This started on Friday afternoon. The car cruises and shifts fine. The car boggs when accelerating up to 3500-4000 RPM, after that it runs normal and everyhting is fine. When it bogs its like it is getting flooded but clears up once I get into the upper RPM. The car starts fine and runs like a top for a few seconds then goes to hell. The idle is real rumbly and irratic, I can hold the car at 1500 RPM at a stop and the idle is noce and smooth. I have no codes, everything is plugged in, and I didn't do anything that can cause anything to mess up. Everything in the ignition is less than 6 months old, the fuel filter is less than a year old, put in new plugs yesturday, have a can of seafoam in the tank and some soaking in the intake right now. What could be the problem. I have gone over all of the basics and everything checks out.

 

I Had that same engine years ago. That problem sounds kinda familiar, I think it was the egr, but it wasnt giving any codes for some reason

 

I don't even have the EGR anymore lol. Its all gone.

 

Did you check your fuel pressure? Maybe the pump starting to go

 

Why would it be that. The car runs fine otherwise. I'll cheack anyways. It runs great for a couple of minutes after startup, then it will bog when I come to a stop. Idle starts out good then slowly goes to hell.

 

I have had fuel pumps do strange things. It sounds like the TPS,but that should set off the SES light.

 

Thats what I thought too, I had a bad one just the idle was irratic, no bogging. No SES lights. I'll recheck everything tommorrow and I'll check the fuel pressure, I'll just buy a cheap gague. What are the specs for fuel pressure? Also I put some seafoam through the intake and as far as I can tell it may have helped. Took it for a test drive and the idle was still bad but when I got home it seemed better.

 

I think your engine has a cold start valve on it. Id check that. I Don't know how to test it though or if you can. Its probably not cheap either. My Haynes manual says the fuel pressure should be between 34 and 39 psi, but I would see if a parts store would just loan ya a gauge or rent one. Most likely the pump is fine anyway.

 

 

IAC, MAF, TPS, IAT all are less than a year old.

 

 

The filters were done a few weeks ago, fuel filter is less than a year old but I am keeping that as an option, I don't have an EGR anymore and the butterfly is clean along with the IAC. Airbox lines?

 

Sounds like you dont have much left to change. Probably is the cold start valve then. Will set off the SES light?

 

That wouldn't have anything to do with it bogging even when the motor warms up though. The cold start injector is only for start up.

 

I thought it ran fine when it warmed up though

 

It runs fine when I'm just cruising down the road at a constant speed. Its just on acceleration when the car bogs and looses power. In fact when the motor is below 4000 RPM is when it bogs. I'm not sure what is going on. I'll dig deeper into it this afternoon. I have to put the nut back on the tranny mount, it fell off last week.

 

Then that could be the fuel pump, Mine was just doing about the same thing a few weeks ago, i changed the pump and all is well.

 

I'll be checking the pressure today after I buy a cheap tester.

 

I started to get the same problem yesterday. I finnally got around to changing my spark plug wires (because they were starting to arc) after this everything went to crap. I turned the car on and the engine started to idle irracticly and the car shook when i first gave it gas. Once i got the car up to a crusing speed the car ran beutiful. Other than that it runs terrible- I hit the gas and it moves like a slug. I thought it may be the fact that I need to readjust the vehicles timing anyone know a quick way of doing this?

 

 

I don't have any airbox lines, or at least what you are descirbing. I did replace my injectors over the summer with ones from the JY cause my old ones got damaged while sitting outside the car back when I had to pull my head. The injectors are from a 3.1 (I'll need them soon anyways for the new motor) but they have worked great since the middle of summer. I am about to check my fuel pressure in a few minutes.

 

Checked fuel pressure today and it is sitting at about 45 running which I believe is good correct? That seafoam I put through the car helped a little bit.

 

I think 45 is too much but I could be wrong

 

It might be a little off. The gague I bought leaks from the gague itelf so I am going to take it back and get my money back if I can.

 

well if it ran better after the seafoam then do one better. First take a few spark plugs out to see what they look like. If black then you have some carbon build up. Instead of using seafoam use water pouring very slow. Then again i did this on a carb motor don't know if you could. The water steams up and cleans everything really good.

good luck though!

 

The seafoam helped but not very much at all. It starts to pick up at like 3K RPM now. Its weird that when I start it up the car doesn't bog for a minute then it will bog the next time I accelerate up to speed. I'll pull a plug and see what it looks like, the ones in there are only a couple of days old.

Checked the #2 plug and everything is clean, no smell on it, it looks like nothing is wrong but something is. I am starting to wonder if I have a vaccum leak somewhere. I don't hear any kind of leaks and I fixed all of them that there were. I may dig into teh topend this weekend and inspect the gaskets if it doesn't clear up by then.

 

45 psi is actually in the range...my chilton manual stated 40-46 psi. What you might want to check is keep the fuel pressure gauge connected while running and then snap the throttle wide open quickly. there should be an increase in pressure of 4-5 psi. if theres no increase, you may be looking at a pressure regulator. Also, keep the gauge connected after running to see if pressure leaks down. could be a possible injector problem...even if the injector spray pattern is crappy it could cause the motor to bog. Also, maybe you want to hook up a vacuum gauge...vacuum should be above 17 inHg

 

had a similar problem im my 1988 way back when. ended up being a vacuum leak. it was the line that runs along the firewall. ended up driving to a meijer and getting a rubber line there and putting on in the parking lot.

 

Now I got a sugestion on another board to unhook the MAF and it ran much better but still bogged some in that RPM range but much better. I also advanced the timing a little but and that helped alot. Now the MAF is unhooked. I am thinking about taking that one back to the parts store and see if there was any kind of warranty on it. I got it back in Jan/Feb. Maybe it had a 1 year warranty on it. If not then I'll but a new one. I don't think it is a vaccum leak. The car idles nice and smooth.

 

Unplugging the maf puts it in 'creep home' mode where it runs off fixed tables. I don't suggest messing with the timing, verify that it's at 10 deg advance before you try to diagnose it. Reman v6 mafs are known to go bad quickly, if it was reman get a new one this time.

 

The timing was set at 10* before. I just bumped it up to 12* and it helped. I forget if it was reman or not. I just try to buy new parts if I can.

 

I was able to replace the MAF and it runs much better but there is still a little bit of hesitation. Its not much but is there anything else that it could be that I overlooked beside a vacuum leak? I'll be looking for that. Another question I got is on the vacuum system what is the small tube that connects to the back of the intake go to? I know it splits but it disappears into the wiring harness.

 

The small tube is for dash vent control. Runs all the way to the back of the vent controls. Keep looking for vacuum leaks, check the throttle shaft as well. After some time a vac leak can develop as it wears on the housing. Cleaning your intake may have exposed it.

 

How would I fix the throttle shaft if it was the leak? I know I would probably have to disassemble the TB but what would need to be replaced?

 

You either replace it or get a new throttle shaft. They were coated with something from the factory so they would wear-mate, but over the years it wears off. You could try powdercoating the shaft or something like that to seal it up. Don't use paint it will flake and wear too quickly.

 

Here is the weird thing. This morning the car ran rough like it did before with the new MAF. So after I got out of class I unhooked it and went to work and home afterwards and ran fine without the MAF. This time I cleared the computer and took it for a test drive with the MAF plugged in and it ran great, the motor was already warmed up. Now I aam wondering if it just runs rough when the motor is cold. I'll see tommorrow morning what it does. Also it idled smooth without the MAF plugged in so I don't think that I have a vacuum leak. Could it be an electrical problem somewhere? All of the wires that I can see are in good shape so it isn't grounding out in the engine bay.

 

Hmmm, well lets see what we've got. Your ignition system is still fresh, you've got new(ish) injectors, you've checked the fuel psi and the rest of the fuel system I assume is in decent shape, you've got fresh air filter(s) and a new maf and cleaned out the whole works with seafoam, you're sure the other fueling-related sensors are good... so what's left? Did you test the fuel psi like 91chevywt suggested by giving the throttle a stab and seeing if psi goes up? And have you done a compression test yet?

 

Haven't done compression. I did replace the fuel pump and the system is in good shape. I checked out the FPR and it had some sort of clear jelly in it?? That I cleaned out. The fuel pressure is good although the damn gague leaked gas. I'll check out the compression whenever I can. Now the car runs real good without the MAF plugged in but with a very slight hesitation in the 3K range. I'll have it plugged in again tommorrow to see what happens once the motor is warmed up. This morning it idled like I had a big *** cam in the motor. I thought it was a bad vaccum leak but it cleared up after school once I unplugged the MAF. I'll let you guys know how it goes tommorrow.

 

Well its still doing it so I am just going to run without the MAF until I can figure this out. It doesn't matter if the motor is cold or warm, open or closed loop. I still need to look for vacuum leaks, just been real busy lately. Could this be an electrical issue?

 

this could easily be an elecrical issue. what i do when i'm bored might work 4 u. just check every wire u c and make sure every connection u find is good. could be vaccum too though, play with that idea too.

 

I'll be doing that tommorrow since I actualy have some free time. Are there any relays between the MAF and PCM that could be the culprit?

 

I too the UIM and TB off to inpect everything. All of the vaccum lines look good, so do the injector o-rings. I went ahead and replaced the TB and UIM gaskets just in case. They don't seem to be the culprit. Also as far as I can tell the wiring for the MAF looks good. I am getting a vacuum test done today. Also something I wanted to ask is where can I get repacement seals for the throttle body shaft if that is leaking. There was only a little bit of side to side play in it.

 

I for one think its a 100% fuel pump problem. I know this from experince ive had 2 camaros do this too me I would check the fuel pressure it would be good. So i would start nickle and diming myself on everything else i could think off and yes it would make the car run better bc it was basically me donig a tune up but the problem would always come back. Your fuel pump is going out itll work sometimes then it wont its not much longer till itll die completly. One of the camaros ran perfect the whole day went too work got out of work drove the camaro out of the parking lot and it sputtered and died the fuel pump can go at any time! Same problems boggin and high rpms and speed i would change it before you go broke fixing everything else in your car.

 

I already replaced the fuel pumpn (not reman). I am thinking of replacing the FPR. With the new fuel pump nothing really changed. No vacuum test. I stopped at a shop on the way to work this morning just to see if they could do one in like 15 min but they wanted me to drop the car off for the whole day and I can't really do that. I think that it is a vacuum leak but am open to all suggestions.