Reimu

I've had a hell of a time with this car over the past few months but it's almost back to normal. Rogue has sent me 3 different replacement chips lol.

When driving around out of boost it does perfectly fine. 14.7-15.1 AFRs while cruising, no missing or hesitation or anything. However if I try getting on it the AFRs change very little once pressure goes positive. The car will stumble once it gets up to 5psi so I don't think it's a wideband sensor issue. If I slowly roll on the throttle it seems to do a bit better but it still only richens to maybe 13.5 at best, and it doesn't change all the way up to 9psi. I tried it at WOT as well and there was no difference so I don't believe it's an o2 sensor issue.

The car didn't do this a few months ago when it was running, it would fall to the low 13s pretty much immediately after leaving vacuum and continue richening all the way to 11.7

-I checked the fuel pressure on my 3 bar fpr and it was at 49psi. I replaced it just in case and there was no change.
-I also checked my fuel pump delivery rate which turned out to be higher than stock, I noticed nothing strange.
-I have no leaks behind the maf sensor and plugged everything off for testing just in case
-I get 20hg of vacuum at warm idle and cannot find any leaks, the vacuum lines leading to the fpr and MAP sensor are good
-I tested MAP sensor signal voltage at the DME and it was correct

What next?

refresh951

Have you looked at the plugs?

Tom M'Guinn

+1 Very often, cars that stumble on boost have a weak ignition. Either the plugs are poorly gapped or old, or the wires are old/arcing, or the cap and rotor are arcing. A car generally won't stumble because it's running 13.5:1 (absent horrendous pinging...) but your AFR readings may be inaccurate if the gas is not burning as/when it should. If the ignition all checks out, however, you might test the WOT signal from the KLR, just to make sure the TPS is sending a good signal to the KLR and that the KLR is triggering the (richer) WOT maps...

Reimu

Plugs are a year old, pulled and cleaned them anyway
Checked the ignition wires, all are within spec
Pulled the distributor cap which is also new, cleaned it up a little but it wasn't too bad. Rotor is new/good as well
Ignition coil is within spec

It never richens even at 1 or 2 psi, I thought ignition troubles usually come about at higher boost levels
Injectors are all getting the right voltages

Not really sure what else to check

Tom M'Guinn

Ignition problems tend to surface as cylinder pressures increase, but if they are weak enough they can act up at load levels well below boosting...

What spec are you checking for the wires? Ohms alone doesn't rule out arcing. How long have they been in there?

Have you checked to ensure the KLR is triggering the full throttle signal? Sure your wideband is working right?
Have you done a compression or leak down test?
What injectors do you have? Crazy Eddie had a brand new set of injectors that even passed all tests at Witchhunter, yet would act up under boost.
Do you have a way to log your engine signals and/or fuel pressure?

Spidey944

Ignition coils may Ohm out ok, but be producing a weak spark still. Especially when hot.

Reimu

-Replaced ignition coil with a working spare
-Swapped with working DME
-Drove around and watched voltage readings from MAF and MAP sensors
-Watched in the dark for anything arcing
-Pulled injector and spark lines to check for anything suspicious
Nothing

Unplugging the o2 sensor didn't help the boost leaning issue but it did drop the non boost driving down to 12.5
I don't think it's a wideband issue because it seems to act as it always has, showing the moment I let off the throttle to cut fuel and it shows the usual variation around 14.7 when driving. There is also the stumble that can be felt once you get up into boost.

The car went into boost fine last year before having an electrical problem. Now that it's running again this lean issue came out of nowhere. My speed sensor connector is all but destroyed, is it possible that the issue could be here? I don't have any tach problems and the car starts/runs fine otherwise. The sensors also get good signal to the DME plug while off.

Also a new symptom has crept up where when I slow down to a stop my afr will drop to 16 or 17 but will go away if I give the throttle a small jab.

Tom M'Guinn

If you car is stumbling under load, but does better when you roll on the rpms without heavy loads, that is a classic symptom of a weak ignition. AFR's are not a good indicator of much when the motor is stumbling and the air-fuel mixture isn't burning consistently as intended. If it were my car, I'd change the cap, rotor, plugs and wires (or try them on another car) before chasing less likely causes -- unless I had a much better reason to believe they were ok. The tests and cleaning you've done don't confirm they are ok.

Arominus

Stock coil? might be worth trying an MSD blaster or having rogue burn a chip with the settings for that mega hot HVC-2 Coil.

Reimu

New plugs, new plug wires
No change
I have to admit I like the stock style wires more than magnecore ones, nice satisfying "snap" when you put them in.

I get something like 12.6 volts at the coil power wire as well

I had a MSD blaster on there and switched it out for a stock unit
I don't need anything bigger as there are people making more power than I do with stock coils

Tripl7

How did the plugs look before you cleaned them? What about the injectors? You should be able to hook up a meter to the O2 sensor to get an idea of the voltage coming off of it to check against the WB. I have a feeling its fuel related, I agree with Tom about the TPS.

Reimu

All of them looked the same, smudged up with some carbon to dark gray but otherwise fine. The TPS tested fine, I replaced it with a spare anyway and there was no change.
Also checked the DME grounds just to be sure

It's like there's a delay for the AFR to change. If I go into boost and hold it there it will be at 14.7 for a few seconds before going down to 13.5. The car will stumble a little if I boost too high.
Probably will end up replacing the wideband sensor anyway.

boost feen

Have you checked into the clear hard original hose going into the KLR from intake? Maybe the KLR is not gettting boost signal? Its also possible that your KLR computer is bad as it sure sounds like a fuel metering related issue being so lean like that?

Also you may have good pressure at idle or jumping pump but make sure the fuel filter is new and the pre screen threaded into tank is clean as these clog easy. Check your fuel pump out too?

Fuel injector wiring harness goes bad right were they crimp over you might pull boots back where they plug into injectors to see if the wires are shorting out?

good luck

Reimu

My KLR has the clear boost line removed, and always has
Never been a problem before
I pulled and resoldered the KLR just in case but there was no change

I replaced my fuel filter last year. I checked the fuel pump when I first started dealing with this issue and it flowed around 40oz in 30 seconds. It's more than the spec listed on clarksgarage so I don't know what's up with that.
I get 12.2 volts on each injector post

boost feen

As always its almost impossible to bench test this stuff in driveway as it always will test OK but when you get out on the open road and load everything thats when the circuits start dropping amps and volts go down because of old wiring, corroded, brittle broken connector ends etc....

Maybe you should try hooking your KLR computer back up to intake manifold so that it can adjust accordingly as it does still have some function NO?