help...stall at coldstart & jerk at drive
 

Hi everyone,
Not too long ago, I posted a thread on a problem I had at cold start. My 93 GT will start and then stall. After getting it to start propertly (giving it some gas..) it would hesitate and jerk a bit during driving. The idle would also be choppy too. But one it was warm, the problem would go away.
It was suggested to change the ECT, ACT sensors and look into the 02 sensors too. Well, I popped in new ECT, ACT sensors and even a new EGR valve (the guy at the DMV told me I was failing the NO on emmissions). I'd figure the 02 sensors are ok since I just replaced them about 1 year and half ago. I also replaced the distributor cap, checked plugs etc.
Well...after all these replacements, the problem hasn;t gone away! FYI, no 'Check Engine' lights go on, all the diagnostics appear to be ok. I did have problem scanning the EEC-V, but I probably ended up with the wrong scanner anyway.
Could anybody give me any other suggestions on what could the problem be? The mechanics down the block insist it's the 02 sensors...Could it be a compression problem? Need some feedack!
Ciao!

Get a can of GOOD carb cleaner, no cheapo stuff. Hit the idle air control motor, and passages. Careful on the gasket, but go ahead and reuse it. Next up is the mass air flow sensor. CAREFUL cleaning here too. You'll see a small thing that looks like a resistor hanging in there. Clean that real good. If that fixes it, great. If it helps it out a bit, but doesn't cure it, get a different mass air sensor.

I would have guessed coolant temp sensor, but you already replaced that. Make sure the plug on it is OK, and make sure that there isn't another one. Some of those engines had 1 for the gauges, and another for the computer. Check it out.


Good Luck!

I agree, also clean the crap out of the TB w/ throttle body cleaner. Mine did the same thing, agter cleaning the gunk out of the TB and IAC, it ran much better.

question- whats best to use when cleaning the MAF? i thought u can't use carb cleaner on it. i was thinking alcohol and a q-tip?

...thanks fellas,
I actually went thru a can of STP carb & choke cleaner on the TB and a little on the IAC, although I didnt pull it out and cleaned it thoroughly since I replaced it last year (it should still be failry clean, right?? hmm...) .
I'm still thinking about those BOSCH O2 sensors I payed for last year. I refuse to think they're already bad...but then again I do have a BBK pipe (w/ cats) and shorties. I'll look into the MAF too, and the PCV valve too...
boy..gotta hate those cold starts!!!!
thanks!
fongo

what the jester said.... spray away!

I use carb cleaner on the MAF sensor all the time. Use the "red needle" that comes with the can, just don't put it right up against the sensor itself. Usually it "looks" OK, but after cleaning it, you'll be surprised just how small that little resistor in there really is.

I've also had problems with the Bosch sensors on EEC-IV and V systems. Car runs like crap with a brand new Bosch, take it out hang a Ford unit in there, and presto! It's a few extra bucks, but in my opinion, money well spent.

i have the same problem it runs like crap when u started and after hitting the gas it is ok ,any ideas my is 88 ,and same think happens when u turn it off and start back on ,someone told me that it could be the tp sensore is that true ,let me know thanx

I'll let you fellas know how it goes (..try it this weekend).
I haven;t had any TB TPS problems though. Once the idle holds, it hold steady at about 500-600 RPM, nice and smooth too.
You know....I failed to mention another thing. When I start cold, I also hear like a 'detonation' coming out from under intake or exhaust, almost like an internal backfire. Could it be I'm running lean as the result of a dirty Mass air sensor..or is it really the O2 sensors?
Mr. Jester ; I'll try the ol' spray thing on the MAF.
XBAJBUSX: With a voltmeter, check the TPS on your throttle body. Your volt setting may be off too. With a Phillips screwdriver, you can adjust it to 0.8V (Is this it guys? someone please verify this setting, and help out XBAJBUSX! thanks!)

Happy Stanging!

Electrical contact cleaner works good on the MAF. Your o2's could be causing it to run lean. As jester said, the bosch units aren't that great. What is the timing set at? What is your fuel pressure? Do you get any smoke out of the mufflers? These just essential things that you should know how to check and some of the first things you check anytime you have a problem. My .02.:)

key on, engine off, (KOEO) 0.995-.998 D.C. High TPS voltages
are characterized by a very erratic idle or stalling when coming to a stop (ECM error code 66). Set the throttle by
removing the connector from the Idle Speed Control Motor, with the engine warm and the air conditioner off, using the
throttle screw set the Idle Speed at 700 RPM ( or desired RPM). On '94 and later models use the idle bypass screw
at the right side of the throttle body covered with a plastic cap. Reset the TPS to obtain 0.995-.998 volts D.C.
between the black and green wires on the throttle pot. If the unit has no voltage, check the voltage between the black
and orange wires. This should be 4.9-5.1 volts D.C. with the ignition on. If the voltage is 4.9-5.1 D.C. and there is no
voltage on the green wire, the throttle position sensor is no good. If there is no voltage on the orange wire, you must
find a break in the wire. Reconnect the Idle Speed Control Motor and check for engine stability

DONT GO OVER 1.00!!!!!

ok i got it work great thanx jester i just clean the idle speed control with carb cleaner and it works fine ,the idel control was very very dirty ,thanx