for the trees - if you want to put the 3.0 heads on the 3.2 engine, you have to remove all the engine wiring first, and then reinstall it after. Clearly, you don't save any wiring effort with that approach, and you spend a bunch of time and money to do it.

Putting the 91 engine wiring on the 94 engine is no big deal. The only problem is you will need to adapt the alternator connector, since the later ones are 3-wire (only 2 are used) and the early ones are 2-wire. Everything else is plug and play on the engine harness.

Using 3.0 intake cams on the 3.2 will let it breathe better at higher rpms, making more horsepower.

 

[revhardSHO]

Might look into a junkyard motor or something on ebay/craigslist. If you can find a decent motor just drop it in and forget about it.