Mach

Ok I am having a problem with my cars start up and idle. The car will turn over just fine but then the rpm's drop substantially and then will finally equalize. It also requires a good 5-10 mins to warm up, if I drive right away after it sitting all not it will lug extremely bad from about 1k-3k rpms. Sometimes even got a bit of a pop or back fire.

As well as when I am driving when I push in the clutch the rpms drop to roughly 400-500 and acts like it almost wants to stall. Then sitting at a light the rpms after will bounce around by about 500-650. My idle is set at 750-810 I believe.

Its going into the shop next Friday but was wondering if anyone had any ideas?

Also, just starting yesterday the fuel gauge and digital read out of the miles til empty was way off. It would start out reading a fuel take and then drop over the next 10-15 to be where it should be at (about 3/4 of a tank right now).


Any ideas?

bigray327

Two thoughts...
1. Your idle air control valve might be bad.
2. Do you have the capability to data log? If you have a handheld tuner, log fuel pressure and see if anything looks goofy.

Simon1

Sounds like drivability issues related to the MAF. Consult a tuner who knows how to get these cars to drive properly and you should be okay.

Prior to going anywhere, I would also recheck all the connections within the intake system on the SC. Pipes move back and forth and sometimes need to be tighten again.

Has it always done this or is it new?

Mach

Mmm the start has pretty much been constant from the time of install. Just thought it needed its warm up time. The off idle came about 2-3 months ago after my battery died and replaced the battery. I re-tuned with my handheld afterwards and that did not fix the issue. The gas gauge started yesterday.

mygt500

Sorry no help but think its the MAF that might need to be cleaned......but damn that car is HOTT!!! love the mods man!

Mach

How would you go about cleaning the MAF? Do you mean just the connector that plugs in? Thanks for the kind words! I love the kit on yours too!

dkersten

very similar problem to mine, been chasing it for 6 weeks now. Last night I found a huge vacuum leak in the back of my KB supercharger, pulled it apart and put it back together with better gasket maker and fixed the leak, but NO change to the problem. Very frustrating, I thought I had it.

I have changed the MAF, no change. Monitored IAT and FRP, looks fine. Changed plugs, no change. I am about ready to sell the vehicle and start over, I haven't slept well for a month.

Unfortunately, the only solutions I have found online have been "my tuner adjusted the cold run and it works now". There are 2 problems with this: 1) they don't know what was adjusted, and 2) this has got to be a mechanical issue or everyone with that tune on these cars would have the same problem, so tuning out a mechanical problem is a bad idea.

I really hope you find your problem, and if you do, please post the solution. It acts like a vacuum leak problem, but in my case, I smoke tested last night after fixing the one big leak and no more leaks. In your case, I would start there. If you have an AF ratio gauge, and you are seeing it go lean at partial throttle when the engine is cold, most likely it is sucking air before the supercharger and after the MAF. I would check that first.

Nuke

I'm thinking Arbys.... I mean, TB and MAF cleaning.

Riptide

dkersten are you serious about giving up? If it came to that would you think about shipping the car to KB and having them look at it personally?

Part of what sucks about living in small population states like this are the lack of experienced tuners/builders around here that you can trust when some PITA problem like that comes up.

haproot

Sounds like idle hunting due to not enough ignition timing at idle due to the added load caused by the supercharger. Not all superchargers may create this load but some probably do.

From the Subaru world we would have to lower ignition timing @ idle when say having a lightened crank pulley or flywheel. Otherwise it hunts like that. Maybe in your cases here you need some added in the idle and low engine load areas on your map?

Also I'm not sure how a map/tune on a mustang looks like but on ours (subaru) there is a table for ignition timing compensation in relation to coolant temp. If the issue goes away when warm maybe a similar table needs to be adjusted on your tunes/maps.

Just a couple thoughts. Good luck I hope you guys get it figured out.

To the OP Yes I would definitely start with cleaning the MAF.