car misses???? Need advice please

[1/2 bent]

My cobra has been missing for a couple weeks now. It all started when i put the diablo predator 91 octang performance tune in (i think). I now have a 2.93 upper pully with the predator 91 octang pully tune in. The car Misses from 1.5- 2.3 k. If i put it in neutral and hold it around 2k i can hear it missing. Same goes with on the highway in any gear at that rpm. I can actually feel the car jerk as it does this. Now it wont do it when under a slight load say if I'm going up an incline at 2k. It only seems to happen when i barely give it gas. Also when i idle it at 2k it does it. This drives me nuts as i can hear the exhaust missing and i feel it. I changed my stock motorcraft 22fm1 plugs to NGK tr6's gapped @ .034-.035 and i still get the same miss. Ive cleaned my maf out with electronics cleaning spray and that doesn't seem to help.
What could be causing this? I really don't want to put the stock tune back in as then ide have to put my stock pully back on. Should i gap my plugs wider? maybe a different plug? The car seems to have lost some power also. Could be me just getting used to the pully. My pully also slips.Even with the gatorback 4080745 belt and upr idler/tensioner. Any help would be appreciated.

Bryan

 

[JohnsDSGVert]

You too????

I have the exact same issue.....switched from Motorcraft 22's to NGK TR-6's....gapped at 35. I get this hesitation at about 2100 rpms......mine has an intermittent dip in RPM at Idle from 700 down to 300 or so when it is warming up...and lunges hard when first started if I immediately take off at regular speed.

I checked my TPS voltage.....I was at 1.1v.....was told to adjust to .98v.....the closest I could get was 99v.....it seems to help a little. I bought a set of Motorcraft 12's....and will install them when I get the TPS right....I am going to oval my holes on the TPS a littlle more and see if I can get the voltage a little lower.....I was told the computer is seeing the higher voltage and trying to slow the RPM's down.

I think I will gap at 36 on my 12's.

 

[2814v]

Maybe its just a bad tune, call whoever wrote the tune and loaded it. I'm sure they well give you a new tune.

 

[smokedbystang]

Mine does the exact same thing and I am stock except for exhaust. I had the stall reflash done in hopes it would help the idle and miss. My idle is still a little rough and mine has the exact same symptoms as yours. It is really annoying.

 

[Tim03cobra]

Mine also does the same thing. If you just cruise around without a load it jurks and makes a popping noise threw the exhaust. The car still runs good at the track though. Maybe this is normal with 4 cams:shrug:

 

[1/2 bent]

Originally posted by smokedbystang
Mine does the exact same thing and I am stock except for exhaust. I had the stall reflash done in hopes it would help the idle and miss. My idle is still a little rough and mine has the exact same symptoms as yours. It is really annoying.

Exactly. It must be the Diablo predator tuner then. I wonder if they are going to fix this. Thanks for the comments all. Atleast now i know its not just my car and probably wont hurt anything its just annoying.

 

[Torch Red 10th]

It's not the Diablo tune. I have the SCT tune for a 2.93 from Apten. Tuned for 91 octane also. I run TR6's and have the exact same issue "1/2 bent" described. Tried stock plugs, no change. Cleaned the MAF and it seemed to fix it, but it is back now. Seems to still have great power as before, but cruising around holding low RPM's it will miss. Holding RPM's from 800-2500K in neutral will cause it. I have loud exhaust and can hear it pretty prominent also while driving under low RPM's. Not really a big deal since the power is still there when I get on it, but cruising through the neighborhood kinda sucks now at 25-35MPH. Reminds me of a Harley or a car with an aggresive cam because it smoothes out once you get on it. It's just weird because it didn't start doing it until about 3 weeks ago. Well after my last mod. Gonna try some Autolite 103's anyway. Maybe then the stock CAI. Gonna play with it some to try to figure the source out.

 

[Neoclasiccl]

Get your airfuel read. My car was doing this after the KB install and it turned out to be a rich condition. A lean condition will also do this. Get it checked.

 

[orange2004cobra]

Its not the tr6's..
I see a re-tune in your future...
L.

 

[03 svtvenom]

Mine does it too but more when I was running lean and now I am running a little rich. Alot of our cars do it so I am hoping its normal.

 

[1/2 bent]

I don't think the tr6's or the problem either. Ive only had them in 2 days and it made no difference. I'll leave them in as my stock plugs were a bit pink in color. The new plugs are gapped smaller. I think i'll call diablo next week and see what i have to do to get a custom tune in my predator. Thanks for the help.

Bryan

 

[Silver 03 Cobra]

How bad is the miss.

Check to see if any water has gotten into any of your plugs especially on no. 7 and 8 cylinders. I've seen this a few times including mine. It drove me nuts until I found out I had water in the no. 7 cylinder. It came from being sloppy with icing the intake or washing the engine. The plug seal on the plug wires does little to keep moisture out of the coil packs.

 

[Torch Red 10th]

I've pulled and inspected the plugs. They look fine. Like new still. I ran the TR6's w/ no problems for a while. Now there is a slight miss. More annoying than anything really. Car still has great power. I ran the tune, the pulley, and the plugs for a month w/ no problems. After the first month, the miss started occuring.

I do smell a new weird smell coming from my exhaust when I really get on it now. Smells like burnt, already shot fireworks. NOT the rotten-egg smell, it's sulfur, or gun-powder type smell. I assume it's the MRT cats or my Magnaflows. Who knows.

 

[1/2 bent]

I have the same smell now also. I think its the pipe just getting older. I have the mrt catted h as well. Best h pipe out there imo. I run it with the 3 inch mac catback. Going to check my plugs today since ive put 300 miles on them and re-clean my maf to see if it helps. Other than that it has to be something with the tunes. Not necessarily a certain one either. I use the predator tuner.

 

[sam]

that seems to be the normal range that these motors seem to miss. probably runs allitte lean there. if you notice with more thottle, this all disapears as the tps starts to richen the afr.

 

[silvercoffin]

...

My car starting doing this after having Bassani X pipe and Bassani Cat Back. I also got new plugs and I know my mechanic gapped them differently than before.. He checked the Air Fuel on the dyno and said it was good. The car seemed to fine on the way home but is now hesitatting especially noticable at lower rpms while cruising along...

Im going to call monday and get back in for another tune. Maybe things changed after the exhaust broke in???? or somethings up with the plugs.....

I only got new plugs for the hell of it...figured i should after two solid seasons of racing....now the cars running shitty ahhhhh

 

[Jon]

Mine has the same problem. Changing plugs won't help, I've tried TR6, 103, 104, Platnum, stock, and Iridiums.
The only thing that helps is to open the plug gap to about 0.040".

 

[kaboom]

CHANGE YOUR FUEL FILTER!!!!!!!!!!!

 

[Painter]

I have just noticed the same problem with low rpm hesitation, So far the advice is check ur tune and change your fuel filter! Where is the fuel filter?

 

[kaboom]

Originally posted by Painter
I have just noticed the same problem with low rpm hesitation, So far the advice is check ur tune and change your fuel filter! Where is the fuel filter?

It is right in the carbourator next to the jets you need a special tool to take it off;-)