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Chugging and RPM Dump

S

Savior

CEG'er
Joined
Dec 6, 2002
Messages
306
Location
Honolulu, Hawaii
A few days ago, my engine began to chug when I would accelerate. It got worse as the day went on and yesterday it stalled out completely and I had to park it along the street. It had gotten progressively worse as the gas gauge went down, and at the time that I had to park it by the side of the street it would idle OK, but would stall if I pressed the accelerator at all. The gas gauge was near empty at this point.


It exhibits a weird behavior: Whenever I rev to 3,000RPM, the tach needle instantly drops to zero RPMs and the engine chugs and nearly stalls, then quickly recovers and settles itself at normal idle. It's like it can't rev past 3000RPM. It rarely stalls completely, and is *sort of* driveable, very slowly.

I thought my PCM might be on the fritz since I had disconnected the battery terminal a few days ago, leaving the PCM to feel out its settings and recalibrate itself, so i used my XCal2 to return the programming to stock, then back to the 91-Octane performance tune, neither one of which had any effect. Then I limped it to a gas station and filled it with premium gas and let it idle for several minutes. The problem went away! Bad gas? With water in it? That would explain why it got worse as the gas tank got closer to empty (doesn't water float in a layer along the top of the gas?).

But now it is doing it again, intermittently. I poured some HEET water remover into the tank, it seems to have helped a little. What else could be wrong though? Do you think it is just bad, watered-down gas? Do I just have to burn it out? Or is it something more severe, like a dying fuel pump or something?

Oh I forgot, I've had a CEL for about 2 weeks now, it is a P1000 code and a P1131 code. I've read about them a good bit though, and the general consensus seems to be that they don't affect performance, and that it's probably my downstream O2 sensor going wonky. This chugging/stalling/RPM limit just started a day or two ago. Are these things connected?

[EDIT] - The P1131 code specifies that it is trying to compensate for and "over-lean mixture" in the air-fuel ratio, or something like that... If my O2 sensor were dying on me, could the car's attempts to compensate for the O2 sensor's false readings result in this problem? Is this something completely different, or should I replace my O2 sensor?

[EDIT 2] - OK, now it won't start at all.. It just chugs and dies. Crap. Help!
 
Savior said:
A few days ago, my engine began to chug when I would accelerate. It got worse as the day went on and yesterday it stalled out completely and I had to park it along the street. It had gotten progressively worse as the gas gauge went down, and at the time that I had to park it by the side of the street it would idle OK, but would stall if I pressed the accelerator at all. The gas gauge was near empty at this point.


It exhibits a weird behavior: Whenever I rev to 3,000RPM, the tach needle instantly drops to zero RPMs and the engine chugs and nearly stalls, then quickly recovers and settles itself at normal idle. It's like it can't rev past 3000RPM. It rarely stalls completely, and is *sort of* driveable, very slowly.

I thought my PCM might be on the fritz since I had disconnected the battery terminal a few days ago, leaving the PCM to feel out its settings and recalibrate itself, so i used my XCal2 to return the programming to stock, then back to the 91-Octane performance tune, neither one of which had any effect. Then I limped it to a gas station and filled it with premium gas and let it idle for several minutes. The problem went away! Bad gas? With water in it? That would explain why it got worse as the gas tank got closer to empty (doesn't water float in a layer along the top of the gas?).

But now it is doing it again, intermittently. I poured some HEET water remover into the tank, it seems to have helped a little. What else could be wrong though? Do you think it is just bad, watered-down gas? Do I just have to burn it out? Or is it something more severe, like a dying fuel pump or something?

Oh I forgot, I've had a CEL for about 2 weeks now, it is a P1000 code and a P1131 code. I've read about them a good bit though, and the general consensus seems to be that they don't affect performance, and that it's probably my downstream O2 sensor going wonky. This chugging/stalling/RPM limit just started a day or two ago. Are these things connected?

[EDIT] - The P1131 code specifies that it is trying to compensate for and "over-lean mixture" in the air-fuel ratio, or something like that... If my O2 sensor were dying on me, could the car's attempts to compensate for the O2 sensor's false readings result in this problem? Is this something completely different, or should I replace my O2 sensor?

[EDIT 2] - OK, now it won't start at all.. It just chugs and dies. Crap. Help!
Click to expand...

my first leaning is towards ur fuel injectors. when u say chug, what exactly do u mean? its not a word i hear used with regards to cars. do u mean like jerking? truth is, it could be anything in ur fuel system, so start with cheapest repairs and work ur way up. first do a fuel system flush.
 
yeh what he said, definitely sounds like fuel system and do the cheapest first.

I have seen a partially blocked fuel filter cause these exact symptoms. If it hasn't been replaced in the last year or so do that first, only $10.
 
Silver Bullet said:
yeh what he said, definitely sounds like fuel system and do the cheapest first.

I have seen a partially blocked fuel filter cause these exact symptoms. If it hasn't been replaced in the last year or so do that first, only $10.
Click to expand...

Hmmm... For the last three years straight, my car has sat under a tarp in my parents' back yard, through two winters and three summers while I was being deployed and getting settled here in Washington (Navy). I brought it up here to WA in Feb of this year, but haven't replaced anything yet... Not even the oil, oil filter, spark plugs/wires, fuel filter, etc. Guess I better get on that, huh?

I have purchased a full set of new spark plugs (the AutoLite APP764 ones), six quarts of Royal Purple 5w-30 oil, a new oil filter, a can of the Engine Restorer formula from Auto-Zone (is that stuff snake oil?), and I'm currently debating over what kind of spark-plug wires to get.

And yes, when I say chugging, I mean violent jerking due to the rapid loss and restoring of power.

But you think the most likely thing would be the fuel filter? How much does a fuel system flush cost? would that fix a clogged injector? I ran a couple bottles of gas treatment/fuel injector cleaner through, but that didn't help either.
 
Savior said:
Hmmm... For the last three years straight, my car has sat under a tarp in my parents' back yard, through two winters and three summers while I was being deployed and getting settled here in Washington (Navy). I brought it up here to WA in Feb of this year, but haven't replaced anything yet... Not even the oil, oil filter, spark plugs/wires, fuel filter, etc. Guess I better get on that, huh?

I have purchased a full set of new spark plugs (the AutoLite APP764 ones), six quarts of Royal Purple 5w-30 oil, a new oil filter, a can of the Engine Restorer formula from Auto-Zone (is that stuff snake oil?), and I'm currently debating over what kind of spark-plug wires to get.

And yes, when I say chugging, I mean violent jerking due to the rapid loss and restoring of power.

But you think the most likely thing would be the fuel filter? How much does a fuel system flush cost? would that fix a clogged injector? I ran a couple bottles of gas treatment/fuel injector cleaner through, but that didn't help either.
Click to expand...

wow. after all that sitting, u really shouldnt have been driving that car without replacing vital fluids. i dont think a fuel flush would fix clogged injectors. but it would eliminate clogged filter and lines as culprits. i'm not sure how u troubleshoot for faulty injectors. look around or search. sumthn should come up. fuel system flushes are around 80bucks here. my guess is that after all that sitting, u've accumulated quite a bit of moisture and crap in ur tank. thats why it ran better when u filled up.
 
Well, I watched my 'tour hauled off to an auto shop last night on a tow truck. I successfully replaced the fuel filter and it started right up after I re-pressurized the fuel system, but it still did the strange RPM-drop thing; like intermittently, every 5-7 seconds, the check-engine light would flicker on for a split-second as the RPMs would drop to zero and the engine would chug, then it would quickly recover itself and go back to normal idle. The check engine light would only come on for a second though, until the RPMs went back up to regular, so I can't even get a CEL code with my XCal2. :( I guess its outta my hands now. Oh well.

I'm awaiting word on a diagnosis. Should be in an hour or three.
 
You could really, really, really help to to help you, help you, help you, help you, if you would tell us more about your car.

Year, YEAR, engine, model, trans, etc.

Knowing what year would help a lot, as the fuel system is different for a late 99 and 00 and would make a difference in how we could help, help, help.

Lack of information is a common illness. I hope you recover.
 
Hehe... Right, sorry.

-1998.0 E-0 SVT
-Stock 2.5L engine
-Stock MTX-75 transaxle
-XCal2 with Performance Tune (the one that comes with the XCal2), for engine code RJL1
-K&N cone-style cold-air intake filter
 
does he have the dreaded fuel-pump disc-screen & sock issue ? or could he have a bad cat ?
 
Big Jim said:
The dreaded fuel pump disc-screen would not apply to his car. That only applied to the returnless system of late 99 and 00.
Click to expand...


OK, so the Dreaded Fuel Pump Disc-Screen thing doesn't apply, but would a bad cat cause such violent reactions?

I went back to get my SVT two days after dropping it off, and was treated to a $711 bill, apparently the front drivers-side wheel bearing was shot and needed replacing, my e-brake cable is broken, all my spark-plugs were fouled (did not surprise me at all since they sat unused for like 3 years straight), and there was moisture in my PCM module which they said was causing all this violent RPM-dropping and stalling stuff.

So I drove it about two miles towards home before it started intermittently dropping the RPMs to zilch again, causing the car to violently chudder with each RPM-drop. It happens about once every 4-6 seconds randomly, lasts only a second, and during the RPM-drop the Check Engine light flashes on and then flickers off as soon as the engine recovers itself to normal RPM range, so I can't get any kind of reading on a DTC code.

I turned it around and limped it back to the shop at like 20mph, jerking and shuddering. Their main mechanic was already gone for the day, meaning not only was the car not going to get looked at until Monday due to the holiday weekend, but I was now stranded at the auto repair shop. The older guy behind the counter apoligized a lot and gave me a loaner to beat around in and get me to work, Thanksgiving dinner, etc. It's a faded-blue, 1982 Chevy Cavalier with a 4-banger pushing about 95whp. Wheee!

So yeah. My dad suggested that there could be water in the distributor cap, shorting out the electrical charges to the spark plugs? I don't even know at this point.
 
Search for multiple threads of this exact problem.. including myself.

Search for a thread from me (title was "PATS Problem.." IIRC??) where I outlined every symptom in detail, every thing I checked and my final resolution. This resolution has applied to two others that had this strange problem, too..
 
Okay, does this sound familiar?

  • CEL light would "flicker", or sometimes STROBE very rapidly.
  • PATS light would illuminate and do a 1 second "prove out" test, as if you just turned on the ignition.
  • tach would drop/dive towards 0
  • car power wasn't affected.. radio, lights, etc, remain
  • fuel and spark were GONE during that time. no acceleration, no idling (when it got worse, that is).. nothing..
  • voltage at the BATTERY wouldn't move.. would drop from 14.2 to 13.7-ish but that was only because the engine wasn't turning over any more and the alternator stopped producing power, for a second..
Click to expand...
If so.. check this out:
http://contour.org/ceg-vb/showthread.php?t=406&highlight=VREF

If you want to see more, simply search for the word "VREF" and start reading.
 
Wow, that sounds just like my problem. I had no idea what a PATS system or TPS was, but now I get the idea. Searching would have been difficult, since I lacked this knowledge and used different descriptive terminology than the guys in the other threads.

I am going to print these pages and highlight the solutions, and see if the guys at the shop can figure it out based on this info. They won't charge me for any more labor since they already sent me home with a defective car after charging me so much, and they'll probably be all kinds of embarassed that the mechanically-inept guy whose car they're working on found the solution on the intarweb and brought it in to them before they could figure it out.

Thanks for the info though, this has been a serious cause of anguish for quite some time now! I will update as soon as I get a status change.
 
If that is your problem, then just keep in mind that it may NOT be the TPS.. it may not even be the wiring to the TPS... It could still be anything that uses a VREF signal, as well.
 
Well ive been batling the same thing for a week i finally got some iridium plugs from ngk and cleaned the maf egr and tested the coil then put a full tank with some cleaner and booster it hasent done it sence and i really dont know what the deal is but its better so i would just do a complete tune up and then check evrything via scanner....
 
Alright, Ray is a genius. I printed out the threads mentioned and highlighted the solutions. I dropped by the shop on the way to work, before they were open, and stuck the papers in their door-jam for them to find. Then I went to work. Within an hour of arriving at work, they called and had fixed the problem.

It WAS the TPS wiring harness, only mine had somehow become loose, hung down too low, and dragged on an engine pulley which had eaten through the wires' insulation and was shorting them out! They patched up the wires and all was well. They also fixed my e-brake. Now everything is working great on my car except my transmission!
 
Yay! Glad to hear that it worked for you! I'm not genius, at least not for this problem, I just happened to have gone through it before with my own car. I am glad that it worked well!
 
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