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New engine with Vortec heads and still runs like crap when cold

B

BayouBlazer88

1/2 ton status
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Lafayette, LA
Over the summer I put in a rebuilt bored out 350 (355) in my 88' TBI Blazer and when she's cold and you give it gas, it pauses for a second (as if it's not getting enough fuel) but then zooms right back a second later and runs pretty good at normal operating temp. Also, my gas mileage has worsened with the new engine (about 11 city). I've narrowed down the cause of this to 3 things: EGR valve, incorrect timing, and the fuel system(cam and TBI).

EGR: I used the GM Vortec Intake (with EGR passage) as well as the vortec heads with the 64cc conmbustion chambers. And since my stock setup had EGR, I went ahead and installed the EGR valve and hooked it up to the EGR solenoid so I wouldn't have the "Check Engine" light on all the time. But as some of you may know, using EGR on Vortec heads with headers requires a fabricated EGR pipe from one of the headers to the valve. And since I am lazy and not very experinced with welding, I just left the EGR open so it would just suck in air from the compartment rather than hot exhaust gases.

Timing: I have been messing with the timing on this thing since the summer and found that it runs decent at about 5-6 derees advanced (with the computer advance wire disconnected). I always run 89 octane gas. What are you guys with vortecs and tbi setting the timing at?

Fuel System: I bought one of those tbi rebuild kits from Oreilly with new gaskets, seals, and filters and put this on the TB and cleaned it up really good. I'm thinking maybe the injectors themselves need to be replaced or rebuilt also. Also, JET sells an adjustable fuel pressure regulator for TBIs. Have any of you tried one of these? Would it work well with my setup?

So, what would you recommend I do? Should I get a new chip? If so, what kind and where can I get it? Should I replace my injectors or have them redone? Also, I forgot to mention, I'm running a stock cam in this motor. Should I maybe look into a different cam?

Thanks in advance for the help.
 
Have you done a fuel pressure test to see if the fuel pump is getting weak? I had the same kind of problems with my 89 K5 350 TBI and after replacing all of the emission sensors, tune up, and a few other things, I replaced the fuel pump and it ran great after that.

Doug
 
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I have the same thing with my truck when it's cold and it's totally stock......... /forums/images/graemlins/thinking.gif

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What are you doing posting in a tech forum spanky?? /forums/images/graemlins/eek.gif /forums/images/graemlins/rotfl.gif Get yer ass back to padville where it belongs! /forums/images/graemlins/angryfire.gif /forums/images/graemlins/tongue.gifBut about the question, I don't think engines are really meant to be "got on" when they're cold. Everything hasn't had a chance to expand to it's operating tolerances, such as rings, so there is a lot of blowby and other undesirable things going on before an engine reaches operating temp. Just about every car we have, no matter what condition the engine is in (except my Mom's new car) will get very upset when you try to floor it cold. On carbed motors, I think there is even some type of valve that prevents you from opening the secondaries before the engine heats up.
 
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I don't think engines are really meant to be "got on" when they're cold.

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-I'm not talking about flooring it, just normally accelerating. I don't drive it hard at all. But thanks for the reply.

-As far as the fuel pressure goes, what can I do to test the fuel pressure and what is considered acceptable fuel pressure for a 350tbi? Thanks.
 
First of all if you dont have the EGR hooked up correctly disconnect it or block it off and live with the CEL. Either that or hook it up right.. By bringing in fresh air instead of exhaust gasses you are leaning out the fuel mixture too much and might burn a valve or cause other engine damage.
Also If it isnt operating right and stuck open when it is cold. Your engine will run too lean causing problems like you are having when it is cold.

Have you ever put a scanner on it?
is it throwing any codes.?
How is the coolant temp sensor?
Have you checked all the hoses for vacume leaks?
Do you have ALL the sensors hooked up and operating properly(a scanner would tell you this)


Normal fuel perssure should be between 9-12 lbs

i dont think you have a injector problem if it runs ok afterit warms up.
 
No, it's not throwing any codes and No, I've never hooked up a scanner to it. I'm pretty sure there are no vaccuum leaks since all the hoses are brand new and clamped tight. Now by coolant temp sensor, do you mean the sensor that mounts on the intake and goes to the computer? If so, how do I know it's functioning properly? I'm pretty sure it's the original sensor, should I consider replacing it? I'll run to the hardware store tomorrow and get a threaded cap or plug to close off the open EGR port. Also I forgot to mention, I don't have the vaccuum ball in there right now (the one against the firewall on the driver side) because I accidentally broke the plastic nipple that the hose connects to so for now I just have the hose plugged. Could this be part of my problem? Thanks for the help.
 
What cam are you running? It will be hard to diagnose without the stock cam. Most aftermarket cams add for duration and valve overlap (give you the "lumpy" idle). This eats away at the the strong vacuum signal required at idle for TBI to function properly. More lift is about the only cam profile change TBI will work well with. Maybe someone can chime in with the stock vacuum spec for a TBI 350 (you'll need a vacuum gauge).

Basically the ECM is trying to open the EGR to let it some inert exhaust gas to use as a "filler" in the cylinders. Leaving it open will make it lean under certain conditions. You should be able to tune the engine with the EGR plugged off, just will have problems with emissions and may affect economy until you get it hooked up.

A friend of mine found the correct EGR fitting in the plumbing section at Home Depot and welded it into the header. I think it was for natural gas /forums/images/graemlins/thinking.gif
 
One way to check the fuel pressure is to take the fuel filter out and replace it with a fuel pressure gauge. On TBI motors, it should be anywhere from 9-13 lbs. Check it at an idle, then power brake it and put it under a load to check the pressure under a load condition.
 
The machine shop that I purchased the engine from said that it has a new cam with stock specs. I have no clue what those specs are.
 
I have vortec heads and I have the same problem Ive learned to live with it, but I have concluded it to be a number of things...first Vortec heads don't have a exhaust hot air passage to allow for quick warm ups your TBI might have the same I can't say ive never seen a TBI vortec intake except the orignals that came on 96-98 trucks......ive got a carb with no EGR it does have provisions for you to plumb coolent into the intake and flows under the carb for quick warm ups...also if your running headers and you have no heat riser that in it self is typical for cold enginges to act that way...also I would say say scrap the EGR unless you want to drill and weld into you header..
 
I think he was refering to the fact that you have to disconnect the computer control before adjusting the timing.
 
FWIW late 80's-early 90's 2.8 camaro's use a flexible steel EGR pipe that fits (with some slight grinding of the hose end) my Vortec TPI base, which I'm assuming has a similar EGR connection.

www.sdpc2000.com also sells the EGR "kit" for the Vortec TPI base, I would guess that would work in your application too. Still going to have to weld, but I couldn't think of any way to run EGR with the Vortec setup short of what SDPC sells.
 
What are your Block Learn vs. Integrator numbers in the am when you first fire it up...sounds like its lean to me...

BTW...get a set off vortec exh mans and the pipe to go with the drivers side man and the egr problem is gone...

DW
 
[pad]I have a '75 block over .040 with '96 Vortec heads and an Edelbrock intake, no EGR and even worse, no place to mount the stock mechanical choke. It just don't run for shizznit cold. If I plan to get anywhere in the early morn' I have to plan 15 min early just to warm the damn thing up. Of course that is not gonna help you with your TBI problem. [/pad]
/forums/images/graemlins/grin.gif
 
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www.sdpc2000.com also sells the EGR "kit" for the Vortec TPI base, I would guess that would work in your application too. Still going to have to weld, but I couldn't think of any way to run EGR with the Vortec setup short of what SDPC sells.

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-I bought the EGR kit from them, and no it doesn't fit, the pipe that they give you to connect the Header to the manifold is way too short.

and to K5 NUTT, what in the hell are "block learn vs. integrator numbers"? sounds way too technical for this novice mechanic.

-And once again, does anybody know if not having the vaccuum ball hooked up can cause any problems?

-any computer chip reccommendations?
 
How can it be too short? Just bear with me on this. I've seen pictures of the Vortec TBI base, and IIRC, the EGR "in" is located just inside of the #1 cylinder intake bolts. Is this correct?

My TPI base EGR "in" is just inside of the #8 intake bolts, and I had enough length of that metal piece they make, with the included steel flexible pipe, to go BEHIND the valve cover, and still reach the intake. If I went over the valve cover like they suggest, I would have had to shorten the heck out of the metal adapter piece you are supposed to weld to the header tube.

I guess if the TBI "in" is farther towards the center of the vehicle than the TPI one, length could be an issue, but it just seems that there is plenty of length there for even an additional couple of inches difference.

On CCC cars the vacuum reservoirs weren't used for anything other than the vacuum controlled AC blend doors, so I doubt it's an issue. Injection needs to know "current" engine conditions, can't think of any EFI component that would need a vacuum reservoir to use in times of low engine vacuum.
 
Block learn is a number used by the ecm to tell us where the fuel map is...128 = 14.7-1...the ideal fuel to air mixture...integrator is more of a short term calculation we can watch to figure out how the engine is running...find a bud with a lap top and run winaldl...a free program...Howell Engine Development will need to see some saved data in order to burna new chip to get it running right...they usually want cold at idle...hot idle...30 mph...65 mph...and a WOT blast to see how the ecm parms are working with your mods to make changes to tables in the ecm chips programming....if you think its lean then you can remove the top of the tbi injector pod to gain access to the bottom of the fuel psi regulator...the nut on the bottom is staked and has left hand threads...put it in a vise and turn counter clockwise 2.5 to 3 turns...put it back together and see if things get at least a little better...but with the vortec heads you will need a new chip to make it run correctly.

DW
 
Again FWIW, that 2.8L pipe I mentioned up above could probably be used in conjunction with BOTH of the SDPC pieces to extend it further, if wanted.

I imagine more than just the 2.8 Camaro's used that pipe. The two I pulled off of wrecking yard cars were both in real good shape for their age, didn't show any signs of failing any time soon. Might even be stainless.
 
Thanks, I'll have to try that next time I go to the junkyard. Then again, I'm sure I could rig up something from the hardware store like one of the other members mentioned. Either way, I just hope it at least helps my cold running problem until I can get a custom chip burned.
 
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