Sputtering, bucking when cold

Topic: Sputtering, bucking when cold - 88 Cougar 5.0 (Read 4111 times) previous topic - next topic

Sputtering, bucking when cold - 88 Cougar 5.0

September 09, 2010, 01:44:21 PM

Hey guys. I have recently acquired this 88 Cougar LS 5.0. I was just trying to get it running to be my winter driver...

The car runs and drives reasonably well AFTER it is warmed up. But initially, the car wants to buck, sputter and generally run rough after initial start up.

I ran codes and got Code 34 C,O - Insufficient EGR flow or EVP voltage high (SONIC) or PFE sensor voltage high or out of specification.

I did a little search and it seems that this is most likely a bad PFE sensor. But does that really make the car run this bad during warmup?

Thanks!

Sputtering, bucking when cold - 88 Cougar 5.0

Reply #1 – September 09, 2010, 07:10:55 PM

PFE sensor has something to do with the egr. I am not sure our cars had one. Try unpluging the egr and see if it changes. Just pull the wires out and cap the vacuum line.

Sputtering, bucking when cold - 88 Cougar 5.0

Reply #2 – September 10, 2010, 08:51:39 AM

Take off the air idle control motor and clean it out with carb cleaner/tb cleaner.

Take off the egr plate and see if it is carboned up and clean out if necessary.

Sputtering, bucking when cold - 88 Cougar 5.0

Reply #3 – September 10, 2010, 09:05:42 AM

Hi haystack. Capping off the vacuum line and port to the EGR valve and disconnecting the EVP sensor seemed to help ever so slightly. It didn't buck as bad this morning, but it is still doing it.

Mike, It very well could be the IAC valve since the idle does seem to hunt when first started and will die after 30-60 seconds.

I will remove the IAC and EGR and give them a thorough cleaning tonight and report the results in the morning.

Thanks for you input guys!

Sputtering, bucking when cold - 88 Cougar 5.0

Reply #4 – September 12, 2010, 11:12:17 PM

OK.
- I removed the IAC and cleaned as described. I checked that it would open with 12 volts applied - it does. Then reinstalled it. I started the car and then unplugged the IAC. The car wanted to die, it idled down. So the IAC seems to be working.

- Next I tested the EGR valve for movement. I hooked a vacuum pump up to the EGR valve and was able to move the EGR diaphram in and out with vacuum. No vacuum leak.

- I set the Throttle Position Sensor (TPS) to 0.96v at idle at it appeared to climb in voltage evenly through the throttle valve opening.

- I checked the Engine Coolant Temperature (ECT) sensor and it was reading 0.99 volts, which is somewhere between 158 and 176 deg. F. Seems accurate.

But the car still does not run quite right after startup - either cold startup or warm startup. Once the car is "warmed up" and running for a while, the engine runs very smoothly and idles well.

I'm stumped.

Question for everyone... The SO engine does have the HO upper intake, EGR spacer and Throttle body. Does this move more air than the computer is programmed for and may affect the engine's running performance?

Sputtering, bucking when cold - 88 Cougar 5.0

Reply #5 – September 14, 2010, 12:04:48 AM

I swapped an H.O. intake onto mine, kept the EGR and throttle body off the H.O. I noticed no difference, but my car also sometimes bucks, and did before. I have not looked into my problem at all. It idles fine though.

Sputtering, bucking when cold - 88 Cougar 5.0

Reply #6 – September 14, 2010, 12:05:29 AM

What kind of shape are you're vacuum lines in?

Sputtering, bucking when cold - 88 Cougar 5.0

Reply #7 – September 14, 2010, 10:27:15 AM

Thanks for the feedback Haystack. I ordered a vacuum gauge kit so I can see if I have a leak somewhere. There are a few splices in the vacuum lines, but overall in good shape.

The car seems to run better every day I drive it. But after startup, even when warm, it seems to go through a little hesitation, sputter, back-fire thing when first driving it. Then after a couple minutes it smooths out.

I have replaced the fuel filter and the air filter is in great shape. The car has been sitting for a few years so I'm sure it just has to clean out the cobwebs. The car did have about 1/4 tank of old gas. I filled it up with 93 and added fuel system/injector cleaner to it. So maybe as I continue to flush the tank with fresh fuel. I'm sure the injectors could use a good cleaning.

I'll keep you posted. Thanks!

Sputtering, bucking when cold - 88 Cougar 5.0

Reply #8 – September 14, 2010, 10:34:56 AM

According to fordfuelinjection.com, the "cold" drive away strategy uses the TPS, MAP, ECT and ACT (Air Charge Temp) sensors to dictate fuel/spark. I'll need to check the ACT to verify that it works as it should.

Otherwise, I wonder if it could be something with the catalytic converters. Some backpressure problem?

Sputtering, bucking when cold - 88 Cougar 5.0

Reply #9 – September 14, 2010, 11:48:10 AM

What about the MAP? Which one are you using?

Sputtering, bucking when cold - 88 Cougar 5.0

Reply #10 – September 14, 2010, 12:43:15 PM

Hey Mike. I'm not sure. I will check the part numbers and get back to you. I assume it is the SO engine MAP original to the car. Does the HO engines use a different MAP sensor?

Thanks for your input everyone.

Sputtering, bucking when cold - 88 Cougar 5.0

Reply #11 – September 14, 2010, 03:57:08 PM

Check the hot idle with the IAC disconnected, if it is less than 550-600rpm reset it and then reset the TPS voltage... If you still have a cold problem and the air and coolant temp sensors are in spec, you likely have dirty injectors...