Hey, got the 383 running good at idle, but when I am on the road at around 2000rpms it is starting to "cut out". What I mean by this is it feels like either spark or fuel is being taken away for just a second, then it comes back and the rpms dont drop but it does for a second feel like it might stall. I havent revved past this rpm yet, but it didnt do this yesterday so it seems to be getting worse quickly. Any suggestions? mods in sig... I just tightened up the header bolts/exhaust bolts and it sounds really good, if it could be roller rockers it probably is, but I have adjusted those things like 4 times now, and they seem perfect.

what would cause this?

 

Don't see anything in your sig about fuel system, such as injector sizes, pump or supply line change or TB change.

Also don't see anything about ignition.

Since it idles ok but has a problem under load, perhaps you want to look at fuel supply under load. If the pressure doesn't fluctuate, perhaps you need to monitor the A/F ratio when the problem occurs. Once you rule out fuel, then start looking at the spark waveform on a scope while the problem occurs.

 

Do you have anything to scan it with. Datamaster would come in handy right about now.

 

ya sorry about that, 42lb lucas injectors, stock fuel pump, stock fuel lines, and I took it to firestone the other day and got the thing scanned, but I do not have a data logger. I did not put my Crank position sensor back on because I could not find enough room on my crank key for the cps reluctor plate. This was the only code that was thrown last week, but the day after I got it scanned this started happening. I really think it is opti, because today I went out to start her up and see what was goin on, even without load (just sitting in the garage) when I revved it the rpms would drop for a sec and then go... but then again that could very well be fuel pump going out too correct?

does anyone have any experience with a fuel pump going out? I have a fuel pressure guage so I will bring that out later today or tomorrow and see if I can notice any drops in FP, but wouldnt the opti going out drop FP also?

there was a very little bit of gasoline that we couldnt get syphoned out of the tank, but I am not sure if this is related because I put some fuel system cleaner in with the tank I put in.

thanks again

 

The distributor has nothing to do with fuel pressure. Fuel pressure is independently controlled by the FPR and engine vacuum. As vacuum decreases like when your foot is in it, fuel pressure increases.

After a good session of the problem appearing, I would remove the plugs and check what running condition they indicate such as lean or rich.

I would also find out if it is a problem related to closed or open loop. Does it run fine from cold until it warms up and then goes to hell or does it run crappy from dead cold? Depending on what you find will determine where to look next.

 

Ok, I changed the fuel filter and checked FP. It seems fine, around 43 at idle, when I rev it up it goes up a little, not much, when decelerating it goes down to about 38 or so. I am pretty sure it does it in both open/closed loop, I started the car, gave it quick throttle, and it did the bog then rev up thing again. After this I pulled it outta the garage and sure enough right near 2000rpms it cut out big time again. Could this be my exhaust causing some big time knock? With my exhaust set up around 2000rpms it used to get really raspy and loud.

I will pull the plugs if this seems neccesary, but there are 2 plugs I need to take the headers off to get to so I can get an idea of each side, but not sure how good this idea will be w/out 2 plugs out.

thanks for the help, hopefully someone has been through this before.

 

plugs on both sides were very ugly, obviously runs rich.

 

anyone else have any ideas? Wont hit this "2000rpm wall" in garage, only hits under load, plugs fouled, new tune... I guess I should call madz28 tonight?

any help is appreciated

 

Would probably be a good idea to see that the O2s, short term and long term fuel trims are doing.

 

I am going to clean the MAF and the IAT and then if those dont fix it the O2s will be checked. Hopefully it can make the short drive to get scanned.

 

Also, I did not re-install the Crank position sensor. There was no room on my crank key for the reluctor plate, thus it is not installed. This is the only code I threw last week, I will hopefully recheck tonight for codes. Would this cause hell on my tune? I was told by my tuner that CPS is only for emissions, but with my recent problems I am starting to think maybe the CPS is the problem?

What causes it to run rich (besides an exhaust leak)?

thanks again

 

The crank position sensor or CKP as it is refered to will have no detrimental effect on the engine. It is purely for monitoring only.

If I were you I would look at 2 items right away. First the O2's since a real rich condition can screw them up. The other is knock. See what the timing is doing when you hit the "wall". Maybe you are getting knock retard.

 

ok the knock sensor wire was snapped somehow, so I replaced it w/ new wire and it is in. I am still getting this same stumble, but I havent reset the computer by disconnecting the battery yet. I did re check all the plug wires, they are fine. There was one vaccum line on the opti that was not completely all the way down on the tube on the opti, so I will reconnect all the plug wires again, put it back together and then see if I can get it up to firestone to get the codes ran. Hopefully I can do this tomorrow.

thanks for all the help speedy, hopefully tomorrow I will have codes for you.

 

The Bank1 O2 sensor reads from 415-800 bouncing around badly. The engine load reads 100% at idle not in gear, and the TP sensor has 2 codes for it, the code for intermittent voltage and the one for circuit low input, and reads at 0% all the time. I opened another post about the wiring, but the other forum doesnt have as much traffic... is this PCM related? The wiring looks fine on the back of the PCM and all the way to it its still covered everywhere w/out any burn marks or anything like that. I just cleaned all the grounds and put them back on very tight, and there is still the hesitation in the garage, im sure it will still die at 2000rpms... anyone have any ideas? Ways to check them? I have voltmeter and would like to check the PCM if possible.

 

Always deal with the codes present before drawing any conclusions about any problem. In your case, I believe you have a DTC 121 for TPS insufficient activity and a DTC 122 for TPS low voltage. These are probably from the same problem of a cut wire/grounded wire more likely or a bad connection or a defective TPS. Easy enough to test to find out which. Fix it first before moving on.

BTW in the case of the 122 code, the PCM will use a default sensor value. It will not apply the torque converter clutch and will drop out of fourth gear when the tranny is hot.