"pop" and hesitation at startup

fongo · 08-31-2004, 02:07 PM

Hey everyone. I've never had a start up/warm-up problem with my 93 5.0 (166K..still kicks!)..until this past week.
After startup, the car hesitates on the street and I usually here a "pop" or two coming from underneath the hood. This only happens during startup. After a few minutes, it goes back to normal w/o a problem. Iwas wondering if it's any of the following:
1. Bad 02 sensors
2. EGR valve sticking or defective
3. Vacuum leak.
4. Bad distr. cap
I cleaned the heck out of the throttle body and I pretty much have new plugs and wires.
Need some help. Thanks!
fongo

88fivepointoh · 08-31-2004, 02:15 PM

Here's what you do, check for vacuum leakes, tune it up, clean your egr, and what is the most important is check you Air temp sensor on the intake manifold. If its bad it will pop. pop is from a lean condition. check your injectors and get them cleaned if nessecary.

Capri306 · 09-02-2004, 02:38 AM

Could also be a MAF or ECT sensor, but testing would be recommended....no wait, 166k miles? If they're still the original parts, I'd change everything I could afford but especially those two since they have the largest effect on a/f ratio.

But yeah, you're on the right track. Could also be leaning out due to inadequate fuel pressure. Test the fuel pressure to be sure. My '87 did the same thing right before the fuel pump took a dump.

88fivepointoh · 09-02-2004, 12:53 PM

With that kind of mileage i bet its time for new injectors. And definetly new Vacuum lines. if you haven't changed your 02 sensors do so, and the mass air sensor could be dirty and going bad.. Again also have the TFI module tested.. If thats the original, Please change that.. Its worthless and for sure gunna leave you stranded soon.

fongo · 09-02-2004, 07:59 PM

thanks fellas. After considering the topic along with other fellow car enthusiasts, I'm starting out by replacing the engine cooling thermosensor ECT and the air charge thermosensor ACT. I had new 02 sensors, my MAF appears fine.
God forbig its the TFI..I'm in deep doo-doo if that's the case!
Ciao...

88fivepointoh · 09-02-2004, 08:17 PM

if its the TFI its a cheap fix, 39 bucks max for the unit... Don't sweat it..

5.0 Fiend · 09-03-2004, 01:03 AM

I had the same problem on my 84 carbed motor, I changed the intake maifold gaskets, (oil leak from lifter valley), and I didnt re torque the manifold after a couple of heat cycles, sure enough, I had the same probs.

08-31-2004, 02:07 PM	#1
fongo Registered Member Join Date: Jan 1999 Location: Farmingdale, NY Posts: 139	"pop" and hesitation at startup Hey everyone. I've never had a start up/warm-up problem with my 93 5.0 (166K..still kicks!)..until this past week. After startup, the car hesitates on the street and I usually here a "pop" or two coming from underneath the hood. This only happens during startup. After a few minutes, it goes back to normal w/o a problem. Iwas wondering if it's any of the following: 1. Bad 02 sensors 2. EGR valve sticking or defective 3. Vacuum leak. 4. Bad distr. cap I cleaned the heck out of the throttle body and I pretty much have new plugs and wires. Need some help. Thanks! fongo __________________ 1993 GT, MAC Fenderwell Cold Air Induction; Accel dist.,Splitfire plugs, BBK: 1 5/8 unequal length shorties, hi flow H-pipe w/ cats; Flowmasters 2 chamber American Thunder catback system, Motorsports 3-core radiator, 180º thermostat, BBK adj. clutch quad...the rest is bone stock!..but more mods to come!!

09-02-2004, 02:38 AM	#3
Capri306 Moderator Join Date: Sep 1998 Location: Grand Rapids, Michigan, USA Posts: 1,001	Could also be a MAF or ECT sensor, but testing would be recommended....no wait, 166k miles? If they're still the original parts, I'd change everything I could afford but especially those two since they have the largest effect on a/f ratio. But yeah, you're on the right track. Could also be leaning out due to inadequate fuel pressure. Test the fuel pressure to be sure. My '87 did the same thing right before the fuel pump took a dump. __________________ Capri306, Moderator The Mustang Works Online 1979 Mercury Capri 1987 5.0L Mustang LX Notchback 1993 5.8L Eddie Bauer Bronco

09-02-2004, 07:59 PM	#5
fongo Registered Member Join Date: Jan 1999 Location: Farmingdale, NY Posts: 139	thanks fellas. After considering the topic along with other fellow car enthusiasts, I'm starting out by replacing the engine cooling thermosensor ECT and the air charge thermosensor ACT. I had new 02 sensors, my MAF appears fine. God forbig its the TFI..I'm in deep doo-doo if that's the case! Ciao... __________________ 1993 GT, MAC Fenderwell Cold Air Induction; Accel dist.,Splitfire plugs, BBK: 1 5/8 unequal length shorties, hi flow H-pipe w/ cats; Flowmasters 2 chamber American Thunder catback system, Motorsports 3-core radiator, 180º thermostat, BBK adj. clutch quad...the rest is bone stock!..but more mods to come!!

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08-31-2004, 02:15 PM	#2
88fivepointoh Registered Member Join Date: Aug 2002 Location: Rochester Posts: 553	Here's what you do, check for vacuum leakes, tune it up, clean your egr, and what is the most important is check you Air temp sensor on the intake manifold. If its bad it will pop. pop is from a lean condition. check your injectors and get them cleaned if nessecary.

09-02-2004, 12:53 PM	#4
88fivepointoh Registered Member Join Date: Aug 2002 Location: Rochester Posts: 553	With that kind of mileage i bet its time for new injectors. And definetly new Vacuum lines. if you haven't changed your 02 sensors do so, and the mass air sensor could be dirty and going bad.. Again also have the TFI module tested.. If thats the original, Please change that.. Its worthless and for sure gunna leave you stranded soon.

09-02-2004, 08:17 PM	#6
88fivepointoh Registered Member Join Date: Aug 2002 Location: Rochester Posts: 553	if its the TFI its a cheap fix, 39 bucks max for the unit... Don't sweat it..

09-03-2004, 01:03 AM	#7
5.0 Fiend Registered Member Join Date: Mar 2004 Location: Central PA Posts: 87	I had the same problem on my 84 carbed motor, I changed the intake maifold gaskets, (oil leak from lifter valley), and I didnt re torque the manifold after a couple of heat cycles, sure enough, I had the same probs.