Misfire, bad idle, not want to start hot? (What you think?)

[zBusterCB87]

Hey all,

I been still a year later trying to fix my sisters beretta Z26, it has been having this problem and idk what else it could be:

Vehicle:
1996 Chevrolet Beretta Z26
3100 v6 - AUTO

New Parts:
-ICM
-Injectors (Second set with this issue)
-Wires
-Plugs
-MAP
-CPS (in back of block)
-coils
-fuel filter
-catalytic converter
-gasoline
-fuel pressure regulator
-plastic hoses
-TPS

Not replaced new, but tested working:
-fuel pump
-fuel pressure
-MAF
-Cam Position Sensor
-other crank position sensor behind harmonic balancer pulley (idk...)
-IAC


The vehicle, when COLD, starts up just fine, runs very strong.
Turn off at engine MAX temp when the fan just came on, let vehicle sit for about 30 minutes (outside ambient temp is 75), I try to start vehicle and it will not want to start, I can sit there cranking and nothing.
I try flood mode, and then try normal start again, still nothing...
But, sometimes it will start (IF IT DOES, MOST ALWAYS NOT), and when it does it is missing very badly and you gotta keep the gas peddle down about half to maintain at-least 1,000-2,000 RPM and floor it to get it up to 3,000 RPM (in park).

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What I found:
-I can verify the injectors, fuel pressure, fuel flow, CPS (in back of block), ICM, TPS, IAC, and cam position sensor are all properly functional.
-I try this:
**ran vehicle to max tem when fan just came on and turned it off.
**removed coils and then I put them in the freezer in the garage.
**waited the 30 minutes, re installed the 3 coils, and i did get it to start, right away.
**BUT, it still has its missing problem and slightly rough idle...
**BUT, i don't need to hold the gas peddle like before.

-----------------------------------------------------------------------------

Do I have bad coil packs causing this? or is something else or both?

(These coil packs (all 3) were replaced and are new about 1 year ago and they ran fine.)
they were replaced with the ICM at that time because the ICM went bad.
each part replaced above was replaced within the last 2 years because each item broke at some point or another.

Thanks everyone for the help, I'm confused...
zBuster

[zBusterCB87]

I forgot to add:

Today when I first started it up in the morning after the injectors were fresh installed, I got this following problem:

I started vehicle after 2-3 tries, then it started ran extremely bad, and the "Service Engine Soon" (amber light) came on and was flashing.
Then i turned it off, and it would not start, I got the Auto-X-Ray scanner and cleared all codes and master reset the ECM with that scanner method and again with the battery reset method.

Car started up great, everything reading properly, no codes.
Before with flashy light it had the misfiring codes set.

also, I want to add, I checked the sensor readings when it would not start and cranking and they are all still correct just like when it was cold and cranking.

I have not been able to re create that since...

[heavywoody]

What are the coils ohming out at?

What cylinders are misfiring?

[zBusterCB87]

What are the coils ohming out at?

What cylinders are misfiring?

coil readings: (output side in ohms)
9
8.9
9.15

I can't read input side I do not have anything to stick in the slots...

idk which cylinders are misfiring, I can't tell, idk how really...

[zBusterCB87]

I add it here, I forgot to say the temp sensor was also replaced about a few months ago, the one with 3 wires next to the coolant thermostat that opens & closes...

[3X00-Modified]

use a paper clip.

the out sides (secondary windings) should be around 6k-12k ohms

and the in sides (primary windings) should be around 0.4-1.1 ohms.

[zBusterCB87]

ok, I'm looking for paper clips...lol

If you read I have a new problem, I did not realize I poped the 15 amp fuse for the ECM by accident, thats why that stuff quit working...

But I still dont have anything metal to stick in the coil sides that connect to the ICM...
so I can't take care of that for now... :/

[zBusterCB87]

I just found this:

You have a bad fuel pump. Your trip home and your description of it verifies my opinion as well as hard to start when warm. All this speculation of bad CKPS (only when warm? Sorry, that's ridiculous! They are either bad or good , not good cold and bad warm) and spark screwing up via the ICM at high revs only, etc is wild speculation at best and looking for the hard solution when the easy one is right in front of you. ICM's are generally good or bad or ACT good until they get warm, like coils, then go to hell.

The fact that you cannot always hear the pump cycling when you turn the key is further confirmation.

The reason the car wouldn't start back up when you stopped to use the restroom, was the pump got hot and is weak. The reason your car idles like crap is because the fuel pressure isn't sustaining the injectors at idle. The reason it dies at 3k and above is you're putting load on a bad and already weak pump.

Time to replace that pump. Best of luck.

posted on this thread:
http://www.beretta.net/forum/posting.ph ... =8&p=53217

simaliar to my problem...
but my car does not die at higher RPM's... it is just good cold and bad hot, only after turned back on after sitting for 30 mintues after turned off at max temp...

I just realized it is possible the fuel pump on this car is the problem, because I decided to start looking at it underneath and maybee poking at it, (like run testing it for a few minutes), and the gas tank is dented in in the middle... like someone took a jack to it...rofl

but the pump runs every time I turn the key, I'll double check...

what do you think?

[3X00-Modified]

Pump wouldnt show issues when the motor is hot, since it sees no heat. I think you have an electrical gremlin like Geoff did and his only cure was a harness replacement. He went OBDII and his issues went away.

[zBusterCB87]

oh...
I'm at OBD2 alredy, idk..

I did forget to mention, when it acts like it is missing, there is no smell of unburnt gas or a bit of blask-ish cloudy stuff out the tail pipe...

I was only thinking that the pump could maybe start to freeze up after used for a while when it sits..?
or a dented gas tank, maybe the plastic baffles cracked and did something bad...idk...

I tried clicking the key back and forth to try and get the fuel pump to run when the car sat its 30 minutes of death after being run till hot, and this time it seemed to start right up... but a bit missing...
idk I gotta try it some more to see if it actually does the trick...

(the car is good if you are gona let it sit at-least an hour before you use it again, so it is still usable for stuff like that, just not anything quick...)

[zBusterCB87]

Ok, I have some new data I can give:

When I run the vehicle, temp is just above 1/4 way up, after have been running the vehicle a while...
(This happens regardless of engine temp).

I start the engine, after clicking the key between run & off about 10 times...
starts up, do it less, and it has a bit of trouble, do it more, it does not matter...

once the vehicle is on, I can increase RPM slowly just fine, no misfires, no blanks...
I floor it, and i get misfires/blanks...

I think it is blanks, (but I keep an open mind to misfiring too, just-in-case), because I do NOT smell any unburnt gas at all... no blackish gas fumes either...

At-least I know how the vehile acts, and how I can get it started right away.
I'll just swap cars for now...

thanks for the help & sugestions.

[3X00-Modified]

I know your obdii I was simply using geoffs conversion that ended up replacing his harness fixed a similar issue, Leaving his harness as the original problem.

[SuzukiGhostRider]

Pump wouldnt show issues when the motor is hot, since it sees no heat. ...........

This is a false statement in it's purest sense. If the motor is hot, SO IS THE FUEL pump. It doesn't matter if you're moving or not. Do you think a fuel pump stays cool as it runs? Nope. It heats up.

The only way to TRULY get a sense of that pump being bad or good is do a fuel pressure test when the car is warmed up and refuses to start. If you have weak pressure you have your answer. Btw, fwiw, I've changed MANY a weak/bad pump that you could still hear "prime" upon turning the key.

The other answers are ICM or CKPS. Get the ICM tested (3 of 4 times MINIMUM to make sure it gets properly heated up on the tester) by at LEAST two different stores. It's free.

Trust me, it's a VERY high likely hood you got a weak ICM outta the box. I've gone to AZ to get them before and one time (I always make them test them before I buy them) ALL 5 they had on the shelf ,brand new, failed on their tester. ALL were garbage.

You say the tank is all banged up? It's very possible they damaged the pump. Look into this situation first.

I would almost bet money your pump is almost dead. Being able to turn the key 10 times or more and then get a weak startup tells you the pump is having a LOT of trouble building pressure.

[3X00-Modified]

Ok I guess I'm wrong... Have fun with the pump. It's a bitch if you have a full tank of gas.

He said he verified fuel pressure but oh well, I said it wasn't something so SGR has to disagree with me 100%.

I highly doubt the fuel pump is holding the little bit of heat it does generate for 30 min and still affecting the startup.

Turn off at engine MAX temp when the fan just came on, let vehicle sit for about 30 minutes (outside ambient temp is 75), I try to start vehicle and it will not want to start, I can sit there cranking and nothing.

Good luck, I'm out of this thread.

[DTMAce]

Not to mention fuel in the tank keeps the pump cool. Yeah I don't buy it either, but weird things happen all the time.. LOL I should know!