multiple misfires

[jlizer]

I've had random multiple misfires (code 0300). My chevrolet dealer had my van (97 Astro, 4.3L of course) 4 DIFFERENT times and could not fix it any of the times! When the van initially accelerates from a stop, it drives extremely rough with lots of hesitation and hardly any power. Occassionally there is intermittent roughness at low loads and sometimes high loads as well. After enough I get too pissed and hammer on it, throw the pedal to the floor, and it snaps out of it.

So the brilliant "GM-trained mechanics" told me my fuel filter was bad. They fixed it, to no avail. Get my money back. Then they say, your injectors are clogged. Blow out the poppets with nitrogen. 30 miles later my van is running worse than it was before. Get my money back. So then they tell me, 'your gas is extremely high in alcohol, it's 15%. Do not use ethanol.' To which I say: I filled up last in Minnesota (I live in Iowa); they do not have ethanol. However, I did put an injector cleaner in the fuel, which is probably what you're picking up.' They say it can't be. They send me on my way saying, 'get the gas out of the system, don't fill up with ethanol.' Doesn't fix the problem. I take it back a fourth time. They say: "all six of your injectors are bad as well as your fuel pressure regulator. $1100, please." I've had enough of it, so i replace the injectors and regulator myself. Van drives fine for about two weeks, then i get the same code and problems again!!!!

I change all the spark plugs, plug wires, distributor cap, and rotor. Van was at 13K and was due for it anyways. Made a HUGE difference......for about three weeks. NOW THE PROBLEM IS BACK!

What else could be the problem? Could the timing be bad? I hope to god it's not. I'm also wondering if it could be a bad sensor somewhere or else possibly the coil could be going bad.

But when a relevant repair is made, the problem goes away temporarily, only to resurface later. i'm literally running out of options. the two most prevalent, most likely problems can be ruled out. Sorry for the long post, but somebody here has got to be a bigger genius than those at George White Chevrolet in Ames, IA.

[Kings-x59]

Did the mechanic test the fuel pressure to ensure it wasn't a fuel pump problem?

assuming the fuel pump is ok:
This could be a clogged EGR valve, although with multiple misfires, this sound more ignition related to me.
It could still be a problem with the distributor cap and rotor. Different year models seem to have problems with diffterent manufacturer's caps and rotors. Some year models eat AC Delco caps, but do fine with Bosch and vice versa. You might pop the cap and inspect the condition of the rotor and contacts.
could be a worn out knock sensor.
The ignition coil might be the problem as well.

Does the engine idle rough?

[jlizer]

Originally Posted by Kings-x59

Did the mechanic test the fuel pressure to ensure it wasn't a fuel pump problem?

assuming the fuel pump is ok:
This could be a clogged EGR valve, although with multiple misfires, this sound more ignition related to me.
It could still be a problem with the distributor cap and rotor. Different year models seem to have problems with diffterent manufacturer's caps and rotors. Some year models eat AC Delco caps, but do fine with Bosch and vice versa. You might pop the cap and inspect the condition of the rotor and contacts.
could be a worn out knock sensor.
The ignition coil might be the problem as well.

Does the engine idle rough?

the engine idles pretty smooth. it's only really bad, and then only sometimes, namely when accelerating and sometimes cruising at interstate speeds you can feel it kicking and driving kind of rough.

[Kings-x59]

Ok, did your mechanic test the fuel pressure?

[jlizer]

i don't know. i'm assuming they did since they were suspecting a fuel related problem and they thought I needed a new pressure regulator. But they never gave any indication to me whether it was high, low, or ok.

[Kings-x59]

fuel pressure wouldn't read high, it'd be ok, or low.
You mentioned that after plugs,wires, distributor cap and rotor it made a huge difference for a while.
Have you pulled the distributor cap and looked at the condition of the rotor and contacts on the underside of the cap? Search this forum, you'll find that these vans seem to eat caps and rotors. Different year models seem to do better with different brands of caps and rotors. take a look, let us know.

[mfb496]

having some symptoms like this.thought it might be the pump since it was going bad and giving me hard start problems.put in the new pump but still had the hessitation on the highway,occurs around sixtyfive or whenever theres a load like going uphill or when weighted down with cargo.i checked the fuel pressure at speed with a gauge attached and the doghouse removed.pressure would increase with throttle indicating that tps/fuel pressure reg are working.also the van runs fine from idle all over town,no overheating nothing.my next step to solve this problem is check the catylic converter.

[james wright]

Has same problem noticed that alt. gauge drop considerbly when miss fires started checked alternator found out it was surging. Replaced alternator problem stoped

[mfb496]

ive also noticed some power surging,but havent seen the alt. gauge move.what i see is the gas gauge ,speedometer and headlights flicker.anything like this???????

[Soozie32]

Similar problems since Nov. '05 til now. Intermittent random misfire. Usually at highway spped of 65+ mph. Everytime we fix a relevant problem that we think is "it", after about 3 days the misfire appears again.

We live in Minnesota, with no ethanol, but when we drove to Colorado in December, van ran perfectly after we put gas in in Iowa!

If you find the problem, please let me know!

[email protected]

[MT-2500]

Originally Posted by Soozie32

Similar problems since Nov. '05 til now. Intermittent random misfire. Usually at highway spped of 65+ mph. Everytime we fix a relevant problem that we think is "it", after about 3 days the misfire appears again.

We live in Minnesota, with no ethanol, but when we drove to Colorado in December, van ran perfectly after we put gas in in Iowa!

If you find the problem, please let me know!

[email protected]

This is a old post. Let it rest in peace.
Start a new post on your problem and someone will help you.
MT

[mikemachine]

I recently had to have the IGNITION COIL replaced there was a crack in it. At the time the van had been given, NEW CAP and rotor, PCV valve,wires,PLATINUM plugs along with the new Ignition coil. I have had this van since 2003 and this was my FIRST tuneup on it. All is well now, btw it has 184000 kms on it. Prior to this extensive tuneup I had numerous MISSFIRES and absolutley terrible fuel economy. Also fuel with ETHANOL added is a requirement here and does not seem to effect my astro at all.
Best of Luck.

[MT-2500]

Originally Posted by mikemachine

I recently had to have the IGNITION COIL replaced there was a crack in it. At the time the van had been given, NEW CAP and rotor, PCV valve,wires,PLATINUM plugs along with the new Ignition coil. I have had this van since 2003 and this was my FIRST tuneup on it. All is well now, btw it has 184000 kms on it. Prior to this extensive tuneup I had numerous MISSFIRES and absolutley terrible fuel economy. Also fuel with ETHANOL added is a requirement here and does not seem to effect my astro at all.
Best of Luck.

Welcome to your first post on AF.
But you need to run /start a new post instead of using old post.
Posting to a old post only wakes up the dead.
Check the date on the post before posting to it please.
And if you have a different problem on a diffwerent vechicle start a new post.
And give your make and model and engine .
MT