Found a ignition problem on the Dyno.....Modified stock ECU

[Lil Truck]

End play on the crank is?

Chuck,
Last fall I replaced stock HGs that were leaking coolant under boost. I did some reading about coolant damaging bearings and even though I did not have any visible coolant in the oil I decided to inspect & replace all the bearings just 1000 miles ago. The thrust on the old bearings were good, and I did cut open the filter and inspect the oil for metal flakes all looked good. Oil pressure is 22 hot.

Checked the crank sensor last night, it was tight and clean.

 

[Lil Truck]

its worth a try.

B

Re- gaped Auto lite 23 to .025 and made a test run.... no change?

 

[Lil Truck]

I had similar issues and did a laundry list of swapping parts...It would be worse some days than others and chased it since last fall...Turned out to be a bad wire on the CCCI module that plugs into the side of the ignition module...Just something to check...

Cleaned and inspected the connectors and wiring, all looks great (almost new) at 41k miles. No improvement on test runs.

 

[Pronto]

Stock rockers-maybe some are fatigued and flexing or cracked? How's the rocker shaft, could it be flexing or cracked?

 

[Lil Truck]

The shafts are the TA Perf. HD shafts with RJC shaft clamps, rockers are 40k stock. I inspected them all for abnormal wear, everything looks fresh and new.

 

[20psiofevil]

Could check the maf with magnify glass. The wire in my old tonsil maf had a small piece of debris or fiber attached to it that was barely noticeable to the naked eye. Caused a similar issue but would run great under part throttle conditions, once wot was engaged it would buck.

 

[we4Mateo]

Could check the maf with magnify glass. The wire in my old tonsil maf had a small piece of debris or fiber attached to it that was barely noticeable to the naked eye. Caused a similar issue but would run great under part throttle conditions, once wot was engaged it would buck.

Our cars don't use the MAF at wot unless you run an extender chip and a translator.

 

[TurboBob]

Our cars don't use the MAF at wot unless you run an extender chip and a translator.

yes they do. But the OP's issue is related to the RPM / crank sensor signal.

Bob

 

[we4Mateo]

yes they do. But the OP's issue is related to the RPM / crank sensor signal.

Bob

I thought 12psi would simply max out a stock MAF and it would just read 255? TIA.

 

[TurboBob]

at 12 psi, most cars will not max the MAF out. Many chips will lock the MAF reading at WOT to 255. Usually you have to exceed
230 grams/sec or so to trigger that.

in any case, whether the MAF is locked at 255 or not, the MAF reading is used in the fueling calculations.

Bob

 

[we4Mateo]

at 12 psi, most cars will not max the MAF out. Many chips will lock the MAF reading at WOT to 255. Usually you have to exceed
230 grams/sec or so to trigger that.

in any case, whether the MAF is locked at 255 or not, the MAF reading is used in the fueling calculations.

Bob

So the maf is verifying to the ecm that you are at wot? I'm still not understanding how the reading is being used if it maxes out at 255 or if the ecm is locking it at 255 how it is providing feedback at that point of operation. I'm not trying to be a pain, but I really like to know how the stock ecm functions. It's obviously still sending a reading but how can the ecm use it if it simply locks at 255?

Thanks again for the remedial help I'm requesting and sorry to the OP.

 

[kidglok]

So the maf is verifying to the ecm that you are at wot? I'm still not understanding how the reading is being used if it maxes out at 255 or if the ecm is locking it at 255 how it is providing feedback at that point of operation. I'm not trying to be a pain, but I really like to know how the stock ecm functions. It's obviously still sending a reading but how can the ecm use it if it simply locks at 255?

Thanks again for the remedial help I'm requesting and sorry to the OP.

i think its something like this:
once the maf goes to 255 the chip switches to its WOT fueling. I believe on my TTchip the mid fuel would come in around 140g/s and the wot fueling would take over when the maf exceeded 240g/s. It does this based off the tps, if its over 3.5v it will lock the Maf to 255 so it uses the chips wot fuel calcs.

 

[TurboBob]

Eric may have rewritten that part of the stock chip code. I never did. Anyway, this needs to be its own thread if we want to continue it.

 

[tonka]

Update!

I changed out the valve springs and added some seat pressure 120 lbs, open 300 lbs. Engine runs smooth as before.
Checked out cam lobes, all checked good.
Changed out push rods as they were at .060-.070 pre-load. Now they are .030-.040
Leak down test during valve spring change showed all cylinders at 92-90 @ 100psi cold.

Power is much better, 416-410 vs 373-340 .......... The hesitation from 4500-5000 is gone, but there is a definite power stumble at 4700 and again at 5000. It is stronger at 4700 loosing 30 hp then recovering. No backfire just a short loss of power?

ECM?
Crank pickup?
Cam Sensor?

Have you pulled some plugs after a run to have a good look at them? You listed the car as having a 2-step, is it located where you can watch the LEDs to verify it isn't becoming active intermittently trying to limit rpm, either through high side setting too low or trigger input wiring problems?

 

[Lil Truck]

Have you pulled some plugs after a run to have a good look at them? You listed the car as having a 2-step, is it located where you can watch the LEDs to verify it isn't becoming active intermittently trying to limit rpm, either through high side setting too low or trigger input wiring problems?

It is hidden, so I will disconnect it just to find out. Thanks for the idea.

 

[Lil Truck]

Question,

The Dyno sheet makes it look as if the car runs rough, it runs smooth on the street. On a full throttle run 2&3 gear feels strong and smooth until you hit 4700 rpm, it feels like a miss or quick loss of traction. Then again at 5000 rpm.

Could a miss adjusted cam sensor do this?

 

[Lil Truck]

Well good news!

Just made 2 clean Dyno runs @ 28lbs to 5500 RPM, no hesitation or misses!

We did have a problem with the dyno tack pick up not wanting to register but we got it working.

The only thing I changed from my previous runs was the plug gap down to .020 and disconnected the 2 step.

I verified but never adjusted the cam sensor.

Thanks for all the help!

 

[Fast4Ward]

Voltage reading on the PL is 13.8 before boost, 13.2 during pull, then back to 13.8 after.
.

my battery voltage is always 14 plus in PL files.