Runs like crap during warm up

Batterystang · Jan 29, 2006

My car runs like complete garbage when trying to warm up. It only does this when it's completely cold, IE, in the morning or whenever it sits for a long time. It's hard to rev, will barely idle, idle bounces around from 500-1000. It seems as if the timing is off during warm up. Also earlier this morning after about a 15 minute warm up (me holding gas pedal at 1500 rpms) it went from garbage to perfect, easy to rev, idled right at 1000 rpms, and ran great besides my vacuum problem (only 2 HG at idle).

My idea of the problem is, the timing is bouncing around... But I dont know what is causing it.

Daggar · Jan 29, 2006

Looking at your description and your mod list, i'd say that your open loop tune might require some tweaking.

Batterystang · Jan 29, 2006

Say I start it, and it's running like crap, I immediately turn it off, unplug the o2's, and then start it again. Will it still run the same? How would this custom Autologic chip respond? Would that then tell me, that it needs more tweaking or a o2 is bad if it runs fine after that?

Daggar · Jan 29, 2006

Not necessarily. My theory is that your open loop tune is off. With your 42 lb injectors, I assumed that you have a custom ship burned or a TwEECer or something along those lines that was able to allow your car to run properly with those sized injectors. When cutom chips are burned, your base tables are modified. Those base tables will apply in either closed or open loop operation. Unplugging the 02s will force your EEC into open loop. having said that, you may want to try and get your car up to operating temp THEN disconnect your 02s to see how it responds. If it goes all flakey in open loop then I'd say that it's narrowing thing down to def being in the tune.

Batterystang · Jan 29, 2006

Closed loop means it's going to run how the computer wants it to run, then open loop means it takes the readings and responds correct?

Also, when it was on the dyno a couple days ago, they said they upped the Fuel Pressure a little bit, you think there is a connection?

Daggar · Jan 29, 2006

Open loop is how the car runs before warm up. It disregards inputs from most sensors and runs from the computer's base maps and any "learned" KARMF settings it has saved.

Closed loop is normal operation. This is where readings from the sensors are used to adjust for AFR and power setting.

Another thought just occured to me. Has your car run like this consistently since the last tune when it's cold??? Or is this just something that has cropped up recently? If it's the latter... it may be worth the relatively simple task of disconnecting your battery over night to erase any adaptive control settings then see if it makes any changes in how your cars acts when cold. You may have some undesirables lurking in your EEC.

1bad92lx · Jan 29, 2006

I just read batterystang's post and what jumped out at me was the fact that he knows that his car has a vacuum leak. Only pulling 2hg of vacuum at idle is definitely a problem. I had an intake leak issue with the 1" spacer on my 92 and it did just what you said. The computer will try to compensate for the problem and normally all cars with vacuum leaks will run better once warmed. I would fix the vacuum issue and then if you still have a problem, tune from that point.

Black1987Stang · Jan 29, 2006

1bad92lx said:
I just read batterystang's post and what jumped out at me was the fact that he knows that his car has a vacuum leak. Only pulling 2hg of vacuum at idle is definitely a problem. I had an intake leak issue with the 1" spacer on my 92 and it did just what you said. The computer will try to compensate for the problem and normally all cars with vacuum leaks will run better once warmed. I would fix the vacuum issue and then if you still have a problem, tune from that point.

+1 for fixing the vacuum leak and go from there

Daggar · Jan 29, 2006

Oooops... I totally missed the vac leak.

95GTV8 · Jan 29, 2006

yes, i had the same problem, cold starts i would have to keep giving it gas and hold it @ 1500 rpm idle. Once the engine was warm is was alot better, but i finally found the vacuum leak, it was very small it was the red line coming off of the throttle body that was really making my car unpleasant to drive.

Batterystang · Jan 29, 2006

Well now I'm onto the vacuum problem. Which could be anything. All the vacuum lines are hooked up properly (same as they were before I got it back from the dyno). The motor was just pulled, and O-ringed. Could the intake be installed wrong causing this vacuum leak? I really dont know what else to check...?

95GTV8 · Jan 29, 2006

make sure the intake is tightened down properly? for sealing the sides of the lower intake did you use RTV, or the funky gasket? did it not go in properly and therefor a vacuum leak? I'm just throwing things out there, but hopefully you can keep checking these things and eventually narrow it down till you find the problem. good luck!

Batterystang · Jan 29, 2006

Actually the motor was put back together by the shop this time. I'm assuming they did it right... Fastlane Motorsports in Benson NC.

I'm going to be calling them tomorrow, see what they say, since I didnt have no vacuum problems before I took it to them.

jgonz727 · Mar 6, 2007

Batterystang said:
My car runs like complete garbage when trying to warm up. It only does this when it's completely cold, IE, in the morning or whenever it sits for a long time. It's hard to rev, will barely idle, idle bounces around from 500-1000. It seems as if the timing is off during warm up. Also earlier this morning after about a 15 minute warm up (me holding gas pedal at 1500 rpms) it went from garbage to perfect, easy to rev, idled right at 1000 rpms, and ran great besides my vacuum problem (only 2 HG at idle).

My idea of the problem is, the timing is bouncing around... But I dont know what is causing it.

I'm suffering from the exact same symptoms: after about five minutes it runs great. However, I have determined that my car is running in open loop ALL THE TIME. While the car is running, I disconnect the MAF connector and it has no effect on the engine....it continues purring like a kitten. I've even gone as far as disconnecting the oxygen sensor harness while the car is running and also, no effect on the engine--the check engine light doesn't even come on for that.

Batterystang, I wondered if you were in the same position...

DMAN302 · Mar 6, 2007

I have the issue since my last SCT program was burned...according to the SCT rep it's simply a result of the car coming out of the 'cold start' mode too quickly...he wants me to bring him the ECU at which time he will increase the time at which the car stays at fast idle. As of now the car comes out of fast idle too quickly and is unable to sustain the lower idle when cold.

jgonz727 · Mar 7, 2007

jgonz727 said:
I'm suffering from the exact same symptoms: after about five minutes it runs great. However, I have determined that my car is running in open loop ALL THE TIME. While the car is running, I disconnect the MAF connector and it has no effect on the engine....it continues purring like a kitten. I've even gone as far as disconnecting the oxygen sensor harness while the car is running and also, no effect on the engine--the check engine light doesn't even come on for that.

I have checked for codes, and I get 67 and 95.

jgonz727 · Mar 8, 2007

I don't mean to hijack this thread, but I want to add more info...I have checked the resistance on both the ect and act at the sensor when the car is warmed up, both are within spec.

jason89gt · May 29, 2007

I've tried testing my ect and act with a multimeter for resistance and get nothing on both? I'm having the same startup problem. It idles low and has 10 hg of vacuum and i swear i hear a vacuum leak I haven't checked it with carb cleaner yet! once it reaches 180 degress idles goes up and vacuum is at 16 hg! But in the last 3 weeks this problems just started when i got a custom chip made for my set up to run at 180 degrees!!! so is there a vacuum leak or is it the tune to run differently as it is warming up? Also i have a air fuel guage and at startup the guage has no movement unless you give it throttle once it hitsa 180 degrees it jump all over between rich and lean like it always did before and that is how ith should be. any thoughts? thanks jason

Runs like crap during warm up

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