Stock MX3 GS stalls at 2500RPM

[raven_nyx]

I'm having some trouble with my GS - it stalls every time I get above 2500 RPM. It's stock, no mods, not even CAI, HEI or headers/exhaust - as stock as it can get. Just replaced the alternator, and the battery (optima red top - heard some bad things about gel-batteries so I thought I'd mention it). It's a '93, 1st gen (no airbags - before facelift).

It wont restart until I have turned off the ingnition, remove the key, turn on the alarm, turn it off and then try again. So I initially thought that the alarm was playing tricks on me. So I checked the alarm - bypassed it, and the engine still stalls above 2500 RPM. If I kick the accelerator hard, I can rev it to redline, and the it cuts out.

Symptoms:
Above 2500 RPM, the rev-meter drops instantly and the engine just dies and cannot be restarted until some time have passed or the alarm have been cycled on/off. The starter always turns.

So what's up?

I've read a bit on the subject and I've found that alot of people with different cars (model/make), have had problems with stalling at exactly 2500 RPM, due to VAF malfunction or problems with clogged fuel-filter, clogged fuel-pump or the fuel-regulator acting up. So I'm checking that, as soon as I can.

I started with the VAF - thought it would be the easiest thing to start with (yeah - I'm as lazy as they get ). I disassembled the intake-system, took out the filter-box and the VAF. I found that the accordion-tube had some cracks, and I have just finished trying to seal it with some sillicon. Also, I had a lot of oil in the intake-system behind the VAF (towards the TB). I've cleaned it out the best I could, and I'm looking to get a catchtank so I can avoid it in the future. It might do the trick, and the whole thing is the ECU going all princess on me due to false air being sucked in behind the VAF and oil clogging up the readings, but I doubt it.

Tomorrow I gonna' reconnect the intake to see if it solved all my problems and then pull my codes to see if I've missed anything since the last time. Also, I already have a disti-cap and rotor on the shelf, so I'll change those as well as alot of people in here point to the distributor and coils and such. I will replace the fuel-filter as well if it continues to act up.

I would very much like to know if anybody have any other input? Could the problem be somewhere else? Have anybody else experienced trouble like this and what was the solution to your problems?

[Newfie_dan]

intake tube leaks for the win, these cars are highly sensitive to vac leaks, so thats probably the major cause of your stall issue, secondly the oil in the intake is a faulty pcv valve replace it. As for the rest troubleshoot once the intake tube leaks are repaired.

[raven_nyx]

Well, it wasn't the intake. Cleaned everything, plugged whatever holes old-age had done to the rubber, and still no dice. Changed the disti-cap and rotor in the process. No luck.

I tried to pull my codes - nothing to pull - no codes present.

I haven't replaced the PCV-valve yet. Haven't got a spare, so I need to find one first. I wouldn't imagine that it could be the sole cause for the car not running at all, so I'm shifting my focus a bit now.

New thing is though, that the car wont even start now. It just runs the starter, but the engine doesn't even turn over. I've checked every vacuum-tube I could find, and they all seem fine. Same story with every wire I can see and touch. Double checked everything I have touched yesterday and today against my chilton, and everything is connected the way it should be.

I'm almost certain that it is a fuel-problem now, as the smell of fuel is absent when I turn on the ignition. I've checked every fuse that has to do with fuel-delivery, and they all check out fine. Am I terribly wrong assuming that the next step would be to troubleshoot the fuel-delivery-system?

So, before I start stripping the interior of my car to get to the tank and pump - what am I missing? I get the distinct feeling that I'm overlooking something important.

What I failed to mention before, is that I'm totally green under the hood of a car - please be gentle

[davmac]

The no start problem you've described is fairly classical failure of the distributor - it is usually the igniter, but could be the coil too - both are integral with the distributor. You have a couple of choices to replace the distributor:
- Salvage yard pick up a 92 -93 MX3, 93 - 94 MX6, Probe, 626 with V6 for replacement fairly cheap - probably <$50
- Probably <$100 to do the HEI mod which involves buying a GM HEI ignition module and MSD ignition coil and a little wiring - details in the V6 FAQ section under HEI mod.

- Buy a rebuilt distributor from auto parts store $200 - 300

While the fuel pump is easy to replace before you remove the rear seat test the pump by getting a paper clip or small piece of wire to jumper F/P and GND at the diagnostic box under the hood (small box near driver side firewall). Then turn the ignition key to "on" position (do not start). You should be able to hear the pump running. Tests can be found through the online service manual here.

[Newfie_dan]

to run the car needs timing, spark, fuel and air. First check for spark, remove a plug insert it back into the plug wire crank it over with the plug end against the engine block and look for spark, if you got none then there is your problem. To check for fuel disconnect the fuel line at the filter, put it into a bucket turn the key on see if fuel comes out, if it does then that is good. After that you have to do some diagnosis. And davmac please remember to tell new ppl to troubleshoot a bit before jumping to the distributor as the fault, yes I know that its a common one but with that said you should make sure that is the cause before recommending replacement.

[davmac]

^ agreed

Check for spark, then fuel. The safer way to check fuel pump initially is through the diagnostic block, with jumper and ignition key to on position. I provided the link to the service manual previously. If you're not sure the fuel pump is running then you can confirm by disconnecting the fuel line at the filter (inside engine compartment). Seeing the fuel spray out will confirm your fuel pump is ok - just be careful gasoline is dangerous.

[raven_nyx]

Well, davmac made the correct assumption - no spark.. Took out a sparkplug, re-connected it to the cable, and almost let it touch the IM. Had a buddy turn the ignition, and no spark. Tried to let it touch the IM, and still no spark. The smell of fuel was present at that point due to the open cylinder.

For good measure I tried the F/P+GND as well, and the fuel-pump makes the noise I would expect it to.

So I'm guessing that I should do a HEI mod, consisting of something like a MSD Blaster2 single-coil, and a HEI-mod (I hope the "Intermotor" product can be used). That seems to be the cheaper solution of everything I can do.

But, could this also be the cause of the 2500RPM cut-off?

[davmac]

Ignition modules can act funny when exposed to the heat too long. That's why they often start magically working again when they cool off. Maybe this one is bothered by vibration too. I agree that HEI and coil is first choice - unless you can nab a salvage yard disty or buy one from someone parting a car. Check the parts for sale here.