i replaced my injectors about a month ago and have had slight issues upon start up and poor mileage. the other night i plugged in my modis and started pulling data. blm around 151 and int around 137! at idle only of course. once you tap the throttle all goes normal on the int. took the liberty today to re-gasket the plenum, reset timing, reset min idle speed, reset tps. i have an msd coil, accel 8.8 wires, tpis airfoil, stock dual cat exhaust with new cats with a pacesetter 3'' to dual 3". not much from stock but it recently started acting up. the newest addition besides the wires are my bosch III's. just to verify my o2 wasnt shot i replaced it. heated of course. no vacuum leaks that i could find. any ideas?

 

also 37 psi idle fuel pressure and 45 wot fuel pressure { regulator hose unplugged and capped}. new pump and of course filter

 

Hello,

You have done alot of good work already. What condition is the fuel pressure regulator diaphragm? Mine was torn and sending fuel into the plenum.

hope this helps.

 

new unfortunately. figured id do it when i was in there. its running very lean. idles around 1100 unless in gear then its the normal 650- 500. seems to surge when im coasting down hill. i didn't think of it but can my cold air be affecting my maf sensor. i swapped about a yr ago to an 89 computer system. haven't had issues till now. also im smelling gas occasionally.

 

Hmmm...

What was the O2 doing on the scanner? Check the O2 crosscounts as well as sensor value. With BLM at 151, then the O2 may be stuck at the end of its range too. Is the CTS operating properly?

Do you still have the single wire O2 or have you upgraded to a heated O2?

Hope this helps.

 

I would check for a vacuum leak. Carb cleaner works great for this.

 

checked for vacuum leaks and changed all plenum gaskets just to be sure. it was leaking before but not now... now tonight i got a flip flop. rich as hell. .830v from the o2 sensor. kept cycling cross counts around every 200 or so it would restart the count. i created a vacuum leak at idle and the blm floated a 111. i didnt do anything different. same hotish weather. kept stalling. i do have a modis scanner so gathering my info is easy enough. at this point im just getting annoyed cause i bought new injectors to replace my leaky ones and now im having issues after it running pretty decent. im not looking so wise amongst my peers as i am a mechanic for a living. it damn near dies right after i start it before i even get my hand to the shifter. the cts readings pretty much match my guage. not pegged at -40 or something. so far thanks for the replies. normally im on the helping end so i do appreciate it.

i do run a heated o2. its a 4 wire. i also elected to put my stock manifolds back on for my ears sake.

 

I'm sure your peers are more than helpful right now...ha.

What condition is the IAC in? Did you reset it too, something like...turn key on, jumper A to B on the ALDL, unplug IAC connector, turn key off and remove jumper, reconnect IAC connector. You could check this procedure out, because I am not certain about it.

You said your regulator is new, good. As a mechanic, I am sure you lubricated both rubber "flaps" on the regulator diaphragm when you installed it. I am also positive you made sure that there are no folds or creases in the same flaps, but it doesn't hurt to check.

I installed my new regulator diaphragm and assumed all was good, however I had accidentally driven the last screw right through the rubber flaps and ruined it. It was mis-aligned and I knew it; just thought it would be good enough. Twisted, torn, and destroyed is how I left my brand new regualtor assembly. Lesson learned...take my time and align everything. It was the last thing I did and the first thing I checked.

But I am sure you are a better than that...

Hope this helps.

 

lol. i will check again. as a mechanic we also don't toot our horns on perfection. yes it was lubricated. it didn't appear to be leaking but whos to say that it lined up proper and stayed that way.... i will get back to you on that. it seems that when it comes to my car i always seem to be in a rush to but for "work" stuff i take my sweet *** time. first thing i wanna do is swap in my spare maf and see if it helps. quick and easy. if no change then the upper plenum comes out again. oh well.

 

If the problem started right after replacing the injectors that is where I would start. Have you been able to verify that they are truly 19#/hr ( for the 305 TPI in the mini-sig)?

I doubt it is the FPR as the pressure is OK.

RBob.

 

ordered from southbay. it was an initial start up lag but i do believe i nicked a lower gasket so i replaced them. figured a small leak would cause that. when it was good and sealed it started running lean. last night it ran rich as hell so i swapped my maf { spare in the trunk} and tonight its back to lean. mind you my spare is only my limp home one. its an oe original from 89. my {bad} one at this point is a reman of course from autozone. ive used the warrantee 5 times in 6 months. this one lasted 5 weeks? im going to exercise my warrantee tomorrow as ill be by there on my way to my second job. really just want to do this ob2 stuff..... wifes blazer has minimal downtime and 40,000 more miles.

may end up posting another thread. i like the vortec truck stuff and have most of the sensors from one. can the stock 96 pcm run a stockish tpi ok? both 305. i have probably 3 incomplete harnesses for both the 96 and an 89. easy enough for me to make a harness. is it a more reliable system or am i just day dreaming here? i cant find much on that system only the 0411 and i cant look at that stuff yet.

also the o2 sensor voltages may be useful, first cold start up 275mv to 225mv. closed loop hit and within seconds dropped to 89mv to 54mv lowest before shut down. how can it even run that lean. and why does it smell rich as hell? either way more info tomorrow night as ill have another fresh maf.

 

Do you have a cold start injector? Your sig. says 91 Formula but earlier you said you have a MAF, I am confused.

Does your car smell rich all the time? Even when the O2 indicates a lean condition? Does the computer supply the expected .5V bias to the O2 sensor prior to starting?

It must be dumping gas into the cylinders...maybe try a different set of injectors. Before that though, maybe unplug each injector one by one and look for the idle to stay the same or get worse.

Hope this helps.

 

i swapped with an 89 harness and computer. it came with the engine/ transmission i bought for a very good price. prior to starting i got the 499mv reading. i was thinking a false lean situation myself and thats what led me to swap my o2 sensor. i happen to have quite a few. lol. lets see what today holds for the readings. today i do over a hundred miles of driving round trip.

 

swapped the maf. runs pretty good now. still a hair lean on the bottom tho. getting annoyed with reman parts but cant spring for new.