Pampered-Z

I can't find a reasonable solution so I thought I'd post here and maybe get some out of the norm thinking to look at?

1993 LT1 - A4, 383 - LE3 heads and LE4 cam, all the supporting mods, ported intake, jethot LTs, BBK 58MM TB, 42LB injectors, racetronic pumps.

Pass side way lean and DS side rich, scans show short terms running part throttle 127 - 208, closer to full throttle 136/250. At WOT O2s are reading 639/689 and injector pulse 7.69/9.14 injector DS 60.2/69.7 I assume that cam is causing the high Map readings. At just off idle map is 49.x and as some as you open the blades even 40% it jumps to almost max. KAPA was 102.6 and reading were 98.x-102.x Or is that tell me there may still be a vac. leak?

Swap all the sensors, plugs and wires replaced, wires are not crossed. Replaced O2s, swapped injectors side-side, compression test is right on, readjusted vavles multiple times, replaced intake gaskets, milled intake for better seal, no exhaust leaks. Even another chip burned and ECM replaced and the harness from the ECM to the O2s.

What are we missing?

I was thinking of plugging in my ECMand map ( tuned for 2-bar map ), I too have a 383 W/42LB injectors tuned for boost just to see if that might show anything different. Is that worth a try?

Thanks, JB

Injuneer

The MAP doesn't look all that bad. What is the MAP at idle?

What do the long terms look like in the various cells, ranging from idle through max load?

SSQATCH

I am not all that bright but I had a similar problem after swapping transmissions. Found I swapped my O2 sensors from right to left. Put them in the correct side of the exhaust and things got fixed.

TOM B

BIGCATPOWER

Is All The Egr Stuff Still There. If So You Might Want Check The Egr Valve And See If Its Stuck Open Or If You Are Drawing Fresh Air In The Exg. From A Bad Exg Gasket Or A Crack In A Pipe. Also If Your Runing Open Pipes Close To The O2s You Might Be Runing Into Reversion.

Lonnie Pavtis

There has been a lot of problems with the low speed fuel trims when using an aftermarket throttle body, since they rarely use the idle bleed ports in the intake. I had this issue with a BBK, like you have. The computer will tend to alter the fueling to make the idle mixture consistent. This fuel trim adjustment will carry through when you go to full throttle screwing up the fuel mixture here as well.

What are your idle fuel trims? Start with these as you cannot use the o2 readings at part throttle as they vary so greatly.

Let me know your long term fuel trims at idle & lets see if they relate to the other fueling problems. Log these values, then swap the o2's side for side & see if there is a difference. Remember you will have to put a few miles on it before it starts to learn the new values.

Mr.Whitey

I have the pleasure of owing the car/nightmare that Pampered-Z is talking about. I'd like to thank Pampered-Z, Projectz28, Kazman and BWHunter for the help that they've offered in an attempt to resolve this problem.


Here is a list of the new engine parts.

Golen 383 short block
LE4 cam
LE3 heads
LE ported intake, milled .060 sides and .080 front and rear
ARP 7/16” Pro Series rocker studs
Comp 7/16” 1.6 ProMag NSA rockers
Comp Hi-Tech pushrods 7.0
PAC beehive springs (forget #, same as 918's)
Morel link-bar lifters
ARP head studs
AS&M 58mm TB
Trick Flow hardened guide plates
42# Delphi injectors
Melling HV oil pump (the good one)
TCI flexplate – int. balanced
ATI damper
MSD Opti (95-97 style, using squared o-ring, no pinch)
MSD 8.5mm plugs wires
NGK TR6 plugs @ .035
ACDelco 02 sensors (3-wire heated)
Cloyes double roller timing chain & gears
EGR/AIR removed years ago
PCMforless mail order chip
PCV valve and hose
Impala head gaskets


95% of the datalog info is Greek to me, so here is what the car is doing....

- high idle, roughly 1200rpm according to datalogs, 1400rpm on factory tach, adjusting throttle stop screw does nothing to lower rpm
- no cam lope, guessing due to high idle
- IAC jumps to 160 when put into gear
- TPS set at +/-.50v, but will reach 100% at 3.5v, TPS will go to roughly 4.7 while still at 100%
- car runs good (much better) when accelerating hard, seems to have a miss when only a small amount of throttle is used to maintain a speed
- usually needs some additional throttle applied to start (1st start was perfect, as well as the first start after new intake gasket)
- sometimes the idle will drop down and car will shut off if more throttle is not applied


I'll start with what I haven't tried yet...it's the shorter of the two lists.

- haven’t tested the injector wiring/ground
- haven’t actually set the timing, only used MSD’s lack of product knowledge as a guide
- haven't used compressed air in each cyl to listen for leaks
- haven't removed opti to look inside
- insurance fraud


And what I've already tried, in no particular order....

- replaced entire PS 02 sensor wiring, including weatherpacks, from sensor to ECM
- replaced ECM
- replaced plugs 7x with roughly 3 miles of use total
- swapped 02 sensors from side to side
- removed the basically new 02 sensors and replaced with new
- several tunes from PCMforless
- dozens of datalogs
- five or six oil changes using Valvoline VR1 20w-50
- checked routing/resistance of all plug wires
- swapped injectors, several times
- adjusted rocker arms several different ways, several times each way (from 1/2 flat to 1/2 turn)
- pulled intake to find oil inside of the intake and the head ports, good gasket pinch, rocker studs were LOADED with thread sealant during install
Picture of head ports.
Picture of #6 & 8, seems to be the worst
- compression tested 6 out of 8 cylinders – 215 to 225psi on all tested after turning car over for 8 seconds on each cyl.
- replaced new PCV valve with another new valve, along with new PCV hose
- replaced intake gaskets and used plenty of RTV around ports
- cam was degreed when installed
- adjusted MSD timing screw several times
- attached ground wire to PS 02 sensor to ensure a good ground (new header coating)
- drilled 3/16” hole in throttle body for IAC, also made a small piece of aluminum to isolate IAC passage (used this site)
- 99.99% certain that the opti is installed correctly
- torqued intake bolts after several heat cycles, both times
- vacuum at 1400rpm (factory tach) fluctuated rapidly between 11 and 14"Hg


Is it normal to have the vacuum fluctuate that much?? LE said it is normal, but a GM mechanic, who knows the cam specs, said that there's no way it's normal and there is likely a problem with the valves sealing.

How could so much oil be getting into the intake and head ports? The pan is attached to the bottom of the intake. It doesn't appear to be coming in through the TB from the PS valve cover.



Any ideas/comments/suggestions/explosives?

TIA

Pampered-Z

Sorry, was offline for a few days.

after the car warms and goes into closed loop, At 1000RPm idle Map bounches from low 50s to near 70 (kapa), FT cell is 16 and Lts are 108-122/ 135-160.


When driving:
FTC6 = 108/160
FTC10 =112/149
FTC11 =119/134
FTC15 =128/130
FTC17 =109/128

After stopping and leaving the car idle its in FTC 16 =108/160 and Os2 are reading 830s/480s and maps in the 60s.

Mr.Whitey

BwHunter sent me two links concerning the vacuum gauge readings. Worn valve guides??
1st link
2nd link

Projectz28

just out of curiosity what is the fuel pressure set at?

I have Pampered's old 42 lb injectors and we had a hell of a time getting it to idle right with them. We ended up bumping fuel pressure from 35ish running (vacuum line still connected to regulator) to 45 and the car really cleaned up just from that. Those injectors might like a bit more pressure to fire properly.

Whats battery voltage like?

mzgp5x

I had a condition this summer where the left bank would go lean and not run. I tought O2 was bad, or, wiring. It was neither. I found the injector wiring was bad. The 12vdc power line was broke to a single strand (I run 72# Inj with (2) 12vdc + source for Rt and Lt bank). I also had a broken ground wire on #8 Injector. I saw this condition when it transitioned to closed loop due to the intermittant elecrical wire conduction problem. Also, when it got to temp, it would start to run ragged and left bank would go to lean on the gage. Tore Inj harness all off and did a complete redo (I needed to learn how to solder, and I did). Runs great now. I though it was O2, but not. B. (97ss 383 - D1 M6) Hope this helped.

RBE17

I had a link LJ (Jeff Stevens) had on how to fix this. I can't find it for the life of me. He had this problem and came up w/ a mechanical fix for it.

Edit: Here's the link. Let me know if it helps. http://para.noid.org/~lj/PCM%20Tutor...litBLMinfo.htm

Mr.Whitey

Thanks for the replies.

Fuel pressure is 43psi at idle and the battery voltage is in the 13-14 range. I'll either have to get Alvin to make a new chip, or buy a AFPR. I haven't heard back from Alvin for a while now, so I might be stuck getting the AFPR.

I still have to check the injector wiring.

I already modified the TB using this method.

Mr.Whitey

Could loose valve guides result in oil getting into the intake?

Projectz28

I dont think so. I guess it depends on what part of the intake you are talking about... Plenum area? I doubt it. runners? I still doubt it but I'll say maybe its possible. Dont forget there is still a valve seal sitting atop and "most" of the oil is kept away. Any oil leaked thru the guide would just be sucked into the air stream and burnt. I dont see it going against the grain and up into the intake.

Alvin@pcmforless.com

The split in fuel trims are a obvious indication that there is something mechanically wrong. I believe you are seeing the issue because of leaky intake gaskets.