3.1 engine ignition(?) problem

[michi]

I didnt check the ICM, dont have the tools for doing this and i dont know if shops here can test them... i live in Austria, Europe so i dont expect much for these shops... they are only good to get car parts but mostly just for european cars. I can get nearly nothing for my cars there, so...
Today i checked all sparkplugs again and found out one had a broken ceramic... put a new one in and redid the idle procedure and now it runs better again. Lets see how it does tomorrow...
I am going to look if someone can test the icm but its my daily driver right now so i need this everyday, also my other car is already in hibernation... but I just bought a new daily driver today but this one needs inspection first and will be ready in 1-2 weeks, so after that i can get the icm tested or buy a new one.

Will keep you uptodate... thanks guys for your help!

[1988GTU]

An Ohm test with a cheap multi meter can get you in the general area of bad or good ICM detection. A mist of water sprayed on the ICM while installed and car running will also help decipher if it's possibly faulty as well.

If the plug was gnarly, I'd wager that was your culprit. Any pictures of the plugs you removed?

[michi]

I threw the plug away and forgot to take a picture... also i sprayed some water as good as i could to see if anything happend but it didnt... anyway, i had some stress to get the new daily driver on the road so i drove the beretta until last week. Now the beretta is parked and waiting for the new ICM i orderd... i hope this is going to help.

[michi]

Oh well... got the ICM swapped in and also new sparkplugs. It ran fine when i started it... let it idle some and took it for a testdrive. Seemed to be fine and fixed my problem. Then i thought i keep in in idle for some minutes for completly warme it up... went into the garage and after 5 minutes i heared that the engine idled kinda rough... just like it did before. I gave it some revs up to 2k,3k and then 4k rpm and then black smoke came out of the exhaust then i let it idle again and it sounded like its idling just fine again.

When i swapped in new sparkplugs the old ones looked BAD... all black.

Ignition is completly new now. Looks like theres fuel pressure problems like "money pit beretta" already mentioned what could cause my problem...
Can i swap in a universal fuel pressure regulator to see if this solves my problem? How much fuel pressure should it get?
I also think about to get some remain fuel injectors but first going to see if its the fuel pressure regulator or maybe some of you guys got another suggetions for me.

Oh, and a happy new year guys

[1988GTU]

55psi for fpr on the 3.1's is ideal. I guess, if you really had to you could inline an aftermarket one.

[michi]

Thanks, but are you sure its 55PSI? On rockauto.com the FPR's for the 3.1 are stated at 47-48PSI. I will see if i can put a aftermarked regulator on there... im going to order a new one anyways and also get my injectors ultrasonic cleaned when im already at it.

[3X00-Modified]

pre 2000 engines should see around 43.5 psi or 3bar, the same pressure that most injector cleaning companies test them at. 55PSI is what it was increased to in 2000+ setups with the MultecII injectors vs the Bosch type you have.

[1988GTU]

Correction: 47psi for 3.1mpfi (pre93)

[Money pit Beretta]

How old is that O2 sensor? You did say it was running fine then bad after 5min. That would be about the time needed to get into open loop(computer gets all readings from the O2). A bad O2 will make the car run rich, very rich.

[michi]

I swapped a new one in like 2 years ago(acdelco). Still have the old one which was fine... i could swap in the old one to see if it does better. I had a o2 sensor failture on my old white GT and it was running VERY rich... actually it spitted unburnd gas out of the exhaust and couldnt even idle right so i didnt thought about that the o2 sensor in my car is bad since it doesnt act like this. Also it doesnt show me any codes...

Yesterday i got the injectors out and theyre already at my buddy to get them ultrasonic cleaned. Im going to order a new FPR and intake manifold gaskets so after i get these parts installed again im hoping that its running good again. Im keepin the o2 sensor in mind to swap if this all didnt helped.

[ifixalot]

Just to reiterate. Check each injector for it's resistance. It should be about 11-12 ohms.
Also do all the plugs look like the one pictured or is one whiter than the others? This condition
would help confirm a bad injector.
Again, if one is bad and doesn't open to spray fuel, it will cause a lean pulse which the oxygen sensor
will tell the computer to richen the mixture. The good injectors will then spray too much fuel.
I had one injector on a 92 Buick that measured 4 ohms, the rest 11-12 ohms.
One plug was whiter than the others which were black. The car had a lumpy idle
which became worse after it warmed up a bit.

[michi]

Yeah, will check all injectors when i get them back. And yes, all spark plugs looked like that spark plug you see in the picture. When i took them out we cleaned them and let the car idle for some minutes and take it to a testdrive... after that they nearly looked like the same as on the picture.

[Money pit Beretta]

Ok well never mind on the O2(unless the wire is bad or there is a bad ground), just something I always fall back on. Like shocks and struts the O2 is something most people don't think of replacing.
LOL O2's seem to throw a code when they want to. Knew a guy with a Grand Am that was fogging out the street with no light.
Just an odd thought: coolant temp sensor?

[michi]

hmm im getting the new FPR and some gaskets this week so i will let you guys know. hopefully this problem is fixed then.

[Money pit Beretta]

I hope so too!