LANDSHARK1

Hi all!
Well, my '95 LT-1 six speed had been running incredibly well, but had developed a really bad oil leak due to the rear intake manifold gasket seal. I've worked on countless motors, especially small block Chevys and even then I really took my time, meticulously labelling every single connector and vacuum line as I went about it. The manifold set-down went picture perfect...I also took the time to allow the sealant to properly set up before final torque-down and then let it sit overnight before starting it the next day.

Was so happy and patting myself on the back that all the years of doing this on my cars had culminated in what I believed was the smoothest and best job I had ever done...and then I started it and it has been running rough ever since. The leak is gone though...LOL

Since then, I have checked and re-checked all my connectors and vacuum lines about ten or twelve times. Everything is done textbook perfect. I even went so far as to check the PCV to see if it rattles and cleaned it out anyway, just in case.

Over the course of the past two weeks or so, been exploring every possibility in my head as to what could cause this. Car has the following symptoms:

1. Idles rough...not changing, just not smooth...you can feel it through
the steering wheel and the shifter

2. The exhaust note is strangely different...sounds like it's underwater

3. Engine still revs smoothly, but performance is not the same

4. Gas mileage seems a lot worse, but not confirmed

I ohm'd the injectors (they were the original Multecs or so I believe) and got an average reading of 12.5...all were within +/-.5, but certainly well below the expected 16 so it was time to replace them.

I ordered the upgrade Bosch III injectors from Jon of FIC (he is fantastic...I highly recommend them!) and was very pleased with the product and service. I noticed that he shipped them only 15 minutes after I placed my order (amazing!) and they arrived so quickly despite the distance from Atlanta to SF. I was blown away by how quickly they came so I was able to install them on Saturday. Everything about them was first class!

Super happy with the upgraded injectors and FIC...but sadly, I was shocked to discover that despite improved running, my rough idle problem still exists. UGH!!!!

I need to run the codes on it next, but at this point I am now thinking that it might be either TPS (throttle position sensor) or IAC (idle air control valve) related. When I had it apart for the intake manifold gasket and seal repair, I shot a lot of throttle body cleaner into the throttle body to clean it out so wondering if perhaps that had injured the TPS or moved the grunge within to the pintle of the IAC inside since I did not take that apart.

Tomorrow, I hope to run the codes on it and see what comes up, as well as remove and clean the IAC. I don't have a scanner, but it is a '95 so it has an OBD-II connector even though it is OBD-I. I jumped it with a paperclip before to successfully read the codes, but that was a year or so ago so I have forgotten the procedure and will dig for it on the net before I do it again.

Anyway, I have checked time and time again and have confirmed that there is no vacuum leak...the only other potential problem I could possibly even remotely think of was an intake manifold gasket leak from cylinder to cylinder (impossible...the install went flawlessly!) or that the throttle body coolant hose dripped onto the Optispark (I don't see how since I carefully put a big plastic bag over that area as a precaution before removing that little hose and even then, not much came out.

Briefly considered fouled plugs, but decided that is not possible since the car was running absolutely fantastic when it was taken apart for the intake manifold gasket.

It's not like I don't know what I'm doing, but this is just one of those frustrating things...the car ran absolutely fantastic before the intake manifold gasket change. My luck just hasn't been good lately. Story of my life.

LANDSHARK1

Forgot to mention that the car has two new oxygen sensors from about a year ago. I briefly entertained the possibility that the bad oil leak had somehow seeped into and ruined the one on the driver's side, but then I realized that if this was the case, it should have thrown a Service Engine Soon light which it did not.

aklim

Time to get a scanner to see what the ECM is seeing. For all we know you had a plug wire loose or crossed. Are you SURE, SURE, SURE and SURE that the firing order is right? If so, MAKE SURE one more time. Wanna know how I know this? I'll give you 3 guesses.

Is the TPS bad? IDK. Check it. I damaged a sensor before when I removed stuff. Why should you be any different? With a scanner you can see the value of the TPS at startup. What I would do is turn it on but NOT in run position, see what the initial voltage is and SLOWLY depress the pedal. The voltage must go ONLY UP and SMOOTHLY. Any drop off, toss the sensor.

Beyond that, we really need to see if the O2 sensor is moving up and down or being lazy.

Also, based on my L98, I would THINK that we need to see what the IAC is doing to know if there is a leak or not. Been chasing the idle speed for a while since some *@#$R) borrowed my scanner and had it in the house when his wife tossed him out of his home.

HlhnEast

Got to pull the codes if any because you are shootin in the dark and beating yourself up. One thing I have learned is dont keep looking over the same work if you know its right. Aklim is probly right, there is probly a loose wire or damaged sensor. At least you will rule all that out by using a scanner. If no codes start looking to the fuel side.

Good luck!

Dt86

One of the best things I bought for my car was the red brick snap on scanner. Throwing parts(money) at it because you think it's this or that can get costly and solve nothing. I know this from experience lol.

LANDSHARK1

Thanks all!!!
Totally appreciated!

BTW, you are so right...I need to get a scanner. Which one should I get? Which one do you guys recommend? Not familiar with the red brick scanner, but will definitely google it next. Love Snap On, but sounds expensive already

Also, with the '95 being OBD-I with an OBD-II connector, I thought it wasn't that sophisticated? Didn't know that the scanner could do all that, had previously thought it only threw codes since it's OBD-I...now I'm definitely excited to give it a try.

Thanks again!

Wow, Aklim...that scanner story about your friend getting tossed out of the house after borrowing your scanner totally sounds like the kind of crazy thing that happens to me when I loan stuff out. Many years ago, I loaned a spare Holley 750 double-pumper to my friend to help diagnose his '69 Camaro. His psychotic father flipped at the noise of a new cam break-in done at night and broke every window on his car and then with super-human strength, threw a 2 1/2 ton floor jack (pre-aluminum jack days) into the engine compartment, bending the air horn and ruining my loaned carb.

LANDSHARK1

Oh yes, firing order is correct as since this has the Optispark, I thankfully didn't have to remove the distributor or touch the wires to do the intake.

I've done so many intakes on small block Chevys in the past...can't imagine what possibly could have gone wrong. This was my first LT-1 though.

LANDSHARK1

Okay, looked up the Snap-On Red Brick...impressive!!!

I want one! Sadly, finances are real bad right now. Seen some used ones in the $107 to $161 range, but they are all missing accessories, internal battery, and most important of all, instructions.

The only one that is used, but looks complete is $275.

An investment so normally no big deal, but not working right now. Any cheaper, but reliable alternatives?

http://www.ebay.com/sch/i.html?_jsof...+brick+scanner

Okay, found more searching under Snap On Scanner MT-2500 and MT2500 instead of red brick...LOL

81c3

...and you also got the correct plug on each injector right? Sounds like a firing order issue to me too...the fact that you said the exhaust note changed... as well as gas mileage being poor.

LANDSHARK1

Thanks 81C3!
Oh yes, I carefully marked and tagged each injector connector with a corresponding cylinder number. I've driven the car around afterwards...it just doesn't seem 100%.

Dt86

[QUOTE=" Okay, found more searching under Snap On Scanner MT-2500 and MT2500 instead of red brick...LOL[/QUOTE]
Yes the MT-2500. I should have been more specific. Sorry about that.

LANDSHARK1

That's okay...thanks so much, Dt86!
Your post was most helpful...didn't even know it existed until you wrote red brick so totally appreciated!

Thanks always!

FASTAZU

May be a stupid ? but have you ever changed the opti? had an issue with my wife's 95 as it had 200k miles I did the injectors same issues changed the opti. fixed it.

LANDSHARK1

Thanks We Gone!
It's still on the original opti so anything is possible. It was running absolutely fantastic before the intake manifold gasket change though Car currently has 104K miles or thereabouts.

Got tied up today so didn't have a chance to do anything, but hoping to do some more on it soon. If not tonight, then tomorrow

LANDSHARK1

Hi All!
Sorry for the delay in giving you an update...so much has been going on, both with the car and everything else.

Here's what has happened since my last post:

Checked fuses and noticed a very loose second fuel pump fuse.
Removed fuse and then tried to re-insert. Panicked and thought fuse box had melted or that I had pushed the connector into the fuse box. Took plenty of pics and was entertaining thoughts of sourcing a new fuse box and dreading having to do the work when I checked online and realized the second fuel pump fuse is only for the ZR-1. Apparently, the smog test/repair place that attempted diagnosis for me a few years back shoved an extra fuse in there loosely, but didn't tell me for fear that they had pushed the connector into the box. Reality is that the connector doesn't exist on my '95 NON-ZR-1 so false alarm

Never got around to buying a scanner, but did the jumper across the OBD-II connector for my OBD-I system (1995) and read the codes on the dash. It worked great and although I couldn't see specifics, was able to confirm that the car had no codes at all stored in the system.

Removed the throttle body again and carefully removed the TPS (Throttle Position Sensor) and IAC (Idle Air Control Valve) to inspect for any potential problems. TPS was fine, but it was obvious that this was the first time the inside of the IAC had seen the light of day in nineteen years. On top of that, it looked so bad that I am guessing that when I removed and cleaned the throttle body last time just recently when I removed the intake manifold for the gasket repair, the throttle body cleaner spray I used (without removing the IAC at the time) moved the carbon and carbon goo into the IAC pintle and spring area. I cleaned all this very thoroughly and then installed the new 90 degree throttle body coolant return hose that I ordered off eBay.

The old one which I'm sure was the original nineteen year old hose which could not really be seen or examined very well with the throttle body in place, but with it off, you could tell I caught it just in time before it would have blown and either ruined the engine or pee'd on the opti-spark.

Attempts to use a regular auto parts store hose failed (it kinked at the bend) and then extensive searches and emails to vendors on the internet for that part came up as discontinued. Finally found one online at Davies Corvettes in Florida and I was really happy with them. They responded to my inquiry via email right away, pricing was better than the others, and their shipping was so fast!!!

I installed the hose, started the car and slowly let the car warm up to operating temp.

I instantly noticed that the idle sounded more normal and less underwater like it had been sounding. The engine rev'd even more freely and eagerly and that funny rough and bumpy idle seemed to be gone...right as I was about to finalize my diagnosis that cleaning the IAC solved my rough idle issue, I walked up to the front of the car and saw coolant leaking from the new throttle body hose area.

Thankfully, the coolant ran off the side and did not hit the opti-spark (it's a miracle!) and the car had not gotten too hot yet so no damage done. I examined the new throttle body hose area which I had used the two supplied factory-type spring loaded clamps on and realized that in my haste, I had not noticed that the new hose is the same diameter all the way through. I compared it to my old one and although it is much skinner, I had just assumed that the new one had a larger outside diameter and that the inside diameter was the same. Well...never ASSume...the old one had a slightly different internal diameter on one end, the end that just leaked.

Obviously couldn't return it, not that I would even try since I installed it already (my fault, I should have compared it to the old one first) and I already knew what I had gone through already, just to source this wrong one that the factory numbers say is correct.

So, since I couldn't use a bent regular hose and this factory curved hose (the only one I could find which was supposed to fit, but didn't) was too big on the coolant return side, I improvised and used two traditional hose clamps on that one end for the connector, sandwiching the nipple rib in-between them for now.

I will be sure to post a picture of my old one so if anyone could please let me know where I can get the correct 90 degree curved throttle body hose with the correct inside diameter at each end, I'd totally appreciate it.

So...the plot thickens...I started the car up and really kept an eye on that hose connection this time. The rough, bumpy idle issue seems to be gone now (HURRAH!!!), but I figure I need to drive the car before I can deem it completely fixed. It appears to be though...not a glass smooth idle, but this car never was, especially with the loud exhaust.

Hood was still up and open as the car warmed up and I was sitting behind the wheel about to pat myself on the back for finally having figured out what was causing the idle issue. The new hose with two clamps on that one end seemed to be holding and I was actually having a happy moment when the car approached 190 degrees and then SPLOOSH...POW! From behind the wheel, I could see an explosion of coolant on the passenger side of the car near the windshield.

I immediately shut the car off as my head spun in disbelief. Sure enough, when I walked up, I couldn't believe my eyes! On the coolant surge tank, the one with the radiator cap on it, the little nipple/connector for the small upper coolant line had broken clean off and come off at the weld to the tank. D#mndest thing I have ever saw!

I can't imagine what would have caused that weld to go so spectacularly. I know I didn't lean on it during my intake manifold gasket change and nothing else hits it so just guessing it was a bad weld at the factory (done on a Friday?) that after nineteen years, just gave up the ghost.

Unreal...it just doesn't end! Never a dull moment

Anyway, I checked online and found a brand new coolant surge tank on eBay from Jim Butler Chevrolet in Fenton, MO for a great price. It arrived yesterday and I was really happy to get a brand new factory part for such a fair price. I had previously thought I would have to search the Corvette junkyards.

Opened the box and it was definitely new and virgin. Only one thing, it rattles so loudly! I am hoping that this rattle is normal and that perhaps there is a check valve or check ball within it which results in this noise, but at this point, I do not want to install it until I am sure.

Does anyone here know if this rattle is normal? It seems logical to me that it might have some sort of check valve inside to regulate the coolant, but since I've never had this apart, have no idea. I emailed the seller last night, but haven't heard back yet. Hoping they can examine and shake one of the others in their inventory and let me know if this rattle noise is normal.

So there you have it...it has been quite a rollercoaster...literally one thing after the other, after the other. Eager to drive the car so that I can confirm that the rough idle and running issue is indeed fixed, but cannot until I fix this one last problem.

Oh wait, there is one more new problem that I discovered around the time the coolant surge tank failed at the weld...I have a new aluminum radiator on the car, the large upper/lower hoses were recently changed, but the original factory metal and rubber lines to it are still there. At the T-shaped thing at the radiator, I can literally see that the hose has developed cracks from swelling. I can tell, it's about to blow.

Once again, I checked online and it looks like these combination metal/rubber lines have been discontinued and are no longer available. Does anyone know where I can source these? What is the solution for deteriorating hoses in this area? I vaguely recall someone posting that they replaced these on their car with six feet of 3/8" coolant hose and a metal T-fitting?

Ugh...it never ends...if it wasn't for bad luck lately, I'd have no luck at all! LOL

On a good note, any one of these three coolant leak issues, had they happened on the road with the hood closed could have resulted in major problems so I guess I shouldn't complain that the car conveniently broke at home in my garage with the hood open.

Oh and wanted to say that until recently, this car was super reliable. This is a really great car that is always garaged and has always received proper care, not a neglected beater. The connector nipple coming off at the weld on the coolant surge tank was a freak occurence, but throttle body hose and the rubber part of the metal/rubber lines at the T-fitting near the radiator were a real surprise. Glad I caught those in time.

Our cars are getting up there in years...after almost two decades, now is the time that these parts start to fail, sometimes spectacularly. I highly recommend that everyone check the condition of these and other vital coolant hoses as important preventative maintenance on their cars. Everyones checks the usual big stuff, but these little ones can sneak up on you and do a lot of damage if one is unlucky.

Happy Wednesday, all!!!

LANDSHARK1

Okay, heard back from the seller/Jim Butler Chevrolet and was told that the rattle is normal so next step is install.

Happy Thursday, all!!!

Silver96ce

For the T fitting on my '96, I found a great deal on 3/8 goodyear hi-miler on Ebay and used a Dorman 3/8 tee fitting from NAPA. You can probably re-use the T fitting if you take off the crimp fittings there may be a barbed end on end of the T. Here's a link to some silicone hose on Ebay for a good price -

http://www.ebay.com/itm/10-ft-3-8-ID-FlexFab-5526-Silicone-Heater-Hose-Blue-to-350-F-10-mm-Coolant-/290941564708?pt=Motors_Car_Truck_Parts_Accessories&hash=item43bd77f724&vxp=mtr

LANDSHARK1

Excellent!
Thanks so much, Silver96ce!!!

JrRifleCoach

Odd that the expansion tank fitting would crack off like that.
I'd replace that water line with one a bit longer to avoid stress on the new tank.

Also now is the time to replace as many water lines/hoses you can afford.
17 years is long enough.......

LANDSHARK1

I agree...so strange...and it went spectacularly too! Good thing I had the hood open and was at home at the time.

I actually wondered if perhaps some kind of blockage within the system might result in enough pressure to cause that thing to blow off. I do know that the car has seen regular maintenance and that the engine is not loaded up with stop leak or anything crazy like that. Car has a new DeWitt radiator from a year or so ago as well as a new water pump and obviously new coolant from that time as well.

This new coolant surge tank rattles with a factory ball or check valve inside. Wondering if maybe the one on the old one got stuck somehow? Pure speculation at this point though, but when I do the install and take the old one out, will see if it rattles like the new one. If not, that could be the cause.

I totally agree about replacing as many water lines/hoses as possible...good advice for sure!

That throttle body coolant return hose was a time bomb, just waiting to happen and you couldn't really get a good look at it from above with the throttle body in place either. Just not worth risking an engine or head gasket for a part that only costs a few dollars. Hate to think what might have happened had I taken a long drive like that.