More help with tuning needed

[Ricky Trussell]

I had a post awhile ago on this problem and still have not found what is wrong. I wil ask for help again.

I will be in Memphis for the Fastest Street car World Finals if anyone wil be there and be willing to look at this let me know. I will gladly pay someone to tune this out or diagnose the problem!!

My VE table needs high 90's to 110's at 2000 rpm cells at 42-70 kpa to get a 13.5 a/f setting. I have low 60's before and high 60's to 70 after the 2000rpm cells.

The 1750 cells are +- .8% correction with low 60's. When the engine starts into the 2000rpm cells the 02 takes fuel out at 1900 but as soon as the engine gets fully into the 2000rpm cells it swings to adding 5 to10%.I have a low popping sound out the exhaust at 2000rpm but no where else.

I have checked the timing table, 34* is what I have. I have taken the timing down to 22* and this does reduce how much fuel the 02 adds but engine is still stumbling around. I have not added more timing because of the 02 adding makes me think it's lean, but the popping out the exhaust makes me think fat.
The engine runs good everywhere else. This happens on any speed or gear when in those cells.

If I push the throttle down slowly when it is in the 2000 cells it stumbles, the kpa moves up and then most of the time it pops out the throttle body. Popping out the exhaust I thought was fat, so why the pop out the throttle body? Could a vacumm leak cause this?

I have change wires then changed back. I have changed plugs and heat ranges. All my AE settings are close to what I was told to start with and I have moved them then moved them back with no change.
What should I be looking for on engine issues?

My combo is mild:
B2B system speed density
383 10.5 to1
AFR 190 heads
525 lift hyd roller 219 dur.
700r4 with 2500 stall 370 rear gear
3250 lb. car
I have run 7.90 at 89 mph on street street tires (2.1 60') shifting at 5800 so to me the engine seems okay at WOT.

Sorry for rambling!!!

 

[55Belair]

Ricky,
Are you still using the same(or close) GCT you sent me a while back?
I am going to go back through that and see if anything jumps out.

It is odd. I am running about the same engine combo as you.
383, dart heads, 10:1 compression. The main difference is that I am running an Enderle bug catcher on a tunnel ram (1800 cfm) and I don't have any those problems.
I will let you know if I see anything.
Chris

 

[55Belair]

you have mail.
good luck.

 

[Lance]

I've run into a similar problem before. The customer was complaining that the engine had to be overly rich to run properly and he had popping out the intake and exhaust.

He trailered the car up one weekend so we could work on his tune-up. After pulling our hair out for hours trying to figure out what was wrong, we started looking at other possible causes. He had insisted that the valves were lashed properly and that the springs were good. I decided to double check the lash myself and after pulling the valve covers off, I noticed small indentations on the inside top of the valve covers. Looking a little closer, there were 8 indentations on the top of each valve cover coinciding with the rocker arms.

What was happening was that the valve covers were a tad short and when they were tightened down, they were interfering with the rockers, causing the valves to open slightly or reducing the seat pressure.

It may be worth a shot to take a good look at the valve train. Any problem in the camshaft/valve mechanics can cause similar issues.

Good luck!

 

[ChrisCairns]

Bring up the All Sensor screen and watch the TPS as you ever so slowly depress the gas pedal. Engine off key on of course. See if there's a TPS sensor problem.

 

[Ricky Trussell]

Chris, I have your mail. I will load and look sometime today. Thanks!

Lance, I took the valve covers off to check valve lash. I reset them hot with the engine running. 1/4 turn past no noise. I am running the GM Performance tall valve covers so that should not be a problem. I did have a baffle put under the oil fill spout that I did not check but will check that. thanks, I wll update.

Chris Cairns, will check tps now.

One other thing I have 42lb. injectors with a 55 VE setting at idlefor a 13.4 a/f ratio. This looks high according to others but after I drive the car awhile AFTER it is warm my 02 is adding fuel up to 3 to 5 %.

 

[RickWI]

Boy Ricky, what a pain in the butt problem this is. One thing I would do is take it out of closed loop and see what the O2 readings are and maybe play with the VE's a bit to see if you can get it to run well.

Also it would be interesting to know what the pulse width/duty cycle is at that 2000 RPM trouble spot, still running in open loop. Given VE's of 95 to 100+ it should be way high. At least what this would tell you is that the injector is REALLY dumping a ton of fuel in the motor.

 

[Ricky Trussell]

Chris,I looked at your AE settings then at what I have now. The only difference in what I have now is you stop at -20 fuel out in the AE vs TPS at 21TPS position. I will make that change to see the difference.

I checked tps with engine off, key on. Tps is 14 at closed throttle it will go to 75 at wot.

I will drive the car in open loop with the map like it is 65-90-68 in that area. Then I will set the map like I and most think it should be-- interloped from the 65 to the 68 and see what happens. I will also log this for the ones that want to look at it.

This might sound stupid but I am leaning toward my alternator voltage causing the problem. I talked to masterpower and my alternator comes in at 2200 they say, which is close to the problem area. I will also check bat correction in the log.

 

[RickWI]

You could also log the bat voltage. On that issue, if this is a one wire alternator then yes, on initial startup that is about where the alternator will exite at to begin the charge. Once the alternator is excited though it will stay charging as long as the battery is calling for voltage. So in reality, unless this alternator works totally diffferent than all the other ones I am familiar with once you exceed the 2200 RPM level after initial start the alternator is always charging the battery. The only variation due to RPM would be the total AMP capacity the alternator could put out, which would increase as RPM goes up. Granted the slope of the alternator capacity is quite steep between 1000 to 2200 RPM but should not be a cause of this problem, given normal logic. Do you know if at idle you have good voltage, in other words is the alternator putting out and maintaining 13.7 to 14.7 volts to that battery? If so then everything would seem normal from that standpoint. Just babbling some thoughts.....

 

[Ricky Trussell]

I ran some logs, Rick and Chris you have mail.

I logged BPW (mS) but it did not log nor did RPM but scaled rpm did. The log with the 60 to 70 in 2000 rpm has the 02 maxed out at 24.9% correction. The log with 100's as you will see.

I ran in open loop in another run but the engine ran worse.

 

[ChrisCairns]

Originally posted by Ricky Trussell


I checked tps with engine off, key on. Tps is 14 at closed throttle it will go to 75 at wot.

I didn't mean to check the TPS for initial or final setting. I meant to slowly push down the gas while watching the changes on FAST. This is just to see if there is a bad spot on the TPS.

Since you said that around 2000 rpm there is a stumble I thought perhaps there may be a bad spot on the TPS at that throttle position.

 

[TurboJim]

Do you by chance run an EGR valve? If its an old factory one, its quite possible the spring is fatigued. Try taking the vacuum hose off it and see if the problem goes away. Very common.

 

[Ricky Trussell]

Chris Cairns, I should have taken more time to answer the post. I did look at the movement of the tps. I could not see any problem with engine off, it moved according to throttle movement. I also checked tps movement while driving the car. I logged tps position to see if there was a problem there. I can't see any problem.

Turbojim, I do not run an EGR valve.

 

[Craig Smith]

I would also like to hear about the results of monitoring pulsewidth and battery voltage through this. If you have this info available it will tell us a lot.

 

[Ricky Trussell]

I logged bpw but it did not read. My battery stays at 13.3 to 13.4.

When I logged I had 16 sensors, it did not log rpm or bpw but did log scaled rpm and all others.

I am leaving for Memphis in the car in a hour or so I will have time to run plenty logs. It is about 4 hours from here.

 

[Ricky Trussell]

I have ran logs if any one wants to look at them. I ran in open loop and my voltage was 13.3 with a .8 batt cor.. Those ve numbers are to get a 13.5 A/F ratio

At 2058 rpm
BPW (mS) 5.5
VE is 90
map kpa 48
batt. cor. .8
tps 18
inj. DC 8.3
actual A/F 14.81

I ease the throttle down:

RPM 2008
BPW 9.0
map kpa 78
VE 89.4
tps 22
A/F 15.94
inj. DC 15.0
batt. cor. .8

As you can see at 2000 rpm steady when I ease the throttle down there is no rpm increase but there is map kpa increase. The engine leans out and sounds and feels like a plug loading up and misfiring.

I changed wires on the left side because that is where my 02 is. It changed nothing. I pulled the plugs again and they look okay.

I will pull the valve covers one more time to see if I missed something.

Any ideas on what this might be, throw them out here. I have not given up but after a year of pulling plugs, changing wires, running logs that I can see there is a problem but can't find it, I am over my head here.