nomad350Z

So let me start by saying that this has been a real pain in the @$$. But, here goes nothing.

Car was originally a 305 TBI Iroc-Z. It has since been converted to the following:

L98 350 TPI (using DynamicEFI, modified engine harness and PortMod)
Cam- Crower, 204*int, 210*exh, .484in intake, .505 in exhaust, 114 LSA
Heads- Ported 113's with springs for higher lift cam

Car started giving me problems while driving across the country, died on the way due to ruptured fuel line in tank (PITA to figure out). Then the fun started.

Wouldn't run right when warm, stalled, erratic idle, refusal to start, etc. Checked injectors, 2 bad from stock Multecs. Replaced with FIC injectors, 32#'s in case of forced induction down the road....also installed AFPR to help tune with larger injectors.

Now, refuses to run as it warms up. Car isn't quite fully tuned, still using stock LB9 spark advance tables and PROM, except for modified BPC v VAC (Base pulse constant v. Vacuum) table for larger injectors. Believe it or not, car actually runs lean most of the time, or so it says. I know I need to

Have been using Dynamic EFI on my laptop to check running conditions; nothing out of the ordinary, no check engine codes, no nothing. AFR from O2 sensor says its running around stoichiometric (14-15). Something worth mentioning, when engine does idle (on cold start), pulls about 17inHG vacuum steady....is this normal? Its not that radical a cam, it should pull down more than that, at least I think it should.....

The second the car gets within temp and runs for 30seconds (thus putting it in Closed Loop Mode), the idle drops, jumps around between 900 and 400 RPM, then stalls. Also, when it gets hot, the Knock sensor reports pinging and the spark retard kicks in for higher RPM's. Why?

From what I can tell, all sensors work properly. IAC and TPS were replaced and reset recently; CTS, IAT, O2 sensors display sensible values. Fuel pump was replaced a few months ago, as was the fuel filter. As stated above, injectors are brand new FIC Bosch Design 3's.

I've done some research, and many people suggest replacing the Ignition control module under the distributor....why would it do this upon entering Closed Loop?

Besides a good tune to accomodate the gigantic injectors and checking the hot and cold resistance of the Knock sensor and possibly replacing the Knock filter, what else can I do?

If anybody has any Ideas, it would be greatly appreciated. Please, throw anything in here that I haven't tried. I'm all ears.

Please note, I will be posting this thread in the TPI board. I figure the more educated people that know about this stuff, the better.

nomad350Z

I'd also like to mention that the EGR and smog pump have been removed. The only reason the EGR is taken off is because the '113 heads do not have crossover passages, and the smog pump was simply removed.

SWCASH

When the fuel line ruptured, did the engine quit all at once, or did it run badly for some time? Like backfire maybe. You always want to look at cause and affect. What possible problems could the original problem have caused to make it run the way it is now?
If you had a lean condition you could have fried a piston or valve. Did the fuel line cause debris to get into the fuel system? Possible timing gear failure from backfiring What condition was your timing set in prior to the fuel line failure?
Start with the basics. Monitor fuel line pressure, check ignition timing, pull the plugs and examine and do a compression test. Check for vacuum leaks.
The ignition module can be suspect, and it nrver hurts to have a spare on board, but don't just start changing parts until you have done some preliminary checks like I discussed. I'm told by the folks at Megasquirt that the GM modules give a lot less problems than the aftermarket ones. I would take a used GM before a new Chinese repop The GM units also seem to be less sensitive to radio frequency interference (RFI).
I hope this helps some.
Squido

customblackbird

iTrader: (15)

injectors are too big but u already knew that. tuning for the injectors by changing the injector constants is only part of the battle. you could still be flooding the engine which would explain why the car runs like CR@P when closed loop kicks in bc the 02 sensor sees this insane rich condition. changing the injector constant tells the ECM wat fuel it should be seeing. wat fuel pressure are u running? the ECM will correct for rich/lean with changing the injector pulse width... problem could be that the ECM has lowered the pulse width to the minimum and its still too rich. can u datalog or see wat the injectors are doing? you could drop the pressure and calculate the injector size and then program the ECM for the new injector size to help with flooding the engine perhaps. dont go below 40psi with the bosch's. honestly with the price of the injectors 22lb vette bosch IIIs are like 160$ from FIC... they would be better than your 32lbs... or u could get 24lb which is wat you need.

also how are u saying the engine is lean? i hope your not going by a narrow band 02 sensor lol... they dnt know anything unless its 14.5 to 15:1 A?/F ratio. basically they dont know anything beyond that very small window of adjustability/operation. My car with a narrow band 02 sensor and a narrow band LED gauge says my car is mostly lean all the time... but its so rich u can smell it (not to mention my datalogs say im wayy rich) lol so dnt trust the NB 02. get a wideband and start tuning and stop guessing. btw im running 30lb SVOs at 43psi so theyre about 31lb injectors on a 383 HSR with about 480hp and im RICH... i can guarantee that your rich with your heads/cam. can u smell gas when its running? do your eyes burn?

your vacume is ok... alittle low. im pulling 12-14" with a 230/236 .576/.571 113 lobe comp cams XFI cam.

too much fuel could create a ping that the knock sensor is picking up? wats your compression? i would rule out the control module aka GM module... if there was a problem with that it wouldnt start or the engine would run weird all the time at a given RPM etc... not when it goes into closed loop.

what about timing? closed loop timing? too much? my guess is too little with the stock tune. was base timing are u running? did u set base timing right? did u set it in the tune?

edit: if your going to replace the control module... dnt use Accel, i would stick with e GM/ standard motor products, or if you want performance im running a DUI module.. .they are suppose to the best, i would have tried the pertronix but my accel left me stranded so i coughed up the $$ for the DUI one.

nomad350Z

Its unlikely the fuel line rupture caused all this, as the car was at about 1/4 tank when it happened, and the line that ruptured is the 3" long one between the pump and the steel line inside the tank; the rubber just split enough to allow any decent pressure to leak out, so the car just stalled. Since the tank was relatively low, I'd venture to say no contaminents entered the split fuel line, especially since fuel would push everything out as it flowed out the side of the line.


Fuel line pressure is 45psi, pretty high but I was told that with the design 3's I shouldn't run them too low, as it will cause an uneven spray pattern. How low could I go?

I can datalog, and the injectors are running low impedence, less than 2ms. I am reading off a NB O2 which is coming directly from the ECM, so the reading I'm getting is what the computer is operating off of. When its cold it reads almost stoich, as it heats up it reads really lean, almost 20:1 AFR. It smells a little rich, but nothing to the point of making my eyes water. In fact, it seems ok when the engine is cold. As it heats up, thats when it gets rich.

Timing is retarded back, I set base ignition around 2* BTDC since I was seeing knock readings. I tried using different SA tables, and the engine likes the stock 5.7 tune best. Wouldn't run with a corvette tune, which compared to each other, the corvette tune has less advance at low RPMs, more in mid-range, and about even at the top of the table.

I haven't tried tuning SA tables yet, just different stock tunes to see what it likes best. I'm not too awful familiar with how to precision-tune an engine, kinda a newb actually. What do you suggest?

The car was having these same issues before I replaced the injectors. I imagine the injectors aren't helping, but it did the same thing running 22lb Multecs. Then again, 2 of those ended up being bad. On the other hand, its still doing the same old junk. I can keep the engine alive by adding throttle( 2700 rpm+), but at low RPMs it stumbles and dies.

According to my system, the ECM is showing changes in the spark advance as the engine speed changes. If the ICM were bad, would it simply not react to the ECM's input? What I'm saying is, would it acknowledge that it should change the ignition timing but then not do it? Is there a way to test the ICM? I'm guessing Autozone doesn't carry GM Modules......

Thanks for the input fella's. At least now I have some leads to go on.

Edit: I've been in contact with the gentleman who sold me the DynamicEFI software; He recommended that since I upgraded to Bosch III's that I change the injector correction offest and small pulsewidth correction for a Port fuel injection system. I will be updating my current tune with these changes; I'll let you guys know how it goes.

nomad350Z

Started tinkering around with the car again today, what I found looks like the ICM may be the culprit.

I set base ignition timing at 6*BTDC, and made sure my initial SA in my tune matched it. Changed the injector correction offset and small pulsewidth correction as mentioned in the previous post. Also made sure the BPC tables were set where they should be. Before I had been adjusting them up and down to keep the car running.

After setting these variables where they needed to be, and using a stock L98 5.7 F-Body tune, I started the car and she ran like a champ. A little rich, (not making my eyes water, but definitely rich), but she ran great. Even made it past the CTS and timer threshold for Closed Loop mode. Car ran for about three and a half minutes, and died suddenly out of nowhere. Tried starting it, wouldn't start without applying throttle, and even when it did start, it wouldn't idle correctly nor would it rev like its supposed to. Ran like it was being choked (or the necessary SA wasn't being applied). It behaved exactly how it did before I swapped injectors. I know I could keep it running by keeping my foot nearby, but only to a certain extent until it warmed up flat-out quit.

Does this sound like an ICM on the fritz? I've heard alot of guys complain about this type of behavior, especially when the car warms up and won't run.

I think we confirmed that the closed loop is no longer affecting the engine, since it made it there and ran for 3 minutes in closed loop absolutely fine.

It may not be running right, but its progress. Thanks guys!

customblackbird

iTrader: (15)

with GM type injectors/bosch i wouldnt go lower than 40psi. fords u can go much lower prob to like 35ish.

if the ICM is the problem then switch it out... if its the stock one i would replace it anyways. i like DUI, i got the ICM, and the best cap/rotor that ive seen in a while for like 100$. DUIs cap/rotor had "made in usa" as part of the plastic molding, my MSD stuff said nothing of the sort.

its really hard to diagnose a bad ICM... theres a way to test it but i have no idea wat that is. best thing to do would be to replace it but keep your old one just in case. if u dnt have new plugs and wires i would do them too. i do mine all at the same time.

your lucky tho... my accel ICM ran fine, i shut the engine off and tore the engine out, 4 days later i had the engine back in and it wouldnt start at all. figured out it was the accell ICM that just died for no reason. i had a used standards motor product laying around so i threw it in and walla! i now run a DUI and keep my standard motors one as a spare

nomad350Z

So I purchased a new ICM today; Duralast "made in the USA". Hasn't made a difference. Car still starts up and runs great cold, heats up, goes into closed loop, runs good for a couple minutes, then suddenly dies.

I did notice while trying to re-start it after numerous stalls, that the fuel pump doesn't prime everytime I turn the key on. Is that normal? If I wait a couple seconds it will prime itself again, but after a stall, key on, key off for a second or two then key on again, it doesn't prime. Is it supposed to?

I don't have a fuel pressure gauge to measure immediate fuel pressure; I've been renting one from Autozone whenever I make adjustments. I guess its time to put something a bit more permanent in there.

Besides more extensive tuning, what else should I look at?

I don't get why I can't get this thing to run the way its supposed to, even with large injectors. I have a friend with an '03 Mustang GT and a Procharger that runs 42# injectors, and when he's not on the boost it runs just fine. Then again, he took his car to a dyno service to be tuned. Maybe its something to look into.

customblackbird

iTrader: (15)

lol duralast might be made in the USA, i have duralast rotors on my ford 8.8 on my bird and they are made in china... says on the box. so i dnt believe yours is made in USA.

the fuel pump will not prime everytime the key is turned. once it primes it wont for a min or two if u keep turning the key. no need to prime after its been primed/running since the pressure shouldnt escape the fuel rail that fast. the pressure stays in my rails for hours but it slowly bleeds off.

fuel pressure gauges are cheap and are better to have on hand, u dnt know what shape the autozone rentals are in since most of the ppl who rent them are retards (no offense)

u really need to start checking things off. is it throwing any codes? closed loop just means the ECM is gathering information from the 02 sensor basically. honestly i think it has something to do with fuel like too much of it etc.

nomad350Z

No offense taken. I know I need to get one, and I'd like to see what the fuel pressure is doing while the engine is running, especially when it cuts out.

Its not throwing any codes, except when I adjust the throttle blades to correct for the semi-high idle, it'll throw a TPS sensor too-low code; and since I've been changing my base ignition timing it will throw an SES code for the Spark Control Module since its not hooked up at that point.

Yes, in closed loop the ECM is gathering information; unfortunately, as you pointed out, teh O2 sensor readings are highly innaccurate unless the engine is running near stoich. Sometimes it reads lean, others it reads rich. Sometimes in between, but not for long.

I'm sure its getting too much fuel. The reason I bought the gigantic injectors is for down the road when I throw a turbo or supercharger on it. What else do I need to adjust in my tune to get it running leaner? BobR mentioned the integrator and block lean multiplier tables. Where should I go with these? Up, down, diagonal? In open loop both read a value of 128. As it heats up, they start to rise....

I think they need to make a book "ECM tuning for Dummies". It would make things so much easier for me if I knew ALL the basics instead of just a few of them.

RBob

iTrader: (1)

The ECM will only run the fuel pump prime after key-off for 5 seconds or more. The ECM actually continues to run for about 4 seconds after the key has been turned off. During this time the IAC is reset and the ECM prepares for shutting itself down.

Once it shuts down, about 5 seconds after key off, then a key-on will again run the fuel pump prime.

From your first post it appears that the stalling also occurred when the O2 reading was at 450 mV (due to O2 sensor ground being open). In this case the ECM should not have been going into closed loop. It can't as the O2 sensor is inactive.

Even though the injectors are on the large side, they shouldn't be an issue.

When the engine goes into closed loop you mention that the INT & BLM increase. This means that the ECM is adding fuel. Does the engine suddenly surge before it dies? Does the engine only die when at idle? How is it while driving the car?

Take a data log from a cold start through to when it dies and email it to me. I'll take a look to see if there is anything that doesn't look right.

The other thing is to set up and do VE Learns. Use the BLM method. Do 4 or 5 learns while driving around, hold the pedal steady for the best results. Flash each one in as you go and start another learn.

RBob.

customblackbird

iTrader: (15)

i was gona say the same thing, if the BLMs are rising (as in increasing 128 and higher) then the ECM is detecting a lean condition and is adding fuel.

i dnt know if i trust my BLMs, as in my ECM BLMs are lower than 128 so its detecting a rich condition so its subtracting fuel, but my 02 mvolts are lower than 400mv so its saying im lean lol watttt the cr@p! im installing a wide band today and maybe tmrw so ill see wats really going on.

hey Rbob can i send u a log too? im running a 165ECM, tunerproRT, and a 6Eexpanded mask.

nomad350Z

Correct me if I'm wrong, but If the O2 is reading below 450, I think its running rich. Mine jumps up to 800+, and according to my diagnostic screen its saying teh AFR is above 14.7, meaning its lean.

So you're computer is doing what its supposed to do.

By surge, if you mean the car won't maintain steady idle, then yes. It will jump up and down between 425 and 1000 rpms, then coming back down from 1000 it will die again. The engine usually dies at idle; at part throttle it runs better, but as it warms up it doesn't want to make any power. I'll take a datalog and send it to you. Thanks for looking everything over for me.

RBob

iTrader: (1)

On the Diag display there are two scales. The one in red is for the NB sensor. The scale in magenta is for a WB input (note that the magenta line is flat-lined).

With a NB sensor above 450 mV is rich. Below 450 mV is lean.

You haven't been the only one confused by the two scales. The next release of the WUD won't have the WB scale unless there is a WB input selected in the preferences dialog.

The surging is caused by a lean condition. Look at a datalog during the surging and track the RPM and MAP values that are in use. Then add some to the VE at those points.

For example, if the RPM drops to 500 and the MAP is at 70 KPa, and then it surges. Add about 10% to the VE table in the area of 500 RPM and 70 KPa MAP. Once you add enough fuel to stop it from surging the idle will settle down.

Do other areas that are crossed during the lean portion of the surge.

Once the idle settles down you can proceed with doing VE Learns.

The lack of power as it warms up is most likely from the knock retard. But we can discuss this once the surging and stalling has been corrected. One step at a time.

RBob.

customblackbird

iTrader: (15)

thank you for correcting nomad350z for me about the 02mv. higher than 450-500mv means rich condition, lower than 400mv is a lean condition. the NB and a WB are opposite so a NB the lower the number 400-less is lean but a WB, 14-7(less) is a rich condition.

RBob, can u take a look at a log of mine? seems that my BLM/INT arent working in open loop

RBob

iTrader: (1)

The BLM & INT won't do much in open loop. The BLM will be used but not updated. The INT will be locked at 128.

For the data log, depends upon whether it is 160 baud or 8192 along with what format it is in. If 160 baud it isn't good for much.

RBob.

customblackbird

iTrader: (15)

its a 8192 log using a AUJP bin base with a 6Eexpanded mask.

RBob

iTrader: (1)

AUJP is $8D for the '7730 ECM, not $6E which runs in the '7165 ECM.

RBob.

customblackbird

iTrader: (15)

wat is the stock bin for a 89 MAF car with a 165 ECM?

bc thats the BIN im running and im running the 6E expanded xdf. now i cant figure out why my A/F is lean when in part throttle in my tq converters stall area say 2000-2700ish

RBob

iTrader: (1)

It is possibly APYU.

Rbob.

ASE doc

Hey Nomad, Try checking ECT on data as the problem begins. Sounds alot like ECT sensor failure. Hope this helps. Good luck

ASE doc

Hey Nomad, Just a quick note. High pressure and smaller nozzles creates better atomozation, which is a good thing. I run 24# bosch's @ 70psi (the equivilent of 38#) to support 480hp and it works well. Just a thought for you.