Another Engine not Workin'

TroyT

Contributing Member
Member
#1
Well, sometime in June, I drove the cobra to the VI for the first time and it ran rough from idle to at-speed. It doesn't idle steadily and bogs or loses power at speed. The check engine light stays on. :eek:

Fuel delivery is a Mass Flo EFI. I have followed the instructions to troubleshoot this thing. Here's what I have done so far to find the problem.
1. Cleaned the throttle body and throttle body plates.
2. Cleaned the mass air sensor and sensor vanes.
3. Replaced the fuel pressure regulator vacuum hose (per Mass Flo vendor)
4. Replaced the PCV hose (per Mass Flo vendor)
5. Replaced two of the three capacitors in the EEC. The two were corroded the third one is ok.
6. Performed a diagnostic test of the EEC for codes. I only get "PASS" codes. All good there.
7. Replaced the Idle Air Control (IAC) valve. (per Mass Flo vendor)
8. Siphoned old gas out of the tank and put in fresh premium gas
9. Adjusted the fuel pressure regulator to 40 psi per Mass Flo and Aeromotive fuel pressure regulator instructions
10. I had a spare ignition coil, so I unplugged the wires from the one in the car and plugged into this spare. Car still runs rough.
11. I had the distributor cap off and the rotor seem to look ok.

Last year, I replaced the fuel filter.

What should I check next?
1. Throttle Position Sensor?
2. The TFI module on the distributor?
3. Bad ground on the engine harness?

Man, this thing is about to bring me to my knees. :tickedoff:
Thanks all for your suggestions (Uh, I think I just opened up a can of worms.). o_O
 

Scott Harrison

"Growing old is mandatory, growing up is optional"
Staff member
Contributing Member
Member
#2
1. TPS:

2. I have spare TFI modules if you want to check that.

3. Don't understand how your CEL is lit without any codes.

4. Are you sure you're getting 40 psi at the injectors? Any chance the fuel lines are breaking down with the ethanol fuel, clogging up somewhere? Did you say the car had been sitting for a while when this started? Can you run the fuel pump and disconnect a line into a container?
 

Danbo

FFR6198
Contributing Member
#3
Damn Troy, you just about replaced everything but the kitchen sink. You don't have a TFI with your system do you?
 

TroyT

Contributing Member
Member
#4
Damn Troy, you just about replaced everything but the kitchen sink. You don't have a TFI with your system do you?
Yep. I have one on my Mallory distributor. By the time I find the bugger, everything would have been cleaned or replaced in the process and should run great!
 

TroyT

Contributing Member
Member
#5
1. TPS:

2. I have spare TFI modules if you want to check that.

3. Don't understand how your CEL is lit without any codes.

4. Are you sure you're getting 40 psi at the injectors? Any chance the fuel lines are breaking down with the ethanol fuel, clogging up somewhere? Did you say the car had been sitting for a while when this started? Can you run the fuel pump and disconnect a line into a container?
Scott,
2. I would like to try your spare TFI module to see if anything changes. Will you be at the VI tmw.? If not, I can stop by Cobra, Inc.
3. I don't either. I took a video of the flashing check engine light used to count codes when you perform a self test and sent it to Mass Flo. Chris at Mass Flo was thinking I was not counting the flashes correctly. He also concluded that the light was flashing 11 - code for system pass.
4. I don't know if I am getting 40 lbs at the injectors. Although, they are rated at 24 lbs. Anyway, I was watching the fuel pressure gauge as it was at idle, rough idle that is. It was a little lower than it should be, so I increased the pressure with the vacuum line disconnected as instructed to 40 lbs. It will drop a little once the vacuum line is reconnected. Apparently, this is normal. I could disconnect the line just before the fuel rail and run the pump to see if I get good fuel flow.
 

Tom Wells

Contributing Member
Member
#6
I know I'm here after the fact - can't resist - and probably completely wrong. That's never even slowed me down...

I was taught to always look at the ignition first - then the fuel. Any changes on the fuel side may or may not be helpful otherwise.

Bottom lines: Distributor rotor, cap and magnetic pickup. Plugs and wires. There are some things like carbon tracking and little cracks you can't see but which can affect the engine a lot. For the wires, sometimes idling on a dark night can reveal crossfiring between wires. Plugs, cap & rotor are easy and cheap.

There, now I feel better. Thank you!
 

TroyT

Contributing Member
Member
#8
1. TPS:

2. I have spare TFI modules if you want to check that.

3. Don't understand how your CEL is lit without any codes.

4. Are you sure you're getting 40 psi at the injectors? Any chance the fuel lines are breaking down with the ethanol fuel, clogging up somewhere? Did you say the car had been sitting for a while when this started? Can you run the fuel pump and disconnect a line into a container?
Elder, I’m going to Cars and Coffee instead with a neighbor. If you go there can I a TGI module from you?
 

Hot Rod

Contributing Member
Member
#9
Cleaning the Mass Air sensor doesn't always work. They are sensitive to calibration and sometimes they just need to be replaced.
 

Don Gaboury

Contributing Member
#10
A lot of people replace the tfi but not the pickup. I would swap out the dist. With a know good one. I had to replace mine after almost 30 years of service. Got one at Rock Auto for less than $60.00
 
#13
Troy,
Sorry, been out of town.
PM’d you.
Have you tried swapping out the A9L with a known good one? Easy way to see if you’re chasing ghosts.
I swapped out all the capacitors in mine and it still failed.
 
#15
Hi guys wondering if he ever got this fixed. I had a nightmare with my Mass Flo efi, I purchased Bill Petersons MkIV, after spending way too much to try and get the Mass Flo to work I replaced it with a QickFuel 600cfm VS carb, and an Edelbrock performer RPM manifold and have never looked back car has run great for two summers now no issues.
 

TroyT

Contributing Member
Member
#16
I borrowed an A9L from Scott and it didn't run any better. I also had the loaner TFI module on the distributor too.
I replaced two of the three capacitors in the ECU. Nothing changed on how the car runs.

I spoke with someone who is a Mass Flo EFI guru in MD (referred by a tech guy at Pro-M Racing, formerly Mass Flo). He said that Chris at Mass Flo is not supportive, particularly with the old Mass Flo system (because it's old!). After discussing all possibilities, he suggested that I test my fuel pump. The test revealed that the pump may be the culprit. I have to turn the key on (not start) three times for the pump to gain pressure in the system, which is still below where the pressure regulator is set. at So, in my last ditch effort to get this heap running right again, I plan on replacing my fuel pump this weekend. I bought an Aeromotive fuel pump that is ethanol friendly. I'll keep you posted on my progress on finding the @#$%^! problem.
As for other options, I have not looked into them...yet. The EFI guru I spoke with mentioned Holley Terminator NOT the Sniper as a good trouble free set up from Holley (plug and play he said). :rolleyes:

Thanks Caesar, I'll look into the QickFuel system.
 
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#19
Ugh....I hope you’re not like me. Every time I’ve had fuel pump issues (regardless of car) it’s right after I fill the tank! :buck2:

Did you build in an access plate through the trunk by chance?
 
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