mahoney944

Ok today I did a cold start test on the original LR mtune chip from Lindsey - post update chip. It was about 45°F outside....What I discovered was my AOS seals were bad, leaking quite a bit and the small o-rings inside my throttle body turned to dust as I tried to remove them. So I replaced everything. New AOS and throttle body full reseal kit (see quoted post for what all go changed) due to what I found I thought to myself that had to be why....sadly no, I reset my idle again with everything being changed and let it sit for two days. This morning around 11am I started the car on a cold start with the logger going and the car still experienced the slow drop to idle when reved from 2000 rpm to idle. Once warm it still had the "hickup" in rpms with a few bounces to get to a steady idle. The hickup happens at 1200 to 1400 rpm then bounces its way down to a normal steady idle. Tomorrow I will try chip 1 that josh sent me with further reduced isv correction. And I'll report on that.

blade7

Good luck.

Mike Lindsey

Check your small vacuum fittings, seals and if the bolts are tight at the intake between runners 3 and 4. Check to make sure nothing T'd into the MAP sensor has a leak. It should be o a hose by itself ideally. We sorted one with a loose fitting. Did the same thing.

mahoney944

I'm pretty sure I don't have any leaks at those points. My car has the charcoal evap system completely removed and a venturri delete naturally. So my vac system is very basic, silicon hose with stainless vac "T"s. I have the fuel damper, bov, line to heater core that has the blue/ black valve with a new vac resivor T'ed after the valve, map sensor, and fpr on a small loop to the manifold banjo bolt where the KLR hookup is. I get good vac pressure and all the seals are new on the manifold, torque wrenched the manifold bolts to spec plus a little extra baby turn.

V2Rocket

mahoney944

The only point in the vac system I would question is the heater core itself. I never replaced any of the vac lines from inside the car. I guess I can try bypassing the heater core vac line to roll all of that out.

mahoney944

Ok, today 47 degrees. Chip # 1 installed. (Reduced isv correction) still have slow idle drop on cold start up, same hickup/ bounce to idle. Seemingly rich all around.

Chip #2
Car already warm, so couldnt tell if slow idle drop occured. As it only happens on cold start up. On hard idle drop it dips/ bounces to low rpms, oil light flickers because the rpms get so low and it raises to normal idle.

My conclusions.... It seems the car on all chips runs pretty rich at fqs position 0. Pulling fuel with the fqs seems to improve things but i dont think pulling -11% fuel is a good fix, as it doesnt cure the issue. Reducing the isv correction does not improve the idle issues. Need more ideas....

Some random things.... With my stock setup when I bypassed the isv using the jumper in the test port my afr at idle would be close to 14.7 dipping slightly high or low. When I do it with this setup I get numbers near 11.7. This makes me think that the tune before isv correction is very rich. Possibly the car is too rich and the isv is correcting a good bit to level out the idle afr. This would also explain why cold starts have the slow dropping idle because cold starts are rich to begin with...

I also capped off the vac line that my heater core uses to remove all my heater core vac lines under the dash from the possibility of effecting the map sensor. This did not change anything so I presume my heater core vac lines are fine. I put this back to normal after testing.

Rogue_Ant

Getting the AFRs in-range should be the focus... I would drop fuel pressure back to the 2.5bar unit for the moment.

Also, have you gotten a log yet?

mahoney944

I don't have one, unless I have one in a box somewhere.. Been using a 3 bar for many years. Any other ways to achieve this? Don't really want to buy parts for testing..... I guess I could get a adjustable FPR as a last resort. I'd like to install a fuel gauge to the stock rail, not sure the easiest way to do it though.

blade7

This first, or a new 3 bar FPR, they can supply higher than 3 bar I've read.

markl951

I'm actually in the process of installing a fuel pressure sender on the end of my fuel rail so I can log fuel pressure together with everything else. I have my own custom data logger so to speak. Not sure what I should expect to see. Joshua, have you done this before? Have any plots?

Rogue_Ant

Fuel pressure is pretty 'bouncy' on these cars... If you want to datalog it, you will probably need some filtering to get reasonably non-fuzzy reading. Just a result of batch-fire injection.

bw993

I had similar problems with AFRs, when I first got my M-Tune. The problem turned out to be the Bosch 3Bar FPR. My experience with multiple Bosch 3bar FPRs is that they regulate on the high side of 3 bar by about 6-7%. After sampling 6 different 3 bar FPRs, I have found that they typically regulate at ~45-47 PSI. To get the AFRs correct with my M-Tune, I had to use an adjustable FPR with a pressure gauge on the fuel rail. Once I was able to dial in my fuel pressure to 43-43.5 PSI, my AFRs were 14.6-14.8 at idle and 11.9-12.0 at WOT, with solid idle at 850 rpm.

Just my experience.

mahoney944

I think this might be my next step. Which version of m-tune are you using?

markl951

When I installed my M-Tune kit 2 years ago the fuel pressure was 3.2 bar with engine not running, DME relay jumped, no vacuum. Using a hand vacuum pump on the fpr, pressure drops to 2.4 bar at 27 inHg. I probably need to re-check this as part of my problem diagnosis though.

My car has always run great since installing M-Tune. Only thing I had to do was adjust the idle speed. Lately, I'm having issues with the engine just shutting off. I've been through all things electrical and have zero vacuum leaks. It seems to happen most often in a situation like this... I'm driving down the freeway & blast down the off ramp at WOT. I roll to a stop at the light. The RPMs come down & it idles for a few seconds and then just shuts off. It has never not re-started but it's getting annoying. I plan to do more testing & data collecting as soon as the weather gets better.

I've noticed my fuel pressure gauge jumps around a lot with the engine running like you said Joshua but I need to try something.