When driving my car, starting from a stop, as the car shifts gears from 1 - 2 and 2 - 3 there is a split second of the car have very little acceleration. It is not the car shifting gears either, there is a clear lack of power for about half to a full second. Also when cold the car stumbles when cold and takes off great warm. 1500 rpm idle hot or cold. Warm car acts great cold car acts "rough" for lack of a better word. When accelerating hot car sounds normal and when accelerating cold the car sputters. Exhaust notes are way different. I know when my car goes into closed loop by sound alone, let alone the way it drives.
Also the alternator was replaced with the cheapest one you can buy which was the lowest output one as well. Could this have any affect on anything? Alternator is about two and a half years old but car sat for about 1 and 3/4 of that.
That sounds like almost exactly what I was dealing with on my 87 GT (see the thread here). I resolved the issue nicely by replacing the Intake Air Temp sensor and the Coolant Temp Sensor. After I did...it not only took care of the cold car symptoms, it increased the drivability when warm...better idle at stop and better take off when under additional load ( A/C running for instance). Idle now is pegged at 950 rpm when at rest ...instead of 1200rpm always...whether in drive or in park...better step down when modes change (such putting it into park...or turning A/C on/off). The nice part is that was a relatively cheap and painless fix. I paid only $53 for the parts and a couple of hours wrenching (someone experienced could have done both in about an hour I suspect
When driving my car, starting from a stop, as the car shifts gears from 1 - 2 and 2 - 3 there is a split second of the car have very little acceleration. It is not the car shifting gears either, there is a clear lack of power for about half to a full second.
Are you sure the transmission isn't slipping? Mine used to do that slightly during the 1-2 shift, uphill, when cold, but only once. Turns out I have a very slow fluid leak, topping it up fixed it.
The stumbling and sound difference when cold could be a bad air/fuel ratio in open loop. Once it enters closed loop the feedback from the O2 is helping it to correct for whatever is wrong. It might be temperature sensors. They can be checked with a multimeter:
The IAT might recover it's accuracy with cleaning. Note the CTS and the temperature gauge sender are separate, the CTS (which talks to the ECM) is on the passenger side of the engine, I think pretty much underneath the EGR solenoid.
Maybe im missunderstanding your problem. All engines will stumble a bit accellerating when they are cold. Carb engines are the worse though. If its fine warm, I dont see any problem. You go fooling around with stuff, your just liable to make it worse or make more problems
I guess the next thing I'd suggest is to poke around with some general sensor/vacuum diagnosis. If you're able to hook up a laptop with WinALDL, it might show something going on. But then a lot of times it doesn't.
Check the resistance on the CTS if you didn't already. But I know you said it was replaced so it's not as likely a candidate. I'm a little confused why it idles at 1500rpm even when warm - normally the ECM should drop down to 900rpm once the coolant temperature is reasonably warm.
Does your "service engine soon" light work? It should come on temporarily when you turn the key. If so, is it showing any errors while driving?
Any possible vacuum leaks? That can always cause some running issues. The feed from the EGR valve to the underside of the plenum is a common leaker. One area to definitely check: There's a vacuum connection with a "T" going into the passenger side of the upper manifold. One side of the "T" goes to the MAP sensor, the other end goes to the fuel pressure regulator. If you disconnect the hose that leads to the FPR, is it possible to suck fuel out of that hose? If so, the FPR is leaking, which introduces extra fuel to the manifold that shouldn't be there. It might also interfere with MAP sensor readings.
The MAP sensor might be a candidate for your problem. When the transmission shifts, the TPS isn't moving but the MAP probably changes a lot. If the MAP readings were inaccurate, it could throw off the ECM badly at that moment. What happens if you drive the car with the MAP sensor electrically unplugged? Does it run any better, or just get worse? A vacuum leak near the MAP could cripple it's function. Once the O2 warms up and the car enters closed loop, to some degree it may compensate for static issues with the MAP, but I think it would still have problems with transients like an upshift.
You could check resistance or voltage at the throttle position sensor. Try to see if it changes smoothly when you slowly move the lever on the sensor. They sometimes develop a flat spot in the area of light throttle. This is a fairly common explanation of stumbling problems. However, I don't think this kind of failure would improve when hot, as yours does.
With the key on, both the MAP sensor connector and the TPS connector should have +5V on one of the pins. If that +5V supply is low it could distort the readings.
I used to have a stumble coming off a dead stop. I'm not sure of any 1 thing that fixed it, but I think injectors were a big part of it. However, that's probably the last thing to worry about due to their inaccessibility, lack of good way to diagnose and the cost. If you have multecs (many were swapped into these cars) then those are known for shorting. This can be checked with a multimeter, if you can actually get probes on them. But I think that condition usually gets worse with heat, not better.
[This message has been edited by armos (edited 07-11-2013).]
I will have to have my dad check the resistance because he's the one with all the electrical tools.
The throttle plate screw was tampered with so I did the IAC reset on The Ogres site. With the idle low the car will die all the time so I should have specified I turned the idle up to 1500 not just say it idles 1500 hot and cold. Sorry on my end there. I can get it to idle low with and IAC reset but the car will die when coming to stop signs or stopping in general every stop while cold and a few stops when warm.
My service engine light does work. No codes. I get 12 to flash repeatedly so the system works fine too.
There is always a possible VAC. leak but when I blocked off the EGR it did absolutely nothing to the running. There is no fuel coming out of the Fuel Pressure Regulator. Had the upper intake off a couple weeks ago replacing injectors and fuel rail. When I took off the VAC. line there was ZERO fuel in the line.
I will check MAP sensor when I get home from school.
My dad tested the TPS with two different meters and it worked normal he said.
I will have to have my dad check to see if there is 5v at the sensors.
Cleaned injectors, CTS, IAT, cleaned 02 sensor, checked TPS, IAC, cleaned throttle body, and added grounds. <--- Some things that have been done recently.
COLD START: Start die, Start die, Start hit throttle idles for maybe 5 seconds, Start car give it throttle then let idle put in drive die, Start give throttle put in gear give more throttle while not pushing the break down, now I'm driving away, Normal acceleration for about 2 seconds, Car now bogs for about 2 seconds, After bog down more acceleration 2 seconds, Shift gears into 2 gear bogs down for 2 seconds, Less acceleration than before but accelerates, Stop for stop sign car dies, Restart dies, Restart push throttle runs put into gear dies, Restart push throttle runs put into gear while giving gas takes off like before, ACCEL-BOG-ACCEL-BOG stop sign dies, Restart push throttle runs put into gear while driving takes off give it more gas because pulling onto a bigger road now, less bog with more gas, bog from 1-2 shift and 2-3 shift Stop at stop sign bigger road so I keep my foot on the pedal to keep it running RPM's going sporadic. 1300-500 rpms. Take off from the stop less power than it should have, give more gas acts better does a bog from 1-2 shift, NO bog from 2-3 shift Driving from 20-40 MPH the car accelerates the entire time but sometimes it acts smoother and sometimes rougher, when smoother there is and increase in power with no pedal movement, Does this maybe 2 or 3 times accelerating from 20-40, Driving at 40 car slowly slows down unless i give it more throttle to get back up to 40 then car will hold 40 for a couple seconds maybe 5-10 seconds, Then car slows down slow with throttle in same spot, Accelerate to 50 MPH does the same thing it did at 40 at 50, TCC doesn't lock up for about 10 minutes of driving so TCC is not locked up at this time, After about 1 min of driving 50 car holds a steady speed when at a steady throttle, still no TCC lock up, I can hear/feel the car sound and drive better so I come to a stop after about 6 minutes of total drive time and about 4 miles, After stopping car idles good at 750 RPM in drive with a tad bid of hunting idle about 900 to 600 RPM's of hunting, Turned the fan on with the AC button before coming to a stop, At this time I attempt my first full throttle run in the new rebuilt engine at 2000 miles on the clock after rebuild, Timed 0-60 - 8.59 Shifts at 4800 and 4900 from 1-2, 2-3 Hit 100 MPH total, After the full throttle run driving home it drove better than ever. Came to my first stop with fan still on and car idled great with no idle hunt, Take off from stop onto a state road with no hesitation in acceleration, Drive 55 and drove smooth with no slow decel, Came to next stop acts the same way, great accel no bogging what so ever, Taking off as smooth as my dad 2012 Malibu, Driving 20 in my neighborhood just as smooth, Two more stops acts the same, Stop at home and put the car in reverse at a stop, RPM's drop 100 from 900, Strong idle in drive, reverse, neutral, and park,
Checked a sensor i had from another car and it seemed to be working perfectly. So when I took the one off the car that I'm working on I would be able to keep the hole plugged and drive it still. Also since it tested perfect thought what the heck, can't do any harm. So I put the spare in the car after taking the "new" one out. Reset the ECM and drove into the country and got to 60 MPH and car has never acted any smoother! The car threw a code and died in the beginning though because I forgot to plug the sensor in. After that though the car operated flawlessly like I would expect my fiero to operate!
The so called new sensor I had bought did not react as fast on my dads meter to hot and cold and would sometimes start in the wrong direction then start going the right way. Thanks for all the help guys.
Reset the ECM and drove into the country and got to 60 MPH and car has never acted any smoother! The car threw a code and died in the beginning though because I forgot to plug the sensor in. After that though the car operated flawlessly like I would expect my fiero to operate!
But before all the cheers I haven't done a cold start yet without the ecm in reset mode so fingers are still crossed.
I am pretty confident it will work. As you will recall I had the exact same issues with my 87 GT ....When I swapped the IAT and CTS I got the same result you did when driving it warm (before I could do a cold test). I didn't realize I was having as many drivability issues as I was until I drove drive after the swap....night.and.day difference! And the first time I started it cold, it started instantly had one quick hunt for idle (without a stall) and ran just like it does when warm
[This message has been edited by 92wastheyear (edited 07-14-2013).]
Also to not start another thread is there a way you can tell if the fan switch is working properly?
It is kinda hard to check....the stock fan switch doesn't come on by itself until it hits 235* (I think). That being said, the fan should come on anytime the A/C is fired up...I have done this when stuck in downtown traffic and it starts heating up and I can see the effect withing about a minute. I am going to get one of those lower temp switches one of these days ...they have one that comes on at 195*. You can get them at TFS and Rodneys....Rodneys are cheaper
That is too bad that your cold start didn't do as a well as mine did. I wonder what other things you can try.