Please see this thread. I have tried everything short of pulling the cam abd the car still run like crap. New wires cap rotor plugs. Adjusted vales 3 times. Bought all the acanning stuff and BLMs at between 120-130 during all driving and WOT. Only 3 degrees of spark retard at WOT. THe car shakes bad at idle and in gear....... I took it to the track and was only ably to get a 98MPH out of it. There must me something wrong since it went a 99MPH stock. For those that dont know I did heads, cam, and Stealth Ram intake. WHy is it so damn slow????? Do I need to pull the cam or.............? I am really getting pissed... See this thread for more details: https://www.thirdgen.org/techbb2/sho...hreadid=119065

 

I can't go back through a read the posts. Have you pulled the plug wires ,, one at a time to see if if there is one that makes little or no difference?

Have you done a compression check (leak down is best)? Depending on the values you get now,,, and if you have done this before the swap or not,, this could be extremely helpfull in diagnosis.

Do this also. Measure the distance from the top of the rocker stud to the top of the nut for the intake and the exhaust. This is a crude way to determine if the cam is wiping a lobe,,, or if a stud is loose or pulling up.

Depending on your answers,, I'll list some more.

 

Here's a thought, I m probably way off here, but you might need a stall convertor with that cam. The reason I m saying this is cause I read in the Comp Cam catalog well looking for my cam and they recommend a stall convertor, cause I guess your stock can only do so much when you go with a Big Cam. It can't hurt you with that cam and head combo you got anyway. But also the reason I say that is that I had a 3000 stall on my stock motor. (Yeah Yeah I know way to much stall) I found out the hard way. But anyway it made my idle crazy, It would rev up and down like crazy but drive alright. I didn't see in your sign if you had one, but if you don't I would look it to it. It might be doing the oppsite with your's. With some slicks if that's is the prob, will get you a very impressive time. Also like the last guy said on your post, that will def. get your mph up. It's just a thought anyway, I could be wrong.

 

I noticed in every one of your Bins you changed the injector constant. I had the same problem with the SVO injectors. Don't try setting it were you think they are rated. Set the injector constant were the motor runs best. I set my SVO 30 LB injectors at 25 lb in the ecm and 47lb of fuel pressure at the regulator. My car smoothed right out. I also had the roughest idle. And on tip in I would throw flames like a mother out both ends!!!! Once I sorted out the fuel I tackled the timing. For starters I just let the car warm up and the cranked the distributor around slowly until the idle smoothed out even more. Then I adjusted the idle down with the set screw on the throttle body. Once you find a happy spot on the timing go into you bin file and make the changes to the timing there so the mechanical initial is only 6-10 degrees. You will once again have to set the idle using the set screw and then you will have to set the minimum air per GM instruction. Hope this helps

 

I doubt you have a computer / chip problem. Even though what you are running is pretty far from stock, MAF should still be able to deal with it reasonably enough.

I think you have a real mechnical problem or other blatant fault. Between heads, cam, inateka nd probably the injectors too, etc, there are a lot of things that could have went wrong, even combinations of problems.

Anything from an incorrectly ground cam, to an immediately blown head gasket, to a porous intake casting, to a faulty injector, to improperly set valves, a misaligned intake gasket blocking a port.

I know thats not much help, but there are just some problems that can't be effectively guessed at over the internet. You had the whole top end of the motor off and went back in with new parts. Everything you touched is suspect in my book, and only a fool would try to rule any of it out before it's been tested.

 

Ouch Ed....I apperciate it. Now I am an incompetent fool. Thank you for the insult. I will try to mess with the chip again and see if that helps. If not then I'll pull the valve covers off again and check the valves. I have pulled the injector wires one by one and the rpms droped evenly from cylinder to cylinder.

 

I agree Ed, but I tend to start with the easy stuff and work my way up to ripping apart my many nights of work.

 

Ok, do you have an EPROM burner yet? If so, save your bin and send it to me. I wanna take a look at it. Just to see what you changed.

#2 You have the stock convertor and I assume 2.77 gears. Not a good combo. With that motor you should do what Chris Ja said and get a 28-3000 stall and 3.73's without a doubt. That will net you a lot in the 1/4. You are fighting to overcome the non-existant low end of the motor. Your powerband is no longer Right off idle to 4800. It is now roughly 2800 or 3000 to about 56 or 6000 rpm.

Get the gears and convertor. Also, set your idle to 1000 and unplug your IAC. Idle off your Throttle blades until you can find the problem.

 

Did you degree in the cam? Sometimes cams are ground a little or a lot advanced or retarded from what they should be.

 

like said earlier, I doubt its a PROM problem,id go back to basic stuff,its easy to go way out in left field chasing stuff,been a tech for 20 years ,I know! LOL ! Ck compression,leakdown,make sure springs are not coil binding, etc.If all good I'm afraid Id look at cam timing,with some of the aftermarket gear sets,it can be confusing,I've seen quite a few people miss on cam timing cause of them.

good luck

greg

 

I didn't say you were an incompetent fool. I just said only a fool would assume his basically brand new engine was perfect and try to troubleshoot the problem by blaming the computer.

It's not like your combination is that radical, the LT4 hot cam is actually a pretty mild cam when it comes down to it. MAF should have no problem running it fairly well. Not optimally, sure, but it isn't going to give the kind of issues you are seeing. Not unless there is something grossly wrong with a sensor or something. Or something like the wrong injectors are in use and your injector constant is WAY WAY off. If things are reasonably close and all your sensors work, you can safely rule out the PROM

Basically what i'm saying is, if i were a betting man, i'd put money on it not having anything to do with the chip or calibration. I know tearing into the engine isn't much fun, but it's the only way you're going to get to the bottom of things.

Want a second opinion. Ask on the PROM board and see if they think an ARAP chip will have trouble running an LT4 hot cam, miniram combo. It's been done before, and worked pretty good. If there were issues with the combo, thats how you would find out.

 

Ed's shooting you straight - the cam's not too big, the intake is not killing your power, the heads are not too large. I also doubt the chip is your problem - especially if it's an unmodified (do you know for sure) ARAP bin with the injector constant changed. Like one guy said,, the SVO's seem to like a lesser constant than what they calulate to. A friend burned an ARAP bin for my SVO 24# injectors set at 26#,,, and a stock 88 chip using a 22# injector constant runs better at WOT - for my combination - each will vary.

Before you do anything else,, check all the grounds - especially the firewall to head ground - the EFI cars are extremely ground sensitive and it doesn't take long to fry the computer with a bad ground.

Also,, sounds like you need to buy "How to tune and modify Chevrolet fuel injection". It'll be a tremendous help to you trouble shooting stuff. I played around with the TPI cars back when they were new and "trouble free", but this book was a tremendous help diagnosing all the gremlins in the 86 IROC I bought.

Also,, you're going to have to do a compression check (you can get a cheap $20). I'm not trying to be an a$$, but until you verify the compression (leak down if at all possible) is good and even on the engine, I feel like I'm wasting my time trying to help.

 

The bin is modified for my setup. I have been tweeking it since I now have the laptop, cable, burner, and Craig Moates software to use. The injector constant is at 32lbs since that is where I get most of my part throttle BLMs at 128. The injector constant was used to get my idle BLMs close to 128 more or less 130. The spark table has been modified to get rid of most of spark knock. I am still chasing about 3 degrees of retard at WOT now. All grounds on the back of the heads are solid. Ive done the valves 3 times....first was no tick then 1/2 turn....second time I did exactly the same to be sure they were right...and the third time I did no tick then 1/4 turn. I set the IAC to about 5 counts at idle and if I close the throttle blades all the was it will respond by opening all the way up...so I dont believe there are any vac leaks. CTS...MAF....MAT.....TPS...all seem to be functioning well as displayed by Craig Moates software.
As for the timming chain gears I lined up the "O" on the cam gear with the dot on the crankgear....its a Summit double roller set.

 

Best advice you've been given yet. If it is a head gasket problem, this would show it. Could also show if there is something really funky with the cam.

I'd shoot the intake down with carb cleaner too looking for a change in idle. Be a damn shame if the whole time this was a vacuum leak.

I don't rememebr if you'd said you'd been checking plugs yet, but if you haven't, now would be a good time to start. For grins i'd ohm out all the plug wires too to make sure something fishy isn't going on there. If the dizzy is new, or was beaten around when out of the car, maybe it decided to go to lunch on you to.

I appluad the fact that you are so conscious of how important the chip is to an EFI car. Funny thing is, once we get that knowledge it becomes easy to forget that there are still mechanical aspects to the car. For example i had a goofy idle for a long time, really seemed to be a gflaky IAC. One day on a whim i pulled the distributor cap, cleaned the contacts (which were a little crusty) and it's been fine since.

 

See the problem is that all the mechanical aspects of the engine are eighter new or were in perfect working order before the buildup. I have just put on brand new MSD wires, plugs look fine not oily and are tanish brown in color, ignition module is new, pickup coil is new, heads, cam, and intake are new, lifters are new, pushrods are new, no vac leaks I soaked the intake with starting fluid when the problem first happened, the timming chain and gears are new and I lined up the "O" on the cam gear with the dot on the crankgear....its a Summit double roller set, injectorsa are new and I swapped in the old stock ones to see if the idle improved but it was the same. regulator is new tried 2 of them, fuel pressure is at 45psi, I did at compression test before the buildup and all cylinders were right around 155psi. I will be doing one shortly....

 

Bad parts come out of boxes all the time. Especially electronics.

 

if you put all those new parts on while doing the swap, go through one at a time and put the old one back on. thats a given. if you cant figure it out, retrace your steps until you do. theres only so many things that could be wrong. btw, i bought a new ignition module one time and it was bad straight out of the box, so just because you bought it new doesnt mean it doesnt have a problem.

 

What is your injector constant at. You say you tried the old injectors, but at what constant? BLMs are great for steady throttle, but tip in and idle are another story. If you have some funky timing going on moving the distributor around a little might help to bring the car in or help you find your problem. I know it is frustrating and you say you have checked everything, but if that was the case then the car would be running right. Do not be afraid to kick that injector constant around and you may want to eliminate the IAC while you are trouble shooting.

 

OK....little bit of an update. Had a friend put a vac guage on it and its only pulling about 8 to 9lbs of vacuum at idle. OK thats bad. He also shot each header tude with an infraded heat gun and they were all close in temp to eachother. Here is the whats got me stumped. The car has always smelled rich at idle but he put it on an exhaust gas analysizer and its running pig rich. At idle the Hydrocarbons were almost 3000ppm but the CO2 was alright. Funny thng is that the computer was showing a 133BLM at ldle which isnt that far off and most part throttle was 120-128. On Tuesday we are gonna do a compression and leakdown test. Vac was not steady eighter...it moved back and forth about a 1/2 pound or so.........

 

That vacuum is way too low. I have a bigger cam and more than that. The timing could be off, or you have a massive leak somewhere. I also agree with Ed, the stock chip should work fine with that cam, not ideal, but not so bad that it wouldnt run right.

You said you have a scan tool, whats the IAC at idle? It has to be near what the ecm wants or its going to idle terrible.

 

ECM wants the IAC at 0 and the IAC is at 5.......... Whats gonna cause such a low vac reading?

 

OK, let's go through this logically.

1. The car is screwed up since a major overhaul with a lot of new parts.
2. The computer seems to say everythings OK.
3. The computer is MAF so it has no idea that the vacuum is so low.
4. An exhaust gas test shows the car is running way way rich.
5. The computer only monitors the O2 sensor on one bank of cylinders.

Therefore, we can safely conclude the problem is either the computer is completely screwed up and merrily dumping fuel not paying attention to the O2. OR you have a dead cylinder on the passenger side dumping fuel.

I tend to suspect it's the latter. The ECM would notice running that rich and would peg the BLM if it saw that much fuel in the exhaust. Therefore, the calibration is probably close. And the idle airflow is probably semi-normal since you may only have one or 2 dead holes. Vacuum is horrendous, but it is still moving enough air as to not set the code.

Are you sure you're pulling ALL your plugs. IMO this would show up. Still though, could be a bad plug wire. Leaky/wide open injector. Or mechanical failure like a bad cam, or improperly seating valves, etc.

Just an idea anyway <marquee>

 

on an 4 gas analyzer a bad lean misfire will show up as rich on HC readings

 

I was thinking the same thing about a lean misfire which will show as rich with unburned fuel. With that cam and intake, you should not have the injector constant set way up at 32#. My injector constant was at 26#(24# SVO's) with original engine setup that i started with and ran like crap with huge power losses after the port work and new cam. I moved it down to 22#(last setting at this point) which added fuel and the way the motor acted was night and day. I think that your ECM is trying to compensate for not enough fuel. Hope this helps.

 

I am running 30lb SVO injectors at 45psi.....32 sound right to me no...else I am missing something?????

 

Yep,, running 22# constant with my 24# (26# converted) SVO injectors also.

Edited - attached sig for Dave - Mine is a fairly modified MAF car. I guess it depends on the engine and it's efficiency - Gruvin and my combinations seem very similar.

 

BadSS what motor are you running? I am also running 22 with my 24 SVO injectors. I have a mildly modified L98 with Speed Density. This is starting to look like a common trend for the SVO injectors. They do not run at what they are rated at. Ford did it with their Cobra so why should we think they would be anymore honest with their injectors

 

Just curious to find out if you figured out what was going on.

 

well I did a leakdown test and found that 3 cylinders had bad rings with little to no compression.......strange that the motor in stock trim ran so well...14.0 at 99MPH with minor mods.

 

Forgot to add that the ZZ4 shortblock is on its way...

 

Well, not exactly what i was expecting, but i knew it was mechanical, do i get a cookie?

Maybe it was on it's way out and the new found cylinder pressure/power pushed it over the edge and killed it.

 

something......man you and me both were expecting something different.......this is the last thing I wanted to do...hehehehehehehehehehe....all in good fun...well at least I got an excuse to drink more now....:lala:

 

That is a big bummer! I am interested in hearing all about the zz4 shortblock. I am contemplating an engine build up around this shortblock.

 

Actually, I was thinking more or less you could have fubarred a head gasket putting the heads on. That or maybe didn't clean the block threads good enough and the new head bolts could have been giving you a false torque reading,,, not compressing the gasket enough to seal the heads. That's not a dig on you man,, it's just I've had to fix quite a few that's come to me with that problem.

If you haven't pulled the heads yet,, I'd do it and check the head gasket(s) and check for even indention rings around each cylinder chamber on the heads. If you know for a fact that it's the rings,,, I hate to hear it's a "real" short block problem.

 

Got a few more questions...... When we did the leakdown test I pulled all the plugs and 3 were oil soaked. Now we did the leakdown on cylinder #3 and it was losing about 20% of the pressure. We bumped the engine over till we felt compreeion on that hole......and he said there wasn't enough to put out a candle. Hooked up the leakdown tester and slowly increased the pressure to 100psi. The other guage read about 80psi. We determined it was the rings by listening in the throttle body, exhaust, under the valve cover, and then looked in the antifreeze for bubbles. It was a loud hissing noise...exhaust was quiet...intake he said he heard a little bit but was probably just the echo from the rings leaking. There were no bubbles in the radiator so head gasket was good. When I pulled th plug some oil came out of the hole....... Well i just want your opinons as to weather it could only be the rings. We didnt even bother doing the rest of the cylinders since the plugs looked the same as #3.

 

Put a little oil in the cylinder before you do the compreesion test. If the compression bumps up its you rings. If it doesn't you have a valve train problem.

 

For reference sake, I got ~ 14 " Hg out of my LT4 HC 355.