Hi everyone.

Before I posted, I spent the last 2 days going through the forum, and didn't find anyone with my exact problem, so here it is:

Just bought a '90 vert. (102k) When I got the car, it had been checked out and was throwing 2 codes: #11 and #27. It also ran beautifully at idle, but as soon as it was put into gear and accelerated, check engine, and bucking came on.

I installed another OMP, since code #27 seemed to indicate it. I'm amble to spin the motor up to 7 grand in nuetral with no hesitation, but driving puts me back where I started with the bucking and light. I tried to grab a code again, but as soon as you turn the car off and on again, no engine light, no flashing code.

Help!

Thanks in advance, Mike

 

Hmm, fuel...
Check your filters, the one in the tank on the pump, and the main one on the left rear side of the engine bay

 

sounds stupid but how much gas do you have in the car? if its low, your pre-pump filter could be blocking fuel flow when the gas sloshes back during acceleration.

 

I topped it off with 87 oct and am running a 100:1 pre-mix just to avoid OMP problems.

I did the filter in the engine bay, wasn't aware of a tank filter though...

 

When did you start pre-mixing? There is a little green man that comes inside every first bottle of premix we buy, and he likes to clog our pump inlet filters within days of starting premixing. Why? I dunno...

 

I put the pre-mix in my first tank, but that was after the problem was already noticed. I should mention that the car did sit for 2 years, although the owner did periodically let it run in the driveway. Could this be a carbon/injector related thing?

 

Stupid little green man!!!

 

How high do the RPMs get while driving? It sorta sounds like a TPS problem I was having back in the day.

 

It seems to come on at the dreaded "3800 rpm", although I am able to nurse past this point by feathering the clutch, but after I get through the bucking, I just don't feel any power. The compression was checked and it came back 85%. I believe the Mazda compression tester showed a 6 out of possible 7.

 

My guess is TPS or fuel. You said the car did sit for 2 years, it is very possible that the in tank filter is clogged up with gank.

 

Thanks. I just jacked up the back of the car, but didn't see a filter anywhere. Could you describe where it is and how to access it? (Please please please don't say "drop the tank.....")

 

LOL, OK, we won't say "drop the tank"...oops, said it...

Access the fuel pump under the carpet in the back, on the left side, about 18" forward of the back of the car. A bunch of rusty bolts, Disconnect the harness connector at the left strut tower, and yank that sucker out (well, don't yank)...sock is on the bottom of the pump assy...

 

I deserved that.

Ok, that's what I'm going to do now. Is it an off-the-shelf item, or dealer only?

BTW, this is unbelievably cool. You guys wanna come over for a beer while I'm doing this?

 

Yeh, and we'll roll some up & smoke 'em in the back of the car while you're pulling the pump too

I forgot to mention disconnecting the fuel lines, and removing the fuel line pressures before you break the lines...It's all in the Haynes and FSM...

 

Ok, it's out. There seems to be some very fine metallic in the filter. Can this be cleaned, or should it be replaced?

 

Oh, your question...I don't know about it being a "generic" filter. Mazdatrix may have them, I'm sure the dealer would...

When mine clogged (big time), I took an exacto knife and cut a small hole in the side of it (yeh, yeh, y'all flame all you want, I FIXED it...). I wouldn't recommend this to anybody, of course (just make sure you don't put the hole on the bottom)

 

Fine metallic? WTF????

Try to clean it, see how it goes, unless you've got a new one handy...

 

What hole?

Can't hurt. Especially if I have to buy one anyway. I just sprayed the hell out of it with parts cleaner, and now I'm going to flush it with gas before re-installing.

 

Seriously, (for once), check out your tank REAL good, if you have ANY solid sediments floating around, rust flakes, "globules" of water, etc, think twice about cutting the hole. My tank happened to be immaculate, that's why I went ahead & cut it without worry...

 

Ok, thanks. I'll just clean the hell out of it.

 

No help. Any other suggestions?

 

Just get on the horn with mazdaformance they will have a new one out to you within a day or two and youll be out driving around by the middle of next week. Plus you get the added security of not worrying about a whole in your filter (not flaming just stating the obvious )

 

Yea, solid sediments getting into your fuel lines is a BIG problem. Of course it wont make it to the engine cause you have that second filter up in the engine bay, but lodging something in one of those lines while driving and *fuel flow cut and instant lean out BIG TIME* Possible detonation, who knows...

But hey, this is coming from the guy who decided to drive on only one engine mount, with the theory that "as long as its on the torque side, its ok "

 

Thanks guys, I'm ordering a new one today.
I managed to get a code off of the computer by not shutting it off once the light came on. I'm still getting #27. I'm wondering if it is possible the ECU got screwed up because I've seen a few posts that mentioned this could happen sometimes when the OMP goes bad.

 

question for you...does the car only to this under load? How well does the motor rev up while in neutral? fast? does it buck when you rev it up fast? lemme know