The Oldsmobile Connection

88delta88 · Joined: 09 Jun 2003 Posts: 2407 Location: Canada

Hello all.

I went through the extremely annoying and expensive process of changing my fuel pump on the weekend. I still smell like gas. I get it all back together, to find that the fuel pump was not my problem. At least I wont be swapping the pump anytime soon.

So, I still have a problem. The engine will run just fine untill I start to get greedy with throttle. On acceleration, if I step on it too far, the engine will just totally cut out, and then pick back up again. It occasionally dies at lights. And will have a hell of a time sputtering and chugging if you open the throttle wide up. I assumed this was the fuel pump, not supplying a steady amount of pressureized fuel, but this is definately not the case.

I am left to wonder if maybe my fuel regulator is the issue, or some other unknown cause. How do I test the fuel regulator? Anyone have different suggestions?

speedy266 · Joined: 25 Jun 2003 Posts: 347 Location: Ontario, Canada

It could be your EGR valve letting in 2 much exhaust gases.

85cieraholiday · Posted: Mon Aug 30, 2004 2:15 pm Post subject:

Does the car idle any differently then before if so speedys right its probly the EGR

Turbocharged400sbc · Joined: 18 Aug 2004 Posts: 318

very possible-quick thing you can do to eliminate the possibility pop the egr off and cut an old creal box up to make a gasket/blockoff slap it on and see whats up. but since you have a problem even at WOT (the computer closes the egr/ and goes into open loop- maybe the ecm doesn't know your at WOT-check your TPS to make sure it's not dropping out/glitching (poping banging usually indicates lean condition/bad state of tuneup (i assum that the plugs/wires etc are fine) if the pcm thinks that your at Part throttle but the throttle is WO then it will run lean/ backfire- as for dying at lights the tps could def be a factor but the egr blockoff might fix it if the egr is the dying problem.
you dont have any exhaust restriction do ya? broken/clogged cat?
If you have acces to an Ocilliscope/ Digital graphing multimeter you can check the TPS signal but you might want to find a known good one if you cant and swap em'
get back and let us know how it goes-----Schlim

88delta88 · Joined: 09 Jun 2003 Posts: 2407 Location: Canada

Guys:

Thanks for the input so far. TPS sensor is brand new as of 3 months ago, and provides a smooth transition from bottom to top, tested with graphical multimeter. Plugs and wires are BRAND new. I dont suspect the EGR, because the problem happens regardless of the computer's open or closed loop. There is no error code from the ECM.

The engine does not ping, backfire or run rough - except when the problem happens. The engine will be running just fine until I step on the gas too hard, it will start to accelerate and then just cut right out. Feels JUST like I need a new fuel filter or pump, but I dont need either. When I am travelling uphill, it will push for a few seconds, and then start surging. If I let off the gas a bit, the problem lessens. I think its gotta be a fuel related problem. I'll keep searching!

85cieraholiday · Posted: Mon Aug 30, 2004 5:36 pm Post subject:

Didnt you have a problem a while back with a bad tank of gas? Maybe its the same thing?

Turbocharged400sbc · Joined: 18 Aug 2004 Posts: 318

Is your engine equiped with the magnavox ignition module/one piece coil pack? (it's a bitch-i know but pop the 4 10mm nuts holding it to the bracket and sand offf all the corrosion/as maybe there is an issue with the ignition module gound-Happens allot in the rust belt causing intermitent no starts,dying, and spark drop out while your at it pull the coilpack off the module and check for a burned area of the cases epoxy insulator/or carbon tracking from a coilpack to the module or from coil (secondary) terminal-to another one/ground.
After this your two big buggers (fer the 3.8L)are the cam sensor (sometimes the magnet on the cam gear looses it's power (gauss) and may not properly reference cyl #1 firing point timing. the crank sensor is also a possibility but this usually will result in a complete nostart I am not certain if yours is just a single (7x) crank sensor (behind the dampner) or if it's the later 3x & 7x (both in the same sensor-w/4 wire connector with two seperate reluctor rings on the dampner.
Curiosity here---does it only do it under WOT while driving or also with brake torquing at WOT ??
Now another quick test is this disconnect the Mass air flow sensor and see if the light is triggered if you can get a scanner check the airflow readings- I have replaced a few on a number of GM's that caused problems but never triggered a chk eng light! look inside it and if the element is a thin piece of plastic, with printed wires on it and a window in one area (for the actual sensor thermistor) if it is dirty/cracked you should replace it/check it with a known good sensor (fords have a HUGE issue with dirty MAF sensors that cause the engine to run rich at idle (overestimating airflow at idle) and lean at higher rpm's (by underestimating airflow-the dirty thermistor cant get "cooled" enough-thereby sensing less airflow than actually occuring!)
now if it's a speed density system there is a possibility of the MAP sensor being bad but these in my experience seem to cause problems no mater what Throttle position/RPM is so i doubt it's an issue.
Keep at it man dont let it get the best of you!
If you have a really ballsy friend you can get an inline spark testor and have him hang under the hood and go for a quick WOT drive and see if he can notice that spark disapears when the problem happens and use this method to check all the cylinders (this being if it will NOT occur under brake torque/wot simulating to get it to replicate the issue!--or you can just scare the hell outa him!)- a scope could check this but most arent good at DIS systems.
Just remember that all engines need three things Spark/Fuel/Air! if you eliminate them one at atime youll find your problem!
hope i could point out a couple more things to check out! good luck.
Schlim

88delta88 · Joined: 09 Jun 2003 Posts: 2407 Location: Canada

cool man... I'll check those things out... It does it all the time, not just when you're moving.

I had a bad tank of gas a few months back, I do remember that. But I've boughten gas from a few places since this problem appeared, so I dont think its that, but thanks for the suggestion!

I will check out my coil packs... I should clean the contacts anyways. I'll find the problem sooner or later. Thanks for all your help guys!

85cieraholiday · Posted: Tue Aug 31, 2004 7:57 pm Post subject:

Since you thought it seemed like a fuel related thing, maybe you have dirty fuel injectors? IDK but that would seem like a thing so simple that it could be over looked. I justed dumped a bottle of STP fuel injector cleaner in my Cutlass but it didnt make a diff. so maybe my injectors were clean (or maybe the stuff is just a marketing thing)

88delta88 · Joined: 09 Jun 2003 Posts: 2407 Location: Canada

OK, made some progress last night, but I dont know what I did to make it better.

I have the 3 individual coil packs on a main module, so I pulled each one off to check for corrosion. Each one looked just fine. I probed around at ground points to see if any one of them was loose. I wiggled all my spark plug wires. I took the connector out of the coil pack and reseated it to make sure it made a good connection. I took it for a drive, and the problem was GONE!!! I drove around for 15minutes and the problem had ceased to exist. And then just as I was pulling back home, it happened again. BUT, it is much less of a problem than before, happening a lot less. So it must be an ingnition problem afterall!! There must be a loose connection some where, but I dont know what it was that I did to fix it for that 15 minutes.

I'll take the whole unit off tonight I think, and check it all out. Gotta be a loose connection.

Turbocharged400sbc · Joined: 18 Aug 2004 Posts: 318

hows it goin??? I wonder if the coil insulation is bad? in a dark area spray some soapy water at the soilpack/module with someone loading it up in gear-look for the spark that is probably leaking through the coil towers to ground. it's hard to see but you can see the carbon tracking on the black coil body if you look hard enough- Just another thing for you too look closely!
Glad that you narrowed down the problem!

88delta88 · Joined: 09 Jun 2003 Posts: 2407 Location: Canada

I certainly hate electronics. I was messing around with the ignition, and every once in a while the car would run right. I removed all the coils, took the coil base off and cleaned everything. I put it back together and no difference. Well, was just about at a loss when I accedentally moved the wires for the MAF. The car died instantly. I started it again and moved the wires and it died again.

So I ripped the connector off, took all the pins out of the weatherpak connector, and cleaned and re-sprung each connector. This did not make a difference. I am thinking the maf is bad... :-( I should call and see how much they are...

Is there a way to test the maf to see if it is faulty?

Turbocharged400sbc · Joined: 18 Aug 2004 Posts: 318

there is a way but it is a real PITA to do to and requires a vacum pump/grphing multimeter. borrow one off a similar car or just get a new one. look close at the MAP harness and make sure that when you move it something else isnt happening (like other wires moving too).
did you spray it down with soapy water in a dark garage and look for voltage leakage?

Turbocharged400sbc · Joined: 18 Aug 2004 Posts: 318

Dam i just realized you said MAF pull it off and look inside it if it is a thin sheet of plastic it is very possible that is is one of the older more trouble prone ones- I have replaced quit a few of them that never caused atrouble code but caused all sorts of drivability issues.
I wrot about it in my aug 30th post--if you have acces to a scanner (Snap-on 2500 etc.) you can look at the airflow readings while wiggling it and tapping on the case.
Schlim

88delta88 · Joined: 09 Jun 2003 Posts: 2407 Location: Canada

... Its all better now. I coughed up some more $$$ and bought a new MAF. 120bux. Ouch, that makes it just a little over 800 dollars in work on my car this month. Tires, alighnment, fuel pump, maf sensor... I just hope thats all for a while!!! :-) I'm just happy to be back driving reliably again. Thanks for all your help guys!!! Drives like a new car!