Engine flatlines/jumps

[Aeroking]

Re: Engine flatlines/jumps

Maby your finger has vaccume then.. Humm...

Did you notice any difference with the timing map or was it about the same feeling?

Was just the springs in the WG holding 11psi?

How was the drive the other night?\
~Scott

yes i did notice a difference in the timing MAP. first off, usually when i lift off the gas on decel, then rpms drop low, the engine goes lean, and it surges. Didnt do that this time. Also it slid nicely right into boost. Only problem was it knocked a couple times under low boost, i would assume because of the high timing. My timing map pulls harder in high boost on the top end. but yours makes it easier to get the inital spoolup.

As for the spring, i run a 5psi spring all the time. Since the solenoid valve isnt a bleeder valve, i can pretty much run any boost level with a low spring.

 

[UR50SLO]

Re: Engine flatlines/jumps

Did it still do the cut off/weird thing in 3d then?????

The top of that timing map is much lower than yours (WOT)area. It's very safe.

That engine it was setup on was totally stock except for code 59/FMIC/3bar. The customer

that drives it needs it setup for daily driving and fool proof.

You can bring the top of that timing map up or bring your boost up.

Note where it's knocking in a data log at lower boost for me if you could.

Sounds like progress

 

[Aeroking]

Re: Engine flatlines/jumps

just wnet over the whole topend looking for vacuum leaks (boost leaks at speed) and couldnt find anything. The engine idles fine at 800rpm and 16inHG vacuum, and the IAC position holds at 42~43.

tomorrow i'll test the fuel system.

 

[Aeroking]

Re: Engine flatlines/jumps

back again for a new year.

took the truck out yesterday, same problem with a little different results.

truck winds up to 5200, then backfires and bucks under WOT. Still sounds like its hitting a rev limiter. My 6AL box has a 6000 chip in it.

Running 20psi, no meth. high 11 AFRs. Datalogs show no problems, no knock, or boost spikes/dips, just a hiccup in RPMs.

I'll try to get another video up.

 

[dgoodhue]

Re: Engine flatlines/jumps

back again for a new year.

took the truck out yesterday, same problem with a little different results.

truck winds up to 5200, then backfires and bucks under WOT. Still sounds like its hitting a rev limiter. My 6AL box has a 6000 chip in it.

Running 20psi, no meth. high 11 AFRs. Datalogs show no problems, no knock, or boost spikes/dips, just a hiccup in RPMs.

I'll try to get another video up.

I would try temporarily disconnecting the MSD to just to eliminate that variable. Also do you have the MSD set for 6 cylinders?

 

[Aeroking]

Re: Engine flatlines/jumps

yeah, the MSD is set for 6 cylinders.

i was running a hell of alot of meth. i actually thought i was running not enough, and turned it up even more yesterday. Sucked down almost the whole meth tank in two 0-100mph runs.

but even so, with the meth off, it still stumbles. Plugs are fresh less than 100 miles on them, they're gapped to .025. It has plenty of timing, mid-20s with meth, and 17 without.

I'll try disconnecting the MSD box today, and see if it works out.

 

[Aeroking]

Re: Engine flatlines/jumps

edit:

can someone snap a pic of their Alky control box, i wanna see where the pots are set at. cause i tweaked mine, and evidently you shouldnt.

 

[bezerk]

Re: Engine flatlines/jumps

have you tried to run it without alky in the tank? maybe it sux alky into the engine? normally there is a valve halfway...maybe it's a bad valve?

 

[Aeroking]

Re: Engine flatlines/jumps

just took a couple (auto knowledgable) friends for rides. and they both said its definitely a backfire under WOT at 4900~5000rpms. Followed by a drop down to 4300~4500 then back up to backfire again. All with WOT. Cant tell if its backfiring out the intake, or exhaust.

Alky is off, and tank is empty. The scanner shows nothing.

It doesnt seem to happen when i'm 3/4 pedal, so i tried moving the TV 1 click each way. I disconnected the 6AL box, and still no difference. I pulled/added timing, ran it rich, and lean.

Also it keeps blowing my PVC hose off of the throttle body.

 

[turboj91]

Re: Engine flatlines/jumps

Since the pcv blows off can we assume it is a backfire to the intake rather than the exhaust?

You parked it for the winter and didn't touch it? Took it out and the same problem exists but with the backfire?

What type of fuel do you run and did you put any stabilizer in for the winter?

Also, I listened to your video with earphones. Do I hear a blowoff valve or system reversion. Your boost seems to stay steady but when the rpms drop, I hear something. I don't think it is background noise.

Lastly, IIUC, before winter you could get past the trouble spot and make it to 6K rpms and now you can't get past 5K due to the backfire?

 

[WyoSyclone]

Re: Engine flatlines/jumps

Can you do a DM run with it? If you've got a backfire through the intake I'd almost think it has to be timing related. Did you do anything with plugs, plug wires, distributor/cap/rotor, etc.??

 

[Aeroking]

Re: Engine flatlines/jumps

welp here goes.

The plugs are UR5s new within 150miles. Coil is two year old MSD Blaster, Wires are 1 year old taylor 8mm spiro. MSD box is a 6AL (didnt make a difference whether it was plugged in or not). Ignition module is good as far as i know (i've been through a couple bad "NEW" modules) Cap/rotor are the MSD about 1 year old. Plugs look fine, even pulled it over on the highway and checked #1. I run the DEI boots.

My fuel system is a pair of walbros through a AN 10micron filter. into the stock rail. With a racetronix harness.

I did a couple searches and found some things to check. I'm gonna replace the element in the fuel filter. Ohm my wires. Ohm the coil. Swap out the ignition module. Check my dizzy is on 0. Do a compression test. Hookup a FP gauge to see what it is in boost.

to the earlier response. Yes last year it would spit and sputter at 4800 and if i stayed in it it would jump to about 5600 and shift. Now it climbs to 4800 and backfires hard enough to blow the IC, and PCV hoses off. Needless to say i'd rather not keep my foot in it to see if it goes away at a higher rpm. The scanner again, shows nothing. Timing holds strong, and AFR is steady, all it shows is the erratic RPMs.

i parked the truck with about 1/4 tank, and ran/refilled it on a regular basis. And since being out this summer i've filled the tank twice.

 

[Aeroking]

Re: Engine flatlines/jumps

on a side note. I blow a hell of alot of oil out of my breathers. I have the correct ACDelco PCV valves on the pass side. But both sides spit out oil onto the valve covers. The driver side v-cover has an internal baffle on the cover, and the vent i use has a baffle and filter, but it still spits out oil residue. And on the PCVs, it spits oil out of the front one (going to the cai).

 

[WyoSyclone]

Re: Engine flatlines/jumps

on a side note. I blow a hell of alot of oil out of my breathers. I have the correct ACDelco PCV valves on the pass side. But both sides spit out oil onto the valve covers. The driver side v-cover has an internal baffle on the cover, and the vent i use has a baffle and filter, but it still spits out oil residue. And on the PCVs, it spits oil out of the front one (going to the cai).

The backfires have probably blown the intake gasket

 

[Aeroking]

Re: Engine flatlines/jumps

The backfires have probably blown the intake gasket

this is an old problem. The breathers are packed with oil. And the intake seams are completely dry.

so perhaps too much crankcase pressure.

 

[WyoSyclone]

Re: Engine flatlines/jumps

this is an old problem. The breathers are packed with oil. And the intake seams are completely dry.

so perhaps too much crankcase pressure.

could have blown between an intake runner and the lifter valley.

 

[Aeroking]

Re: Engine flatlines/jumps

could have blown between an intake runner and the lifter valley.

ahh i see, causing the intake to pressurize the crankcase.

would that cause the engine to stop rotating at higher RPMs? since there is equal pressure on both sides of the pistons.


adding to the info. i've always had 15in vacuum at idle. i always thought it was due to the cam (custom), perhaps i broke the intake gasket when i put it the motor together. and its sucking air from the lifter valley, causing low vacuum.

 

[WyoSyclone]

Re: Engine flatlines/jumps

would that cause the engine to stop rotating at higher RPMs? since there is equal pressure on both sides of the pistons.


adding to the info. i've always had 15in vacuum at idle. i always thought it was due to the cam (custom), perhaps i broke the intake gasket when i put it the motor together. and its sucking air from the lifter valley, causing low vacuum.

Nah, it couldn't do that, but it could make one cylinder run extremely lean. What do the sparkplugs look like? Those could give you a clue.

 

[dgoodhue]

Re: Engine flatlines/jumps

ahh i see, causing the intake to pressurize the crankcase.

would that cause the engine to stop rotating at higher RPMs? since there is equal pressure on both sides of the pistons.


adding to the info. i've always had 15in vacuum at idle. i always thought it was due to the cam (custom), perhaps i broke the intake gasket when i put it the motor together. and its sucking air from the lifter valley, causing low vacuum.

I had a V8 motor with improperly machine intake manifold which drew air from the lifter valley. In closed loop, my O2 sensor caused my engine to run rich and cycle back and forth from rich to richer. My Idle vacuum was 12" to 15" and moved around a bunch (should have been 20"). Now this was with closed loop operation so the computer was trying to correct the rich and lean conditions. It probably would act differently with open loop in Code$59.

 

[Aeroking]

Re: Engine flatlines/jumps

I had a V8 motor with improperly machine intake manifold which drew air from the lifter valley. In closed loop, my O2 sensor caused my engine to run rich and cycle back and forth from rich to richer. My Idle vacuum was 12" to 15" and moved around a bunch (should have been 20"). Now this was with closed loop operation so the computer was trying to correct the rich and lean conditions. It probably would act differently with open loop in Code$59.

the vacuum is solid at 15in for idle. any my wideband gauge (surprisingly without adding the capacitor) is nice and steady.