multiple codes

my brothers car, 93 3.1 is giving him problems. he is extremely poor and its up to me to fix it. so, the thing is putting out basically all the codes including a 51 which i know is really bad. does it have to be the computer going bad since its shooting out so many codes? the codes were read by a snap on scanner but i also have a scanner, its an autoxray but has worked very well in the past but now its telling me that the car is not responding! the car idles really bad and really rich. its weird but if you hold a little throttle it will crank and run but tries to surge backwards just a bit while in park or neutral. the car actually tries to move. i guess im hoping that something stupid is up and not the computer.

Need some of the codes here, try tapping the pcm see if anything changes.

sorry for the delay, just back from an extended holiday vacation. for some reason my scanner will not communicate with the computer. it says "vehicle not responding". however i did the paper clip/check engine light code check and there were not any codes stored, only repeated flashing of "12". the problem is its not getting spark on cylinders 2/5. replaced 2/5 coil - no difference! removed the ignition and took to autozone and tested a dozen times to makes sure it was good and hot - tested good(only a year old also)! ordered a new ECM, swapped the PROM and installed - no difference. by the way im checking spark with a separate brand new wire. plugs and wires are new also. could the 2/5 portion of the ignition be bad on the inside and just not test bad? and how can i get autozone to honor the lifetime warranty if it does not test bad but really is? is there any way the the crank sensor could cause this?

I would focus on why no response from the scanner, does it work on another car. A crank sensor on occasion can cause this poor wiring in the related harnesses and/or a bad ign module.

I've had similar results with an aftermarket/custom PROM plugged into the MEMCAL incorrectly. A stock MEMCAL shouldn't exhibit that, but there might be a problem with the PROM or MEMCAL connection. If you have another MEMCAL to connect (even if it isn't correct for the vehicle) you can plug it in and power up without starting the engine, just to see if all the codes repeat.

trans going wacky, runs like crap, without knowing any of the actual codes in the car, would start with ignition switch. test it and see if anything bad there. also check ALL fuses, one PCM fuse blown can make some weird stuffs happen.

after a battle of words, the guy at autozone agreed to swap out the ignition. its now firing on all cylinders and running tons smoother, but now the MIL is flashing "33" (MAP sensor). its still seems to be missing a little and if i hold substancial throttle if misses rapidly sounding same as rev limiters. should i eat a $50 MAP sensor or could the crank sensor do this? i already have a new crank sensor but have not installed it yet in hopes of returning it unused. if all cylinders were firing then i assumed it was working ok. it wont pass emissions testing with the light on and my scanner will not communicate with the computer to turn it off. to answer a previous post, yes the scanner works fine on another vehicle. i loaned my brother my wife's car and need to get it back really soon before i end up having to live with his lazy a**!

A '33' is NOT necessarily a MAP sensor gone bad. What it means is that the MAP is reading intake vacuum (inches Hg) too high (absolute pressure too low) for a given engine RPM and throttle angle. There are many other things which can set a '33' aside from the MAP sensor itself.

In the place of an AutoXRay, try to borrow a Snap On MT2500 to communicate with the ECM. You'll need a MT2500-1097-up or an older model specific cartridge, the MT2500-10 (GM-1) DLC Adapter, and the cable.

i dont have access to a snap-on scanner, the codes were ran by a shop 30 miles away when it first started to run bad.

To simply retrieve error codes, all you need is a paper clip or 2" jumper wire. To retrieve running data, you will need a scanner. You can troubleshoot without it, however. If you have a vacuum gauge and voltmeter, you can test the MAP:

http://72.19.213.157/files/MAPTable.gif

the MAP seems to be ok according to the chart listed above. does anyone know how much vacuum supply should be available to the sensor?

regular engine vacuum, between 17-20(holding steadily) i do beleive. someone have a better number? check another vacuum souce on manifold for baseline, and if vacuum is same at MAP, and there are no leaks, then vacum supply is good.

So the MAP signal output is correct at a given vacuum, which means the MAP itself should be good. The MAP should have a direct intake vacuum supply. Just to verify, what is the intake vacuum at idle? It should be between 16-21" Hg with a stock engine.

The problem now is that the ECM thinks the MAP is too low for the given input conditions (engine RPM and throttle angle). If the TPs voltage is correct and is fairly linear through it's entire operating range, the ECM may be seeing intermittent ignition reference pulses - The reference pulses are what reports engine RPM to the ECM. They also drive the ignition control module (sound familiar?).

vacuum was non-existent, line was broken under the plenum. runs smooth and the engine light is off, but its smoking just a little bit. i hope it maybe just has some gas in the oil from running on 4 cylinders for a little while. i will change the oil and see if that will help. thanks to all for your help, it is very much appreciated.

no prob, that's what we're here for!

vacuum was non-existent, line was broken under the plenum. runs smooth and the engine light is off, but its smoking just a little bit. i hope it maybe just has some gas in the oil from running on 4 cylinders for a little while. i will change the oil and see if that will help. thanks to all for your help, it is very much appreciated.

Which vacuum line was broken, one of the hard plastic lines or a rubber one? My '94 3.1 is doing exactly the same thing you describe, now that I got it running. Also, my PCV line is rock hard! I ordered a new one from the dealer and will replace it.