CSX4005LA engine runs rough

[twobjshelbys]

I also took it for a ride his afternoon - Lyons to Estes Park on Hwy 36 then back on Hwy 7 (the old St Vrain canyon road - really a nice drive with lots of twisty turns that show what a performance car can do.) My goal when I drive this is "no brakes" (goal met). Speed limit for most of it is 40 but the Cobra could easily do 60-80 on most of it but today there were too many cops - it's a Colorado St. Patricks Day enforcement thing. I waved at all of them as I drove by and the one Larimer County deputy gave me a thumbs up (and probably radioed to the three Boulder County deputies I saw. I can hear it: Guy in green Cobra coming your way. He'll probably be going fast down the Canyon. Not while they were watching )

[68fastback]

Tony, glad to hear things are sorting out.

I was wondering if the rough idle now might just be the big cam that engine has. Possibly a vacuum gauge might give some further insight?

Good luck!! She's such a beauty!

[Carnut]

Originally Posted by twobjshelbys

So since Carnut asked here is the latest in the continuing saga.




I still haven't gotten it totally nailed but there has been a revelation.

Every since I'd gotten it I'd noticed that the engine took a long time to warm up and it never did feel like it was right. Last Thursday I took it to a meeting with some old friends and noticed that the water temp was hot -110*C where it used to struggle to get to 80*C. So I figured the thermostat was stuck closed (and before that it dawned on me that it had been stuck open.)

Saturday I changed the thermostat (a total of about 15 minutes with a trip to find one, plus the trip to the local hardware to get a hose clamp that was previously stripped).

Anyway, when I got it back together I took it for a spin to warm it up. The water temp went to about 80-85C - just about right for a 180F thermo. THen the oil temp gauge finally registered.

And the 4000RPM problem is gone. The only thing I can figure is that the fuel injection system has another engine temp sensor and was in safe mode waiting for the engine to warm up. Today I took it for a longer ride and indeed it seems much better now. I still think it runs a little rough at low RPM but I am slowly peeling the onion.

I did finally connect with a guy in Evergreen - EPS (Evergreen Performance Systems) that works on classic mustangs and 289 Cobras and other stuff. Link to their website:

EPS

They have both engine and chassis dynos. As soon as I get the software for the laptop and the cable I'll bring it down. Walt called me while I was on the way back from the airport and said he is upgrading his dyno and wanted to know if I could wait since his results would be much better in a month or so. Not a problem given the above revelations.

Sounds like you "nailed" it. Some FI cars might like closer to 90C. The gas mileage should be a heck of lot better now. I might agree with Dan about the cam, do you know the specs?

If you haven't already, a cleaning of the fuel injectors may help a little, given the car has probably had old gas in it occasionallly.

[twobjshelbys]

Originally Posted by Carnut

Sounds like you "nailed" it. Some FI cars might like closer to 90C. The gas mileage should be a heck of lot better now. I might agree with Dan about the cam, do you know the specs?

If you haven't already, a cleaning of the fuel injectors may help a little, given the car has probably had old gas in it occasionallly.

Re: cleaning injectors. Do any of the fuel additives that claim to do this actually useful here or are they just a gimmic? Maybe one actually has little micro-robots with scrub brushes that clean the shower walls on the way to their fiery oblivion?

[VaporDude]

I agree on the CAM theory plus cleaning the fuel injectors. I would think that any of the big named injector cleaners would work well like STP or something. They have been around for years and if their stuff didn't work, I don't think they would be in business this long.

[68fastback]

Originally Posted by Carnut

Sounds like you "nailed" it. Some FI cars might like closer to 90C. The gas mileage should be a heck of lot better now. I might agree with Dan about the cam, do you know the specs?

If you haven't already, a cleaning of the fuel injectors may help a little, given the car has probably had old gas in it occasionallly.

Roush Performance site lists several 427s. The cam specs are all proprietary but on some it says "Cam Specs: Roush Proprietary (moderate)" but on the top 560HP versions, like this IR, it just says "Cam Specs: Roush Proprietary" which makes me think it's beyond 'moderate' but dunno.

Btw, I like the Lucas injector cleaner because it's not solvent-based like most all the others I'm aware of which can pose a risk of cylinder wall 'washing' and scoring on a real hi-po engines, I think.

[Carnut]

Originally Posted by twobjshelbys

Re: cleaning injectors. Do any of the fuel additives that claim to do this actually useful here or are they just a gimmic? Maybe one actually has little micro-robots with scrub brushes that clean the shower walls on the way to their fiery oblivion?

Actually, there are little tiny squirrels that use acorn shells to scrub the injector inards.

[68fastback]

Originally Posted by Carnut

Actually, there are little tiny squirrels that use acorn shells to scrub the injector inards.

[Joe G]

Originally Posted by Carnut

Actually, there are little tiny squirrels that use acorn shells to scrub the injector inards.

... and lemme guess. Their poop acts as lubricant?





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[twobjshelbys]

Woooh woooh.

Listen to this.

I finally connected with a Roush guy. He pointed me to the keepers of the engine controller ca ble and software (someone at Accel). Within an hour of connecting the cable and warming it up to normal temp I found trouble in river city.

First thing I did was ask for (and got) the original "tune" program. This helped alot. I sent them some screen shots from the engine monitor (real time). Everything now matches. The tach matches exactly what the software says as does the temp.

The closed loop correction for the fuel injection was pegged permanently to lean.

I was asked to calibrate the Throttle Positioning Sensor since it is not sensed and has to be set up. To do this you turn on the key but don't run the engine. Set one thing at throttle closed (accell pedal no contact) and then the other floored.

Mine said 4.65V close and 1.01V open. Ooopps... The TPS cable was wired backwards.... This totally confuses the fuel injection controller. When the throttle is open (and idling and accelerating from start) the controller thinks it's at 7000 RPM. At speed, it thinks it's idling... Sigh. Up down, right left. Swap the wires and thank you it's much better now!

I imagine that the guy in Mexico couldn't figure this out and sold it because it was a pig (it was, but it isn't now). I got a good deal because of a 1-A 3-C cable that shoiuld have been 1-C 3-A.

Now back to the throttle body calibration and eventually to the dyno for final adjusts...

This is fun.

I wouldn't even try this on my truck or Jeep... The engine on the Cobra is so '60's.... Well, with the EFI maybe mid 70's.

[twobjshelbys]

ooops, getting duplicates again...

[Johnny Lupara]

...glad to hear you are getting a good handle on this.....it has been quite an education following this.....John

[twobjshelbys]

I haven't even described the windshield changeover. I neglected to take pictures of the disassembly but I'll carefully document the reassembly.

Again, it's a 60's car. You can do it yourself.

[68fastback]

Tony, this is great news!!! You must be dancing around the driveway! I bet you're right about this is why they sold it. Way to go!!! Persistence and ingenuity always prevails! (...eventually)

[twobjshelbys]

Originally Posted by Johnny Lupara

...glad to hear you are getting a good handle on this.....it has been quite an education following this.....John

"Whipping it into submission".

I trouble shoot complex systems for a living. Lots of people make problems go away, but those that do are eventually faced with a return. I go to root cause. In this case, I believe root cause is a $3 cable... Not done yet, but this is certainly a major find. Now I have to repeat the throttle body adjustments. This may let me pass emissions well enough to get my plates.

Oh, my plate SPRSNAK came in.

If I can't get it to "pass" emissions (HC less than 1000, it failed at 1200) then I have to get another temp and wait until the magicians finish. They have a chassis dyno. Some of the adjustments need to be done under load at which point I surrender.

[twobjshelbys]

Originally Posted by 68fastback

Tony, this is great news!!! You must be dancing around the driveway! I bet you're right about this is why they sold it. Way to go!!! Persistence and ingenuity always prevails! (...eventually)

By the way, I think the other significant find was the correlation of the 4KRPM cutoff to the stuck-open-thermostat. Lots of pros I know missed that one. The software would have probably provided a clue of not warming to operating temp.

The cable (it is "key locked") was $260. That money in the last two days solved two problems - tune and data that resulted in the diagnosis of the bad cable.

[Carnut]

I would have never suspected the TPS connections.

Glad it is beginning to smooth out.

[Joe G]

Wow - sounds simple, but obviously wasn't. Finding the "right guy" (as you did) certainly helped you cut right to the right area to look for sure.


Glad things are coming together.




You said this car was scary fast before?? I can't imagine what it'll be like when you're through with it.


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[gr8snkbite]

great job getting it identified Tony. patience is a virtue...

[Johnny Dangerously]

Great news Tony!

I'm glad you finally got this resolved.


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