fb305svs

Ok- here's the setup!

-Cam- 220/230~ duration/ .510/.510 lift 114 LSA - Custom grind for TPI's LTR's and heads
-Heads- ported vortec heads, larger springs, etc, all tricked out for compatibility with the cam!

-Intake!
-- Scoggin dickey vortec tpi base
-- slp runners ported out - http://pages.cthome.net/ssoares/webfolder/p1001009a.jpg

-- Ported and port matched plenum
-- BBK 52mm TB
-- 24lbs injectors
-- holley fuel pump...

- SLP 1 3/4 shortie coated headers
- Hooker AeroChamber 3" catback/ RT hi-flo cat


Ok, here's the issue, this is a 88 GTA 350 motor.

Basically the issue is it wont idle. It surges, and won't idle at a set rpm- basically go from practically dieing (sometimes does) to 1300 rpm or so.

We've checked:
TPS voltage (.54v right now)
IAC (extended 1 1/8" as book specifies)
Timing at 6*

Keep in mind, It is a stock chip, and keep in mind that because of our plans to get a custom chip, and the fact that there isnt any good way to route EGR gasses into the intake, we installed a block off plate under the egr valve...

It does fire right up, reves up fine, and runs well otherwise...

One other mystery to this whole ordeal is that it will only run when the fuel pressure is turned up to about 53-55lbs! If it is lower, the headers glow red within a few minutes of it running, and it will NOT idle, it will just die if it is set lower. The A/F Gauge showed lean so we decided to try increasing the pressure, and it did improve. Does not seem to be running rich, headers do not glow any longer, and the exhuast smells normal.

We can hear the IAC cycling back and forth, so we know it is working, it was gummed up, but we cleaned everything up and measured and put it back together.

So, my question is, could this be an issue with the egr that is causing this idle surge? or could it be something else? Should the timing be at 8* or would that 2* just not make much of a difference?

What does everyone think? We do plan on getting a custom chip done, but we need to be able to install the tranny and do several tests with it... this is the tranny, and they requier some tests be done to make sure its operating properly before they will warrenty it... it includes checks at idle so we need to get it running somewhat smoothly before we can do that.

Any suggestions welcome! We are expecting about 400 crank HP from this setup, as the fella who is going to be dyno tuning is has done a similiar setup and gotten better than 400 horse, and we are a bit bigger on the cam than the other guy, and a slightly better intake setup.

Steve

Greasemonkey

This may be a dumb question, but I didn't see anywhere if you were using speed density or MAF. Is it throwing any codes? When I got my TPI Cutlass with a 218/224 cam running it ran like crap. Ran the codes and it all led back the the Mass Airflow Sensor. Replaced it and it idles pretty well.

fb305svs

Ahh yes i knew i would forget something! It is a MAF motor.

As for codes, we just ran them, even thought there was no SES light, and found a code 42.

I read in my shop manual for the car that a code 42 present will prevent the ecm from entering the EST mode, which means it will just run off the HEI timing. So we yanked the fuse and will fire it up tommorow with the fuse back in, after confirming the code is gone. We beleive it was set from when we yanked the connector apart for setting the base timing. We haven't had the battery undone since, so the code is still stored.

Anyone know if that would cause it to idle stupid? it runs fine otherwise, off idle, it runs great, not popping or back firing etc.

Steve

HighHopes85

I know a couple of guys who disconnect the EST bypass wire at the strip between runs to set timing and do not disable the code. Their cars still idle fine in the staging lanes.

As far as EGR, EGR does not function at idle (well, *usually* does not, and considering that vacuum is blocked in our cars with an ECM-controlled solenoid, it shouldn't).

And even if your valve was bad, you mentioned you had the blockoff plate for it.

jichniow

My car threw a Code 42 a while back after an engine rebuild. Just going down the road and all of a sudden I had no power and it would hardly idle.

Turns out that I put too much thread sealant on the knock sensor (I've got the same problem with my fan switch sender and they won't come on automatically). I put in a new knock sensor, reset the computer and presto...all better. If you've got a scanner check to see if you're getting any knock. If you're getting any knock this is not the problem!

I was running hot in the exhaust as well, but that turned out to be an exhaust leak messing up the O2 readings. Check for vacuum leaks!! Check the valve lash too!!

fb305svs

Yeah i am gonna go downstairs and fire it up now, see if its ok after we did a few things last nite. I have to go through and double check the valve adjustment (it is still hydrolic roller). I didnt hear any rocker noise, so that could only mean its adjusted right, or its too tight...


I do not have a scanner unfortunately, i wish i had one- would be much easier to see what was making this engine run wrong during idle.

Steve

Ricktpi

Smells like like a vacuum leak causing you to run lean.

fb305svs

Well i did check that before i came up and checked this post here...

I reset the computer, and code 42 came back, so there might be a fault somewhere. We do have an msd system hooked up, but everything *appears* to be hooked in correctly and operating correctly. Could a connection with the msd be causing the ground circuit to not ground, therefore not letting the EST take over?

I put a timing light on it, and it seems as though its working, it holds nice and steady when the connector is unpluged (as you are supposed to do) and the timing DOES change when you plug it back in and re fire the motor.

So as of right now, we have a pesky code 42.

I am convinced the motor doesnt give two hoots about the EGR when idling, i yanked the connector, ran the motor for a good 5 min, no SES light or even a code for it.


1st point of intrest-
I put a timing light on it, while everything was hooked up, in reg mode (not timing set mode) and it seemed as though the timing would very much pre determin the engine speed! The timing would advance, and the engine woudl speed up. The timing would decrease, and the engine would slow down. The peaks were about 10* of advance and 0* when it was about to stall.

It seems as though the timing control is what is causeing the engine to have a surging idle, that is, runs around 750rpm, the goes to 1200, then drops to 500, sometimes stalls.

Someone mentioned the knock sensor- i have no scan tool, nor access to one- any way to make a fakey to make the computer think there isnt any knock? (compression is about 10.5:1 but i dont think that should set it off)

2nd point of intrest-
I did put a vacum gauge on it just a few minutes ago... what i found was a low reading, about 13-15" - keep in mind this is a decent size cam, although suposed to be an EFI friendly grind.

fb305svs

Ok, well now that i have listened a bit more carefully, it seems that it is indeed a vacum leak! dunno if that will for sure solve the idle issue, but it probably will.

I just spent about 45 minutes replacing some old vacum lines, and checking them for leaks, fixed what i thought were a couple minor leaks, only to no avail and only to keep hearing that all familiar faint hissing noise from what seems like something UNDER the plenum :-/

Steve

Ricktpi

This may sound like a dumb question & the only reason I ask is that I have been in the same boat, but are the runners installed on the correct sides? If not, you will get a vacuum leak on the pass side.

fb305svs

Well i thought, bacause it has the cold start injector, that they can only be installed one way...

Will definately look into it... i can't find it in the lines, so its either a cut line or something else

fb305svs

Ok, well there are no vacum leaks, and no strange codes. The iac was rechecked, the minimum idle screw was set, and the valves readjusted, still runs the same.

We called up the engine guy, he beleives the lower vacum is indeed due to the cam, and the ruff idle due to the computer not being able to do whats right with the cam/injector/heads combination.

The higher fuel pressure we are running might have something to do with the amount of time the injector is open, as it might be different for the 24lbs injectors.

If someone else has a good suggestion though, i am definately open to ideas!

Steve

fakezcar

i don't mean to sound like a know it all...but your cam is way to big for the stock computer. The engine guy's right, it's the cmbo messing with the computer. It's ony set to run on a smaller cam, less flowing heads, and a smaller injector. Get the custom chip and she'll idle just fine, and on a lot less pressure. i hope you getting running better.

chris

fb305svs

Well yeah, we already have the deposit down for the chip, the car will be shoved on the chassis dyno and a custom chip tailored to it. Will be a lot of money to do, but is worth it in the fact that the car will get tuned for max perf. and we will have raw numbers on what the car puts down for HP.

With all of this we kinda expected the computer to puke a little, but we were hoping that it might idle ok...

Steve

fakezcar

yeah, you're just fighting a losing battle trying to fool the computer. right now it's reading everything going on i your ngine and it's saying "help, i have no idea what i'm supose to do!" and getting anything on the dyno wih your current chip is useless. You've got to have it hooked up to the writer, while on the dyno so you can change things on the fly (kinda like obd II). and make sure the guys doing it are good. BAD EXAMPLE:--> I've seen a gy try to tune a VTEC controller and not know what he was doing...about 30 sec. after he started messing with it the engine stopped. Just stopped, no sputter, nothing. Turn out he tried changing VTEC activation point and fuel mapping. Motor puked. Smacked valves into the pistons and shot one piston through the sleeve. not good. So make sure the guys know what they're doing and talk to a few previous customers, find out how their cars run. You've got a lot on the line, in the motor and all.

good luck and let us know how things turn out.

chris

fb305svs

Well this is a reputable shop who works with the engine builder-

the only dyno tuning really will be with advance and fuel curves and mapping.

The car will be on the dyno with the purpose of getting tuned, they have all the information about the compenents in use and have a "starter" bin ready to go, they will tweak it from there.

Steve

kevinc

Just so you have a data point, I'm running an LT4-HOT cam (218/228 dur, .525/.525 lift, 112 LSA) and pull 14" of vacuum at 750rpm idle.

The stock chip had the idle down in the 600rpm range at operating temp and the cam didn't like it, similar symptoms to what you described. I brought the idle up to 750rpm in software, changed the WOT fuel and spark tables, and that was it. (this was when I was MAF)

fb305svs

Ok, thanx! its good to know that this is somewhat "normal" for what it could be doing

kevinc

Something else that came to mind...what harmonic balancer are you running? Another member here had problems w/ his new engine misbehaving similar to yours, root cause was the timing mark on the new balancer he bought was in the wrong location. He had timed it precisely on the indicator tab, but not accurately as the TDC mark on the balancer was in the wrong place for his engine.

Before hitting the dyno and wasting a lot of time/$, you can remove the balancer bolt and check the relationship between the crank key and timing mark...or just post the manufacturer and part# of the balancer so it can be checked.

That "glowing headers" thing you mentioned points to a retarded spark timing problem.

Grim Reaper

I too have found this a common "fix" when running a larger cam, even with MAF. Generally a idle speed change from 750-800 inside the chip will do wonders. Also, I found resetting the IAC to idle just under the speed selected in the eprom is another good thing to do...especially if you throw an SES code.

One thing you don't mention is the injector size you are running and how you modified this in your eprom. MAF cars should/must be reprogrammed if you change to a larger injector size or they will run pig rich if the injectors are noticeably larger.

I also find that even though they may be SVO 24#s that I may have to "fiddle" with the injector constant in the eprom along with the fuel pressure. I seldom find my "initial constant" based on the injectors size (ie. 24 or 25.5 based on the fuel pressure running) ends up being the correct one. Once, I had to lower the constant to 21.5 before the engine started to run 128/128 overall. Another time 26.9. I find the "combo" of parts has a great effect and all seem to be different.

fb305svs

Yeah there are lots of things different about this motor- having idle issues was what we expected.

As for setting the idle up, we'll do that, its gonna have a 2800 stall convertor on it anyways, so we should be able to easily get away with a slightly higher idle

As for the motor, i thought i mentioned the 24lbs injectors, but maybe not, but thats whats in there...

fb305svs

Yeah it is the stock damper, and we have been able to confirm that it is dead on, we slid it on a little to confirm that it matched up to the piston being at TDC before putting the heads on. We wanted to check for any possible slippage, and found none.

Steve

BadSS

I'm running a 218/228 cam on a 110 spread with a stock 88 350 chip with 24# SVO. Not a bit of idle trouble. It's just a fraction rich at idle, and with the computer spark advance mine pulls 18 inches of vacuum. Your cam has less over lap, so your cam is not the problem. So,,, I doubt a custom chip is cure.

The only time I had a surging idle was when the cheesy timing hold down tab kept squeezing out on me and the engine was moving the timing around. If I were you I'd redoing everything involved in setting the min idle speed and base timing. Set your min idle to 500 rpm with the timing connector disconnected and with 8 degrees base timing (to start with). I've got my TPS set at .50 at idle and WOT gets me 4.7V - your cam might want a little more or less. The same goes for the timing.

One thing, my TPI combination liked the fuel pressure at 43#. If you're unable to get the car "dialed in" with less than 50#,,, then I'd look at the injectors or fuel pump as possible problem areas.

Hope that helps.

fb305svs

thanx, as soon as the tranny is back in and everything is put back together we will give it a try!

Grim Reaper

As I said, every combo is different. BadSS seems to be okay, but it doesn't mean you will. :I know plenty that this has NOT been true.

I have found that sometimes you STILL have to play with the Injector Constant size a little and may not end up being "24". Some combos wanted it leaner and others want it richer.

fb305svs

Yeah- at this point we just need a decent idle to get a few line pressures from the tranny, as long as we can drive it to the dyno shop, they can deal with it from there, thats what they get paid to do for th ebig bucks....

fb305svs

one other thing worth mentioning to you glen and everyone else- they are 24# injectors from ACCEL.. they aren't svo injectors- any differences or should it not matter?

Steve

brian89transam

Ford SVO injectors are rated at a different fuel pressure setting (you'd have to do a search to find out the exact difference), so they actually put out a little more fuel. But since you have Accel you won't have to worry about it.