my 85 z28 lb9 a4 has been doing this since i bought it..

when its cold {after sitting all night} and i start it in the morning or whenever ,the check engine light comes on when it first starts,and it runs like total crap,misses,backfires,does all sorts of goofy shiat,but it will idle fine,part throttle or off idle throttle makes it go goofy,give it WOTand it runs great and pulls hard.

now heres the kicker,if i let it run for like a minute or two,and shut it off and restart it,the check engine light goes away,and the thing runs awesome,wont throw a code or run weird until it sits overnight and totally cools off again.

also,the damn temp gauge when first starting it cold,pegs out to the high mark{self check?} and it works fine,until i shut the car off again,then it quits working,and the self check thing goes to the 220 mark,once the car starts,it goes to the bottom


another thing im curious about...,the alternator went bad,and it had a 55 amp regular gm alternator in it. the car calls for a 108 amp unit,which my parts store was out of stock on,clostest they had was the 78 amp unit,which is in the car now,will this cause any problems?


btw,im throwing codes 32,33,34

 

32. Fault in barometric pressure sensor circuit OR
Fault in exhaust gas recirculation valve diagnostic switch OR
Fault in electronic vacuum regulator valve

33. High voltage (low vacuum) at mass air flow sensor (or MAP sensor)

34. Low voltage (high vacuum) at mass air flow sensor (or MAP sensor)

Try a new MAP sensor??

 

An '85 LB9 has a digital (FM) MAF sensor, not a MAP sensor. The temperature gauge should move to full-scale when the engine is cranked. It should then return to the correct coolant temperature indication. Check the connection at the temperature sensor on the left head. Since the problem is not consistent, the various error codes and symptoms may point to a common electrical problem. There are a couple of common grounding points for both instrument wiring and ECM sensor grounds. Take a close look at the wiring harness grounds near the rear of the right head or intake. Make sure the ground strap between the firewall and RR of the head is intact.

You may also have a MAF problem, but verify the engine and chassis grounds to make sure you're not chasing a ghost problem. You probably should disconnect the battery for a few minutes to clear the error codes. While the cables are off, cleaning them would be a good idea, too.

As long as the alternator is producing the correct output voltage, the 78A unit should be fine. The fact that you recently lost an alternator could have a bearing on the problem (depending on how it failed), and clearing the ECM may help that as well.

 

I was basing my diagnosis on what he has written in his sig...

Although I guess he could mean eating a lot of beans??

 

ugh,sorry,thats an old sig. refers to my old 82 transam.

i now have the 85 z and my 84 l69 t/a

the code 32 and 33 have been popping up everytime i start the car when its cold,they go away and the car runs fine after a minute of running.this code 34 popped up last night when i started the car to roll the windows up. ,ive had this thing about a month,and its been a nonstop headache since.

it ran good for about a week. ill fix it one more time,if it screws it self again,im ripping the POS off we call TPI and throwing a carb on it.

also,tonight i tried driving into town,and it was just running horrid,it has always ran fine after a minute{after first starting it totally cold} then restarting it after it warms up a minute or so.

it never really got better,so i brought it back home,i started checking a few things and theres a vaccum block at the back by the distributor,i pulled one of the hoses out,and theres no vaccum there {should there be?}

also while it was running i pulled the connector for the maf sensor,and it died immiediatly,i restarted the car with the maf unplugged,and it started and ran,plugged it back in and the idle raised a bit,then settle back down i cant hear any vaccum leaks on the car anywhere,ive checked a billion times.

 

well the alternator on the car was a 55 amp unit,the diode was cutting in and out,the back post was loose,instead of fixing it i bought the 78 amp unit for the car.

also,everytime i clear the codes,the 32 and 33 always come back,34 happened last night.

 

Was the TSB for the PROM ever done on that car? One of the things it corrected was a false code 34 and a lot of driveability problems.

For the code 33...MAS module $$$$$ from GM, Check the classifieds for someone selling one.
Code 32..EGR..ignore it if it comes on during a cold start, the ECM is looking for a feedback signal when it shouldn't be.

 

the tsb for the prom? huh? lol

so you think it needs a new module or the maf?

is there anyway to get rid of the damn ses light on startup,its godawful anoying,and it only does this when totally cold,and it runs like *** during this. once you restart it runs fine and the light goes away.

 

Since you're generating codes anyway, what happens on cold starts if you disconnect the MAF?

 

TSB, Techical Service Bulliten. The proms in the 85 TPI's were bad from the factory. something about them having been exposed to light without the sticker over the UV erase window, the programming is slowly corrupting over time.

The "new and improved" prom should say HLM on it, give a look at yours.

 

ill go try that now.

 

some new info

Learn control = disabled
proportional O2 step = lean
Rich/lean flag = lean
loop status = open/went to closed when i revved it
park/neutral = detected
TCC = not locked
pwr str = not high
prom id = 2541
Iac STEPS 57-42
coolant temp = 194.9*
EGR duty cycle 0%
integrator=128
OXY sensor = 194mvolts
manifold air temp = 140*
engine load = 2
block learn = 108
02 cross counts = 24
maf 8grams second
injector pulse= 1.4 ms
at 3k rpm's the egr duty cycle is 40%
oxygen sensor at 4k rpms is 900mvolts
at 3k rpms the engine load is 27
4500 rpms the maf reads 40 grams per second.


does this help anything?

 

SOMEONE?! all these views and no help .

 

You are running rich, very rich.

What is the prom code on the sticker on the chip?
I would almost bet the TSB was never done on that car and your chip is on its last legs.

If not that then you have leaking injectors or CSI, you are getting too much fuel.

 

Morley, how can you tell it's runnng rich from the information he gave?

 

lostangel, a block learn of 108 means the computer is leaning out the mixture as much as possible.
I wonder if it's the MAF burnoff relay?

 

BLM is bottomed out at 108 (by default that is as low at it reads) & lower is richer and the O2 mv is 900, about as rich as it can read.

 

I just yanked the computer..

the following numbers are on the cover lid on the ECM,

16052541 upper lefthand corner
HLK upper right hand corner

862541m512320245 on the bottom


it also says HLK on the chip under the cover

theres a barcoded label on the printed circuit board that has the following...

255001202855123


on the actual mas module itself the numbers are as follows

0 280 215 001...... 078 {circled}
14080620


does this mean ANYTHING?

 

Well, the HLK on the chip means the TSB was never done. The updated prom says HLM.

 

you think its possible that this is whats causing all the problems im having right now?

im at my wits end,ive boughten everything to switch over to SD,but if this is an easy fix,i might try it.