95 Regal (custom) hesitation/rough idle/not sure but a major problem

[bigjess007]

Hello Everyone, got a pretty big problem and not sure what it is and how to fix. My 95 Buick Regal has a rough idle/hesitation (not sure what to classify as). Sitting idle in park, you can faintly hear the *miss* in it. You can definately hear it at the exhast as there is a rthymic pattern to it. Stick it in gear and go and it will start to stall and then adjust the rpm's and go. I guess I should note that it has never stalled out from this. Going down the road, you will have certain experiences of what I call knocking. Most noticeably is going down hwy at 60, it will start knocking/rapping. Give more or less gas and the problem goes away. Seems to be right around 3000 rpms. Car has almost 100,000 miles on it. I'm not the best technicican, but I did change the plug wires and plugs to no avail. Took it to the dealer to get ripped off for $50.00 for a *computer diagnosis*, they said that it was definately the coil packs. Replaced all three. No dice. Guess I should mention also that the check engine light is NOT on and hasn't been. Yet the problem definately persists. It sounds to me like it's timing, but then again I'm not the automotive's best. I would like to fix it myself as I don't trust any of the dealers in the area (live south of pittsburgh PA - specifically uniontown :o( but I'm not sure what the problem is and if I can fix it. Reading online tells me it could be MAP, CAM/CRNK snsr, EGR, etc. I don't want to have to just start replacing to find the problem. Anyone have any ideas? I wouldn't mind paying someone to do it if they knew what they were doing and could fix it straight out, but so far I've been ripped pretty good. BTW, engine is 3.1L (VIN M) if this helps. Please help, thanks!!

[Hypsi87]

You have already changed the plugs and wires and coilpacks. No codes but still runs like crap. It does sound like a timing problem or fuel, but since both are controlled by the ECM and it is throwing you no codes, Your E-PROM or the entire ECM could be bad. does it spit all sorts of black smoke out?

[bigjess007]

Nope, no black smoke. Also, regarding the computer, let me elaborate, I don't know what codes may be stored. When I took it to the place I bought it, they hooked it up and said bad coil packs, so I changed them. If there were any other codes, they didn't tell me. From what I've read about this, if it spit out any major codes (like a 41 or other major sensor failure), it would have turned on the check engine light, and this never has appeared (even verified that it does come on when i turn the key on, so the bulb isn't burned out).Are my assumptions wrong about the check engine light (only turning on when it actually detects a failure?) Do I need to spend the money and have someone check the comp again? Personally, I think it's a bad sensor somewhere in the mix (MAP, CAM/CRNK, EGR, etc.), it's not enough to cause a fault, just enough to cause the car to run like crap. I'm basically at wits end.

Oh ya, more food for thought, tried running premium fuel, no dice. Tried injector cleaner, no dice. Time to trade it in?

[Hypsi87]

your car would not throw a code 41 or anything like that, it is OBD II. Im not to fimilar with OBD II yet, Im still learning. This is a thread for flatrater. Sorry, I thought that they did not use OBD II untill 1996.

[bigjess007]

i think i'm confused, the car is obd I according to the emissions sticker, i was already down that path, sorry. i'm probably wrong about the codes. i agree, flatrater seems to be da man regarding this and his posts. he's from pa too, maybe i can drive the car to him and he can give it a good kick and all will be good!

[bigjess007]

I guess maybe I should clairfy. I took it to where I bought the car, and they were the ones who did the diagnosis. They are not a GM garage, but I bought a warranty with the car, and it specified I had to take it back to where I bought it. They told me electronic parts are not covered by the car warranty, told me the coils were the problem and the cheapest alternative was to fix it myself. So I tried.

*CENSORED*
My apologies to anyone who was offended.

[Flatrater]

I have edited my post to you! Maybe I should of sent you a PM first. No offense taken . So let me think about your problem and see if I can come up with something.

[Flatrater]

Not much in the way of TSB's for your condition.

One major problem GM is having is trying to keep the injectors clean. First thing I would try is a good injector cleaning. You can start with a bottle of additive for your tank but sometimes it is necessary to disconnect the fuel system from the injectors and run the cleaner thru a pressure pot to clean them.

Now the biggest thing I see is your engine knock above idle could you explain it some more? It could be a carbon issue in the cylinders causing this. Have you tried running a higher octane in your engine? Have you replaced your fuel filter in the last 2 years?

With your kinda mileage I would like to clean and reset the IAC! This will improve idle quality.

Usually an idle miss is caused by a fuel problem and off idle misses are caused by ignition. It is kinda hard to help not being able to hear see and drive the car.

Usually when I get a high mileage car I need to do some reccomended service work, its not cheap but I have to have the car's sensor data streams in range of where they are susposed to be.

I want you to remember that the crank sensor is used to start the car and the cam sensor takes over after the car is started. So that usually rules out the crank sensors, you have 2 crank sensors on your engine.

1995 was a weird year for GM cars, some cars are OBD1 and some are OBD2, and the rest are a hybrid OBD2. What color is your PCM? If its black its OBD1 silver its OBD2 or the hybrid. There has been some calibration changes to the OBD2 computers over the years and it could be possibly that a newer program would fix your car.

I could write a long list of things I have seen that could cause this problem but I don't think it would help you much.

[bigjess007]

First, I want to say thank you for taking the time to look at this and respond. I am definately at the end of my rope with this.

I did run the fuel injector cleaner through it, using lucas fuel injector cleaner from autozone. no dice. can you recommend a specific brand and procedure? tried running highest octane gas, still no dice. don't have a clue on how to disconnect the fuel system from the injectors and run the cleaner through a pressure pot to clean them, but i'm totally open to the idea, is this something i can do and exactly just how to i do this. I'm guessing i mix gas and additive in a tank, pressurize, hook up to the fuel rail (? not sure where and how) and then fire it up??

haven't replaced the fuel filter, i can't remember why, i think it was hard to get to or something. it's been a long ordeal, i'll look at alldatadiy.com again and try to do that asap.

the engine knock is hard to describe. going 60 down the highway, if my foot is on the peddle in a certain place, it's starts "knocking" (maybe i'm using the wrong word here.... rapping, rymthic loud noise). let off or give more gas and it goes away.

need help again with the iac, what is it and can i reset it?

it's definately obd1, connector is black and it says obd1 on the emissions sticker.

[bigjess007]

remembered iac, looked the procedure up on alldatadiy.com, I think I can handle it. also remember on the fuel filter, couldn't figure out how to "Safely" bleed off the pressure. any tips?

thanks again!

[Flatrater]

You can bled off the fuel pressure on the fuel rail. The rail has a cap somewhere with a valve core on it, just depress the core till no gas comes out.

The injector cleaning I talked about uses a mix of gas and a detergent which if allowed to go to the fuel pump can ruin the pump, that is why the system needs to be disconnected.

Injector cleaners that work contain TEC. TEC is a strong detergent, not all cleaners have it. TEC is banned in California. I use the GM injector cleaner or a product the BG products makes. BG products are only sold to service shops and dealers, you would have to shop around to find a shop that uses it.

The knocking still puzzles me!

[bigjess007]

thanks for the tip about the fuel rail. i am going to change the fuel filter this saturday. from what I have found, it only has one filter, it's inline back by the sending unit?!?!

i looked up bp products, it seems their fuel system cleaner is "44k". is this what you are referring to?

the knocking accompanied the rough idle, so somehow they are twisted together.

your tips about the fuel system have me wondering if the fuel filter is partially plugged/injectors are filthy and the car just isn't getting enough gas. guess i'll know more this weekend.

again, thank you.

[autoforum]

I sure hope you get this figured out because I have the same problem! Same year, about 90kmi. I've just started doing all the things you're doing.

[tman]

I'm just gonna add my opinion on this, but I'm saying fuel filter.

And Flatrater- I dont want an argument, but not everyone is going to like you, and you cant lash out at the fellow members. Regardless of opinion on the situation, it says in moderator's guidelines that we are not to have heated arguments with members. I understand why your upset, and I've been upset by some things on here too, but you've just got to live and let live.

[forrest gump] Thats all I have to say about that [/forrest gump]

[autoforum]

I just went through all the basics: compression 185 to 190 psig, sparking good (replaced plugs anyway), wire resistance good (3 to 6 kohm), fuel injectors firing, fuel pump good steady flow, replaced fuel filter, sprayed carb cleaner all over intake and found no vacuum leaks, cleaned throttle body, replaced air filter. Spark plugs had grey/white dry deposits; suspect slightly rich mixture or improper timing. Unfortunately, I can't adjust timing on this computer controlled vehicle. My next thought: the timing chain.