Can someone explain this

[Lee Thompson]

Help!!! Can someone explain what is happening?
This is using a 4000E OTC
On a WOT run, the first frame will be a good reading, lets say--830 milivolts
220 maf
4.80 tps
0 knkr

Then the readings will be something like this
110 milivolts
255 maf
4.80 tps
0 knkr

I will continue to get real low milivolts until I lift. Then they go back to good #
This at 18 psi
I took the 02 sensor out of another car, that is new and was giving good readings. Also tried 2 other 02s , same thing.

Hood mounted fp gage, Fp goes up pound for pound as it should.
Fp holds up, does not fall off.

Tank has 8 gal. 114 VP

02 sensor cycles up and down (740- 230 as an example)

We are having breaking up problems as well, but we feel this is likely related.

Can anyone take a shot at explaining what is happening here?

Thanks in advance. I am open to any and all suggestions.

 

[Sleeper]

What FP are you running static? What chip? What fuel pump, and is it hot wired?What other mods are done to the car?
Shot in the dark...sounds like you have a collapsed fuel sock or you could be cavitating the FP(not enough gas in the tank)

Paul

 

[Lee Thompson]

?

Sleeper, thanks for your reply. To answer your ?
This is a stock short block
O-ringed, ported heads with larger valves
70 turbo
front mount
55 lb. inj. with matching ecm
As I stated we have a hood mounted fp gage and fuel pressure does not drop off.
Red Armstrong in tank pump
Bosch ext. set to come on with hobbs switch (20psi)
It does this at 18 psi and same thing at 24 psi.
Does not show any Detonation
Have had fp from 42-58
Still get low readings when it come up to boost and maf max out.

 

[Sleeper]

What chip are you running?
Have you checked the coil pack? A bad coil pack will cause bucking and surging under high boost. This problem seems to lean towards electrics rathar than fuel supply.

IMHO
I would do the usual checks of all your grounds and connectors, if you haven't already do a plug check and see if anything looks out of the ordinary.

I'm just throwing out stuff here hoping that I may hit on something you may have overlooked.

Paul

 

[Dwayne]

We have gone thru 5 coilpacks.......all good.

We have taken the stock heater box out of the car so it is easy to check the grounds on that head.

It's gotta be electric..............

Here's a ? for you...............Would would it take to get a reading of .ooo to .350 on an otc 4000 at WOT...........................

 

[KendallF]

Originally posted by BigDaddy
We have gone thru 5 coilpacks.......all good.

We have taken the stock heater box out of the car so it is easy to check the grounds on that head.

It's gotta be electric..............

Here's a ? for you...............Would would it take to get a reading of .ooo to .350 on an otc 4000 at WOT...........................

In my experience, when the car starts misfiring, the O2 data goes out the window. I've seen nutso results like you're getting as well; perhaps the misfire leaves some "clean lean air" going out the exhaust (? Weak I know, but hey...) I would work on the misfire with good ol' fashioned parts substitution, plug reading, etc...when you get it fixed I'll bet you find that the nutty O2s were a symptom and not a cause.

BTW, from one of your earlier descriptions of the problem, it sounds sort of like the "MAF dropout" problems some of us have seen; when the car starts flowing a lot of air and maxes out the MAF, the MAF signal can actually overflow the buffer in the ECM, resulting in glitch frames of very low MAF readings (and resulting lean fueling). This happens so fast you'll never catch it on the OTC; you might see it with DirectScan. Most chip burners have a MAF lock patch that should fix it.

Good luck,

 

[STP]

maf dropout

We swapped every hard part imaginable on this car. Kendall, when you experienced maf dropout did you get any knock when it leaned out? I have no experience with maf dropout

Maytag

 

[Mile Hi GN]

Re: maf dropout

Originally posted by STP
Kendall, when you experienced maf dropout did you get any knock when it leaned out? I have no experience with maf dropout
Maytag

We saw MAF drop-out on one of our cars in BG.

No knock would register on DS, but the car would "pop".

MAF lock solved it.

 

[bob547]

Hi, I would try a colder plug(Autolite#23) if you haven't already, and also I would try a different chip, try using a street chip and adjust your boost to 15 p.s.i and then start from there.

 

[Dwayne]

This is the 3rd chip we have tried and we still get the same results.........Called Red A. and his chip has the maf lockout..........I also took the plug gap from 32 to 30 thou.

Keep the ideas coming fellas.....we are bound to hit on something sooner or later....Thanks; Dwayne Thompson

 

[Sleeper]

I going crazy trying to track down this problem that we share Dwayne. I'm going to go over the electrical connections again and am going to hook up a hood mounted FP gauge to see if the pump is spazzing out or not.
Mine only does this in 1st gear or when you first punch it, so I am also thinking that it may be some sort of short. I don't get any voltage spikes on Directscan but it may be to small and quick to register.
Just to throw this at you, how are your motor mounts and how tight is your motor tied down? Do you have much play?

I have a feeling this is going to be one of those simple staring us in the face fixes.

Paul

 

[Dwayne]

My dad and a friend are doing a continuity test on all the wires that lead from a sensor that feeds the ecm........I've also been told that the crank sensor might be bad..........Sleeper, I'll keep you informed.

 

[Lee Thompson]

Found it

Since my last post, the car actually quit running (DEAD) no spark.
I am weak when it comes to the electronics on these cars.
A good friend has been helping me trouble shoot this problem.
Going by the Buick manual, everything checked out good, correct voltage, grounds good, but could not get any spark.
We spent a part of 2 days chasing this.
Finally just started wiggleing wires while cranking the motor.
When we got to the crank sensor, IT FIRED
What it weird is the signal wire at the coil pack showed the correct voltage (6-9), when we tested the crank sensor, it actually should have started.
Tomorrow I will run new wires from the crank sensor to the bottom of the coil pack.
I am sure this will solve all our weird electrical glitches.


The moral of this story is
If at first you don/t succeed, keep on sucking till you do succeed

 

[Dwayne]

Crank Sensor wiring was the problem................I now have the correct 02 #'s at WOT.............I now have the FP set at 50 lbs with the 009's- car is still a little too rich ( and that's at 20 psi.)
but the SumBitch isn't poppin and cuttin out...........I have to thank : my dad (Lee Thompson),Dr. Jerry Pickel, John Spears of Speartech Fuel Injection Sytems , Mark "the intercooler god" Jackson, and Scott "Maytag" Porter.......and everybody that replied to this post..............It's a Beautiful thing when great minds come together and provide help when you need it most....even the ugly ones.

Thanks; Dwayne Thompson

ps.....Sleeper....checked that crank sensor yet?

 

[Sleeper]

Congrats on your find.
I replaced the sensor about two years ago but I am still going to have a look. I have run into some other distractions so I haven't had a great amount of time to trouble shoot. Hopefully over the weekend.

Paul