HELP WITH MISS FIRE IN ENGINE

[ryan 94RT]

I have a 96 gts with a 97 engine in it( why because it is, no one knows). I get a miss between 4500 and 5500 rpms under track conditions. I have worked on this with my viper tech and have done the following.
1 reflash the computer
2 injecter flush
3 replace o2 sensor ( right side )
4 plugs and wires

I need help because it is hard to reproduce except at the track and even then it happens only when the car is hot. ONly @ WOT and mostly on the straights. what is confusing is that sometimes it doesnt happen for a lap and then it happens a couple times in a row.

MY next thought is 100 octane fuel . I need some HELP!!!!!!!!
ryan

ryan

 

[RockyTop]

I am Sure That New Underdrive Pulley will Solve It !

He he.

 

[1TONY1]

Re: I am Sure That New Underdrive Pulley will Solve It !

Already starting with the excuses for the Macon autocross ??? Just kidding. I had a miss exactly at 5000 everytime. Sean Roe suggested a reflash since there was a TSB long ago. Today we did the reflash and no more miss. You should have gotten the latest flash but who knows. Why only four plugs and wires ? Was it setting a code for one engine bank ? Any codes at all ?

 

[GR8_ASP]

Re: I am Sure That New Underdrive Pulley will Solve It !

I think he meant #4 not quantity 4. BTW both my banks have 5! j/k

 

[Nadine UK GTS]

Re: I am Sure That New Underdrive Pulley will Solve It !

What miles on your motor?
Recently replaced the OE in line fuel filter?
Fuel pump OK, (tech can run a test at pressure port with guage taped to windshield for WOT driving conditions to see if pressure OK).
You are running OE Champions (favored for your mild mods)?
BTW, Under WOT (alongside a few other conditions), ECU runs the motor off preset values, doesn't read off the O2's.
My immediate thought would have been wires or plugs, when hot, breakdown gaps will open up to cause a miss. Sounds electrical if intermittent and hot, check connections are tight and clean.

 

[1TONY1]

Re: I am Sure That New Underdrive Pulley will Solve It !

I think he meant #4 not quantity 4. BTW both my banks have 5! j/k

Ron, shhh...don't tell Ryan

 

[Larry Macedo]

Re: I am Sure That New Underdrive Pulley will Solve It !

Check the output from the coils and you may want to check your speed sensor for shorting.

 

[Gavin]

Lets see if I can help - I too have a 96 GTS and have experienced this issue - took me about a year to figure it out - what can I say, us folks from New Zealand are a bit slow.
Note:I did not experience this 'missing' problem until I started run open track events.

There are two things happening with the car . First, you mention this only occurs when the car is hot - if you are getting up into the red on your temp guage the following will happen:
The computer is designed to dump extra fuel into the motor, when it exceeds a certain temp, to cool it off - when the computer does this you will notice three things.
1. engine miss
2. engine warning light will come on and stay on
3. the back of the car will turn black (from the motor running excessively rich) motor will continue to run rich until you disconnect the positive battery terminal under the hood and recycle the computer.

Second - under hard braking the engine ***** oil from the drivers side valve cover, through the vent tube and into the air box. Eventually it will **** enough oil in that the left filter becomes quite clogged. This oil also goes through the motor and if enough of it goes through this will cause a misfire, and could, but not always, have the engine warning light come on. You will also notice the car will not pull as strong as it is down on power ( not able to breathe).

A few things to look at in addition to the above
1. Confirm the battery terminal are tight - a loose terminal will cause a low voltage situation and the symptom is - engine misfire and engine warning light will come on.

2. Have the Viper tech remove all electrical grounds, clean and re-install - this can cause the same symptoms as in 1. above.

I have found the oil in the airbox to be the biggest cause of the misfire - I'm installing a Puke bottle on the car to collect the oil before it gets into the airbox.
At one event, when the ambiant air temp was 105 degrees my car got very hot and I experienced the 'running [******] rich' issue - this was scary - I mean the back of the car was oily black from the excess fuel and the coolant overflow creating a oily mess.

Prior to my last track event we discovered a loose battery terminal so fixed that and checked all the grounds.

I then did the event and had no misfire problems until the second to last session on the Sunday - all I did was look under the car and the oil was dripping out of the air box water drains - nice little puddle on the ground - pulled the air filters and left side was clogged with oil - cleaned them - reinstalled - power back to normal and no misfire.

In my humble opinion, you are experiencing the "oil in the air filter problem" Hope this helps - email me if you need additional help
Gavin

 

[ryan 94RT]

Thanks for all the help! I believe that Gavin may be correct with the oil in the air box because my power was down and oil was dripping at one point in the end( before my power steering pump went Bye Bye).

THanks again
Flyin Ryan is now slow as you go!

 

[Gavin]

Ryan - replacing the power steering cooler with a larger unit is a must - very easy to install once the air box is removed. Also put in a Sean Roe controler that will run the fan after the motor is shut off - reduces heat sink.

 

[Gavin]

Direct from JonB - puking solution
"Buy a $3 vacuum-line T at any auto-parts store. Place this T in the left hand hose that goes to airbox. This T drains into a small pill bottle or film cannister. Glue/seal the base of the T into the lid of the bottle.

Still puking? Do it twice."

 

[ryan 94RT]

Gavin

I am really thankfull for all the help.
1 I am going a different route with the power steering pump.
Get new one under warrenty then install a under drive crank shaft pulley. That should reduce strain on all pulleys by 25%.
2. I will do the vac line and see what happens . I dont understand the part about do it twice? I thought the t was glued in place, how can i do it twice?

thanks
ryan

 

[Gavin]

I have no knowledge about underdriving the steering pump - all the Track folks I know have added a larger cooler and this seems to resolve the issue (cheap solution) - I'm at 40K miles and lots of track events - still have the stock clutch and original steering pump and the car gets hammered pretty hard - by no means am I the quickest guy out there - I have come in first in ViperDays "modified" class twice in the past year.

"Do it Twice" = put two "T's" in series in the line with two collectors.

Glad to be of help - look forward to seeing you at a track sometime.
Gavin