moalaska

OK this was originally posted as rpm specific fuel cut. When my car would get to around 2500 to 3000rpm in second or 3rd gear very light throttle, it would feel like it hits a total flat spot like the injectors are cutting and wideband would go up to like 16's. If I tried to give it throttle it would buck and pop.

I Just got done rebuilding my entire wire harness, with new connectors. new spark wires. other work that I have done from most recent

Spark wires
Wire harness refurbish with new wires and connectors
new knock sensor
exhaust gaskets, welded exhaust manifolds
upgraded fuel pump
vacuum lines all new
venture delete, cycling valve delete
spark plugs, cap, rotor
timing belt, balance belt, rollers
resoldered dme
new temp sensor
new ref and speed sensors
reseal throttle body
jbweld idle valve
fuel filter, tank screener, fuel check valve
intake gaskets
adjustable bypass valve
tial 38
adj fuel pressure reg
electronic boost controller
solid state dme relay
vitesse maf, 55#injectors

There are probably some things I forgot

Diagnostice Ive done
check fuel pressure, I can crank it up to 60psi I don't think its a pressure issue

check voltage at injector harness, 12v both sides, when unplug all connectors one side goes to 10.5v

set idle per procedure

check continuity in injector harness, ohms for temp circuit, ohms for tps pot, function of tps close switch

check spark, there is spark swap out msd blaster for bosch coil, no difference

noid light injectors, all have pulse

check ref and speed sensor circuit ohms

ohms on injectors, all the same

check ground continuity at dme harness, power at harness, ok

check continuity from 14pin connector to injector clips, ok

check all vacuum clamps twice, 3 times

OK one thing, my idle valve sounds like its gushing air through it. and I can hear it pulsating, I don't think that circuit is operating correctly

right now as it is, my car is wanting to idle at a 16 something afr
when I jumper idle circuit pins as to set idle, idle will drop down to about 700ish and my afrs will settle at stoich, I can adjust the screw, but as soon as I pull the jumper out idle jumps backup to like 1000 or 1100 and afrs go back to 15, 16. it obviously runs like its lean, when I squeeze the idle hose it instantly sounds like its running better and goes stoich and idle goes back down to 800ish.

So, with the state of my old harness, could my idle valve connector have shorted something out, they were all bad

Or could it possible be a narrowband o2 sensor issue?

Or bad DME, the dme grounds were not even connected to the bellhousing for the longest time, who knows how long the PO drove it like this.

Bad idle circuit, bad o2, or bad DME, opinions?

numbskull

When you say idle valve, do you mean the beer can under the intake in attached? Did you warm up the vehicle, shut it off and unplug the intake and ic hoses, cap them off? My understanding this is used when cold, and closes when warm. If it's open when warm I do not exactly know what happens to idle or driving, but in warm weather I ran the vehicle without it when mine stopped working without issues.

moalaska

yes I mean the beer can under the intake manifold, the one that's called the idle air control valve. I haven't tried isolating disabling it yet to see how that affects my symptoms, its definitely letting air through when the car is warmed up.

moalaska

if its open when warmed up it will act like a giant vacuum leak, allowing air from before the throttle body to enter the intake manifold.

Tom M'Guinn

Do you have the factory AFM? If so, I'd probably check it per clarks. However, running the DME and KLR without a good ground can damage them! Too much current will run through delicate parts of the circuit looking for a way back to ground.

https://rennlist.com/forums/944-turb...und-strap.html

moalaska

I agree that dme or klr could be damaged from the lack of ground as condition of harness. Running maf. Would shorted idle valve connector fry dme as well? I resoldered most of the dme again last night but some component could be kaput. Going to pick up a ball valve and put it in line with the idle valve, i will isolate that and see how it runs. Will take video.

Tom M'Guinn

You can just pull the electrical connector off the ISV and plug off the hose ends at the I/C pipe and intake. If it still runs lean when driving, that's not your problem. In theory, the air circulating though the ISV is already metered by the MAF anyway, so opening and closing it shouldn't lean out the mixture the way you are experiencing. But if it's leaking, that's a different issue.

As for a shorted ISV frying the DME, I suppose anything is possible, but it seems much more likely that it would simply burn out the ISV driver in the DME, not other circuits in there too. Here's a link showing how others have repaired a bad ISV driver in the DME.

https://rennlist.com/forums/944-turb...n-the-dme.html

Absent a big leak, I'd say the odds of that being your problem are low. An un-grounded DME, however, will overtax multiple circuits in the DME, not the least of which is the injector driver. Which MAF do you have? Some MAF software changes injection modes around 3k, which might further point in the direction of the injection driver. Don't suppose you have a spare DME you could try...?

Did you install new spark plug wires -- brand new without electrical tape, etc.?

The KLR suffers from the same solder issues as the DME, so if you only did the DME, you're only half done on that front.

moalaska

Vitesse maf. Yes new wires see other post, although it looks like one is arcing in the video. Completely rebuilt the wire harness with new grounds. The damage could already be done to dme though. Wouldn't an injector driver issue affect all at once, has anyone experienced injector drivers sporadically misfiring the injectors? I was thinking same thing about the idle air still being metered, but would it not match up with the throttle position pot causing weird things, for example at throttle position 4 it should be getting 4 amount of air so it gives engine 4 amount of fuel, but instead its getting 8. I know that's what the maf is supposed to do and I don't know the function of the tps pot for air and fuel metering. And I imagine it would cause it to run lean at idle with idle switch depressed.
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moalaska

I think i partially found my answer. Also a thought, how would this influx of air affect manifold vacuum pertaining to the fpr? And also when transition to boost, the pressurized boost air would be fighting against what is basically a giant metered vacuum leak at this point right? Position of pot enriches mixture by increasing pulse time and number of pulses. So even though its metered its not matching up with tps, sound right?

Tom M'Guinn

An arcing wire could cause your issues. Vitesse software switches on the fly between batch (2 pulses per cycle) and semi-batch (1 pulse per cycle) so when it switches over it may aggravate a driver issue. It does seem more likely that the driver would just burn out altogether, rather than partly work, but electronics can be funny. I'm not following you TPS 4/4/8 example. The POT in the TPS is used by the KLR to detect when to trigger the WOT signal. When the WOT signal is tripped, the DME switches to WOT maps. During normal driving, the primary input for fueling is the voltage from the MAF, not the TPS POT. What kind of adjustable fuel pressure regulator are you running? Some of those have caused issues too...

Edit: not sure what you mean by a "metered vacuum leak." If the air is metered, it's not a vacuum leak per se, just less vacuum because more air is getting past the throttle plate. Think of the ISV as just a little bypass around the throttle plate. It's the same as cracking the throttle a little bit when conditions call for a stronger idle (like when it's cold, or the AC is on, etc.). In fact, modern cars with electronic throttles no longer need an idle stabilization valve -- the computer simply opens the throttle a bit as needed to regulate the idle speed.

moalaska

Looks like this one not sure of brand friend gave it to me. So the pot doesnt signal any enrichment like other motronic systems, only signal for full throttle? Im just wondering why didn't they just use a contact switch for full throttle? That was my theory, if the tps signaled enrichment too that its signal would be lower then normal for the amount of air entering engine causing a lean condition.

moalaska

Yes but the throttle body is pressurized when under boost, but the hose that comes from idle valve goes from manifold to pre turbo, which would allow boost air to go backwards to the maf pipe correct? Metered boost leak that's what i was getting at. Might cause air turbulence in maf pipe too right?

moalaska

Nevermind had hoses mixed up in head

moalaska

maybe idle valve is leaking

Auto_Werks 3.6

I doubt this is really the cause of your trouble, but you mentioned a new knock sensor... I was reading through some older posts trouble shooting some similar issues I was having. One thread in particular detailed someone (casturbo) bought multiple brand new knock sensors and they were defective. Both new ones measured the wrong resistance, and he ended up digging up a used one that fixed his problems. I understand they are also very sensitive to proper installation torque.

It would be helpful if you could get a hold of a Rogue DME, so you could turn the KLR "off" you could eliminate any of its functions as part of your trouble.