Newly Cammed LT1 Runs Poorly In Closed Loop

[sweetbmxrider]

What lifters are on it? Preload? Did you ever do anything with o2's?

[Pampered-Z]

Looking at the one scan, the car seems to run fine in open loop, once it goes into close loop I do seem some very odd O2 splits for 1-2 cells, such as RB at 880 and LB at 53. Which I think could be a miss or maybe an injector sticking. But for the majority of the time the O2s are running close together and the injector pulse and LTs look fine.

I'd like to look at a scan of the car under load and when it starts acting up badly, so I can get a better veiw of the fuel trims, spark advance, knock etc.

[1994lt1]

Lifters are Ls7. I had the guy at the shop adjust the valves again he did 1/2 turn preload.

I'll get another scan of it under load tonight for you. I still dont know how to upload them so maybe ill email it to you?

[1994lt1]

Ok I just logged the car again this time under a load. I sent them to WildBillyT's email so he can post them here for me.

This time out I finally got a code, 33: MAP High which says either bad sensor or vacuum leak to me. I still want to check the timing. When it gets posted tell me what you think! Thanks again guys.

[WildBillyT]

Originally Posted by WildBillyT

http://www.njfboa.org/WBT/log3.uni

http://www.njfboa.org/WBT/log5.uni

See above .

And start looking for a vacuum leak.

[1994lt1]

I do have weak brakes and my fan directory doesn't work, I'm just wondering if this is a result of the engine possibly being out of time. I'm almost positive i didn't set it up right at this point

[LTb1ow]

Did you install it dot to dot? Its reasonably diffucult to really mess up the mechanical timing to the point where it won't run well, but not to the point where you kiss valves.

[1994lt1]

I did dot to dot I'm just not 100% sure the engine was tdc when I did it. It has to be close to run, but I've been doubting myself since someone brought it up to me.

[LTb1ow]

I am not sure if you mentioned it, but is it audibly pinging or knocking? Or are you just going off the knock sensor readings

[1994lt1]

Not all the time, but at times it makes ping noises when it is acting up.

[greenformula92]

If it it a timing issue i don't see how you could screw the opti up, it only goes on one way. now if the cam is a little out of time compaired with the rest of the bottom end than that would cause a problem. but I would think it would cause the problem all the time. The problem is occuring when the ECM starts to use its sensors. so something related to them is probobly what is screwing it up

[Pampered-Z]

you would know if you were off a tooth dot-todot would be pretty obvious.

As greenformula92 stated, the car seems fine in open loop. I'll look at the scans ASAP.

[1994lt1]

When you install the timing chain, the cam dot has to be at 6 o clock and the crank at 12 which will put the cam dowel at 3 right? And all this HAS to be done with the engine at #6 TDC correct? I think I might have been off on the tdc part if anything. I have to check it or it'll always be on my mind.

[Pampered-Z]

If the dot on the crank it at 12 O'clock your at TDC FOR BOTH #1 and #6. Remember that the crank goes two revolutions to complete a cycle, and the cam goes one rev for the cycle. The first revolution is intake/compression (IGNITION) then second revolution is power/Exhaust. If the cam dot is up your on the #1 cylinder ign part of the cycle, if cam dot down you on #6 ign cycle.

BUT, that is only really important on a conventional SBC where the distributor can be installed in various positions, and you want to be on #1 TDC/ignition so that you can get the distributor properly oriented ( Basic timing is pointing the rotor at the #1 spark plug).

Since the opti only goes on one way – as long as the dots match up, your opti will get installed correctly.

[1994lt1]

Oh ok that makes sense now

[greenformula92]

If you can't find any bad sensors then you are going to have to start digging through the harness. could be O2, CTS, MAP, MAF. you don't have any codes right? You have to look at the values of each sensor and see which one is way off. As far as the timing thing goes Im pretty sure thats not your problem.

Also I would comb over for vac leaks just to make sure. But I wouldn't be surprised if you didn't find anything.

Another option is maybe a corrupted tune file? Im just spinning wheels on that. Did you get a base tune to run the cam. I know the ECM is a little forgiving on that but I don't know how forgiving

[1994lt1]

The car acted exactly the same before the tune was installed so I don't think its that. Only code I have is 33 map high

[1994lt1]

Ok so this morning I still have Code 33 while running it. Also I noticed that my IAC is maxed out at 160... I'm thinking now that I do have a serious vacuum leak somewhere. o2's seem to function normally, going from .1xx to .8xx frequently.

I drove it a little to take a video for you guys. In the video I am applying even throttle pressure trying to accelerate and you can see it gets caught up around 1500 to 2000 rpms and makes some weird noises which sound like theyre coming through the intake.
http://www.youtube.com/watch?v=IcFsEaTDGRQ

[greenformula92]

you need to rule out a vac leak. another thing you can try is unplugging the MAP and see if anything changes. in other words if its a faulty MAP sensor throwing everything off you can eliminate it by unplugging it and the car will run. not to its full potential but it will run. if you have a vac leak the problem will still be present, if you don't the problem should be kinda solved, then you replace MAP and you are good to go. Potential vac leaks could be anything from a simple hose or the plenum and lower intake gaskets and so one and so forth. it could be a real can of worms

[1994lt1]

Ok so today I figured I'd take a look at the plug wires the guy said were bad thinking there was just one. There were 3 on the p.s. that were cut into from the belt. These msd wires are too big for their own good. So now I'm looking at wires, problem is that I have otvc wires. Also I looked at my drivers side o2 sensor and it looked rust color, so I'm not sure if i should order 2 sensors or not. I might just to do away with that as a possibility

[LTb1ow]

What kind of headers do you have? !AC or no?

[1994lt1]

I have Pacesetter LT's. !EGR and ! A.I.R. but I still have ac

[1994lt1]

Ok so I just had to order new OTVC wires and 2 o2 sensors. I have to get the ball rolling here this is ridiculous. Ltslow I looked up the length of stock wires and found out that I was nowhere near where I needed to be, longest was like 34 inches or something. Thanks anyway though.

So now I just have to wait for the wires to come in. Question I have is: While I'm waiting should I do anything else? The car is already semi apart so if I were to do something else now would be the ideal time. Also did PamperedZ or anyone else get a chance to look at those datalogs under a load yet?

You guys have been so helpful and great I really do appreciate the help.

[LTb1ow]

Change teh spark plugs and figure out how you plan on routing the wires to avoid them getting caught by the belt this time round.

[1994lt1]

Alright well heres the update, I hope I havent lost people's interest because I need you more than ever!

Replaced the plug wires with new, also did brand new AC o2 sensors and a new throttle body gasket. Car started right up like always and ran at 800 rpm (desired idle). I took it out for a ride and it did seem noticeably better than before, however still has SES light (code 33 low MAP).

Now what is interesting is that the light only comes on during light throttle operation or idle situations. When accelerating or at increased rpm it does go away. This to me says vacuum leak more and more. When the car is "acting up" it bucks and knocks and makes weird noises out the intake. (Weird?)

How do I go about finding a vacuum leak? Where do I look?