URG8RB8

If a throttle position switch thought to be factory original, (22 years old 121,000 miles), passes all tests from Clarke's Garage test procedure, could it still be bad or intermittent? The switch looks good and appears to function properly, but I have an intermittent problem with an unstable idle and surging at times with mid to wide open throttle. I am wondering if this is the switch or something related to my M-tune. At nearly $100.00, I really don't want to replace it just for the sake of replacing it.

zerMATT951

Check to make sure that both of the sensors in your M-Tune MAF pipe are nice and tight. I just swapped out my pipe last weekend and both sensors weren't much more than finger-tight when I removed them. I also had a very unstable idle, and now it's much better. Not sure if it was those sensors, or of it was something else that I disconnected/reconnected, but it's now acting normal.

Does your Tial BOV vent to atmosphere? I suspect my recirc valve is causing occasional surges at part throttle. If I accelerate slowly in 5th gear with 2-4 psi of boost then jump off the gas, it will occasionally buck with an acceleration lurch. I have a Forge style recirc valve and I've tried all 3 springs, and it still occasionally does it.

URG8RB8

I have the same issue in 4-5 gear and also have the Forge recirc valve with yellow spring installed. (The Tial is on my FL car, and that is a dissaster right now.) I will check both sensors in the M-tune MAF pipe. I know that Josh is working on a new idle code. I need to contact him to see if it is available, but not sure if that has anything to do with my issue. Are you running E-85? All my issues started after switching to E-85. I also have an issue with hard to start when dead cold in the morning after sitting all night. I have to turn it over a minimum of three times 5 secs each. When warm no issue. Again, no issue like this prior to E-85. However, all my fun started after switching to E-85 also...

zerMATT951

I have a new chip waiting to be installed that is a new idle code, but I've got to work most of the weeken so I dont know of I'll get it installed.

I have had the same hard start when cold problem... crank several times, then it's chug-chug-chug-stall. Tap the starter again and it fires off immediately and acts fine.

Yes, running E-85, and it's only been cold a few mornings so far (40-50 stuff). I haven't run gas since highs were averaging above 90 a few weeks ago.

URG8RB8

That is a little discouraging. I have the same exact issue. My temps are the same here in Milpitas, CA. I am not sure where Cowtown is. I just got back upstairs from the garage. I remeasured values all the way back to KLR and DME. They are perfect on both with 560 ohms at closed throttle to 3800 ohms at WOT. I don't think my TPS has any issues. It might be old, but functioning perfectly. My temp sensor was loose as you suggested. I tightened that, but not sure if that will help my issues. I also have a issue in the morning when trying to go WOT. It happens every time, every morning. I have a nice on ramp around 1 mile from my house. Every morning, I get on it hitting this ramp and temperature gauge is still reading full cold. When I hit around 3-3.5K in third gear, it is like I hit a rev limiter or something. Bad break up and scares the hell out of me. Let the car warm up and issue goes away. My idle issue is bad both warm and cold though. Idle hunts all over the place from 1000 to 1400 usually, but sometimes dips below and looks like it is going to stall. I might have to switch back to gas for a while and see what happens. I had none of these issues for three weeks on gas.

Rogue_Ant

E85 is a cold fuel - as such, when it is cold out, until the engine warms up it will be a bit sluggish. This is pretty normal.

URG8RB8, the cut-out your hitting is a protection built-in when the DME doesn't believe the MAP sensor - I have a fix for you, send me an email or give me a call.

zerMATT951

Mine did the exact same thing the other day. I got the car started, let it warm up a bit, then drove away. I tried to accelerate onto the freeway, and the engine cut - hard... I thought something broke. I lifted and tried again, same thing. Vacuum wouldn't pass the transition to pressure, I thought the waste gate was stuck open and maybe the DME was still sending fuel causing the motor to flood. It did that several more times until the car warmed up more, then I was finally able to build boost.

Joshua, is that fix in the new chip that you sent me?

Clown

Hate to jump in this boat but I am experiencing similar idle problems and engine cutting out as well.

I am running C-Tune which Josh tested extensively on his personal vehicle.

Just yesterday I was driving down the road after cold start, maybe 5 miles away from home. Punched the gas and no power punched let off and punched it again nothing. Let off and baby it and it was fine. Parked the car did some fishing and then left 2 hrs later car ran great. No more cutting out even when in boost. It was about 45 Degrees outside.

Replaced my TPS a few weeks ago but no change.

Also the car useually idles around 1100 RPM and idles pretty good most of the time but about 10 percent of the time will occasionally dip and want to stall even after warm.

I also have a hard start issue after I drive the car around and warm it up then park for 10 minutes to run into store. Come back out to the car and start it up, RPM's drop and car stalls. I realy have to give it some gas to prevent it from stalling immediately. After I get on the road it is fine again. Josh explained that this is caused by the hot engine bay air affecting the MAF sensor temps which makes sense. I think this is something he may be able to tune out or maybe I need a LR MAF trap.

With that said the C-Tune has worked great thus far and Josh has gone above and beyond to help me with any problems. The above problems may or may not be a result of the C-Tune setup. I also changes several other items at the same time I installed the C-Tune.

s14kev

My M-tune setup is doing the same. Problem seems worse when when the engine is warming up. Consistently I will have a hard stumble/hesitation it seems during the transition from vacuum to boost. It is most apparent in second gear at roughtly 40-70% throttle while accellerating (usually the transition from vacuum to boost is ~2800rpm which is when the cut is). Seems to be much less frequent once the engine is warmed up.

At this stage almost everything is new (T4R BB turbo, 72lb injectors, ignition system, pretty much complete engine bay/wiring overhaul). I am just finishing putting in new sensors (speed/ref, DME temp, O2 sensor) and new idle control valve. After trawling the forums I thought maybe my new injectors were faulty from this post:

https://rennlist.com/forums/944-turb...ain-loads.html

But if more people are having the same problem I would guess the injectors are probably fine given they are new from racetronix.

Idle has also been a little funky. What does improve it is if the TPS is set so that the microswitch never activates when the throttle is shut. Ie. the DME never goes to idle map.

Except for the stumble issue, M-tune has been great. Josh has been great so far with updates, availability and in seeking a fix. Hopefully this can be sorted. Unfortunately, because of this problem the car is not track ready since the hard stumble is somewhat dangerous. Looking forward to a fix soon.

refresh951

Interesting...I am running M Tune with E85 and 80# injectors (from Rogue) and have not seen any of this except a slight idle bump when coming off throttle which is not an issue.

URG8RB8

[QUOTE=Rogue_Ant;8982788]E85 is a cold fuel - as such, when it is cold out, until the engine warms up it will be a bit sluggish. This is pretty normal.
QUOTE]

Josh:

I can understand this, but curious as to what constitutes "cold". My car is in a heated garage, so upon starting in the morning, it is at least 70 degrees. Outside temperature this week was in mid 50's in the morning. What would happen say in Michigan outside below freezing? Maybe I need to due some more research on E-85.

I have triple checked every thing under the hood all the way back to the DME/KLR this morning and I am convinced that everything is working properly mechanically. I will await your suggestions. Florida vs Georgia game on in 2.5 hours, so it will all be a blurr soon. Go Gators! We are going to need alot of help today.

refresh951

Go Dawgs!

URG8RB8

[QUOTE=supes6;8983060]This is what I am seeing as well, happens in pretty much every gear. When I let off the throttle the rpms will drop, jump up to 1300, and then settle down again... which causes the lurch when crusing along and letting off the throttle. My throttle response was great with my original M-tune, when I upgraded to the #80 injectors and latest software update I started having problems.
QUOTE]

I have this issue as well. Since my signature is a little missleading as it shows my FL car and I am talking about my CA car, here is my setup:

1989 Turbo S Galcier Blue pristine condition, M-tune complete package with injectors, running E-85, Fabspeed 3" turbo back no cat, Huntley Racing Stage II BB turbo, Pauer Tuning Tial WG, MBC, BBS 18" 996 CS4 true hollow spoke wheels, 295/30's in the rear, Not much, but very effective!

URG8RB8

Noticed your location, not fair your car is running good! This might be your year, but I think with Brantley back we have a shot. Just a good game would be a breath of fresh air for us. Rebuilding Sucks!

Go Gators!

Bri Bro

E85 will have cold start issues. Just look at the Flash point of Ethanol vs gas and you can see why they sell a blend of 85/15%. Diesel fuel has a higher flash point then Ethanol so they need glow plugs to get the heat in the cylinders. I think E85 will have some issues and people will get us to them. Gas is pretty amazing stuff, great energy vs weight and a very low flash point.