Long time lurker, first time poster here. The motor is new with less then 800 miles on it. I am the second owner of the car and has only 36K miles on it. The car has been down for nearly 2 years.

Specs of my car are:
92 Transam (speed density)
385ci stroker
Lunati hyd. roller (.477 int .490 ext) duration 219 int 230 ext.
1.6 RR (giving me lift then the specs above)
11.1 compression on AFR 190s
Edelbrock base and runners
52mm tb and ported stock plenum
inital timing is 10 degrees
Custom burned prom
and all the usual bolt ons
MSD Digital 6 sitting in my garage

Additional specs:
30lb injectors
AFPR (set at 40psi)
inline Bosch fuel pump

New sensors/parts:
fuel filter
knock sensor
Oxygen sensor

The engine is throwing code 43 (ESC/knock sensor). It throws the code right after it comes out of "warm up" mode. The motor is low on vaccum too. It is at only 7 inches at idle(already looked for leaks but could find none). My buddy thinks that the cam might be to aggressive, but I am not convinced. The car has no issues running or at idle but lacks serious power. It has a very slight stutter at a constant rpm.

The valves are a little louder then they should be for a hyd roller. I will be pulling the valve covers and adjusting the rockers. I will eliminate this probelm from the equation.

I already have a couple of ideas on how to create vaccum (reverse the smog pump or convert to a carb and ditch the TPI) but I want to exhaust every other option first.

I already had the motor on a scanner and it is telling me that car is running the correct air/fuel ratio. However, when I pulled the plugs, they were white. The plugs tell me that the motor is running lean. I put a fuel pressure guage on it and it held a consistent 40-41 psi at idle(this should be more then enough psi with the injectors and inline pump).

The plugs have a conservative gap(can't remember the gap right now because I did about 20 different adjustments/tests last night).

I won't be able to work on the car until next weekend but I would appreciate any ideas/thoughts.

Scott

 

Hi.

Firstly what type of fuel you using? You did say the motor is 11:1 and that can be too much for regular pump gas. You air/fuel readings could be good at idle but when you start putting it under load it can be detonating with regular pump-gas. This may be why your plugs seem a little white ect...

I don't think your cam is that agressive. The extra cubes of the stroker & more compression tend to tame down cams so you should be ok in that area.

 

Well, the car was in Florida and I was using 93 Octane. Now I am using 91 Octane in Phoenix. There was no difference between the two fuels. The compression is a little on the high side but my timing is not that aggressive. I actually went down to 6 degrees(stock) intial and made no difference at all.

We actually have a few gas stations in the valley that have 100 octane. I was going to get some this gas after I adjust the rockers.

Will the lower octance relate to the low vaccum I have?

 

That cam is not particularly aggressive for the rest of your setup, in fact I'd say it's rather too mild in the lift department, it's costing you some power at higher RPMs. The duration is OK though, shouldn't be causing any trouble like poor idle vacuum.

Exactly what rockers are you using? What push rods? Do you by any chance have self-adjusting rockers? Still running stock-length (7.290" or 7.300") push rods?

Try backing the timing off a good bit, like down to 4°, and see if the knock sensor complaint goes away. Also, if you over-torqued your knock sensor, it will become extremely sensitive, and will tell the ECM there is knock even when there is none. Dropping it or hitting it can also cause this. You should put it in with no more than about 15 ft-lbs of torque, with about 4 wraps of Teflon tape.

 

are you running a gear drive timing set?

 

What are you running for an eprom? There is NO WAY a stock L98 eprom/Memcal is going to work with that setup.

Also, while you MAY be seeing 14.7:1 as your AF ratio, that doesn't mean your mixture is correct. The O2 sensor will make you go to 14.7:1 in part-throttle and closed loop. What you need to look at is your BLM/INT values to determine the closeness of your fuel mixture.

Your vacuum reading is really low, much lower than you should be getting. 7" Hg correlates to a MAP reading of over 70 Kpa at sea level. Definitely going to cause problems. What is your idle speed?

Also, on the code 43, have you checked the wiring? Generally, if you are throwing a code 43 after the inital warm up (actually > 67*C), this is an indication of a wiring problem like a short (closed) or broken (open) circuit.

 

RB- I am using Crane 1.6 roller tips. I don't know the exact the length of the push rods(the motor was built by Dallas Export Sales) but they are not the stock ones, because I bent them when I blew up the original L98. I didn't use a torque wrench when I installed the knock sensor. I just used the "it feels snug" setting.

zippy- I am using a chain, not a gear.


Glenn- I am using a custom burned prom. I went with the same guy that burned my first prom when I had a 10lb paxton on the stock motor. My car went .2 faster then the car(89 Formula 350 it came off of) with the same exact mods and being heavier. Anythings possible and the prom could be wrong. Most of your reply is foreign to me as my tuning abilities are not that great(although I have several friends that are more knowledgeable then I). If you have an idea of where my BLM/INT and Kpa settings should be, I would appreicate your input. Also, I thought about the wiring issue. I followed the wire(from the knock sensor to the ESC module) as well as I could but I did not see anything that looked bad, of course this was at 10:30pm and 6 hours after I started this little project. The engine throws the 43 code about 7 seconds after the car is started, whether if the car has been running or sitting for a couple of days.

 

I know you say you checked for vaccume leaks but consider this:

<b>Lunati hyd. roller (.477 int .490 ext) duration 219 int 230 ext. </b>
What LCA is on that cam? a 112 or 114 LCA would yield well over 15" of vaccume at idle...
Is your idle rough? it shouldnt. If it is, that is evidence of a vaccume leak. You say a <b>"slight studder" </b> occurs? again, vaccume leak. ALSO <b>consider your air/fuel being correct, yet the plugs are white</b> Again, vaccume leak. whats your idle at? over 600 RPMS in gear? 700 out of gear? vaccume leak.

Vaccume leak dont have to occur around hoses, they can be anywhere. Under the intake manifold, around the head (compression leak), the gasket that separates the throttle body from the intake, the throttle body itself may have developed a leak somwhere. and check hoses that connect anywhere, like cruise control hoses etc... it may be connected at the throttle body but be leaking somwhere behind your dashboard. even the brake booster can leak where its connected.

 

11:1 is way to high for iron heads, which I assume you have. 10.5: 1 would be conservatively performance minded, and good for your fuely set-up.

If you want to swap to a carb, sure, but you will have to live with some issues with your motor. The atomization from the carbureator will definately not come close to handling that compression. You will fail emmisions. And you will give up at least 20 hp and 30 lb.ft. throughout your entire powerband. Not the best idea. And will your edelbrock runners, you lose even more.

There are aftermarket vacuum pumps, both electrical and mechanical, which will give you your brakes back.

 

Hummm. . . I didn't think a '92 speed density setup had a ESC module, other than the one in the MEMCAL. Shouldn't the wire run directly from the knock sensor to the ECM?

Also, Autozone has tried to sell me the wrong knock sensor for a 90-92 speed density setup, TWICE! On '86-'89 it's 100k of resistance and the 90-92 is 3.9k. I don't know about all brands but the 100k one they tried to sell me has white plastic on the end and the one I needed has black plastic. When I converted from MAF to SD it threw a code almost instantly when I started it and continued to until I bypassed the ESC module and wired in the correct knock sensor for the 730 SD ECM.

I have no idea about the vacuum issue. My 383 .495/.502 218/224 SLP 51006 cam idles at 650rpm with about 49kPa to 55kPa depending on if I'm in gear or neutral. I'd supect a vacuum leak though. What is your IAC valve position when idleing?

 

King- You are right about many things pointing to a vaccum leak. I am going to look for any other possible leaks this week. I used carb cleaner to check everywhere(everywhere around the plenum, runners, intake, tb. I even double checked a couple of my bypass mods on the tb, just to be sure. Still nothing though. With such a low vaccum reading, I am thinking a leak should be fairly obvious to the ear. Not to mention, the motor should run like crap if the leak was that bad. Again, I need to double check. LCA is 112.

Green- I run AFRs. They are aluminum heads. I didn't think AFR made iron heads. Also, the brakes don't seem any worse but I really haven't driven the car that much since the install of the new motor. This is why I think a vaccum leak is not the issue.

SMasterson- My friend has a 87 Z28. I pulled his ESC module to try and identify it on my car. My car has the similar plugs as the 87 module but my module looks completely different(located on the driver's side firewall, just off to side of the distributor). The ESC module I pulled from the Z28 was closer to the fender, on the firewall. Based on the plug being similiar, I thought it would be the ESC. I am also relying on the Chiltons manual too(which isn't exactly a GM manual in any way). I can't remember the color of the plastic on the knock sensor but I will double check that too. Also, I don't know what the IAC is at. Where should the IAC be at? How do you bypass the knock sensor without the computer freaking out?

The idle bounces a little when I come to a stop but smooths out after 5 seconds. I contributed this to the lobe of the cam. When the idle smooths out, it's around 750-800rpm. This is pretty close to where the stock motor idled at.

Please keep the thoughts/ideas coming.

 

Compare these two diagrams:

86-89 MAF:
ftp://ftp.diy-efi.org/pub/gmecm/manu...165v8tpi-3.jpg

90-92 SD:
ftp://ftp.diy-efi.org/pub/gmecm/manu...730v8tpi-1.jpg

You shouldn't have a ESC module under the hood.

I didn't bypass the knock sensor, I bypassed the (now unused)ESC module when I changed the wiring to SD. Actually, for a few days I just programmed the error code out of it until I had time to fix it.

Check the dark blue wire at GF9 on your ECM to a GOOD ground with an ohm meter. It should be about 3.9k. That should diagnose the cause of your ESC code.

I set my throttle blades so the IAC will be at 20 or so with it idleing in neutral and a fully warmed engine.

Oh, and I should mention, once the code 43 is set, the engine will NOT perform well. I suppose the ECM uses some *safe* timing or something because of the knock sensor error. I really never read up on why, I just fixed the problem. Maybe others will have an idea for you.

 

<b>LCA is 112. </b>
355 with:
A 224 Duration cam with a 112 LCA pulled 16" of vaccum at idle on my motor. Swaped out for a 234/244 LCA 112 and pulled 12" of vaccum at idle. Somthing is wrong here....

I hate to say this but im going to point my finger at your valvetrain now.
Are your valves lashed correctly? Is your cam installed correctly?

Vaccume is a BIG Finger pointer, somthing is WRONG!
Is the guage you are using good?....

just thinking... of all possibilites...

 

oh and hey...
wana sell the digital 6 ?