Bucking B*****d (who likes puzzles?)

[SonicRiot]

My car is missing like a bastrd whenever I dip into the throttle hard. If I nurse it or shift very smoothly, it's ok and a stab from half-throttle yeilds plenty of performance and no misfires.

But stabs from a closed throttle (while at speed) yeilds bucking, then it's fine until I shift and stab the throttle hard again. The car tends to bog heavily if I shift quickly before 5500 RPM.

At idle, when I twist the throttle hard and fast for a split second, the car will miss so bad it threatens to stall (which explains why I've been stalling so much more... I have to slip the clutch a little more than usual). The car bogs heavily on hard launches if I do not drop the clutch at anything above 2500 RPM and do not smooth out my throttle control.

The car runs fine on the highway, except for the triple-buck I get when I stab the throttle. The car is NOT backfiring at all, but I did manage to get a small backfire when I was playing under the hood with the throttle. There is a loud, hollow CLACK in the intake if I twist the butterfly fast.... and then it threatens to stall for a split second, then will continue on up into the revs like nothing happened.

If I stay at half throttle (in any gear, at any RPM), the car will surge in power ever so slightly, but I can feel it. I do know my power steering pump has been acting up, but I'm not sure if this symptom is related to the misfires or my PSP is playing games with me.

Also, the lights dim every now and then, especially when the A/C compressor kicks on, I up the fan speed quickly, or I'm using more than one window button at a time. I have not full-fielded my alternator yet, so I don't know it's out put (anyone know what to jump on this particular model and what the specs should be? Yeah. I'll do a search). The only reason I include this symptom is in case any of you think it could be ignition related?

And lastly, the car starts a little hard every morning... like it's going to stall out. It then surges to 1500 RPM when it's done couging like a 50-year-old-smoker and settles to 900-1000 RPM idle. My car hasn't been run for the past 3 days, so when I started it up this morning, the car sputtered out blue smoke and sat in a lumpy, threatening-to-stall, noisy, 300-400 RPM idle until I hit the gas and it surged and it leved out. For the rest of the day... no more blue smoke from burnt oil, but I can smell something abnormal when it misfires and I get out of the car.

I haven't run a cylinder balance test yet, but does anyone agree that's where I should start? The CE light is not illuminated, and I have seen it work (I pulled the MAF), but I will run codes and post anyway.


THE SHORT VERSION:

So any suggestions or ideas? The car misses, but does not backfire. On a regular basis, there is no smoke. Starts hard. Idles fine afterward. Seems to be no loss in power (except below 4000 RPM from a standstill and the bucking thing).

Thanks in advance.

 

[Slo-Sho]

When was the last time you replaced your plugs/wires? Also, when the motor is running at 3-400 rpm the bearings are getting a real good @ss kickin'.

 

[Ferendon]

I'd say plugs and wires. Might also check for a vacuum leak that's making your secondaries stay partially open, allowing too much air into your heads. But most likely plugs and wires.

 

[Trusty89]

If the cause of the bucking was plugs & wires wouldn't the miss be constant? It sounds like the car runs fine under certain scenario's, highway cruising, over 4000 rpms etc.

 

[sdpatt]

If your engine is experiencing a misfire without a CHECK ENGINE light indicating a component failure, the cause is almost certain to be the spark plugs and/or plug wires. This source of misfires will not cause a constant miss because the conditions in the cylinder vary significantly with engine load, throttle position and fuel mixture.

Not knowing the maintenance and parts service history of your car also makes me suggest that you clean the MAF sensor filaments, check the continuity of the throttle position sensor output and reset the idle speed programming.

Have you checked the EEC codes? There could be more clues to your car's maladies within those numbers.

 

[UnsungZero]

Check or Change Your Fuel Filter Too

i had the same problem

the misfiring part at least...changed the filter it went away

 

[morebhp]

Chris,

How old is your fuel filter? If its more than a few years, try replacing it. It could be restricting the fuel volume just enough to throw off the mixture.

My '95 MTX was doing this. I kept thinking it was plugs and/or wires. I never could get rid of the problem. Then I haplessly replaced the fuel filter because it was old. To my surprise, throttle response was greatly improved and the bogging and stumbling below 4K RPM was gone. The car feels much stronger through out the power band.

This may not be your problem but it made a huge difference for me.

Mark

 

[SHO_Driver]

Also if your lights are dimming under load check your alternator for weak output or loose wires and your battery. Alternator problems have been known to cause strange behaviour.

 

[twr]

You say the lights are dimming, you should check the alternator output. TPS might be wacked out to.

However, my 89' did this exact same thing when it had a bad fuel injector (stuck open) The car didn't like anything below 4k rpm, above that it ran like a champ. No CEL light either. I finally pinpointed the problem by examining the plugs and finding #1 was fuel fouled and cylinder balance indicated #1 with both the old plug and a new one. I moved the suspect injector to #3, the cylinder balance test then showed #3 as low. Rebuilt injector solved the problem.

 

[SonicRiot]

Thanks for all of the replys. I have been away for a while... been hectic because I just started my new job as a Porsche tech in Fairfield.

I'm going to run codes right now and the CBT. I'll post the results.
Next, if no codes show, I will try the fuel filter.

Last: Anyone know how to full field this alternator (stock)? Also, I can't seem to find a number for max output...

 

[SonicRiot]

Here's the deal: I have no CE light, but some codes showed:

87 - Fuel pump circuit fault (check inertia switch) intermittent in fuel pump primary circuit

88 - Throttle Kicker Solenoid Variable Voltage Choke relay circuit fault Fan Control circuit fault A4LD - Converter Clutch Override solenoid Electronic Ignition - IDM DPI or spout circuit fault

I understand 87. It explains why the car starts really funny on some mornings. Could it also be the cause of my bucking/misfiring? Could a clogged fuel filter cause this code to be thrown? And what exactly would cause this particular problem?

And what the heck is 88 supposed to mean?

Thanks for any help.

 

[SHO--ripper]

How many miles on your SHO?