guess theres no other experts on this board anymore huh

 

come on people please help me out here i really hate to just start replacing parts that crap get exspensive

 

Have you inspected and cleaned all the engine ground wires?

 

no i havent you woudnt possable be able to give a link with pictures as to were they all are would you?

 

Hello POPS, having trouble I see. Well the first puzzling thing I see is you said the fans were not on when you took the data but the primary fan is requested to run. Use your scanner to cycle the fans to be sure they are working.

The next thing I see that stands out is your throttle is wide open but your speed was only 42. Does that sound right?

Obviously the knock is major problem but let's address the items we know.

Next, how old is the opti? I assume (you know what happens when you ***-u-me) the opti is old. One problem with the correct-a-caps on the opti is they arc internally and misfire inside the cap. It may be time for a new opti. A look inside the cap can suprise you. Double and triple check the length of each wire to be sure they didn't arc to ground or burn somewhere and that they are seated properly.

Also, normal tune-up items like cleaning the EGR, the MAF, the TB and the IAC may be helpful. Don't forget the O2's if they are old. Also the TPS is easily warn out and should be replaced. It wouldn't hurt to replace the fuel filter either. Pull on the battery to see if it rocks around. If so you may have the proverbial broken clamp. We all have that problem.

You also mentioned a hard starting condition. Has the items your brother replaced corrected the issue? Hard starting conditions are many times from a fuel problem. What you should have if you don't already, is a fuel pressure gage. For LT1's it's as essential as a tire pressure gage. Get the one with a hose on it so you can tape it to the windshield. You want to check the pressure during a drive to see that it's at least not dropping. You should also check the pressure after the engine is shut down to see how fast the pressure drops. Quickly dropping pressure after shut down is indicative of hard starting issues.

The grounds are in a couple of spots. One is behind the battery near the positive cluster. Remove and clean both. Disconnect the battery terminal first.
The others are on the drivers side I believe at the engine and the frame. It wouldn't hurt to remove and clean them too.

Let us know what you find.
Dave

 

As far as tearing down the opti, you should just open the casing and look inside. I know that mine went out due to rust in the system. The opti needs to have vacuum lines hooked up to it to remove the 03 that is produce during the high intensity electrical discharge through it. On my system, the vacuum lines were not hooked up correctly, and so it rusted in about 2 weeks flat. The opti has a bad history of being the culprit in many situations. The fuel leak down test is also a good one to try (ie, how long does your fuel system pressure hold after you turn the engine off)

Jonota

 

To correct some confusion in the posts above:

"Normal" for long term fuel correction is "128" (not 120 as stated in one post). 133/131 is not anything out of the usual... within normal tolerances. Appears the O2 values are pretty good (recognizing the limited accuracy at richer A/Fratios). The pulse widths are also similar, so it doesn't appear that the problem is unique to one side (bank) of the engine.

Several people are confused by the "NO" in the spark retard and the A/F learn.... "NO" in this case seems to refer to the "number" of the fuel cell, and Cell 15 is normal. The PCM willl "add fuel" (use the greater than 128 LT fuel trims from Cell 15) if the LT's for that cell are more than a certain percentage above 128, and in this case, it doesn't appear that they meet that criteria, to it defaults to 128 BLM's. I don't think there is anything unusual there.

There is 12deg of retard. 12 retard + 22 advance = 34 deg, which is what you are going to find on the spark timing map for that RPM and MAP. Nothing unusual there as far as picking the advance value from the timing map, but obviously the 12deg of knock is a problem. There is NOT a limit of 10deg knock retard, as someone stated. I think the stock programming limits it to about 15deg retard. Knock may be realted to the excessive coolant temperature. 229degF is pushing it. One fan should be on at 229deg - stock programming turns the first one on at 226degF, and the second one on at 235degF. One of your fans should have been running. Not sure how you would know if it is actually running at WOT/3,0000rpm/42mph????

EGR % duty cycle is set by RPM and MAP. It never works at idle, or above 3,500rpm. You are only at 3,053rpm, so the fact that you are getting 31% DC on the EGR isn't unusual.

Your fuel pressure looks "odd". Are you saying you see 50psi at idle with the vacuum line off (you really should use some punctuation and correctly us caps in your sentences, they are extremely difficult to decipher)? That is above spec, which is 41-47psi. Then you indicate at WOT, the fuel pressure is only 41psi?? You have to wonder why it is losing 9psi at WOT. The 41psi is still within spec, and the O2's indicate it PROBABLY isn't running lean, but there is something screwed up with the fuel system if those are the pressures you are seeing.

The code is for the skip shift circuit - no problem.

Why would it be unusual to see 42 MPH and 100% throttle at the same time? I'm totally lost on that comment. You can go 100% TPP off idle with the car not moving.

In general, the scan looks fairly normal, except for the knock retard. Is it possible that the hesitation caused by the knock retard is what you are interpreting as the problem?

 

ok people update for you. First of all let me thank you all for your help and second let me apoligize for my grammer and puncuation skills. I just re scanned the car again heres what i got this time.
RPM_______________880--------------Left Int____128-----Right Int----128
open/closed loop--OPEN --------------coolant deg. F---------127
Left o2s (mv)_______451--------------Right o2s (mv)---------460
Left Blm____________128--------------Right Blm____________128
A/F learned_________NO---------------Ft cell________________16
Tps (v)_____________.2--------------Throttle (%)___________0
Left Bpw (ms)_______3.6--------------Right Bpw (ms)________3.6
Airflow (gm/sec)_____8----------------Iac position___________35
coolant (deg. F)_____127--------------Mat (deg. F)__________86
Fan 1 requested______NO--------------Fan 2 requested_______NO
Map ("hg)___________10.3-------------Map (v)______________1.32
Baro ("hg)___________29.3-------------Baro (v)_____________4.80
Knock_______________NO--------------Knock Retard_________NO
Spark Advance_______21---------------Ignition (v)___________13.5
ccp duty cycle_______0----------------Egr duty (%)_________0
Time________________0:16------------Desired Idle___________800
A/C request__________NO--------------A/C clutch___________NO
A/C press (psi)_______4----------------A/C press (v)_________.24
Vehicle speed_________0
stay tuned for more scan results please

 

You've given us one frame from the scanner, on an engine at idle that's only been running for 16-seconds, and the PCM is still in open loop, O2 sensors aren't even heated up. Everything (except TPS voltage) looks completely normal, but the cold, open loop condition, at idle has little to do with your problem.

TPS voltage (0.2V) is borderline on setting a code for low voltage. The PCM will accept anything between 0.20-0.90V at closed throttle, and set that as the "0 % TPP" value. Most stock LT1's seem to show TPS voltage in the 0.60-0.67V range. Some people claim they get the best results at 0.50-0.65V.... not sure why though. In any case, you might want to check the TPS voltage at closed throttle with a volt meter, and then rotate the throttle slowly, watching for a smooth increase in voltage over the full range of motion, from fully closed to fully open. You should also jiggle the harness connector to see if it imparts any erratic chages in voltage, due to a loose or corroded connection.

 

More scan results.
RPM____________3163-------------Left Int_____133----Right Int_____128
Open/closed loop_____closed-----------coolant (deg. F)______226
Left o2s (mv)________513--------------Right o2s (mv)_______420
Left Blm_____________134--------------Right Blm___________129
A/F Learned__________YES-------------Ft cell______________17
Tps (v)______________1.00-------------Throttle (%)________14
Left Bpw (ms)________3.0--------------Right Bpw (ms)_______2.7
Airflow (gm/sec)______25---------------Iac position__________20
coolant (deg. F)______226--------------Mat (deg. F)_________91
Fan 1 requested______NO---------------Fan 2 requested______NO
Map ("hg)____________7.7--------------Map (v)_____________.84
Baro ("hg)___________29.3--------------Baro (v)____________4.80
Knock_______________NO--------------Knock retard_________0
Spark Advance________37--------------Ignition (v)__________13.0
ccp Duty cycle________0---------------Egr duty (%)_________0
Time________________9:20-------------Desired Idle__________800
A/C request__________NO--------------A/C clutch___________off
A/C press (psi)_______4----------------A/C press (v)_________.24
Veh speed___________0

Stay tuned for more scan results please

 

Another frame that really doesn't help. The engine is decelerating, as evidenced by operation in Cell 17, and the MAP = 7.7"Hg. You aren't going to solve the problem of why it stumbles under load by looking at cold start, and at deceleration. You really need a good scan log for a full acceleration, through the RPM point where the stumble occurs.

 

More scan results

RPM_______2530---------Left Int_____129--------Right Int____132
Open/Closed loop________CLOSED-----------coolant (deg. F)__223
Left o2s (mv)___________474---------------Right o2s (mv)___142
Left Blm_______________135---------------Right Blm________131
A/F learned____________NO----------------Ft cell__________17
Tps (v)_______________.86----------------Throttle (%)_____10
Left Bpw (ms)__________2.4---------------Right Bpw (ms)___2.4
Airflow (gm/sec)________16----------------Iac position______17
coolant (deg. F)________223---------------Mat (deg. F)_____102
Fan 1 requested________YES---------------Fan 2 requested__NO
Map ("hg)_____________6.8----------------Map (v)_________.68
Baro ("hg)_____________29.3--------------Baro (v)_________4.80
Knock_________________NO---------------Knock retard_____0
Spark Advance (deg.)____37---------------Ignition (v)_______12.9
ccp duty clcle__________0-----------------Egr duty (%)_____0
Time_________________25:30-------------Desired Idle_______800
A/C request___________NO----------------A/C clutch________off
A/c press (psi)_________6-----------------A/C press (v)_____.26
Vehicle speed__________0

Stay tuned for more scan results

 

ok hers one with 100% throttle again
RPM_____6160------------Left Int___133------Right Int___125
open/closed loop_________closed--------------coolant____229
Left o2s (mv)____________62----------Right o2s (mv)____412
Left Blm_________________128--------Right Blm_________128
A/f learned_______________NO--------Ft cell____________18
Tps (v)__________________4.58-------Throttle (%)______100
Left Bpw________________13.2--------Right Bpw________13.8
Airflow (gm/sec)__________147--------Iac position_______52
coolant deg. F____________229--------Mat deg. F_______133
Fan 1 requested___________YES-------Fan 2 requested___NO
Map ("hg)________________28.1-------Map (v)__________4.58
Baro ("hg)________________29.1-------Baro (v)_________4.76
Knock___________________NO--------Knock Retard______14
Spark Advance____________23--------Ignition Volts______12.5
ccp duty cyle_____________0---------Egr Duty %________0
Time____________________8:48-------Desired Idle_______800

 

Ok when i first looked at the car tonight i put the fuell pressure gauge on it turned the key to koeo it read 41 psi, i then started the car and it dropped to 39 psi,I then shut the car off and it returned to 41 psi, i then restarted the car with the vacume line off the regulator the gauge read 49 psi. I then took the car for a test drive and came back with the gauge still atached i shut the car off the presssure went from 39 psi down to about 35, with the key all the way off within 5 minutes time the pressure went from 35psi up to 42psi. yes i typed that right the pressure increased with the key off.
Now for the egr test i pushed the diagram open with hardly any effore i then un plugged the vacume line and hooked a vacume pump to the valve and coudnt get any vacume at all. I am thinking that it is possable a bad Egr valve and also a bad fuell pressure regulater and quite possably a dirty fuell filter any advise would be well appreciated

 

This one is showing some problems.... 100% throttle, 6,000+ RPM, and its only flowing 147gps of air flow..... WAYYYYY too low (possible MAF problem, or is it possible you have a tear in the intake elbow that only opens up at high engine air flow?). You should be seeing over 250gps at that RPM. Additionally, the O2 mV's are WAYYYYYY low.... 62mV on the left, and 412mV on the right. The knock retard is a disaster, but with it running that lean, its to be expected.

In reading your fuel pressure measurements, I didn't see one for the engine at the above conditions... max rpm/max load. Appears your pump may not be holding pressure at WOT... you indicated earlier you only got 41psi at WOT, compared to 50psi at idle. Might be a sign of a restricted return line, not a faulty fuel pressure regulator.

The fuel pressure climbing after the engine was shut off for 5 minutes isn't impossible... that's what happens to the pressure when the key is off, and the fuel in the rails starts to heat up from the heat soak. That would indicate the FPR diaphragm is healthy, and the check valve in the pump is healthy.

The logic for suggesting a restricted fuel return line... at low rpm, like idle, and at low load, the fuel pressure regulator has to pass most of the fuel back to the tank. If the line is restricted, it can flow enough back to the tank, and pressure goes above the regulator's setting. At high rpm/high load, the engine is using most of the fuel, and very little gets returned to the tank, so the restriction in the return line restricts the flow less, causing less pressure in the rails.

Check the fuel pressure at WOT, over 5,000rpm.