Hi all. I have an issue with the manual shifting on my 05 crossfire coupe. It will run fine as long as it wants then, with no warning, it will act as if its downshifting ..or like someone stepped on the brakes as shifting takes place. Again, it will shift, then suddenly "pull back" for a few seconds. Then it goes back to fine. On the highway, in high gear, it will continue the "slowing down" process till it's not going fast at all. I'll pull over, wait and restart, and it's like nothing happened. Checked pressure , emission, and connections, and can't find a thing. What do you all think could be the cause?

 

You are not doing a very good job of describing what we are looking at here.
"Manual Shifting"? Is the car a manual or automatic? I suspect auto and I suspect you don't mean "manual shifting" but I have no idea what you MIGHT mean.

"Act like it is downshifting"... so the car lurches and slow and the tach jumps up to higher rpms? That is a downshift, but why would the car downshift unless you are hitting it hard and causing a downshift? (Assuming an automatic.)

It will shift, then suddenly "pull back"... " Again, I don't understand what you are trying to say.

 

Tom,
Pizza guy is right, a better description of what's happening is needed.

I will take a shot in the dark and describe an issue I had with my auto transmission. Once my car was warmed up, under moderate/heavy acceleration the trans would downshift but the car would not pick up speed. The engine was revving and tach increasing to high rpms. I replaced the transmission conductor plate and that solved the problem.

Comparing the new and old plate it seemed to me what I think was the speed sensor on the old plate wobbled around more. I think with the bad speed sensor the transmission did not know what to do once it down shifted. Hopefully this helps you.

I see you are new to the site (welcome). You will receive a lot of help from the members here.

 

The car has a manual transmission, and lets say I'm shifting into ( any ) gear, once I let go of the clutch, at first it will continue upping the rpm towards the next shift, as it should. But suddenly in a random, unintended, unprovoked manner, it will slow down ( feeling almost like a downshift ) It will do this for a few seconds, then reset itselft , back to normal rpms and shifting. And , to make sure I'm clear, it does this "whenever"., and it can happen in any gear. Sometimes it will go for days and not do it at all. When it does it on the highway, however, it will not reset itself. Instead continuing to slow down to a crawl, no matter what I do. . That's when I find a shoulder, wait a few , restart the car and it's like nothing ever happened. I sent the RCM to DJ Tighe in case it's the fuel pump relay, but I'm wondering if anyone had a similar situation, and could help with a dx.

 

Not an automatic, hence the "manual shifting" description. It behaves like a normal shift, then slows downs for no reason, then goes back to business as usual between gears. The feeling is that of a downshift, or as if someone stepped on the brakes for a sec.

 

I know some were having trouble understanding my somewhat confusing description. Sorry about that. But I can't believe nobody else has had a similar issue? Anyone? anyone? Bueeller? Ok, so getting my RCM back tomorrow after DJ fixed it, let's see if it was the fuel pump relay causing all that trouble

 

MODERATOR HAT ON:
This particular quote says it all: YOU are a good example of why I put up the "New members looking for technical help" post that is referenced my signature below.
We are not standing next to your car, YOU are. ALL we have to go on, is what you type here.

Quote:

Again, it will shift, then suddenly "pull back" for a few seconds..."

You just told us the car shifts on its own and WE are the problem here? How entitled are you?
You clearly have no "downshift" issue, and you can't, because with a MANUAL, the DRIVER performs all shifting functions, that is why we assumed you had an automatic, as the ECU and TCM do the up and downshifting for you, and when the conductor plate acts up, that is one of the big issues. The above line is nonsense, how can you complain about our help when YOU set us up for confusion? ONE MORE TIME: We are not standing next to your car, YOU ARE.

READ THE POST IN MY SIGLINE. We have no obligation to work harder at this than you do.


BACK TO REGULAR FORUM MEMBER:
You CLEARLY have an engine performance problem, not a transmission problem. Fuel pump, Throttle body, MAF, Throttle PS, PedalPS, CrankPS, CamPS would be my guesses but the last four should throw codes and a CEL. (PS is position sensor).

I vote in this order: Fuel pump, Throttle body, cam or crank sensor. I doubt it's the RCM, but it's always a good idea to send the RCM to DJ if there is any doubt. But first thing I'd do is check fuel pressure when it is acting up. You are now describing what my Ranger did as the fuel pump was dying. A fuel pressure test took five minutes and it was obvious. The easiest thing to check is fuel pressure, but you must do it when it's acting up. Altho if you test the pressure when the car seems OK, if the pressure is lower than 50psi, you found your problem, 55-59psi is spec. At 40 psi, the car will run, but not well. Below 20-25 or so, it might idle, below 20, it wont even idle.

Beyond that, since you say it 'resets' (my Ranger would develop fuel pressure by turning the key off and starting again, for about 5 miles) I say fuel pump. Of course, I have seen one Throttle body do this as well. That car had 180,000 miles on it. If you turned the key on, and sat there, the TB would make all sorts of goofy sounds, constantly, it had gone insane.

 

Also change the fuel filter, it has to be change regular and if it is blocked the engine can't get enough fuel and it came to misfire so the ECU switch of the ignition and the car slowed down. But first I would read out the ECU for stored errors.
And as pizzaguy sayed it could have many causes.

 

A SIMPLE fuel pressure test would tell him the condition of the fuel system. That is, in my mind, the most easy and fundamental test one can do on today's fuel injected engines.

EVERYONE should keep in mind: The ECU has NO CLUE what the fuel pressure is, there is NO SENSOR to tell it what the pressure is, so the ECU assumes 58psi. If the pressure is off, there will be a struggle to get the fuel/air mixture correct. Why the HELL there is no fuel pressure monitoring on today's cars is beyond me.

 

Not entirely true, my '11 CTS with direct injection monitors both low (from tank) and high (engine to rail) fuel pressure.
Agree, a good fuel pressure gauge (cheap ones may leak) is very handy for a "cranks but does not run". And spark plug lights and a set of noids (for injectors) are very handy.
Also helps that I have the best of both worlds, a Crossfire Coupe and a SLK320 retractable with the same drivetrain so can do comparison testing.
Happy, happy, joy, joy.

 

Is that the one with "variable compression ratio"?
In any event, that car is pretty much in a class by itself.

 

Nyet, is GM "corporate" 24 valve v6 with VVt, code LLT. LFX is a bit better. 304HP and a 3.73 posi. 4-6-8 V8 was a few decades earlier.

 

To the guy with the moderator hat: Ease up Nelly! I appreciate any help, and my wondering if anyone else had the same issues was more of a "scratch my head and wonder" how strange this gremlin could be that nobody's had a similar thing happen ( nor do I wish it on anyone ) than a demand or entitlement of any type. I described the issue as I felt it, and what it felt like. Apparently not clearly enough, but I guarantee that anyone without a mechanical background , after experiencing what the car does, would describe that it feels like a fricking downshift. Again, I am thankful to anyone who has the time to lend a hand, like that regular forum member..you should try to be more like him. Thanks for the help.

 

the rcm came back in and the car seems to be running ok. Then, again, It's been known to do that and then go back to , well..whatever it is .
I took it to a shop where they ran a bunch of tests and everything was ok, or at least no lights showed. Crank sensor is new, will look into your other suggestions. Thanks for taking the time.

 

MBATR: OK you have the six speed manual and on a shift "sometimes" there is a lurch as if the engine slows down. Offhand I can think of two things that could do that:
1) momentary loss of fuel pressure
2) momentary loss of Throttle Position Sensor (TPS) signal (assuming you back off the accelerator during a shift. (keep in mind the Crossfire is "Fly By wire" and there is no mechanical linkage to the gas pedal, just two Hall effect sensors).
Both are going to require instrumentation to determine, otherwise are just throwing money at it., The first a fuel pressure gauge, the second a scanner like Torque Pro, monitored when happening.

 

Thanks for the input. So the mechanic said the pressure was around 60lbs ( does that sound right? ) and while the TPS hasn't been checked, I don't think .. the "slowing down" happens after shifting. That is ; I shift , it's ok, then as I accelerate to get to the next gear (after the shifting was completed) it slows down, during what should be a natural accel before shifting again. And it's not a slow process, either ..it feels exactly like if I had thrown it into a downshift , abruptly.

 

You don't want help? Why you always write something with shifting up or down? As sayed before you haven't any shifting problem, it's your engine what caused the issue.
Why you haven't let read out your ECU as the mechanic checks your car?
And a fuel pressue if the car stands still don't say, that it don't drop down while accelerating.

 

Have to remember some isn't as larned as us.
"as I accelerate to get to the next gear (after the shifting was completed) it slows down," that sounds exactly like a failing TPS. Yoy press on the pedal but the ECU thinks you took you foot off. Dead spot maybe ? Why you need a scanner (e.g. Torque Pro) that can monitor and keep a log. Intermittents are hard to find. If steady will set a P0122 or P0123 but intermittants are too short to set a code (and "foot off" is a valid reading).

 

After 2 weeks back and forth, the mechanic experienced the issue while monitoring the pressure, and said it stayed at 58, ruling out the fuel pump. Claims ECU shows no errors , but from what I'm reading here, that may not be a true indication that there isn't a dead spot of some sort?
At this point, maybe a need another mechanic to pick up from where this fellow seems to be stuck, or if I can find a good place to purchase the parts you all say may be going? ( tps, etc ) , out of sheer desperation, I'm about ready to start replacing them myself .
Crazy thing is in 96 I had an Eclass, and another in 01. Both had that 3.2 engine. Drove them to the ground, and never any issue like this. Had the limp mode on the 01, which was fairly easy to fix, and a bad o2 sensor..also easy piecy, but this is making me nuts

 

And the TPS ? Is what needs monitoring for dropouts. Can check that with Torque Pro ($5).