Anybody get horrible driveability for about 30 seconds after a cold start?

[RacEoHolic330]

I've been dealing with this issue for a while, but I'm really getting sick of it. When I start my car up after its been sitting for a while, it will run fine for about a minute, and then it goes very lean and if I try to drive it, the engine will buck and stutter and stuble and pop. This will last for about 30 seconds, and then it goes away and the car runs fine. During this 30 second period of crap, the car idles amazingly steady though, but it sounds very different...its hard to explain. It won't happen if I shut the car off and then start it back up right away. But even if I let it sit for about 20 minutes when the engine is still somewhat hot, it still pops and stumbles.

At first, i thought it was because I replaced my left o2 sensor with a wideband o2 sensor. It did have a simulated narrowband output though (PLX M-300). I recently welded in a seperate bung just for the wideband and put a new stock sensor back in, but that did nothing.

So it seems that the computer is going into some sort of loop mode for a little while. Could my right o2 sensor be going bad? If anybody has had similar issues and could offer some input, I'd appreciate it.

-Scott

 

[BlownFiveLiter]

I'd honestly like to know what's going on, too. My 95 does the same thing, almost like running a carb with no choke until the O2 sensors warm up and take over. I'm absolutely sure I need to step up to some 24lb injectors though, since I'm still running stock 19's with the mods in my sig...

 

[86bluecobra]

30 seconds? Umm I think you guys should just let your cars warm up. No doubt there is an issue, my 302 EFI pick-up does the same thing, but you should be letting your car warm up efi or carb before you start out. Atleast till the high idle comes down. That should be within the first minute. Perhaps the car just needs a tune up. Are the spark plugs gapped correctly? Whens the last time you looked at your dizzy cap?

 

[RacEoHolic330]

The thing is that mine will still do it whether it's warmed up or not. I can drive the car to the store, turn it off, come back out 30 mintues later, and it will run like crap for less than a minute and be fine afterwards. When it's idling during this time, it idles between 820 and 850 rpm. The idle is extremely steady, but the engine sounds very different. My plugs are gapped at .035 and all of them are indexed. The dizzy probably has about 1000 miles on it. I'm leaning towards this being some sort of o2 sensor problem. My wideband shows the car going very lean when its running in crappy mode.

 

[Aliate X]

yeah same crap happens to me regardless how long i let it warm up

 

[vristang]

Pull the diagnostic codes and see what the computer says.





jason

 

[hillie16]

Its ur air idle control on the throttle body. Take it off, get some
brake parts cleaner, spray in part and let it dry out and put it back on.
Carbon build-up causes that.

Looks like she replied with this, but accidentally clicked it as "Report This Post" instead cuz this just came in my e-mail.

 

[HISSIN50]

The thing is that mine will still do it whether it's warmed up or not. I can drive the car to the store, turn it off, come back out 30 mintues later, and it will run like crap for less than a minute and be fine afterwards.

The issue seems to occur after starting the car up, irregardless of engine temp. That sounds like an idle surge issue to me. If the issue goes away within 30-120 seconds, it's probably not the O2's (the O2's come online after that time and might actually be helping to fix the issue, right?). I'd wonder about ECT calibration and MAF cleanliness (other things that are used for Trim when O2's are not online).

As wisely suggested by Jason, see if any codes come up. You might end up with a calibration issue rather than an absolute spec code, unless something is really whacky during that surge time.

Good luck.

 

[Mustang5L5]

Looks like she replied with this, but accidentally clicked it as "Report This Post" instead cuz this just came in my e-mail.

I got it too, must have hit the wrong button

 

[BlownFiveLiter]

I have no codes in my particular case, but I can't speak for the OP. I also don't believe my IAC is the problem as it worked perfectly fine prior to swapping the new engine in. If I had to guess, mine's likely because of going lean in open loop with 19lb injectors, because it's strictly running on the fuel tables in the EEC at that point. Once it goes into closed loop it's fine, but I was hoping someone would be able to offer up another reason that it may happen.

 

[vristang]

I have no codes in my particular case, but I can't speak for the OP. I also don't believe my IAC is the problem as it worked perfectly fine prior to swapping the new engine in. If I had to guess, mine's likely because of going lean in open loop with 19lb injectors, because it's strictly running on the fuel tables in the EEC at that point. Once it goes into closed loop it's fine, but I was hoping someone would be able to offer up another reason that it may happen.

A little off topic, but oh well...
It turns out that the adaptive strategy that is learned in CL is in fact used in OL.

This means that if the Adaptive learning sees that the mixture is constantly rich in CL conditions, the ecu will apply that same correction factor to the OL operating conditions.

There is no learning at WOT though.


jason

 

[speedytang]

Sounds like a leaking injector to me.
If you put a fuel pressure gauge on the rail you can see if the pressure is dropping.
I replace individual injectors all the time for the same things you guys are having problems with.

 

[RacEoHolic330]

i'll check the codes tomorrow, we have a storm on its way in soon.

speedytang, are you talking about the fuel pressure when the car is running or after the engine is shut off?

 

[86bluecobra]

The thing is that mine will still do it whether it's warmed up or not. I can drive the car to the store, turn it off, come back out 30 mintues later, and it will run like crap for less than a minute and be fine afterwards. When it's idling during this time, it idles between 820 and 850 rpm. The idle is extremely steady, but the engine sounds very different. My plugs are gapped at .035 and all of them are indexed. The dizzy probably has about 1000 miles on it. I'm leaning towards this being some sort of o2 sensor problem. My wideband shows the car going very lean when its running in crappy mode.

From "The Official Ford Mustang 5.0 Technical Reference & Performance Handbook 1979-1993" Ford Racing Part No. M-1832-Z4

Page 274
"Spark Plug Applications" table
Year---------Engine--------------Motorcraft number-------Gap (inches)
1979---------5.0L (49 state)-----ASF-52------------------.050
1979---------5.0L (california)-----ASF-52-6---------------.060
1980---------4.2L (all)-----------ASF-42------------------.050
1981---------4.2L (all)-----------ASF-52------------------.050
1982---------4.2L (all)-----------ASF-52------------------.050
1982-1985---5.0L carbureted-----ASF-42------------------.044
1982-1985---5.0L CFI------------ASF-52------------------.050
1986--------5.0L H.O.------------ASF-34 or 44------------.050
1987-1993---5.0L H.O.-----------ASF-42------------------.044
1993--------5.0L GT-40 (Cobra)--AWSF-42C---------------.050

1. Factory electrode gap specifications are shown on each Mustang's VECI label that is affixed underhood. The relatively wide gaps specified created the fat, long-duration spark needed to ignite the lean mixtures prescribed for most normal operating conditions.
2. Most non-Cobra 5-liter motors typically run well with spark plugs gapped at .052 inch. For normally aspirated engines in high-performance service, a plug gap between .040-.045 inch is suggested by many tuners. Those same sources also suggest .028-.034 inch in turbocharged, supercharged, and nitrous-fed five-ohs.
3. Some 1993 GT-40 Cobra motors were factory fitted with colder, AWSF-32C spark plugs.


I notice that you are supercharged so I realize the reason for the .035 gap. But for ather people perhaps there gap is the issue.

 

[Nutty 5.o]

I had similar issues until I tuned it out with the PMS. You may want to look into stangtuning.com as they helped me out alot. Just needs some more fine tuning!

 

[BigHairyMonkey]

My car does the exact same thing, thats why i refuse to drive it until it has sat idling for at least 2-3 min upon cold starts. If i drive it before hand itll run like **** and pop outa the intake (not everytime but most). After i let it warm up it runs fine

 

[speedytang]

Check pressure when not running. It should hold for sometime before dropping off because of fuel/pressure returning to the tank. It can also be a bad fuel regulator if you smell fuel when you remove the vacuum line to the regulator.

 

[HISSIN50]

Check pressure when not running. It should hold for sometime before dropping off because of fuel/pressure returning to the tank. It can also be a bad fuel regulator if you smell fuel when you remove the vacuum line to the regulator.

The one exception I can think of is that some aftermarket AFPR's bleed down very quickly upon shut-down.
Now the stock FPR's seem to very often hold pressure quite well for 30+ mins.

 

[Black1987Stang]

I've been dealing with this issue for a while, but I'm really getting sick of it. When I start my car up after its been sitting for a while, it will run fine for about a minute, and then it goes very lean and if I try to drive it, the engine will buck and stutter and stuble and pop. This will last for about 30 seconds, and then it goes away and the car runs fine. During this 30 second period of crap, the car idles amazingly steady though, but it sounds very different...its hard to explain. It won't happen if I shut the car off and then start it back up right away. But even if I let it sit for about 20 minutes when the engine is still somewhat hot, it still pops and stumbles.

At first, i thought it was because I replaced my left o2 sensor with a wideband o2 sensor. It did have a simulated narrowband output though (PLX M-300). I recently welded in a seperate bung just for the wideband and put a new stock sensor back in, but that did nothing.

So it seems that the computer is going into some sort of loop mode for a little while. Could my right o2 sensor be going bad? If anybody has had similar issues and could offer some input, I'd appreciate it.

-Scott

Mine did the same thing, except it was doing it all the time, it had the same "different sound" to it as I think you mean.... It would fix itself when I put on another maf then start doing it againa few days later. I got another good maf and still did it, but then took the stock catted h pipe off and put on my o/r x pipe and by the end of the night it was fine once it edited the fuel trim without the cats......So I'm assuming it had somethign to do with the cats.....I just reused the same 02's btw....I would pull the codes and go from there....Maybe you can mess it through the PMS?.....I don't think it's the gap or fuel problem since it just does it for 30 seconds, if it was them it would be doing it more or all the time. Just ,y 2 cents

 

[RacEoHolic330]

Thanks for the replies. I'll definitely check for codes tomorrow. As for the fuel pressure dropping when the car is shut off, it gets to 0 after about 10 minutes or so. It doesn't drop off quickly or anything. We'll see what tomorrow brings.