Jumped the gun still having stumbling issues

[-=Jeff=-]

I drove it the other night.. scanned for twice as long as before the car worked GREAT.. nice day figured i would drive it to work.. (about 8 miles) when 1/2 way and needed to get gas.. stumble, and a backfire pop from the TB, pulled in to the station and filled up... Restarted, ran FINE until I pulled in the parkin glot at work.. Same thing TB Pop, then died.. Restart and I have a misfire. I got it parked.. I am guessing when I go to lunch in 4 hours, it will run fine.. cause it will have cooled off.. I am thinking it is definitely heat related..

Coils will be swapped next.. Tuesday night was cool and it was cool the night I drove it in November too, so maybe this issue has been there but did not show up in cool weather.. Not sure what else to check

I did not have my scan tool hook up this am.. probably should have brought it today

[Paul Workman]

Yeah... My training is in electronics, and I agree that it fits a heat-related breakdown somewhere. The coils are easy enough to replace, so I hope that is all it is. (That, among others, was part of my stumbling problem too. The new AC/Delco coil packs seems to have cured the problem - along with replacing the mouse-chewed wires.)

And, although my Z has been running fine with the new ignition stuff, I still store my scanner in the cubby in back...just never know when it might come in handy! But, FWIW, I did not get any codes during the entire time my ignition problems were going on...which makes sense, knowing what the ECM needs before throwing a code.

Like I said...I hope it is just those coils (and not the spark mod). I may be off work on Friday, if ya need another pair of hands...or someone to hold a beer and kibitz while you work!!! LOL!

P.

P.

[-=Jeff=-]

Paul,

I read you older posts...

what did you replace?
Wires, Plugs and Injectors?

[bradslt5]

sure does sound like the coils are going bad .when i first got my black(first) zr1 i had the same problem car ran great for 10 min.,then it sounded like firecrackers .putting the lettle bolts back inthe coil mountings can be an adventure . i used super glue on ths socket stuck the bolt on for a couple of min. then put it in . hope this helped .

[-=Jeff=-]

drove it to lunch 5min away.. it was fine, it sat for 45-50min. drove back.. died parking it again..

at lunch I smelled raw fuel, but there was also a stall truck and wind was blowing from the stalled truck to me, Guessing he had Fuel issues too.

I will check pressure on the injectors when I get home after work. I will pinch off the return line.. I am thinking it is one of these 3:

Coils
Injectors
ECM

that is in no order

I wonder if the ECm has issues when it switches from open to closed loop. Although I felt the stumble in open loop, I also noticed when I pulled in to fill the tank, if I gave it more go pedal it roared back to life.. HMMM

[bobbyhi]

A bad cam sensor can cause the stumbling also..............

[-=Jeff=-]

A bad cam sensor can cause the stumbling also..............

would it cause what I have described?

any good way to test it?

[LGAFF]

I am going to say good call on the cam sensor, wifes BMW had similiar issues and no code. Swapped the sensor, and back in business.




LGAFF
92 ZR1
#234

[-=Jeff=-]

Left work.. car ran bad 90% of the way home..

got home.. check Fuel pressure

Key on, not running, Return line pinched.. holds at ~47
key on, not running return line normal, holds at ~47

Coil packs: ohmed out 2 at 20K, 2 at ~18.5K

how hard is to change the cam sensor? WHERE is it?

I NEED the car running by Bloomington Gold, end of June..

this SUCKS

[-=Jeff=-]

Cam sensor should show a Code 31...

I have no SES.. car will load up, stab the throttle and it clears up sometimes..

[Jeffvette]

Cam sensor is located on the driver side head, just below the mating surface for the cam cover. The sensor plug connector is by the brake booster.

[bobbyhi]

It is one (1) bolt holding on a metal shield. Take the bolt out and remove the sensor. Put rags under the hole as a little oil will drip out. I don't know how to test. The end of the sensor should be magnetized. Try to pick something up. I used a razor blade and it would barely attach. Maybe Jeff knows how to test correctly. I replaced with a used sensor and it only stumbled at 4000 rpm once today. They are a pricey item to replace. Somewhere in the $300.00 bracket. I still don't know if this fixed my problem. I did take out the Accel coil packs and replaced with GM. Don't know if it helped or not.

Good luck and keep us posted!!!

[XfireZ51]

Jeff,

Looking at a =Jeff= scan, his O2 sensors are hardly moving. They sit there at .45v. Both of them. He goes in and out of C/L but is mostly in OPEN although his BLMs change???. Learn control is OFF. Also Diff MAP registers a constant .6 volts but when he stabs the pedal,voltage goes up and Scdys Open. :confused: I suggested he put original chip back in and see aht happens. There's no SES.

[-=Jeff=-]

Jeff,

Looking at a =Jeff= scan, his O2 sensors are hardly moving. They sit there at .45v. Both of them. He goes in and out of C/L but is mostly in OPEN although his BLMs change???. Learn control is OFF. Also Diff MAP registers a constant .6 volts but when he stabs the pedal,voltage goes up and Scdys Open. :confused: I suggested he put original chip back in and see aht happens. There's no SES.

Original PROM...


NO CHANGE

[bobbyhi]

It is one (1) bolt holding on a metal shield. Take the bolt out and remove the sensor. Put rags under the hole as a little oil will drip out. I don't know how to test. The end of the sensor should be magnetized. Try to pick something up. I used a razor blade and it would barely attach. Maybe Jeff knows how to test correctly. I replaced with a used sensor and it only stumbled at 4000 rpm once today. They are a pricey item to replace. Somewhere in the $300.00 bracket. I still don't know if this fixed my problem. I did take out the Accel coil packs and replaced with GM. Don't know if it helped or not.

Good luck and keep us posted!!!



Just an add to my post:

I didn't have any SES (codes) until today before I switch the cam sensor. The code was for faulty cam circuit. The stumbling occurs when gentle acceration is applied and at around 3500-4000 rpm it starts "missing". Key on or key off - still did it. The it would go away and not happen for a couple of days. Only happened when the engine was hot. Very perplexing!!:mad:

[XfireZ51]

bobby,

So you finally got a cam sensor code?

[LGAFF]

Jeff, I doubt I will be running my car this weekend, if you want to come over and try my cam sensor on your car before you dump $300 let me know.

LGAFF
92 ZR1
#234

[XfireZ51]

Jeff, I doubt I will be running my car this weekend, if you want to come over and try my cam sensor on your car before you dump $300 let me know.

LGAFF
92 ZR1
#234

Lee,

I just offered him my ECM since I'm out of town this weekend. However, I have to say that a cam sensor shouldn't make the scan look the way it does. There are a number of contradictory readings on the scan. Although the ECM says the system is in O/L, the BLMs are changing. Both his O2 sensors read .45v constantly. No X counts. His secondaries are opening even tho his diff MAP shows .6 volts. Something is screwed up.

[-=Jeff=-]

I have an ECM on the way tomorrow, will have it next week.. switching it no matter what.. did some Service manual reading..

the O2s are Biased to 450mV by the ECM, the O2 sensor then helps to adjust up or down (rich/Lean) there are 2 signal inputs to the ECM Left and Right O2. There are also 2 Ground pins on the ECM for left and right O2.. which are shorted together and then grounded to the engine. I ohmed between both Left right grounds at the ECM.. confirmed short... Ohmed from both to ground ( both chassis and engine) seems to be open.. I ran a new wire to creat the ground.. it is later here and I will nto get a chance to try again until saturday AM..

So that might explain the O2 problem, but not the changing BLM in Open loop..

[XfireZ51]

Jeff,

Sounds likke you still need to fix that open ground regardless. I would fix that first before installing new ECM and see what happens. Is the O2 ground tied into an ECM ground by any chance?

[-=Jeff=-]

Jeff,

Sounds likke you still need to fix that open ground regardless. I would fix that first before installing new ECM and see what happens. Is the O2 ground tied into an ECM ground by any chance?

I have a fix to test on Sat. not going to try tonight or have time tomorrow

no o2 Ground is its own ground..

[bobbyhi]

bobby,

So you finally got a cam sensor code?


Yes, a code did come up. I was at Doug Rippie's place when the code occured. Doug did not give me a code # but said it was the cam sensor fault.

[XfireZ51]

Jeff,

Have you thought of looking at the ECM grounds? Odd that O2 sensor ground would be bad. :confused:

[-=Jeff=-]

Jeff,

Have you thought of looking at the ECM grounds? Odd that O2 sensor ground would be bad. :confused:

it is not the sensor ground directly.. if you look in the Service manual there is a Ground out of the ECM for the sensor circuit.. I found the ground location, everything is connected, I also found what else goes to that same point. so far everything that goes to that ground point works.. Now that is not to say that the wire is bad, but the is a (S) connection (short) where both ECM O2 Circuit Grounds tie together and then go to the ground point. It is possible, that the leg going to the grounding point broke away at the short.

One step at a time.. going to check this fix this weekend. see if I got anywhere. then move on to the next issue

[-=Jeff=-]

Diff MAP registers a constant .6 volts but when he stabs the pedal,voltage goes up and Scdys Open.

I looked at this in the manual, I need to read through it again, but that voltage appears to be correct..

[XfireZ51]

it is not the sensor ground directly.. if you look in the Service manual there is a Ground out of the ECM for the sensor circuit.. I found the ground location, everything is connected, I also found what else goes to that same point. so far everything that goes to that ground point works.. Now that is not to say that the wire is bad, but the is a (S) connection (short) where both ECM O2 Circuit Grounds tie together and then go to the ground point. It is possible, that the leg going to the grounding point broke away at the short.

One step at a time.. going to check this fix this weekend. see if I got anywhere. then move on to the next issue

So IOW,you'll check to see if fixing the O2 ground issue is the culprit before swapping ECMs? Also, the Diff MAP sensor readings in the scan were strange. Any chance similar issue is going on there and would the two be related?

[-=Jeff=-]

So IOW,you'll check to see if fixing the O2 ground issue is the culprit before swapping ECMs?

Yes.. check that first

Also, the Diff MAP sensor readings in the scan were strange. Any chance similar issue is going on there and would the two be related? how are they strange?

Again, from what I read in the Service manual they seem to be fine.

[XfireZ51]

Yes.. check that first

how are they strange?

Again, from what I read in the Service manual they seem to be fine.

I re-read the manual just now. Looks right. See you later next week. Keep me posted.

[-=Jeff=-]

Update..

Injectors are FINE, Coils FINE..

I am working out a coupe things and don't want to speak too soon, but I thank I might almost have the issue resolved

[XfireZ51]

I'm on pins and needles! :pray

[tccrab]

Update..

Injectors are FINE, Coils FINE..

I am working out a coupe things and don't want to speak too soon, but I thank I might almost have the issue resolved

Well?
Any luck?

Tom

[-=Jeff=-]

Well?
Any luck?

Tom

not sure yet. Drove it Saturday and the issue did not show up..

Need to drive it again. not sure if I will get a chance today

[tccrab]

not sure yet. Drove it Saturday and the issue did not show up..

Need to drive it again. not sure if I will get a chance today

Soo.....
What did you change/repair/fix/hit with hammer?:D

Tom

[-=Jeff=-]

Soo.....
What did you change/repair/fix/hit with hammer?:D

Tom

So far, I fixed a grounding issue with the O2 circuit

[bobbyhi]

So far, I fixed a grounding issue with the O2 circuit


And did that fix the stumbing issue??

[-=Jeff=-]

And did that fix the stumbing issue??

So far.. I think so..

[bobbyhi]

So far.. I think so..

What did you fix on the O2 sensor?:confused: Was the problem limited just one of the sensors or both??? Sorry for all of the questions but mine is doing basically the same thing:mad: I'm getting tired of just putting in parts, at a great expense, and not fixing the problem.

[bradslt5]

jeff if i can ask what were the o2 sensors acting like that caused you to ck them.? i might have an intermittent issue with my 92.

[-=Jeff=-]

okay.. there are 2 grounds OUT of the ECM, one right, one left. both tie together to one ground lug. somewhere from the tied point to ground the line was open. I tapped a new wire in and grounded it that fixed the O2 issue.

with no ground from the ECM for the O2 s I was reading .45v ALL the time on BOTH sensors

[tomtom72]

Nice catch! Kudos to ya Jeff!:thumbsup: