Piston gets stuck at TDC

[mikes94q]

Im trying to rehab my 94q, it only has 60k on it but had a knock like a bearing went bad. I pulled the motor, pulled the oil pan and the bearings are fine. When manually turning the crank all pistons work perfect except for when number 5 and 8 hit tdc one of them is sticking. You can turn past it but it takes a good effort. Not sure what is causing the issue. Any help would be greatly appreciated. I really want to get this car on the road again.
Modified by mikes94q at 9:17 PM 4/4/2010

[djwarner]

Is this with the spark plugs in or out?

[mikes94q]

actually with them in or out

[mikes94q]

Does anyone else know what I should look for? I would really like to save taking the heads off to avoid the costly gaskets.

The motor will still crank over its just gets difficult to get past those two pistons at tdc

[djwarner]

Looking at the firing order and this being a 4 cycle engine, cylinders 5 and 8 are in sync. So yes, I agree that one or the other will be causing the interference if it is ocurring at TDC.

I imagine this is fairly uncommon or the techies on this site would have seen this before.

I would suggest that either: something is in one of the cylinders, or the engine has been subject to improper maintenance at some time in the past.

In your other thread you mentioned the engine only had 60K. Considering the age of the vehicle, I would suspect the engine sat without running for some extended period of time. If it sat with a piston near TDC on the exhaust stroke, the valve may have been open enough to allow moisture and rust to develop. Another potential problem may be part of the head gasket protuding into the chamber.

In either of the above cases, inspection with a borescope would be in order. I don't know how common this is in the automotive world, but a light aircraft mechanic (called an A & P ) should be able to locate someone with one and the skills to use it.

Beyond that you start thinking about oversize piston rods and other ugly thoughts. Don't even think about how such a thing would have gotten there.

Good Luck

[mikes94q]

I thght the same thing about the rust.. Its just real uncommon here in New Mexico to get rust on a car. I'm going to try and locate a bore scope and see if that will help diagnose my current problem.

What are everyones thoughts about buying the JDM engines off ebay? Like the ones that are in the Nissan Pres.[QUOTE=djwarner]Looking at the firing order and this being a 4 cycle engine, cylinders 5 and 8 are in sync. So yes, I agree that one or the other will be causing the interference if it is ocurring at TDC.

[Infinitiguy19]

Didn't you already make a topic about this?

Didn't I tell you to check out the link in my signature?

If you did you would know all about JDM takeout engines.

[mikes94q]

so I found alot in there about the ecu but not the JDM engines..

I'm just looking to save a buck or two. If I pull my motor apart and have everything machined, I'm looking at the cost of a JDM engine before I start putting mine back together.

I just wanted to know what other peoples experiences with the JDM engine.

[Infinitiguy19]

$1218 is for just the chain guide replacement and a new oil chain.Valve cover reseal and an oil pan removal [if required] adds another $1000 [$1100 ifit is a 't' or 'a' model].Removing a [driver’s side] head, sending it out for rebuilding would add$1200-1500-$1800 if the valve cover was off {$300} [very time consuming with engine in car.Pretty soon you get to the price of a used take out engine which still requires newchain guides and oil chain plus who known how much in new hoses, water pump,reseals, knock sensors R&R in general.To do the job right for the long haul is $5,000 to $6,000 unless you can find techswho work for nothing.The thing is all engines [valve covers] leak sometime and all hoses and electricalharnesses become brittle and all connectors get corroded.In the 90-93 Q case all the engines are the same age low miles does not mean asmuch as heat exposure and good maintenance does.If you are going to keep an engine 10-12 years you are going to have to go throughthese expenses....buying a 93 engine may or may not have less heat exposure [hotidling vs highway driving] to the rubber hoses.It is always more economical [faster] to replace all external components when it issitting on an engine stand.Warranty is our problem -- the customer expects everything to work for a year eventhough we may use his old injectors, rails, plenum, throttle body, etc. We try toguess [correctly] which old or older [cleaner]parts to use.One warranty claim to replace a knock sensor can cost us $800 or an injector $250-$550 or a crank angle sensor or worse add a tow to either ...there goes the jobprofit.What the take out company engine warranty gives you is another rough engine [for3-6 months] where you get to do all the R&R again and pay to ship the bad oneback.May the FORCE be with you in selecting one.A used Japanese take out engine will still require that you change out the old styleguides, water pump, reseal the valve covers, change the plenum hoses, injectors ??,new spark plugs, and knock sensors and harness.One to two days of R&R before you even think of putting it in a car as it arrives.Transfer the starter, build it up with PS pump, alternator new belts , thermostat, newwater hoses, charge ac system.Some times you can get one as bad as you are taking out.We end up charging $2,000 just to get the take out engine $2,500 ready to installthen the $1,000 for the swap.

Why am I so damn nice.

[mikes94q]

seems like your pretty knowledgeable on the Q.

What would you recommend? -Pull the heads and check clearances?

[Infinitiguy19]

I am not Q45Tech from which the text I quoted is. I am not that smart when it comes to the Q but I am learning.

[3Q Jay]

i would undo the rod cap one at a time on 5 and 8 and see which is the problem. if a valve is hanging open enough to cause interference, you would also see poor compression on that cylinder.

[mikes94q]

So it wasn't 5 or 8. Pulled both heads tonight. After final inspection it is #2 piston skirt hitting the crank at the bottom of its stroke. What now. Not sure what would cause this.

Any thoughts to a resolution would be great, not sure if I should pull the crank and have it machined or the piston. It just barely hits. Like I said earlier you can muscle past it. I'm surprised that it didnt crack the piston skirt.

[Infinitiguy19]

How much do you want to spend is the true question?

You have balls for pulling the engine and doing all of this but its far to hard to machine the engine to near new. When the engine was built by hand they had all the tools and knowledge they needed.

I remember reading a post by Q45Tech where he took the head and crank to a friend of his who owned a machine shop. His friend said no thanks because its far too much work.

Most would have replaced the engine by now but you sound like me. I like to pull stuff apart and see if I can make them better or at the very least fix them.

Can't source the exact post but you might want to ask the VH section for some help.

[silkysmoothyjud]

How good is the rest of the car? 1-2k engine replace is worth it for a good Q...

[mikes94q]

Just pulled everything else off. Its a bad rod. Man i Feel stupid for it taking so much to diagnose that. I'm a neewbie but man. Just barely bent.

As far as the rest of the car its like a very well taken care of 60k car great interior(missing radio, and switch on right hand side of steering wheel)

Any good sources for a rod, piston, and ring set?

[maxnix]

Any good sources for a rod, piston, and ring set?

Star with http://www.infinitipartsusa.com for new.

The whole assembly with harmonic balancer was balanced together at the factory.

[mikes94q]

I called them today, getting the rod ordered. Also, needed to get the bearing. But they have 3 different grades, the guy told me that the number is stamped on the cam. 0,1, or 2. Well one head has 1 stamped on the cams and the other has 2 stamped on the cams.

What grade do I get? Am I just looking at the wrong stamp?

[Infinitiguy19]

Technical Service Bulliten for the Crank Bearing ID: http://docs.google.com/filevie...hl=en

Crank bearing: http://cgi.ebay.com/ebaymotors...t_749

Post up which crank bearing you have and I will see if I can look it up to save IOS some time.....

[mikes94q]

ok so I went and looked at the counter balance and the numbers are as follows:

2 22 1 1 01 11

The rod that was bent was#2 cylinder.

[Infinitiguy19]

So you just need the rod bearings right?

If so then this it: 12111-60U01- Thats for the Grade 1.

And I am am going by what you say and what the TSB says about number on the top and bottom. There are two rows of number right?

[mikes94q]

yes it is two rows of numbers, and just need the bearings I'm ordering the rod and I believe there is only on variation of that (at least I hope so)

Im going to order that part also.

During the wait for the parts I'm going to go over all the other stuff with a fine toothed comb, hoses, fuel injectors (apparently prone to failure) vacuum lines.

Since the car sat for so long, is there anything I should look at prior to putting it all back together? Ie., exhaust, steering, braking, componets?

[Infinitiguy19]

Hey man just read as much as you can from the link in my signature. There are almost a 100 documents as far as I know maybe more and after you read most of it you will be amazed. I actually feel I don't deserve to own a Q after reading all of it...

It will blow your mind.

[Q451990]

it is #2 piston skirt hitting the crank at the bottom of its stroke. What now. Not sure what would cause this.

It's probably the result of a bad injector o-ring that caused flooding and hydrolocked the engine.

Heath

[silkysmoothyjud]

I am not worthy! I am lucky my starter was old and cracked in half when trying to start a hydro locked motor when I first got her. I had a "mechanic" change the first injector w/o pulling the fuel pump fuse. The gas leaked down b4 the ebay replacement starter came....I paid that bastard to replace the starter to dee dee dee....