Go back to previous topic
Forum nameTurbo/Nitrous Tech
Topic subjectLow RPM Studdering/Jerking Problem, Upper stage guys please read!
Topic URLhttps://forums.2gnt.com/dcboard.php?az=show_topic&forum=i8&topic_id=32958
32958, Low RPM Studdering/Jerking Problem, Upper stage guys please read!
Posted by Super20G, Oct-18-02 08:13 AM
Ok guys, got a little problem.

My engine is running like crap and I don't really know how to troubleshoot it.

Ok, got a lot of bits and pieces of observations I have made, so you kinda gotta piece it together to make sense out of it if it does make sense at all, hehe...

The idle: Idle is preey steady, revs good and steady as well. No problems there it seems. Fuel pressure is 47psi at idle, which is usually what it is... Map value at idle is -7.3psi per the calmap software, didnt check with the datalog software to see if its the same on the OEM sensor, I can if anyone thinks that would be useful in determining a problem.

I removed the spark plugs, they are black and suity, with just the tip of the electrode being white... rest black...

The problem: The problem is under load. When taking off in 1st, it will bog down real bad if and shake the car. If you feather the clutch and the gas and finess it, its minimal, but just driving it normally, it bucks like a bronco, this is in all the gears by the way, not just lower ones.

It seems to buck like this on average from idle rpm to about 2800 rpm. If its bucking, and you give it more gas, then it just bucks harder and want to fall on its ass it seems.

If on the highway, shift to 5th for example and be around 2000 rpm's, step on the pedal to wide open throttle and it will buck and slowly rise as it does so till it gets to about 3000rpm, then it will get out of its funk and kick some ass... but when its in its funk, its like its loading up on fuel real bad, or misfiring or some shit i dunno, but I dont know what to do to check this out...

I had a default file for the DFI saved, i think its the Hahn Stage 5 map for the 20g, but i am not positive, i loaded it and its still the same... I thought the DFI might have "lost" the base fuel map wince i have been messing with the battery lately...

I have also made sure the plug wires are getting a good connection, dunno if the coil pack might be bad, doubt it, i tested it a few weeks ago and it was within range...

Like I said, once its out of its funk around 3 grand, it will build the rest of the boost it has to go and be fine... but lower rpm's are really nasty :-(

Any helpful hints would be much appreciated. If a screen shot from the base fuel map on the Calmap software would help, or datalog values or gauge or sensor readings, just name it and I'll do it... no shop here will touch my car cause they're scared they're gonna fugg it up, or some shit... plus i dont have a job, hehe...
32959, RE: Low RPM Studdering/Jerking Problem, Upper stage guys please read!
Posted by Fast420A, Oct-18-02 08:51 AM
Anytime I have had any studdering between 2k and 3k rpm it has been plug wires that needed changing. I know you already tested them but maybe you should get another set just to be sure.

________________________________________________________________________________________
current status - unknown
Project: Baby on the way


http://hometown.aol.com/ohshootuhh/
www.Fast420A.com


32960, RE: Low RPM Studdering/Jerking Problem, Upper stage guys please read!
Posted by JustOne, Oct-18-02 09:06 AM
Is the map sensor for the DFI plugged in and ok?

I was working on my car one day and pulled the wires out of the harness and didn't see that I did it. It was loading up the car very bad and would jerk or buck like I had hydraulics on the car in the low rpms.

Check that sensor out just to make sure its ok.

32961, RE: Low RPM Studdering/Jerking Problem, Upper stage guys please read!
Posted by Super20G, Oct-18-02 09:19 AM
Ok, so it drove fine a minute ago.... You never know with these cars, hehe.... Could it have been cause it took me shutting the ignition off and back on for the base fuel map i loaded in the dfi to take effect? Cuase after it loaded the file, i drive it and it acted up still, but nextime i get in the car its fine... maby i just jingled the right loose wire or someshit i dunno, but i'll take all the luck i can get, hehe... Now I can work on my power drain problem that isnt consistent.. sometimes car wont start 30 minutes after i drive it, sometimes it goes for a day or so and will still start back up... hehe... then i'll replace the rear main seal thats causing my clutch to slip, then i'll take a gun out and shoot myself, lol.
32962, RE: Low RPM Studdering/Jerking Problem, Upper stage guys please read!
Posted by fly1, Oct-19-02 10:43 AM
Hmmm, I'm thinking either you're running very rich or a connector to the DFI or MAP is loose. I'd doublecheck for any loose connections because the problem seems to be intermitten.

If you could post a screen shot of your fuel map, I'd like to see that. Also, did you try altering the TPS Acceleration percentages in "Acceleration Enrichment." At the first throttle (rpm)/fuel enrichment % set point, I tried lowering Pulse Width to 2.21 (mS), which is the point between 2-3K rpm's. Now, my car accelerates pretty smoothly when driven around town.